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CarlingWood
04-13-2009, 08:11 AM
Why does no one fly the Tempest? Whether it be arcade, coop, redvsblue, I barely see ANYONE fly the tempest at all. I mean, its a amazing aircraft. Using 70 pp and wep you would never overheat, amazing hispanos, and amazing speed. Yet I rarely see Tempest flyers at all. Its either P51s, Spits, 109s, Kis, Doras, you name it, but not tempests.



http://forums.ubi.com/images/smilies/disagree.gif

CarlingWood
04-13-2009, 08:11 AM
Why does no one fly the Tempest? Whether it be arcade, coop, redvsblue, I barely see ANYONE fly the tempest at all. I mean, its a amazing aircraft. Using 70 pp and wep you would never overheat, amazing hispanos, and amazing speed. Yet I rarely see Tempest flyers at all. Its either P51s, Spits, 109s, Kis, Doras, you name it, but not tempests.



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Feathered_IV
04-13-2009, 08:41 AM
Personally I don't fly it because the rear view is very poorly represented.

crucislancer
04-13-2009, 08:53 AM
I use it whenever it's available. http://forums.ubi.com/images/smilies/25.gif

Choctaw111
04-13-2009, 10:00 AM
It is a powerful machine, and in the right hands is very deadly. It is one of those planes that takes some time to learn to be effective with it. If you choose to turn fight, you will think it is a very poor performer. When flying with a RAF squad, I would take the Tempest whenever I could.

Metatron_123
04-13-2009, 10:13 AM
It builds up speed very quickly and has in my opinion the best armament combination. Even moderately good aiming obliterates enemy planes, much like the Fw-190. It's a great plane.

na85
04-13-2009, 12:05 PM
I see it used quite a bit online.

Very deadly, even in novice hands.

dirkpit7
04-13-2009, 01:45 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Feathered_IV:
Personally I don't fly it because the rear view is very poorly represented. </div></BLOCKQUOTE>

Doesn't the 6DOF mod remove this issue?

danjama
04-13-2009, 02:07 PM
I fly it nightly in my own co-ops, and alot of friends join me. We love her!

Come online and join me for my Ardennes campaign featuring the Tempest as the star!

Ba5tard5word
04-13-2009, 02:08 PM
The aiming is a bit tricky because the tracers look slow, but it doesn't require much practice to get used to.

It's kind of like the Allied version of the Fw-190A--not great at turning (mainly because it will flip over easily), super fast, loses speed quickly if you do anything other than fly straight, and good strong armament. Better visibility and maneuverability than the Fw-190A though.

na85
04-13-2009, 02:10 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by dirkpit7:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Feathered_IV:
Personally I don't fly it because the rear view is very poorly represented. </div></BLOCKQUOTE>

Doesn't the 6DOF mod remove this issue? </div></BLOCKQUOTE>

Not really. It helps a little bit, but you can only lean so far over, and the rear headrest is quite large and obstructing.

DKoor
04-13-2009, 02:18 PM
Few 109's has issues with that too... very poor rear view in what many considered to be the best 109 in game, G2.

dirkpit7
04-13-2009, 02:42 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by na85:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by dirkpit7:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Feathered_IV:
Personally I don't fly it because the rear view is very poorly represented. </div></BLOCKQUOTE>

Doesn't the 6DOF mod remove this issue? </div></BLOCKQUOTE>

Not really. It helps a little bit, but you can only lean so far over, and the rear headrest is quite large and obstructing. </div></BLOCKQUOTE>

Ok, thanks for your answer. What is the actual problem then (compared to real life), is the headrest modelled too large, or is the leaning ability more restricted than it would actually be?

And indeed this problem is not related to Tempest only, all bubble canopy equipped planes are more or less affected. But Tempest probably suffers most.

na85
04-13-2009, 02:56 PM
No idea what the tempest's rear view is like in real life.

I just know that it's not very good in game.

dirkpit7
04-13-2009, 02:58 PM
I think I've read pilots saying they had perfect 360 degree view.

na85
04-13-2009, 03:01 PM
I doubt that very much.

gizmo60
04-13-2009, 03:08 PM
There are other posts about the Tempests bad rearward view.

The real plane did not suffer as the one in the game does.
It is because the camera position was set too far back in the cockpit, right against the headrest.

Cheers

VW-IceFire
04-13-2009, 03:53 PM
I fly it all the time http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

But I do fly other planes too...I like to stay up on all of the types so that I'm a well rounded pilot.

ROXunreal
04-13-2009, 04:33 PM
Beautiful plane, cockpit and guns, but I can never seem to recover altitude after a dive....or maybe I'm just too much used to the 190

TgD Thunderbolt56
04-13-2009, 04:36 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by CarlingWood:
Why does no one fly the Tempest?
http://forums.ubi.com/images/smilies/disagree.gif </div></BLOCKQUOTE>


Where I fly, people fly them all the time. Check out the Warbirds-of-Prey servers http://www.warbirdsofprey.org/modules.php?name=Forums and the late war maps almost always have them available.

http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

na85
04-13-2009, 05:27 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by ROXunreal:
Beautiful plane, cockpit and guns, but I can never seem to recover altitude after a dive....or maybe I'm just too much used to the 190 </div></BLOCKQUOTE>

High aspect-ratio wings on the 190 have less induced drag than those of the tempest, which might account for the difference in zoom performance.

Buzzsaw-
04-13-2009, 07:19 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by na85:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by ROXunreal:
Beautiful plane, cockpit and guns, but I can never seem to recover altitude after a dive....or maybe I'm just too much used to the 190 </div></BLOCKQUOTE>

High aspect-ratio wings on the 190 have less induced drag than those of the tempest, which might account for the difference in zoom performance. </div></BLOCKQUOTE>

Complete nonsense. At high speeds and low G's the historical Tempest's laminar flow wing was far superior.

na85
04-13-2009, 07:30 PM
Superior in what regard?

Are you saying that high aspect ratio wings don't produce less induced drag?

JtD
04-13-2009, 10:21 PM
Aspect ratio is just one thing that determines induced drag. This is all academic, though, as at high speed parasitic drag is much more important.

Kettenhunde
04-14-2009, 12:39 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> At high speeds and low G's the historical Tempest's laminar flow wing was far superior. </div></BLOCKQUOTE>

How much of a zoom climb is high speed and low G?

Answer - about equal to the portion that is low speed, low G, and High Speed, High G. These are areas laminar flow airfoils are not the best choice.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> High aspect-ratio wings on the 190 have less induced drag than those of the tempest, which might account for the difference in zoom performance.
</div></BLOCKQUOTE>

While the total drag picture does play a part in zoom climb performance, the largest factor is entry velocity and that is followed by weight.

All things being equal, the lighter aircraft will out zoom the heavier one. It takes surprisingly large differences in drag and thrust to overcome this fact.

It also does not mean this will reflect a trend in combat. Generally speaking, aircraft are not traveling at the same speed in a dogfight as their best performance numbers are tied to the design of the plane.

If one aircraft's performance numbers occur at a higher velocity, then that aircraft will out zoom the slower one in a fight.

This is why we see the P38 for example dominating the Zeke in the Pacific. If a P38 pilot flew his airplanes best performance speeds and the Zeke pilot flew his airplanes best performance speed, the P38 will always out zoom the Zeke because the P38 is traveling faster. This also contributes to the Zeke's turning superiority as velocity and radius are the most important relationship in turn performance. The slower velocity aircraft will generally outturn the faster velocity aircraft.

Trying to match an opponent’s performance numbers with a different design is generally speaking, a recipe for disaster.

All the best,

Crumpp

VMF-214_HaVoK
04-14-2009, 01:17 AM
Who says its underrated? It does what its suppose to do and does it very well.

Chevy350
04-14-2009, 01:27 AM
i love the tempest but dont fly it cause i cant see behind me http://forums.ubi.com/groupee_common/emoticons/icon_frown.gif

Metatron_123
04-14-2009, 06:00 AM
You've already lost the fight if you're looking behind you! http://forums.ubi.com/images/smilies/winky.gif

DKoor
04-14-2009, 06:16 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Metatron_123:
You've already lost the fight if you're looking behind you! http://forums.ubi.com/images/smilies/winky.gif </div></BLOCKQUOTE>I was flying yesterday on Italy map in 109F and that damned water all over + mist + dusk created environment 'heavy' for spotting planes.
However, only my habit of checking six every once and while saved my butt... I just couldn't believe it when I saw a Spitfire appearing less than 200m away from me on my 6. Literally half second after I'd be toasted if I hadn't spotted him.
Anyhow I rolled, closed radiator and vertically dived for deck (from what seemed to be 2,500m alt at the time)... I also put some rolls in dive knowing that would disrupt the Spitfires' aim for sure on high speed.
And so... I lived to tell the tale.

That probably wouldn't be the case in Tempest. http://forums.ubi.com/images/smilies/16x16_smiley-indifferent.gif

Feathered_IV
04-14-2009, 06:46 AM
Might be possible to reduce the tempest headrest somewhat using alpha channels etc. Anyone got a pic of a real pilots rear view?

JtD
04-14-2009, 09:14 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:

All things being equal, the lighter aircraft will out zoom the heavier one. It takes surprisingly large differences in drag and thrust to overcome this fact. </div></BLOCKQUOTE>

This is not 100% correct, it depends on the circumstances, like starting speed, ending speed and climbing angle.

Kettenhunde
04-14-2009, 09:42 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> This is not 100% correct, it depends on the circumstances, like starting speed, ending speed and climbing angle. </div></BLOCKQUOTE>

Baloney, It is 100% correct.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> All things being equal, the lighter aircraft will out zoom the heavier one.
</div></BLOCKQUOTE>

JtD
04-14-2009, 10:35 AM
Thank you for your kind response. In particular it was very kind to repeat yourself in bold, so I could read it from further away. However, you are mistaken.

With two aircraft of equal drag yet different weight a higher percentage of the initial kinetic energy will go into the drag losses for the lighter aircraft. This means a higher percentage of the initial kinetic energy will go into the potential energy for the heavier plane. This percentage is directly proportional to the altitude reached.

In shallow climbs, where induced drag plays a larger role, in high powered planes where the initial energy plays a smaller role or at low speeds where sustained climb performance plays a larger role, the lighter aircraft will come out on top. Normal zoom climb conditions will usually have these factors dominate.

But to say that the lighter aircraft will out zoom a heavier one is not 100% correct. It is possible to find conditions, equal conditions for both the lighter and the heavier plane, where the heavier plane outzooms the lighter one.

Kettenhunde
04-14-2009, 10:48 AM
Lets look at two objects traveling at 10,000ft altitude and 400fps velocity. Lets see how high they would go if shot straight up to zero velocity and how much energy each needs to reach that altitude.

TE = W*h + 1/2mV^2

Object 1:

W = 10,000lbs
h = 10,000ft

m = 10,000lbs/32.2ft/s^2 = 310.6 slugs

TE = (10,000lbs * 10,000ft) + 1/2 310.6 slugs * 400fps^2

TE = 100,000,000 ft/p + 24848000 ft/p

TE = 124848000ft/p

TE = TE by the law of the conservation of energy

At zero velocty then KE = 0.

124848000ft/p = 10000ft*h + 1/2 310.6 slugs *0^2

124848000ft/p / 10000ft = h

h = 12484

Since we started at 10,000ft we can subtract that from our new height to get the change in altitude.

12484 - 10,000 ft = 2,484ft

Object 2:

W = 5,000lbs
h = 10,000ft

m = 5,000lbs/32.2ft/s^2 = 155.28 slugs

TE = (5,000lbs * 10,000ft) + 1/2 155.28 slugs * 400fps^2

TE = 50,000,000ft/p + 12422400ft/p

TE = 62422400 ft/p

TE =TE

Since Velocity is zero, our KE = 0.

TE = W*h

Our new height is then:

62422400 ft/p / 5,000lbs = h

h = 12484 ft

Since we started at 10,000ft we can subtract that from our new height to get the change in altitude.

12484 - 10,000 ft = 2,484ft

Our more massive object at 310.6 slugs required 124848000ft/p to reach the same altitude while the smaller mass object at 155.28 slugs only required 62422400 ft/p of energy.

A more massive object requires more energy to reach the same altitude or velocity.

A heavier airplane will not zoom as high as a lighter airplane everything else being equal.

If we use the rectilinear equation:

How high should my more massive plane zoom compared to a less massive aircraft??

Characteristics of our theoretical aircraft:

Aircraft Number 1:

Weight 9000lbs
Thrust in lbs = 1000lbs
Air resistance in lbs = 500

Zoom climb from 300mph to Vy at a 45 degree angle:

300mph = 441fps
Zoom Angle 45 degrees
Vy = 150mph = 220.5fps

Zoom height:

Sum the forces on the flight path -

9000lbs * sin 45 = 6364lbs
1000lbs – 500lbs – 6364lbs = 5864lbs

a = F/m

m = 9000lbs/32.2 = 279.5 lb-s^2/ft
a= 5864lb/279.5lb-s^2/ft
a = 20.98 ft/s^2

s = (V1^2 – V2^2 ) / 2a

s = (441^2 – 220.5^2)/(2 * 20.98ft/s^2) = 3476.18 ft

3476.18 ft * sin 45 = 2458 ft

Aircraft Number 1:

Weight 4500lbs
Thrust in lbs = 1000lbs
Air resistance in lbs = 500

Zoom climb from 300mph to Vy at a 45 degree angle:

300mph = 441fps
Zoom Angle 45 degrees
Vy = 150mph = 220.5fps

Zoom height:

Sum the forces on the flight path -

4500lbs * sin 45 = 3182lbs
1000lbs – 500lbs – 3182lbs = -2682lbs

a = F/m

m = 4500lbs/32.2 = 139.75 lb-s^2/ft
a= 2682lb/139.75lb-s^2/ft
a = 19.19 ft/s^2

s = (V1^2 – V2^2 ) / 2a

s = (441^2 – 220.5^2)/(2 * 19.19ft/s^2) = 3800 ft

3800 ft * sin 45 = 2687 ft

2687 ft - 2458 ft = 229ft

The less massive aircraft ends up 229 ft above the more massive aircraft.

Lighter aircraft will zoom higher everything else being equal.

Heavier aircraft are poor zoom climbers everything else being equal.

Velocity is the key component to zoom climb performance and the faster aircraft will zoom the highest.

All the best,

Crumpp

Kettenhunde
04-14-2009, 10:52 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">But to say that the lighter aircraft will out zoom a heavier one is not 100% correct. It is possible to find conditions, equal conditions for both the lighter and the heavier plane, where the heavier plane outzooms the lighter one. </div></BLOCKQUOTE>

I gave the math in algebraic form so you can work it.

Feel free to show any condition that all things are equal except weight where the heavier aircraft outzooms the lighter one.

All the best,

Crumpp

JtD
04-14-2009, 11:06 AM
Try drag &gt; thrust.

Kettenhunde
04-14-2009, 11:27 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Try drag &gt; thrust. </div></BLOCKQUOTE>

Many airplanes fly like that were you are from? I don't know of a single aircraft that attempts to zoom climb with a reverse thruster!

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Feel free to show any condition that all things are equal except weight where the heavier aircraft outzooms the lighter one.
</div></BLOCKQUOTE>

All the best,

Crumpp

Xiolablu3
04-14-2009, 11:37 AM
Excuse me for interupting, but I just thought of an interesting comparison....


If you had a 2 balls attached to 2 poles, sort of like the game swingball where you hit a ball on a string back and forward.

Both balls are the same size, but one is heavy like a cricket ball, and one is light like a tennis ball.

And you drop each from a height and see which swings the highest after the drop...surely the heavy cricket ball would swing higher?

Of course neither of these are powered, unless you introduced some king of equal throw/force downwards to start on each...If the force is quite strong then the lighter ball will probably 'zoom' higher, but if the force is light, it would probably be the cricket ball, I would have thought...

Kettenhunde
04-14-2009, 12:12 PM
Xio,

An Italian guy already figured that out for you.

You can use the TE equation to determine the results provided the objects have the same shape, area, and surface texture.

TE = W*h + 1/2mV^2

This topic has been convered and I will leave your forum to wrestle with it.

All the best,

Crumpp

JtD
04-14-2009, 12:40 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Try drag &gt; thrust. </div></BLOCKQUOTE>

Many airplanes fly like that were you are from? I don't know of a single aircraft that attempts to zoom climb with a reverse thruster!

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Feel free to show any condition that all things are equal except weight where the heavier aircraft outzooms the lighter one.
</div></BLOCKQUOTE>

All the best,

Crumpp </div></BLOCKQUOTE>

Thanks again for your kindly worded reply. I'm sorry that I was so cryptic. Of course, I should have explained. The "&gt;" sign stands for "larger than", so I meant to say you can try with drag larger than thrust, for instance in a power off zoom climb.

"&gt;" by no means refers to negative, or in that case to a reverse thruster.

Col.BBQ
04-14-2009, 01:38 PM
I rarely fly it because its so easy to shake off pursuers with the boosted engine thrust that can blow the green off the grass.

M_Gunz
04-14-2009, 04:23 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
Xio,

An Italian guy already figured that out for you.

You can use the TE equation to determine the results provided the objects have the same shape, area, and surface texture.

TE = W*h + 1/2mV^2

This topic has been convered and I will leave your forum to wrestle with it.

All the best,

Crumpp </div></BLOCKQUOTE>

Oh come on now, neither Leonardo nor the TE equation deal with air drag much less thrust.

In a dive at over top speed, say 500mph in a P-47, higher mass during that dive should help make a higher end speed.
But as for being an overall aid in the down to up transition... the same extra weight (small load of lead bricks)
that's giving more inertia is also being needed to change direction which somehow I expect will not give more than
it takes away due to that third law of thermodynamics.

In his appendix section on zoom, Shaw points out TE zoom and then goes on to a more real case using Excess Power
and show that the higher T/W plane will zoom higher given equal start speeds. Everything else equal, the lighter
plane zooms higher. Different start speeds, the faster one zooms higher. Different pilots, the better wins.

People need to get on past these things before they can start comparing performance in different altitudes and speeds
to find what styles and tactics they should be using in that plane vs any particular other, and what conditions to
not let themselves be tempted or forced into.

Kettenhunde
04-14-2009, 10:58 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> I meant to say you can try with drag larger than thrust </div></BLOCKQUOTE>

I know what you said. There is not a practical way to do that with a power producer. It is nonsense!

I think if you had practical experience in using the rectilinear equations to determine performance for an aircraft you would know this fact. In using the formula, we take the average forces on the vector and sum them. While in a high speed dive for a power producer, the condition of drag exceeding thrust does exist for a short time on the vector, the average will always have thrust exceeding drag, though.

We could close the throttle and treat our aircraft as a glider, but what would be the point? We would just determine the performance of a very poor glider design!

Your assertion has no application to powered aircraft. It only serves to add confusion and mislead others.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">JtD says:
But to say that the lighter aircraft will out zoom a heavier one is not 100% correct. It is possible to find conditions, equal conditions for both the lighter and the heavier plane, where the heavier plane outzooms the lighter one. </div></BLOCKQUOTE>

M_Gunz,

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Oh come on now, neither Leonardo nor the TE equation deal with air drag much less thrust.
</div></BLOCKQUOTE>

True and that is why:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> You can use the TE equation to determine the results provided the objects have the same shape, area, and surface texture.
</div></BLOCKQUOTE>

In Xio's experiment, the objects will have the same drag if they meet those requirements and the effects will cancel.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">In a dive at over top speed, say 500mph in a P-47, higher mass during that dive should help make a higher end speed. But as for being an overall aid in the down to up transition... the same extra weight (small load of lead bricks) that's giving more inertia is also being needed to change direction which somehow I expect will not give more than
it takes away </div></BLOCKQUOTE>

Don't discount the first law!!

Energy can neither be created nor destroyed. It can only change forms.

While the heavy aircraft converts more energy in a dive it requires more energy in the climb.


<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> In his appendix section on zoom, Shaw points out TE zoom and then goes on to a more real case using Excess Power and show that the higher T/W plane will zoom higher given equal start speeds. Everything else equal, the lighter plane zooms higher. Different start speeds, the faster one zooms higher. Different pilots, the better wins.
</div></BLOCKQUOTE>

Shaw is correct, big revelation huh?

Shaw better never post that nonsense on these boards! Folks will straighten him out in jiffy with that thinking cause they got homemade charts!

http://forums.ubi.com/images/smilies/blink.gif

All the best,

Crumpp

JtD
04-14-2009, 11:27 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> I meant to say you can try with drag larger than thrust </div></BLOCKQUOTE>

I know what you said. There is not a practical way to do that with a power producer. It is nonsense!

I think if you had practical experience in using the rectilinear equations to determine performance for an aircraft you would know this fact. In using the formula, we take the average forces on the vector and sum them. While in a high speed dive for a power producer, the condition of drag exceeding thrust does exist for a short time on the vector, the average will always have thrust exceeding drag, though.

We could close the throttle and treat our aircraft as a glider, but what would be the point? We would just determine the performance of a very poor glider design!

Your assertion has no application to powered aircraft. It only serves to add confusion and mislead others. </div></BLOCKQUOTE>

Thanks again for your careful choice of words. As you have seen now, there are conditions where the heavier aircraft zooms higher. Like I said right from the beginning, the conditions are not common.

I'm glad that for once you had the brains to understand my point, though you still lack the guts to say it.

Buzzsaw-
04-15-2009, 01:36 AM
Salute

Now that we have finished with the comments by the theoretical experts, lets see what the real test pilots found when actually flying the aircraft.

From the AIR FIGHTING DEVELOPMENT UNIT tests of the prototype Tempest versus various allied and german aircraft, this Tempest which by the way, was running only +7 boost, less than the ingame +9 version, and far less than the mid '44 +11 boost version, or the late war +13 version.

&gt;&gt;&gt;

From the comparison with the Typhoon:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
Dive

17. For the same reasons as the zoom climb, the Tempest pulls ahead. As the speed is increased it does so more rapidly. The fact is it has the best acceleration in the dive yet seen at this Unit.
</div></BLOCKQUOTE>

Ie. better than the Mustang, 190A, or P-47.

From the comparison with the 190A:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
COMBAT TRIALS AGAINST FW.190 (BMW.801D)

Maximum Speed
38. The Tempest is nearly 50 mph faster at all heights. It is estimated that the Tempest V may be very slightly faster than the new FW.190 (DB.603) up to 20,000 ft.

Climb
39. Except below 5,000 feet the FW.190 (BMW.801D) has a slightly better maximum rate of climb. Because of the Tempest V's speed and clean lines however, the Tempest has a markedly better zoom climb, where the speed is kept high. Against the new FW.190 (DB.603) it is estimated that the Tempest will have a markedly superior climb below 5,000 feet, but a similar maximum climb above that height.

Dive
40. The Tempest pulls away rapidly in a dive from all heights.

Turning Circles
41. There is very little difference in turning circles between the two aircraft. If anything a very slight advantage lies with the Tempest.

Rate of Roll
42. The Tempest V cannot compare with the FW 190.

Conclusions

43. Similar tactics should be used against the FW.190 as used by the Typhoon squadrons, advantage being taken of high speed. Such handling should prove most effective. The Tempest has an exceptional ground height performance even (estimated against the FW.190 (DB.603).
</div></BLOCKQUOTE>


"...marked better" in both dive acceleration and zoom climb... does that tell us anything about the aircraft'S VERY clean airframe?

The AFDU trials were done in February '44, before the 190D saw active service, at that time the Allied intelligence services only knew there was a new 190 with an inline engine to appear. They were under the mistaken impression that the Daimler Benz 603 would be the powerplant, that is what Kurt Tank originally intended, but reliability problems required the use of the Jumo.

Kettenhunde
04-15-2009, 01:43 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Crumpp says:

Your assertion has no application to powered aircraft. It only serves to add confusion and mislead others. </div></BLOCKQUOTE>


<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> I said right from the beginning, the conditions are not common.
</div></BLOCKQUOTE>

No, let’s be very clear in my carefully chosen words before you cause further confusion in your personal vendetta against me..

The conditions are stupid and have no bearing.

That would be obvious to anyone who did the legwork to determine the forces summed on the vector.

Your motivation for posting is because you spouted erroneous concepts in the past which I corrected you on. You know everyone of those times has been about very complicated subjects that I was actually impressed at what you did know about them.

All the best,

Crumpp

Kettenhunde
04-15-2009, 01:50 AM
Great example of the principles at work!

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Because of the Tempest V's speed and clean lines however, the Tempest has a markedly better zoom climb, where the speed is kept high. </div></BLOCKQUOTE>

Do you know what V speeds are Buzzsaw?

As the physics, math, and Mr Robert Shaw show us:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> In his appendix section on zoom, Shaw points out TE zoom and then goes on to a more real case using Excess Power and show that the higher T/W plane will zoom higher given equal start speeds. Everything else equal, the lighter plane zooms higher. Different start speeds, the faster one zooms higher. Different pilots, the better wins.
</div></BLOCKQUOTE>

The Tempest is heavier than the FW190A and its design performance speeds are higher! It will outzoom the FW190A if the both pilots fly their V speeds.

All the best,

Crumpp

M_Gunz
04-15-2009, 02:37 AM
It's very easy to dig up examples to contradict what is said given "all other things equal" when you ignore the given part.
Or maybe when your attention span is too short to either attach the ideas or remember the one when reading the other though
I think that the more usual case is forgot that part in a rush to contradict what is already known can be.

Back when Oleg still posted here and there was calls on zoom climb he did post that the better known zoomers also ran
faster dives to zoom back up from.

I think that if the zoom upwards started and ended at beyond top level speed then for sure more weight would help that
plane lose speed at a slower rate than without the extra. This totally ignores getting there in the first place and
everything later on just to find a way that the equations would favor the same plane only heavier.

I think that Crumpp should remember the "example" of one plane given a 1 or 2 kph higher speed at zoom start losing out
to another weighing half as much but otherwise the same (the first must have had one hell of a bombload) -- as a lame
way to show that a very small square can be less than a very large difference. It's all in the math if not exactly
in a reasonable (or even same planet) approximation of planes in actual performance tests which IIRC was specified
long before that thread got that far. But then we have people who don't remember what they posted on the last page.

AllorNothing117
04-15-2009, 05:10 AM
I think it's very good but haven't flown it much. However I vow to fly it today! My Dad likes it too but we both hate the rear visability. However we got the mod pack and I haven't been in it since. Theres 3-4 versions after you put the mods on, which one is best? What are the diffrences between them? If Ice fire likes it, it must be good http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif I will go fly it now http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

PS: I haven't been online much but I saw it allot on Skies of Fire/Skies of valour.

danjama
04-15-2009, 06:17 AM
Hi mate, shift-F1 improves rear visibility alot and brings you closer to the windscreen of the plane, which is a more realistic sitting view IMO. Enjoy the plane, i recommend all 3 versions.

CloCloZ
04-15-2009, 09:42 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by AllorNothing117:
I think it's very good but haven't flown it much. However I vow to fly it today! My Dad likes it too but we both hate the rear visability. However we got the mod pack and I haven't been in it since. Theres 3-4 versions after you put the mods on, which one is best? What are the diffrences between them? If Ice fire likes it, it must be good http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif I will go fly it now http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

PS: I haven't been online much but I saw it allot on Skies of Fire/Skies of valour. </div></BLOCKQUOTE>

I don't fly online but fly Tempest offline a lot, especially +9lbs "standard" game version and +13lbs.
+13lbs version reaches, on the deck, almost 650 km/h (as shown by Wonder Woman View gauge), about 20 km/h faster than +11lbs and 40 km/h faster than +9lbs.
+13lbs accelerates faster and has more torque than +9lbs.
In my opinion, +9lbs is more stable than +13lbs and so is a better gun platform but, all in all, I prefer +13lbs and its brute strength! http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif
Maybe +11lbs could be the best balance (although I've flown it much less than the other two).

Both +11lbs and +13lbs, the modded models, "suffer" from being overmodelled over 6000 mt (see http://forums.ubi.com/eve/foru...283/m/1531048547/p/2 (http://forums.ubi.com/eve/forums/a/tpc/f/23110283/m/1531048547/p/2) and the following page).
AFAIK, no fix has been applied so far.

Buzzsaw-
04-15-2009, 12:00 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
Great example of the principles at work!

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Because of the Tempest V's speed and clean lines however, the Tempest has a markedly better zoom climb, where the speed is kept high. </div></BLOCKQUOTE>

Do you know what V speeds are Buzzsaw?

As the physics, math, and Mr Robert Shaw show us:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> In his appendix section on zoom, Shaw points out TE zoom and then goes on to a more real case using Excess Power and show that the higher T/W plane will zoom higher given equal start speeds. Everything else equal, the lighter plane zooms higher. Different start speeds, the faster one zooms higher. Different pilots, the better wins.
</div></BLOCKQUOTE>

The Tempest is heavier than the FW190A and its design performance speeds are higher! It will outzoom the FW190A if the both pilots fly their V speeds.

All the best,

Crumpp </div></BLOCKQUOTE>

Sorry Crumpp, that is not what the AFDU test showed. RAF AFDU tests were done comparing the aircraft at similar 'e', ie. side by side at the same speed, or one following the other. This test shows that when BOTH aircraft were at the SAME high speeds, the Tempest has a better zoom, because of its cleaner airframe/power combination. Only when both aircraft were at a low speed, in a climb, would the FW-190 show better.

Kettenhunde
04-15-2009, 10:18 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Buzzsaw says:
Sorry Crumpp, that is not what the AFDU test showed. </div></BLOCKQUOTE>

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Buzzsaw says:
This test shows that when BOTH aircraft were at the SAME high speeds, </div></BLOCKQUOTE>

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Crumpp says:
Do you know what V speeds are Buzzsaw?
</div></BLOCKQUOTE>

Let's look at that again:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Because of the Tempest V's speed and clean lines however, </div></BLOCKQUOTE>

If the AFDU used the FW190A and Tempest V speeds, there is no way they could have the same entry speed. These aircraft are different designs and do not have the same Pr curves!

By definition V speeds are dictated by design.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">V speeds are speeds that define certain performance and limiting characteristics of an aircraft. They are established by the manufacturer during design and testing, and are specific to the aircraft model. </div></BLOCKQUOTE>

http://enc.slider.com/Enc/V-Speeds

You are making assumptions based on emotions without facts.

You do not understand what the report is telling you because you do not understand the terminology it is using.

Here you can examine the report and point out what you feel is in error.

http://www.wwiiaircraftperform...est/tempestafdu.html (http://www.wwiiaircraftperformance.org/tempest/tempestafdu.html)


All the best,

Crumpp

JtD
04-16-2009, 11:29 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Crumpp says:

Your assertion has no application to powered aircraft. It only serves to add confusion and mislead others. </div></BLOCKQUOTE>


<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> I said right from the beginning, the conditions are not common.
</div></BLOCKQUOTE>

No, let’s be very clear in my carefully chosen words before you cause further confusion in your personal vendetta against me..

The conditions are stupid and have no bearing.

That would be obvious to anyone who did the legwork to determine the forces summed on the vector. </div></BLOCKQUOTE>

Here we go again. Can't you even try to go through a debate without being offensive? So hard to follow the forum rules, or at least the common concepts of human conversation?

As to the my statement - I said you statement is not 100% correct - I didn't even say it was wrong. But as a matter of fact in WW2 it did happen that folks would dive to speeds beyond their top level speed, they would also do so without flying at WEP and they would pull into zoom climbs. Under these conditions, the heavier aircraft is the better zoom climber and may eventually come out on top depending on when the zoom climb is finished. Now you won't find these conditions when flying a bloody Cessna, but they still exist. So your blanket statement could use a little bit of discussion.

I'm sorry you take it personal, but there's is nothing I can do about that.

Brain32
04-16-2009, 12:10 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> But as a matter of fact in WW2 it did happen that folks would dive to speeds beyond their top level speed, they would also do so without flying at WEP and they would pull into zoom climbs. Under these conditions, the heavier aircraft is the better zoom climber and may eventually come out on top depending on when the zoom climb is finished. </div></BLOCKQUOTE>

Sorry but as impartial observer I really don't see how the above example proves Kett was wrong even 0.0005%

He said:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> All things being <span class="ev_code_RED">equal</span>, the lighter aircraft will out zoom the heavier one. </div></BLOCKQUOTE>
I believe speed is included in "all things"...

Now I think I know what you are getting at, heavier planes usually have better dive acceleration and can therefore attain higher speed in the dive and then zoom higher. This however assumes condition that is outside of Kett's statement above...

Bremspropeller
04-16-2009, 02:21 PM
You guys are greatly oversimplyfying the issue.

Nobody talks about drag or thrust.
Those two figures are of fundamental importance.

Physically describing maneuvering aircraft is a bit more complicated than describing the dynamics of a point-mass.

M_Gunz
04-16-2009, 02:28 PM
The real trick/challenge/near-impossibility(?) is in identifying the -averages- used for thrust and drag.

In cases where the zoom starts and ends where the average drag is more than the average thrust, JTD has a point.
Considering what happens with prop thrust as speed increases, there should be some margin of truth just by the numbers.
Even with a long zoom it is possible to talk about relative accelerations and distances in only the high speed part.

thefruitbat
04-16-2009, 05:55 PM
i miss these threads.

You guys are much to civil with each other these days...

but as always, good info tucked away in the depths...

fruitbat

Kettenhunde
04-16-2009, 09:08 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Nobody talks about drag or thrust.
</div></BLOCKQUOTE>

The thrust and drag forces are included in the rectilinear equation example I posted in this thread. We sum the average of these forces over the zoom climb.

This is why even when a powered aircraft exceeds its top level speed, the average will never have drag exceeding thrust.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> I believe speed is included in "all things"...

Now I think I know what you are getting at, heavier planes usually have better dive acceleration and can therefore attain higher speed in the dive and then zoom higher. </div></BLOCKQUOTE>

Exactly, speed is included.

People seem to think the fact the physics dictates:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Everything else equal, the lighter plane zooms higher. Different start speeds, the faster one zooms higher. </div></BLOCKQUOTE>

That it means "lighter aircraft will out zoom heavier ones in combat". That is just not necessarily true and is in fact not looking at the aircraft as a complete system.

Weight is a bad thing for aircraft, it shrinks the entire envelop and design firms are always conscious of weight creep. A balanced design however does not necessarily mean the lighter of two different designs is the better aircraft.

Once again, real airplanes are flown by their V speeds. I think the importance of this fact is lost on non-pilots as you don’t have to pay much attention to your speeds in these games.

This is very important to understanding how real dogfights are played out. If the pilot does not fly the plane by these speeds then he will not get expected performance. In the real world, the range of best performance speeds occurs within defined limits of the design. The way real aircraft performance works shows us it is possible to have an aircraft with a poorer sustained turn for example out turn a much better sustained turning aircraft that is being flown at an improper speed for best performance. This range becomes even wider if we move into instantaneous performance. Remember, all aircraft at the same velocity and angle of bank will make exactly the same turn. This is one reason why the ability to change the orientation of the vector of lift is so important.

Heavier balanced designs have higher V-speeds. Since they are traveling faster, their turning ability will not be as good as a slower aircraft but their zoom ability will be much better. It takes an impractically large weight or thrust advantage to overcome even a surprisingly small speed advantage. Because Prmax occurs at a higher velocity, it is quite common in aircraft performance to find aircraft which can sustain a higher load factor at a higher velocity but cannot sustain a slower velocity turn against an opponent. Rate is what is important in combat, not radius. That is not to say these fighters are necessarily angle fighters but it to say that they can force the slower V speed design onto the defensive if it tried to match the higher V speeds.

This is why Design firms like Republic did not scrap their aircraft based the single characteristics of weight. These aircraft that exhibit a design balance make excellent versatile dogfighters in the real world. Generally speaking, higher wing loading in balanced design leads to faster V speeds, more stable gun platform, decreased vulnerability to gusting, and easier to manage crosswind landings. Generally speaking, a heavier balanced design can pull turns at higher speeds that would damage the airframe of a lighter opponent trying to match.

Folks need to look at these aircraft as a system and not one characteristic.

All the best,

Crumpp

M_Gunz
04-16-2009, 10:20 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
This is very important to understanding how real dogfights are played out. If the pilot does not fly the plane by these speeds then he will not get expected performance. In the real world, the range of best performance speeds occurs within defined limits of the design. The way real aircraft performance works shows us it is possible to have an aircraft with a poorer sustained turn for example out turn a much better sustained turning aircraft that is being flown at an improper speed for best performance. This range becomes even wider if we move into instantaneous performance. Remember, all aircraft at the same velocity and angle of bank will make exactly the same turn. This is one reason why the ability to change the orientation of the vector of lift is so important.

Heavier balanced designs have higher V-speeds. Since they are traveling faster, their turning ability will not be as good as a slower aircraft but their zoom ability will be much better. It takes an impractically large weight or thrust advantage to overcome even a surprisingly small speed advantage. Because Prmax occurs at a higher velocity, it is quite common in aircraft performance to find aircraft which can sustain a higher load factor at a higher velocity but cannot sustain a slower velocity turn against an opponent. Rate is what is important in combat, not radius. That is not to say these fighters are necessarily angle fighters but it to say that they can force the slower V speed design onto the defensive if it tried to match the higher V speeds. </div></BLOCKQUOTE>

These are *exactly* the things that many veteran sim pilots have used in online combat since long before IL2 came out.
There are and have been sites and articles on sites about using the differences and suckering or even pushing an enemy
out of his envelope and into yours by means of tactics. In fact most tactics I've learned are based on these things
and I did learn the better ones from others.

I hope that habitual flap-users take notice of the second paragraph up there. Once you slow down you have lost the vertical
fight until you can again have the higher energy. But since unless the enemy screws up badly your main option is to turn
turn turn (with flaps, LOL) there isn't much chance unless the enemy screws up, probably from not understanding the situation.

I had read from one of the test pilots of the AFDU tests with the Farber 190 that during the climb compares the pilot who
had flown the FW kept the speed high and was thus able to outclimb the Spit. They both ran the same speed yes, but that
speed favored the FW and it was the speed the German FW pilots were using cross-channel. It's not spelled out like that
in the report which has lead to a lot of people quoting the report and saying it applies at all speeds. It was one of
The Joke's favorites in fact. The less details tied to any quote, the more it seems to get used to mean "always".

julian265
04-17-2009, 12:58 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Because of the Tempest V's speed and clean lines however, </div></BLOCKQUOTE>

If the AFDU used the FW190A and Tempest V speeds, there is no way they could have the same entry speed. These aircraft are different designs and do not have the same Pr curves! </div></BLOCKQUOTE>

Tempest MkV, not tempest "V speeds"!

The original statement was probably referring to the Tempest's ability to reach a higher level speed, and thus zoom higher.

I'd like to see the original test description / data if it's available on the web.

Kettenhunde
04-17-2009, 01:10 AM
Good eye, Julian!

Our report's quote would then read:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Because of the Aircrafts speed and clean lines </div></BLOCKQUOTE>

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> the Tempest has a markedly better zoom climb, where the speed is kept high. </div></BLOCKQUOTE>

Demonstrating the physics:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Everything else equal, the lighter plane zooms higher. Different start speeds, the faster one zooms higher. </div></BLOCKQUOTE>

It also does not change the fact aircraft are flown in the real world by their design performance speeds or V speeds. When comparing performance you must examine the aircraft as a system.

All the best,

Crumpp

Kettenhunde
04-17-2009, 01:16 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> The original statement was probably referring to the Tempest's ability to reach a higher level speed, and thus zoom higher.
</div></BLOCKQUOTE>

You edited your post but can see from my reply, I am in complete agreement with you.

I have the original report buried in my office. It came from the UK National Archives on the most inconvenient size of paper I have ever seen in my life. It is almost poster size with an ~ larger than 8x11 copy in the middle of it. Unfortunately I am overseas at the moment. Mike Williams tends to display the entire report so I don't have any reason to believe he did not this time.

All the best,

Crumpp

Buzzsaw-
04-17-2009, 01:57 AM
Salute

Kettenhund/Crumpp continues to insist that the actual test pilots conducted their aircraft comparisons in a way which buttresses his assertions.

Ie. one aircraft was travelling faster than the other prior to the zoom.

Below is a link to a typical USAAF test, this one between a P-47N and a P-47D.

The test is a comparison of the respective aircraft's zoom climbs, from a starting alt of 1500 ft to a terminal point of 8,000 ft.

Note the P-47N weighs in at 15,300 lbs, the P-47D at 13,300 lbs.

Both aircraft start side by side at a speed of 220 mph.

The results:

"...the P-47N began pulling away from the P-47D immediately and maintained its superiority to 8,000 ft."

Complete report: (courtesy WWII Aircraft Performance)

http://www.wwiiaircraftperform.../p-47/p-47n-zoom.pdf (http://www.wwiiaircraftperformance.org/p-47/p-47n-zoom.pdf)

Kurfurst__
04-17-2009, 03:45 AM
That report quite clearly attributes the better zoom ability of the P-47N due to its higher power.

Between 1500 and 5000 feet they zoomed similiar, then the P-47N pulled away with its greater WEP output.

You don't seem to bother yourself with actual report, do you?

M_Gunz
04-17-2009, 08:45 AM
Even at the same start speed, the faster plane will have more Excess Thrust *at high speed*.
T/W Thrust in props is Excess Thrust, what it makes beyond the drag it has.
With props, Thrust decreases steadily with speed while Drag increases at high speed by squares.

So you have two planes and one is 20mph faster running top speed - 20mph of the slower,
the faster top speed plane will have a LOT more Excess Thrust than the slower top speed plane
(top speeds at the alts they are flying through). Even if it's heavier it probably will have
higher T/W until speed drops a good bit.

So sure they can start at the same speed and still the faster design will benefit more from
both starting at high speed. Simply the slower plane is flying farther beyond its best speed
than the faster one, and those are the V Speeds.

Kettenhunde
04-17-2009, 09:11 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Even at the same start speed, the faster plane will have more Excess Thrust *at high speed*.
</div></BLOCKQUOTE>

Exactly.

We can do a quick parametric study to see the effect of thrust.


Characteristics of Airplane 1:

Weight 9000lbs
Thrust in lbs = 1000lbs
Drag in lbs = 500

Characteristics of Airplane 2:

Weight 9000lbs
Thrust in lbs = 500lbs
Drag in lbs = 500

Zoom climb from 300mph to Vy at a 45 degree angle:

Airplane 1:

300mph = 441fps
Zoom Angle 45 degrees
Vy = 150mph = 220.5fps

Zoom height:

Sum the forces on the flight path -

9000lbs * sin 45 = 6364lbs
1000lbs – 500lbs – 6364lbs = 5864lbs

a = F/m

m = 9000lbs/32.2 = 279.5 lb-s^2/ft
a= 5864lb/279.5lb-s^2/ft
a = 20.98 ft/s^2

s = (V1^2 – V2^2 ) / 2a

s = (441^2 – 220.5^2)/(2 * 20.98ft/s^2) = 3476.18 ft

3476.18 ft * sin 45 = 2458 ft


Airplane 2:

300mph = 441fps
Zoom Angle 45 degrees
Vy = 150mph = 220.5fps

Zoom height:

Sum the forces on the flight path -

9000lbs * sin 45 = 6364lbs
500lbs – 500lbs – 6364lbs = 6364lbs

a = F/m

m = 9000lbs/32.2 = 279.5 lb-s^2/ft
a= 6364lb/279.5lb-s^2/ft
a = 22.77 ft/s^2

s = (V1^2 – V2^2 ) / 2a

s = (441^2 – 220.5^2)/(2 * 22.77ft/s^2) = 3202.9 ft

3202.9 ft * sin 45 = 2265 ft

2458 ft - 2265 ft = 193ft


Remember in hypothetical Airplane 2 thrust = drag while Airplane 1 had an average excess thrust of 500lbs.

That is the effect of thrust on our aircraft zoom ability.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> That report quite clearly attributes the better zoom ability of the P-47N due to its higher power.
</div></BLOCKQUOTE>

Exactly.

For some reason we keep having difficulty with a few thread participants in coming to grips with the condition "all things being equal".

That report is another great example of how airplanes need to be examined as system. Good design can easily overcome the effect of a single characteristic.

All the best,

Crumpp

M_Gunz
04-17-2009, 12:30 PM
To my way of thinking it should be a matter of overlaying Ps curves except those are alt-specific.
Okay, so nothing is simple.

JtD
04-17-2009, 01:54 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Brain32:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> But as a matter of fact in WW2 it did happen that folks would dive to speeds beyond their top level speed, they would also do so without flying at WEP and they would pull into zoom climbs. Under these conditions, the heavier aircraft is the better zoom climber and may eventually come out on top depending on when the zoom climb is finished. </div></BLOCKQUOTE>

Sorry but as impartial observer I really don't see how the above example proves Kett was wrong even 0.0005%

He said:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> All things being <span class="ev_code_RED">equal</span>, the lighter aircraft will out zoom the heavier one. </div></BLOCKQUOTE>
I believe speed is included in "all things"...

Now I think I know what you are getting at, heavier planes usually have better dive acceleration and can therefore attain higher speed in the dive and then zoom higher. This however assumes condition that is outside of Kett's statement above... </div></BLOCKQUOTE>

No, what I said is that, all other things being equal, the heavier plane zooms higher as long as drag is larger than thrust.
I also said that these conditions can be found after a dive, where planes are going faster than their level top speed.

I can read white against grey in standard just as well as red against grey in bold. I also know the meaning of "equal" and as a matter of fact the meaning of "all things" as well.
And I am not talking about dive performance.

Feel free to reproduce Kettenhundes equasions with drag = 1000 and thrust = 500. Kettenhunde says these conditions do not exist, but they do. For instance, after a dive.

M_Gunz
04-17-2009, 02:48 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JtD:
Feel free to reproduce Kettenhundes equasions with drag = 1000 and thrust = 500. Kettenhunde says these conditions do not exist, but they do. For instance, after a dive. </div></BLOCKQUOTE>

I dunno about the numbers but I do agree that in certain narrow conditions where the zoom ends at still high speeds,
perhaps somewhat less than top level speed but not much, that the numbers support what JtD is saying.

It won't work if the zoom is carried much farther and certainly not to full height or even sustained climb speed though.
Problem being that Drag &gt; Thrust slows the plane much more than in zoom where Thrust &gt; Drag, the average moves accordingly.

Perhaps that or some other condition is in one person's evaluation and not in another's. Both could be right about what
they say and still differ since they would be talking about different things. Always look to your assumptions.

It'd be real hip to have enough data to do a stepwise approximation on the PC but oh my it's hard to fly acceptable tests!
I had asked someone before about clocking top speeds at different power settings but the reply was that we don't know what
50% really means, 0% is idle and really like 10%-15% according to Oleg back in 2002.

Kettenhunde
04-17-2009, 09:32 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Problem being that Drag &gt; Thrust slows the plane much more than in zoom where Thrust &gt; Drag, the average moves accordingly.
</div></BLOCKQUOTE>

Exactly. JtD assertion is non applicable to powered aircraft.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Crumpp says to JtD:

I think if you had practical experience in using the rectilinear equations to determine performance for an aircraft you would know this fact. In using the formula, we take the average forces on the vector and sum them. While in a high speed dive for a power producer, the condition of drag exceeding thrust does exist for a short time on the vector, the average will always have thrust exceeding drag, though.

We could close the throttle and treat our aircraft as a glider, but what would be the point? We would just determine the performance of a very poor glider design!

Your assertion has no application to powered aircraft. It only serves to add confusion and mislead others.
</div></BLOCKQUOTE>

All the best,

Crumpp

Wurkeri
04-17-2009, 10:42 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
It'd be real hip to have enough data to do a stepwise approximation on the PC but oh my it's hard to fly acceptable tests!
I had asked someone before about clocking top speeds at different power settings but the reply was that we don't know what
50% really means, 0% is idle and really like 10%-15% according to Oleg back in 2002. </div></BLOCKQUOTE>

This sounds like something we discused in PM sometime ago.

The error free testing is pretty much impossible without internal knowledge about the game physics; Il-2compare is based on such knowledge from 1C and in the other side (modded world) such knowledge is available as well. However, if you want go with regular game, you should accept that there is allways some error despite what ever test method is used.

So it's up to you: You can join the bandwagon of the Ks and talk the talk, endlessly, without actually walking the walk. Or you can actually do something: Make a test and report the results, walk the walk in other words.

You see; if you have used just 5% of the energy, you have used to argue with tagert and others, to actually test something, you might had reached something relevant allready. As an example you could have tested the ROC of the 109s to check the shape of the power curves (it takes just few runs with the autopilot). And this does not mean that I like the way tagert appears in this forum, infact I don't like it at all. However, unlike most others, he has actually done some testing ie walked the walk.

Kettenhunde
04-18-2009, 12:19 AM
I will point out that on multiple occasions offers of help have been extended to anyone who would like the help. To characterize someone who points out a flawed methodology as "unwilling to help"" is childish rhetoric.

If they did not want to help out, they simply would keep their mouth shut and allowed the error or flaw to propagate nor would they offer solutions to fix the flaw.

It is the individual’s reaction to that help and subsequent behavior that is responsible for their isolation. It is a bed of their own making.


All the best,

Crumpp

M_Gunz
04-18-2009, 01:50 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Wurkeri:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
It'd be real hip to have enough data to do a stepwise approximation on the PC but oh my it's hard to fly acceptable tests!
I had asked someone before about clocking top speeds at different power settings but the reply was that we don't know what
50% really means, 0% is idle and really like 10%-15% according to Oleg back in 2002. </div></BLOCKQUOTE>

This sounds like something we discused in PM sometime ago.

The error free testing is pretty much impossible without internal knowledge about the game physics; Il-2compare is based on such knowledge from 1C and in the other side (modded world) such knowledge is available as well. However, if you want go with regular game, you should accept that there is allways some error despite what ever test method is used.

So it's up to you: You can join the bandwagon of the Ks and talk the talk, endlessly, without actually walking the walk. Or you can actually do something: Make a test and report the results, walk the walk in other words.

You see; if you have used just 5% of the energy, you have used to argue with tagert and others, to actually test something, you might had reached something relevant allready. As an example you could have tested the ROC of the 109s to check the shape of the power curves (it takes just few runs with the autopilot). And this does not mean that I like the way tagert appears in this forum, infact I don't like it at all. However, unlike most others, he has actually done some testing ie walked the walk. </div></BLOCKQUOTE>

The fact is that I HAVE run tests and had them objected to on real grounds.
I had been running devicelink on OTHER people's tests and pointed out where they were at fault.
And I was doing that BEFORE, DURING and AFTER all the HYPE, SMOKE and BS from Tagert.

One difference between him and myself is that when I see it's being done WRONG, **I** STOP.
Tagert just bulls along ignoring the errors and pushing his view with spam and attacks until he's banned, repeatedly.

AFAICT the 109K user test that shows no sawtooth may be due to a run that should have been thrown out.
All it would take is starting with excess speed.

While trying to get Ps for P-40B I did a low speed dive and climb where at bottom the plane was going a whole 190kph
at about 500ft just to bring it up at higher angle and lower speed than possible starting out level. I wanted to
find the lowest full power level power-on speed. What I found was that at 140kph and very nose high, 100% power,
the P-40B would climb (not the best) with stick full back and held there. I quit at about 15,000 ft. What to make
of that? I did get a lot of rudder practice but otherwise it was uninteresting.

After a few years I came to the conclusion that I am in the majority of humans not up to being test pilots.
I've also seen that AI pilots are really not there except that in certain static situations they can hold the planes
steady and that does NOT include near stall flying as they use aileron to stay level, something I sent emails about
to the AI program maker now it is years ago.

I don't waste time on bad work. I don't buy BS excusing bad work either. Not for myself or anyone else.
You have a better way?

M_Gunz
04-18-2009, 02:33 AM
BTW W, what do you think of a comparison between two planes that has one fly 70 seconds and the other fly 110 seconds,
both at full power the whole time and NO accounting for energy input differences?

Come on. You are more qualified than I. Why do you stand for it? It is the same as cheating at lab.

M_Gunz
04-18-2009, 04:30 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Problem being that Drag &gt; Thrust slows the plane much more than in zoom where Thrust &gt; Drag, the average moves accordingly.
</div></BLOCKQUOTE>

Exactly. JtD assertion is non applicable to powered aircraft. </div></BLOCKQUOTE>

Doesn't that depend on how long the zoom is kept up?

I mean sure if you're going for total zoom height then for sure the average will be at lower speeds.
But there must be a range where the average is drag &gt; thrust given that there are starts where that is true.
Nothing says you have to zoom past some speed let alone stall.

I look at two cases;

1) zoom starts at 1000 ft or less.
-- top level speed at alt is pretty low compared to FTH.
-- all the way up, top level speed increases so the average goes to thrust &gt; drag quicker.

2) zoom starts way above FTH.
-- top speed at alt is again low compared to FTH.
-- all the way up, top level speed decreases so the average goes to thrust &gt; drag slower.

Kettenhunde
04-18-2009, 06:41 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Doesn't that depend on how long the zoom is kept up?
</div></BLOCKQUOTE>

Sure.

You can use the formula to determine any range of zoom velocities.

I did a quick SWAG on the actual numbers for the Bf-109G2. This uses a spreadsheet and the scope of the calculations is beyond a single post in this thread.

If you dive the Bf-109G2 at 6770lbs to Vne of 750kph, you can zoom to 496kph before you will begin to lose out to a lighter aircraft all things being equal.

That is as best as we can get for this airplane. There is nothing beyond Vne and we have already seen the importance of speed. The portion of the envelope drag is greater than thrust only gets dramatically smaller and the effects dramatically less as we get closer to top level speed.

Now a gamer might look at that and conclude this is useful. As a pilot, I don’t see it as being very useful at all. Your speed range is only ~250kph with some very scary stuff going on in this range. Diving to Vne is no joke. If you safely reach it, you are going to have to recover from the dive. That is going to take an awful lot of altitude to just come out of such a dive safely provided you can even do it. The airframe can go that fast but that does not mean you have the room to recover it. A dive like this generally requires ~10,000 feet to safely recover.

All the best,

Crumpp

M_Gunz
04-18-2009, 07:28 AM
In game it's not so hard though for 109's you need to use trim. http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

I don't think there's much tactical use to just that region of zoom, the differences wouldn't be large and the follower
would be peeling off at the same alt, not left any lower and speeds exiting the zoom wouldn't be all that different.
It's just nice knowing that if you're riding a lead sled that in dive and zoom that perhaps pushing for the highest
speed you might squeeze a couple extra cents out of it and to get out of the zoom by high cruise to not lose that extra
and then much much more.

Case 2 above... take a 109E-4 up to 10,000m, dive to 7,000m and zoom up (high-low attacks on bombers at 8,000m perhaps)
you will have longer periods of drag &gt; thrust yet still not most of the maneuver.

JtD
04-18-2009, 07:57 AM
One does not fly full power (WEP) all the time. If you assume maneuvers at max continous power, or Kampfleistung, military or what they are called, it will shift the limit somewhat.

One scenario I can imagine is if you dive down onto a bomber and zoom up for another attack. You'd have to maintain a fairly high speed, you wouldn't need to fly at WEP power and you'd start from a speed way above top level speed. In this scenario it also hardly matters.

I think Kettenhundes last post is quite a good conclusion to this disscussion.

Kettenhunde
04-18-2009, 08:05 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> In game it's not so hard </div></BLOCKQUOTE>

That is not very realistic for any plane to routinely dive to Vne.

It is very hard on the airframe. The limits assume a pristine condition airframe and no asymetrical loading.

http://www.ntsb.gov/ntsb/brief...20001214X43489&key=1 (http://www.ntsb.gov/ntsb/brief.asp?ev_id=20001214X43489&key=1)

If it is a gusty day, you do not have to be at Vne to exceed it.

http://www.ntsb.gov/ntsb/brief.asp?ev_id=14695&key=0

All the best,

Crumpp

Kettenhunde
04-18-2009, 08:13 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">One does not fly full power (WEP) all the time. </div></BLOCKQUOTE>

The calculation is at max continuous not WEP. You can see it is a very small portion of the envelope even if we push the airframe to maximum velocity. In your game, that is probably not a big deal and might be useful to you.

It is just not useful for powered aircraft and we certainly cannot say it is a trend.

If we are talking about comparing glider performance though it would change the general conclusions.

I am glad we all agree that Shaw is correct and you understand the physics a little better.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Everything else equal, the lighter plane zooms higher. Different start speeds, the faster one zooms higher.
</div></BLOCKQUOTE>

All the best,

Crumpp

Kettenhunde
04-18-2009, 08:26 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Design V-Speeds </div></BLOCKQUOTE>

That is the real reason as well as being the combat useful characteristic of heavier aircraft. It is why they have better zoom climbs compared to lighter ones.

The V-speeds tend to be higher on heavier designs.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Once again, real airplanes are flown by their V speeds. I think the importance of this fact is lost on non-pilots as you don’t have to pay much attention to your speeds in these games.

This is very important to understanding how real dogfights are played out. If the pilot does not fly the plane by these speeds then he will not get expected performance. In the real world, the range of best performance speeds occurs within defined limits of the design. The way real aircraft performance works shows us it is possible to have an aircraft with a poorer sustained turn for example out turn a much better sustained turning aircraft that is being flown at an improper speed for best performance. This range becomes even wider if we move into instantaneous performance. Remember, all aircraft at the same velocity and angle of bank will make exactly the same turn. This is one reason why the ability to change the orientation of the vector of lift is so important.

Heavier balanced designs have higher V-speeds. Since they are traveling faster, their turning ability will not be as good as a slower aircraft but their zoom ability will be much better. It takes an impractically large weight or thrust advantage to overcome even a surprisingly small speed advantage. Because Prmax occurs at a higher velocity, it is quite common in aircraft performance to find aircraft which can sustain a higher load factor at a higher velocity but cannot sustain a slower velocity turn against an opponent. Rate is what is important in combat, not radius. That is not to say these fighters are necessarily angle fighters but it to say that they can force the slower V speed design onto the defensive if it tried to match the higher V speeds.

This is why Design firms like Republic did not scrap their aircraft based the single characteristics of weight. These aircraft that exhibit a design balance make excellent versatile dogfighters in the real world. Generally speaking, higher wing loading in balanced design leads to faster V speeds, more stable gun platform, decreased vulnerability to gusting, and easier to manage crosswind landings. Generally speaking, a heavier balanced design can pull turns at higher speeds that would damage the airframe of a lighter opponent trying to match.

Folks need to look at these aircraft as a system and not one characteristic.
</div></BLOCKQUOTE>

All the best,

Crumpp

JtD
04-18-2009, 09:56 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
The calculation is at max continuous not WEP. You can see it is a very small portion of the envelope even if we push the airframe to maximum velocity. </div></BLOCKQUOTE>

Thanks for the clarification.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> In your game, that is probably not a big deal and might be useful to you. </div></BLOCKQUOTE>

No, it's not a big deal. But it still isn't useful. It's not a good idea to try climb away from a better climber at co-speed.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">It is just not useful for powered aircraft and we certainly cannot say it is a trend.
...
I am glad we all agree that Shaw is correct and you understand the physics a little better. </div></BLOCKQUOTE>

I haven't learned a thing about physics in this topic. If anything, I have taught. My entire point was physics, not flying or usefulness. Had it been for the latter, I wouldn't have bothered with commenting your initial statement.

Kettenhunde
04-18-2009, 10:30 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> My entire point was physics, not flying or usefulness. </div></BLOCKQUOTE>

Exactly, as I said from the begining.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Crumpp says:

Your motivation for posting is because you spouted erroneous concepts in the past which I corrected you on. </div></BLOCKQUOTE>

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> of drawing nonsense lines on an engine charts as JtD demonstrates.
</div></BLOCKQUOTE>

http://forums.ubi.com/eve/foru...861000817#8861000817 (http://forums.ubi.com/eve/forums/a/tpc/f/23110283/m/8141036117?r=8861000817#8861000817)

As you say:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> But it still isn't useful. </div></BLOCKQUOTE>

If we are determining the performance of a glider, it is useful.

Why do you think gliders carry water ballast?

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Crumpp says:

We would just determine the performance of a very poor glider design!

Your assertion has no application to powered aircraft. It only serves to add confusion and mislead others.
</div></BLOCKQUOTE>

The correct conclusion you can draw about the effect of weight on zoom climb performance is found in Shaw's book and proved by the math in this thread.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Everything else equal, the lighter plane zooms higher. Different start speeds, the faster one zooms higher. </div></BLOCKQUOTE>


All the best,

Crumpp

JtD
04-18-2009, 11:53 AM
Dear moderators, can you please ban Kettenhunde from this forum? He keeps on dealing out personal attacks, which imho is clearly violating the forum rules. I have been turning the other cheek quite a few times now, but if he isn't gone some time soon I won't do it anymore. I'm sick of having statements labelled nonesense or stupid just because Kettenhunde fails to understand them.

Please notify me of your decision, so I can word my next reply accordingly. If I get no info, I'll assume his behaviour is ok and I will get insulting, too.

Xiolablu3
04-18-2009, 11:59 AM
Ahh come on you two, you are obviously both knowledgable about this stuff, it would help if you could get on, and debate without getting personal?

I have absolutely NO idea who is correct, and to be honest, IMO its not worth falling out over.

If this thread does just turn into insults we will have to lock it...

Wurkeri
04-18-2009, 02:24 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
The fact is that I HAVE run tests and had them objected to on real grounds.
I had been running devicelink on OTHER people's tests and pointed out where they were at fault.
...
AFAICT the 109K user test that shows no sawtooth may be due to a run that should have been thrown out.
All it would take is starting with excess speed. </div></BLOCKQUOTE>

Ok, why don't you just try it then? It's not just tagert's testing but also Il-2 compare and my own testing which indicates simplified power curve.

I made couple test runs on the K-4-C3, G-2, G-6 late and the G-6/AS. I used following script:

W_RelTime&gt;2
A_Bank=0
R_Slip=0
E_Alt=50
T_Spd=266
W_RelTime&gt;60
E_Spd=266
T_Spd=2000
C_WEP
W_Alt&gt;99999

Nothing special in this; first one minute at 50m at 266km/h IAS (value is from Il-2 compare), then elevator keeps the speed at 266km/h IAS and full throttle + WEP if available. Crimea map and easy settings. The autopilot.ini appeared to work good enough with the dive test settings (see my dive test thread), there were some oscillations but the plane settled to quite steady climb at around 800m. I ended test at 7500m and testing these took about 50 minutes including an extra test on the G-2 with T_Off (manual throttle) to check if the test was repeatable that way. Most of time I was actually watching TV, making sandwiches and playing with kitten, so real work time was something like less than 15 minutes ie less than writing this reply will take. If I have tweaked the autopilo.ini it would have taken much, much more time but the results seem to be steady enough.

So, please, check it out and report the results and if you find something to improve, it will be great. Thanks in advance. I can open a new thread for the results if needed because this is not the topic of this thread.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
While trying to get Ps for P-40B I did a low speed dive and climb where at bottom the plane was going a whole 190kph
at about 500ft just to bring it up at higher angle and lower speed than possible starting out level. I wanted to
find the lowest full power level power-on speed. What I found was that at 140kph and very nose high, 100% power,
the P-40B would climb (not the best) with stick full back and held there. I quit at about 15,000 ft. What to make
of that? I did get a lot of rudder practice but otherwise it was uninteresting. </div></BLOCKQUOTE>

I was under impression that you tried to make level flight acceleration tests so IMHO there is no need to go to such extreme situations; you can see the trend from faster speed and extrapolate extreme cases. IIRC you complained then that there was too much wobbling during the acceleration part and I made some autopilot.ini tweaking for you and could minimise the wobbling to few meters. I was pretty satisfied with the results despite I saw the climbs as a better method for Ps testing (IIRC Viper also suggested so). Sadly, you did not proceed back then.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
I don't waste time on bad work. I don't buy BS excusing bad work either. Not for myself or anyone else.
You have a better way? </div></BLOCKQUOTE>

Yes, if you are unhappy with your method or test, you can actually still post it public and explain the problems you are facing. Someone might appear with the solution sooner or later. Overall I have found people who really do in game testing, not just talk, very helpfull outside this forum.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
BTW W, what do you think of a comparison between two planes that has one fly 70 seconds and the other fly 110 seconds, both at full power the whole time and NO accounting for energy input differences? </div></BLOCKQUOTE>

I'm not sure what you are refering here, I quess this is connected to tagert's energy calculations?

First I must note that the conflict between you and tagert has grown to such measures that my opinion does not matter despite what ever I will answer. Infact it does not matter at all who is right or wrong, you both will continue that for ever. Shame on you both.

Anyway, if the time difference bothers you, you can limit the analysis to the first 70 seconds. After all the TE is allways calculated for a specific moment, it does not matter what was situation 70 seconds or 100 years ago or how much input energy has been used.

M_Gunz
04-18-2009, 03:26 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Wurkeri:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
The fact is that I HAVE run tests and had them objected to on real grounds.
I had been running devicelink on OTHER people's tests and pointed out where they were at fault.
...
AFAICT the 109K user test that shows no sawtooth may be due to a run that should have been thrown out.
All it would take is starting with excess speed. </div></BLOCKQUOTE>

Ok, why don't you just try it then? It's not just tagert's testing but also Il-2 compare and my own testing which indicates simplified power curve.

I made couple test runs on the K-4-C3, G-2, G-6 late and the G-6/AS. I used following script:

W_RelTime&gt;2
A_Bank=0
R_Slip=0
E_Alt=50
T_Spd=266
W_RelTime&gt;60
E_Spd=266
T_Spd=2000
C_WEP
W_Alt&gt;99999

Nothing special in this; first one minute at 50m at 266km/h IAS (value is from Il-2 compare), then elevator keeps the speed at 266km/h IAS and full throttle + WEP if available. Crimea map and easy settings. The autopilot.ini appeared to work good enough with the dive test settings (see my dive test thread), there were some oscillations but the plane settled to quite steady climb at around 800m. I ended test at 7500m and testing these took about 50 minutes including an extra test on the G-2 with T_Off (manual throttle) to check if the test was repeatable that way. Most of time I was actually watching TV, making sandwiches and playing with kitten, so real work time was something like less than 15 minutes ie less than writing this reply will take. If I have tweaked the autopilo.ini it would have taken much, much more time but the results seem to be steady enough.

So, please, check it out and report the results and if you find something to improve, it will be great. Thanks in advance. I can open a new thread for the results if needed because this is not the topic of this thread. </div></BLOCKQUOTE>

AFAIK means As Far As I Know

Thank you for clarification.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"><BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
While trying to get Ps for P-40B I did a low speed dive and climb where at bottom the plane was going a whole 190kph
at about 500ft just to bring it up at higher angle and lower speed than possible starting out level. I wanted to
find the lowest full power level power-on speed. What I found was that at 140kph and very nose high, 100% power,
the P-40B would climb (not the best) with stick full back and held there. I quit at about 15,000 ft. What to make
of that? I did get a lot of rudder practice but otherwise it was uninteresting. </div></BLOCKQUOTE>

I was under impression that you tried to make level flight acceleration tests so IMHO there is no need to go to such extreme situations; you can see the trend from faster speed and extrapolate extreme cases. IIRC you complained then that there was too much wobbling during the acceleration part and I made some autopilot.ini tweaking for you and could minimise the wobbling to few meters. I was pretty satisfied with the results despite I saw the climbs as a better method for Ps testing (IIRC Viper also suggested so). Sadly, you did not proceed back then. </div></BLOCKQUOTE>

I did more than you saw. I did post about that one to a PM, I thought I invited you, I was asking then how right or wrong
it seemed.

I was at the testing and running down different alleys years before we started exchanging PM's, btw.
I ran devicelink on three different people's tracks and sent data to them that you probably don't know about.
I ran tests on dives and climbs and did post here about results and what I see as the significant parts, for example in
dives the final speeds are the biggie. This was after chucking out the useless parts and doing basic match-up of curves
and conditions.

BTW I lost those autopilot settings when the PC they were on died from lightning strike almost a year ago.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"><BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
I don't waste time on bad work. I don't buy BS excusing bad work either. Not for myself or anyone else.
You have a better way? </div></BLOCKQUOTE>

Yes, if you are unhappy with your method or test, you can actually still post it public and explain the problems you are facing.
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">

Been there, done it, whether you saw it or not.

[QUOTE]Someone might appear with the solution sooner or later. Overall I have found people who really do in game testing, not just talk, very helpfull outside this forum. </div></BLOCKQUOTE>

Yes, we see their results here so often, NOT. And some even say that others who have done quite a bit are just talk.....

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">[QUOTE]Originally posted by M_Gunz:
BTW W, what do you think of a comparison between two planes that has one fly 70 seconds and the other fly 110 seconds, both at full power the whole time and NO accounting for energy input differences? </div></BLOCKQUOTE>

I'm not sure what you are refering here, I quess this is connected to tagert's energy calculations? </div></BLOCKQUOTE>

You must be kidding?

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">First I must note that the conflict between you and tagert has grown to such measures that my opinion does not matter despite what ever I will answer. Infact it does not matter at all who is right or wrong, you both will continue that for ever. Shame on you both. </div></BLOCKQUOTE>

I asked very clearly nothing to do with personal politics.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Anyway, if the time difference bothers you, you can limit the analysis to the first 70 seconds. After all the TE is allways calculated for a specific moment, it does not matter what was situation 70 seconds or 100 years ago or how much input energy has been used. </div></BLOCKQUOTE>

I did. The result is much less than what has been claimed. AFAIC the claim is an agenda-pushing hoax.
And we have been notified by the self-expert that SOW will be treated likewise.
Yeah, tagert is going to keep Oleg honest! LMAO!
In the meantime Raaaid will be running the United Nations!

Kettenhunde
04-18-2009, 11:35 PM
Wurkeri,

IIRC, M_Gunz was given the instructions on how to use Total Energy Concepts to determine Aircraft Performance.

He did what I thought was rather extensive testing on the several planes in your game including the P40 series. I remember looking at some of the data and making suggestions to help which I hope he found useful.

There were some environmental/data issues with your game and I don't think he was satisfied with the ability to precisely hold a track for the test aircraft.

I suggested the acceleration testing because I thought it might be easier to program a script to fly a level straight line than trying to perform a climb. That level acceleration data can at least give you good agreement with the results a climb schedule can and IMHO will be probably more accurate as the variables are reduced, the fewer variables, the smaller the margin for error.

The acceleration testing eliminates such as altitude effects from your basic data. You only have to resolve one altitude.

It just makes things simpler.

I am not attacking your climbing methodology. Either method is acceptable.

M_Gunz,

As always, I am here to help if you need it.

All the best,

Crumpp

Kettenhunde
04-19-2009, 06:11 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">He keeps on dealing out personal attacks </div></BLOCKQUOTE>

Relating someone else’s actions is not a personal attack. It is just statement of fact as what is happening.

I draw no conclusions about you personally only discuss ideas and not people.

The action I discuss is being petty over what everyone readily admits is an insignificant detail that does not alter the general conclusions I originally related..

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I will get insulting, too. </div></BLOCKQUOTE>

Why don't you just bury the hatchet? You are a smart guy and seem to have quite a bit to contribute. I am interested in what you have to contribute.

You have a passion for these aircraft and I respect that. That is also why I got involved with the restoring and flying WWII aircraft. We have common ground. You think I can talk to me wife about this stuff? I would be single in no time.LOL!

It was never my intention to alienate you and I really do apologize that I come across as a know it all ***** sometimes. I will work on being more sensitive to that impression.

That really isn't me but unfortunately it is hard to tell from a BBS post.

I don't have anything personally against you at all. If we can't get beyond that then I think it is best that we just use that option on the internet to simply ignore.

If I thought that option would be more productive, I would have simply taken it without bothering to make an attempt to avoid it.

All the best,

Crumpp

Wurkeri
04-19-2009, 02:50 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
...Thank you for clarification.
</div></BLOCKQUOTE>

I was quite clear there allready: mentioned that the simplified power curve can be verified from Il-2compare and by simple testing as well.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
I did more than you saw. I did post about that one to a PM, I thought I invited you, I was asking then how right or wrong
it seemed.
...
BTW I lost those autopilot settings when the PC they were on died from lightning strike almost a year ago. </div></BLOCKQUOTE>

I recall some testing on the P-40B, at least I tweaked the autopilot for it and for one particular altitude. I saw it like a proof of the case; it could be done but required quite a lot of testing. I probably have the tweaks saved somewhere but I don't think that these are particularly valueable testing wise; same can be done easier with E_Angle command at steadier conditions (much less tweaking needed).

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
Yes, we see their results here so often, NOT. And some even say that others who have done quite a bit are just talk..... </div></BLOCKQUOTE>

Ok, check your pm.

Kettenhunde
04-19-2009, 10:23 PM
Enlighten me as to what is so hard about using level aceleration in your game? Is it a computer script issue?

It is very easy in RL to perform a level speed run at one altitude from stall to top level speed. It has the benefits of not having to worry about altitude effects as you remain at one altitude!

Convert speeds at ONE altitude and then we are ready to crunch numbers.

Doing 20 level aceleration runs every 1000 ft will take much less time than running sawtooth climbs.

Sawtooth climbs can be more accurate but are much difficult to fly. Additionally there is a specific methodology that must be followed, not any climb is a sawtooth. It is very, very, time consuming process to gather the data using sawtooths if done properly.

Specific Excess power from level aceleration is calculated as follows:

(Average TAS Velocity in fps / aceleration of gravity)*(Change in TAS velocity in fps / change in time)

If our airplane acelerates from 100KTAS to 300KTAS in 28 seconds, what is our Specific Excess power?

Average KTAS Velocity = 200KTAS * 1.69 = 338fps

Aceleration of Gravity = 32.2ft/s^2

Change in Velocity = 338 fps - (100KTS * 1.69) = 169fps

Change in time = 28 - 0 = 28 seconds

338fps / 32.2ft/s^2 * (169fps / 28s) = 63.4fps

Specific Excess Power = 63.4fps

The higher the Ps, the more energy the aircraft has and more rapid the aircraft can change position. You have an instant relative standing at that altitude.

Some excel work and you have the entire aircraft performance envelope.

How high can this plane zoom over a 10 second zoom climb?

Ps = dH/dT

63.4fps = dH/10

10*63.4 = 634 ft change in Eh

If you have excel skills, you can easily construct a chart to determine performance at any Ps.

No matter what method you use:

Plot the Eh over time curve from our Ps data and then use the slope to get your Ps lines at altitude. Add the Eh lines and you have the airplanes entire envelope.

All the best,

Crumpp

M_Gunz
04-20-2009, 07:40 AM
The biggest problem is the starts;
For the AI, anything at very low speed.
For me, trying to keep either alt or speed rock-constant.

Last time I had AI do it the nose was micro-bobbing to hold level flight.
The constant elevator movement... in IL2 slows the planes (maybe too much?), it is why better trimmers fly faster.
A human at the stick is bad enough, the AI **was** much faster and more bumpy. W did help with that.
I can fly smoother but I don't stay +/- less than 1m for long!

Kettenhunde
04-20-2009, 08:44 AM
Ok, it is a computer game mechanics issue, got it.

IIRC, we went over how to properly conduct sawtooths and some tips to make your data more accurate did you remember?

How hard is it to do a script to properly conduct sawtooth climbs and glides?

You can actually determine quite a bit more performance off a sawtooth if properly done.

All the best,

Crumpp

M_Gunz
04-20-2009, 11:07 AM
I have a totally different idea.

1) Fly smoothly by hand trying to get either change in speed only or change in alt only.
2) Get the data out via devicelink.
3) Find suitable stretches in said data to glean data points.
4) Build a mosaic of data points and try to keep filling it in.
5) Plot a best-fit curve which is how it's done IRL anyway.

A number of steady speed climbs at 100% power through all alts at the different speeds and
a number of level flights at 100% power at different alts and starting speeds with some
duplication or near-duplication and then pick best-fit curves. But not trying over and over
to get "a good flight" since that seems to be the hardest way.

I am pretty sure that if criteria for what are acceptable stretches are found and posted
with examples that quite a few members will surely want to run their favorite planes.
With so many planes, how else to cover more than a very few?

Also, what are the chances of using IL2Compare data?

tagert
04-20-2009, 07:12 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
I have a totally different idea.

1) Fly smoothly by hand trying to get either change in speed only or change in alt only.
2) Get the data out via devicelink.
3) Find suitable stretches in said data to glean data points.
4) Build a mosaic of data points and try to keep filling it in.
5) Plot a best-fit curve which is how it's done IRL anyway.

A number of steady speed climbs at 100% power through all alts at the different speeds </div></BLOCKQUOTE>

Totally different idea?

Maybe.. for you..

Totally new idea?

Hardly..

Been there done that years ago..

http://i582.photobucket.com/albums/ss267/GSENN/IASS.jpg

http://i582.photobucket.com/albums/ss267/GSENN/ROCS.jpg

http://i582.photobucket.com/albums/ss267/GSENN/TTCS.jpg

Those tests were part of my ROC testing of the P38J..

These test results and data was sent to Oleg and used by him to justify making a change to the in-game P38J ROC..

And by change I mean increase it! http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
and a number of level flights at 100% power at different alts and starting speeds with some duplication or near-duplication and then pick best-fit curves. But not trying over and over to get "a good flight" since that seems to be the hardest way. </div></BLOCKQUOTE>
Been there done and doing that for some of the new AAA stuff..

If you want to save time..

DON'T even try to fly it manually!

Use the 3rd party auto pilot utility written by LesniHUs..

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
With so many planes, how else to cover more than a very few? </div></BLOCKQUOTE>
Simple.. Learn how to write script files for LesniHUs auto pilot program and goggle PID tuning..

PID tuning basics is all you will need to tweak and tune LesniHUs PID based auto pilot program..

If you need help with that feel free to PM me and I can talk you through it!

In that a lot of what I do for a living (read job as a Engineer) has to due with tuning control systems.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
Also, what are the chances of using IL2Compare data? </div></BLOCKQUOTE>
Not recommended!

In that it was said way back when that the IL2Compare stuff is based on the in-game auto pilots (read AI) flying the planes..

Bad thing about that is the in-game AI uses slightly different FMs..

Where as LesniHUs auto pilot program flys the 'users' FM.

Thus if you learn to use LesniHUs program there will never be any doubt as to if the user can obtain the values you did.

tagert
04-20-2009, 07:27 PM
By the way..

Didn't read the whole thread..

Just scanned threw some of it..

And I get the impression your trying to obtain level speed and acceleration plots per altitude(s)?

If so let me know..

Been there done that too!

Havent done it for the Tempest..

But have done it for other planes..

So if that is what you need let me know..

I can put something togther pretty quick for you!

M_Gunz
04-20-2009, 09:11 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by tagert:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
I have a totally different idea.

1) Fly smoothly by hand trying to get either change in speed only or change in alt only.
2) Get the data out via devicelink.
3) Find suitable stretches in said data to glean data points.
4) Build a mosaic of data points and try to keep filling it in.
5) Plot a best-fit curve which is how it's done IRL anyway.

A number of steady speed climbs at 100% power through all alts at the different speeds </div></BLOCKQUOTE>

Totally different idea?

Maybe.. for you..

Totally new idea?

Hardly.. </div></BLOCKQUOTE>

Didn't you just whine about trolling?

TOTALLY DIFFERENT FROM WHAT WAS BEING DISCUSSED.

Funny, I don't remember YOU being part of that.

And NOW here YOU are trying to make what I wrote into SOMETHING ELSE AS USUAL.

Get yourself a life, TROLL!

BTW, what I discussed above was done YEARS AGO and is not subject to your Troll Revisions.

Kettenhunde
04-20-2009, 11:01 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I have a totally different idea.

1) Fly smoothly by hand trying to get either change in speed only or change in alt only.
2) Get the data out via devicelink.
3) Find suitable stretches in said data to glean data points.
4) Build a mosaic of data points and try to keep filling it in.
5) Plot a best-fit curve which is how it's done IRL anyway.

A number of steady speed climbs at 100% power through all alts at the different speeds </div></BLOCKQUOTE>


That will work just fine and so won't a autopilot script.

All the best,

Crumpp

Kettenhunde
04-20-2009, 11:05 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">A number of steady speed climbs at 100% power through all alts at the different speeds </div></BLOCKQUOTE>


Power off glides as well need to be done in conjunction with the climbs. It all has to be done within the correct methodology. I am not familiar enough with a script to know of one that will work on the sawtooths and they do require some degree of skill to fly properly.

First we need to nail the TAS speed and build the PEC curves as we discussed. That method will work very well in your game. I will also build a CEC correction table. Once we have that, it will easy to get the PEC curves for any aircraft.

All the best,

Crumpp

tagert
04-20-2009, 11:22 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
Didn't you just whine about trolling? </div></BLOCKQUOTE>
Yes in the 109K4 thread..

You were way out of line there!

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
TOTALLY DIFFERENT FROM WHAT WAS BEING DISCUSSED. </div></BLOCKQUOTE>
So what part of me asking..

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by tagert:
By the way..

Didn't read the whole thread..

Just scanned threw some of it..

And I get the impression your trying to obtain level speed and acceleration plots per altitude(s)? </div></BLOCKQUOTE>

Did you not understand?

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
Funny, I don't remember YOU being part of that. </div></BLOCKQUOTE>
Funny, I don't remember YOU being the one that gets to decide who gets to post where..

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
And NOW here YOU are trying to make what I wrote into SOMETHING ELSE AS USUAL.

Get yourself a life, TROLL! </div></BLOCKQUOTE>
Yes..

Just NOW..

On this page was my first post to this thread..

As for the TROLL here..

Simply take a look at your TROLLING <span class="ev_code_yellow">PRIOR</span> to me even posting in this thread!!

Allow me to cut-n-paste and sum up your TROLLING thus far

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
<span class="ev_code_yellow">And I was doing that BEFORE, DURING and AFTER all the HYPE, SMOKE and BS from Tagert.

Tagert just bulls along ignoring the errors and pushing his view with spam and attacks

BTW W, what do you think of a comparison between two planes that has one fly 70 seconds and the other fly 110 seconds,
both at full power the whole time and NO accounting for energy input differences?

Come on. You are more qualified than I. Why do you stand for it? It is the same as cheating at lab.

I did. The result is much less than what has been claimed. AFAIC the claim is an agenda-pushing hoax.
And we have been notified by the self-expert that SOW will be treated likewise.
Yeah, tagert is going to keep Oleg honest! LMAO!
In the meantime Raaaid will be running the United Nations!</span> </div></BLOCKQUOTE>

Let me guess..

You think it is ok to break the forum rules and smear/troll people just as long as they have not posted in the thread yet?

I don't know what is funnier/sadder..

You thinking that..

Or

You trying to play the part of the victim afterwards

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
BTW, what I discussed above was done YEARS AGO and is not subject to your Troll Revisions. </div></BLOCKQUOTE>
Let me guess..

This test you did was in the same dream where you saw that 'rule' I broke?

Right?

Which is why we will never actually see this test you did..

In short..

You can talk the talk..

But have yet to walk the walk..

SAVVY?

na85
04-20-2009, 11:43 PM
Oh for christ's sake. Both of you just stop it.

If you want to discuss testing then I suggest

a) Starting a new thread

b) Do it constructively and leave demons from your pasts at the door.

M_Gunz
04-21-2009, 02:18 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">A number of steady speed climbs at 100% power through all alts at the different speeds </div></BLOCKQUOTE>


Power off glides as well need to be done in conjunction with the climbs. It all has to be done within the correct methodology. I am not familiar enough with a script to know of one that will work on the sawtooths and they do require some degree of skill to fly properly.

First we need to nail the TAS speed and build the PEC curves as we discussed. That method will work very well in your game. I will also build a CEC correction table. Once we have that, it will easy to get the PEC curves for any aircraft.

All the best,

Crumpp </div></BLOCKQUOTE>

TAS won't be hard. No-cockpit view has a TAS gage. Any doubts about that can be checked easily enough with a long flight
between two map landmarks. I did much the same before to check for sure if IAS is needing correction as IRL and no it does
not. IAS = CAS, the game engine does not model instrument error.

I can do scripting and am getting more advice on smoothing the AP. The AP is weak on changing flight and very slow flight.

As I outlined above, I believe that good usable segments can be picked out of flight data logs and no I haven't seen the
like of **I** actually stated posted on this board yet. Something PARTLY like what I said, yes, but what I said, uh-uh.

Hopefully the methodology can be proved by the data as how else to say which segments are good and which are not?
From what I learned before, what is desired is change in only PE or KE with of course power and all else set properly.
Given acceptable tolerances, such can be identified from data logs by code I am still capable of writing. The process
can be near-automated to save time finding what's acceptable ***if*** this method can work at all.

Kettenhunde
04-21-2009, 02:48 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">From what I learned before, what is desired is change in only PE or KE with of course power and all else set properly. </div></BLOCKQUOTE>

That is it.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> TAS won't be hard. No-cockpit view has a TAS gage. Any doubts about that can be checked easily enough with a long flight
between two map landmarks. I did much the same before to check for sure if IAS is needing correction as IRL and no it does not. IAS = CAS, the game engine does not model instrument error.
</div></BLOCKQUOTE>

That makes things much simpler.

All the best,

Crumpp

Xiolablu3
04-21-2009, 04:10 AM
PLEASE can you two (tagert adn Maxguns) cool it? You are causing other members distress...

Maybe open your own thread where you can b*tch at each other all you want, (till a mod gets bored and locks it, or you kill each other through repetition...)

tagert
04-22-2009, 10:00 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Wurkeri:
It's not just tagert's testing but also Il-2 compare and my own testing which indicates simplified power curve. </div></BLOCKQUOTE>
Maybe we are not on the same sheet of music here?

Tell me..

What 'data' in IL-2Compare, my testing, your testing, etc do you think indicates a simplified power curve?

That is to say..

1) What is your definition of a simplified power curve?
2) What data do you think supports your claim?

If I had to guess..

Your basing it on the ROC and/or Manifold data..

Right?

As for the Manifold data..

Oleg told me in an e-mail that the Manifold data has nothing to do with the actual plane performance.. It is just an output used to drive the gauges in the cockpit.. I found it hard to belive at the time but that is all I had to go by so I accepted it. Now that the code has been broken, I guess we could now find out for sure.. But I digress.

To be honest..

I don't see what you say your seeing..

Maybe after you expand/explain your portion better maybe I will agree with what you saying, but as it stands, I don't see it your way, in that I think the ROC data indicates an ability to have a rather complex engine model (aka power curve).

Or are you NOT referring the the simulation of the engine?

Are you talking about Ps curves?

If so..

I never bothered to post the Ps curves I have made.. In that there is no real world (read WWII) data to compare them too. As you know the whole 'energy' method of aircraft analysis came into use post WWII. Prior to that the way to test performance was two fold.. An rate of climb (ROC) test and an top speed per altitude (TSPA) test. Long story short, it is hard enough to find real world ROC and TSPA data.. Even harder to find 50s style performance testing of 40s planes! http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

JtD
04-30-2009, 02:25 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:

Relating someone else’s actions is not a personal attack. It is just statement of fact as what is happening.

I draw no conclusions about you personally only discuss ideas and not people. </div></BLOCKQUOTE>

Then maybe you refrain from using terms like "baloney", "nonsense"and the like when discussing my statements. To put it simple, I do understand very well and my statements are usually very well thought of and true. In particular when it comes to flight physics. In addition you may want to leave sentences out that start with "you are", "you do", "you aren't" or "you don't" - this is always personal and from my experience you will usually end this type of sentence with some type of attack on a persons qualification - which is offense.


<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">The action I discuss is being petty over what everyone readily admits is an insignificant detail that does not alter the general conclusions I originally related.. </div></BLOCKQUOTE>

If you post "Pi equals 3.1" on a math board, would you expect people to leave this without a comment because the error is irrelevant for most practical purposes?

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">...

It was never my intention to alienate you and I really do apologize that I come across as a know it all ***** sometimes. I will work on being more sensitive to that impression. </div></BLOCKQUOTE>

You came across as a "thinks and pretends to know it all and unwilling to reconsider" guy. Which is exactly what drives me up the wall with ease. You still think I've "spouted erroneous concepts in the past which" you corrected me on. Truth is you've made numerous wrong interpretations and still think they are right.

I accept your apology, would like to apologize too and hope we can get back to debating planes and flying.

Kettenhunde
04-30-2009, 02:52 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Posted Thu April 30 2009 01:25 </div></BLOCKQUOTE>

Why so long?

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">If you post "Pi equals 3.1" on a math board, would you expect people to leave this without a comment because the error is irrelevant for most practical purposes?
</div></BLOCKQUOTE>

Aircraft performance is not as exact as "Pi" by its nature. It is a bad analogy that has no bearing to the discussion.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> You still think I've "spouted erroneous concepts in the past which" you corrected me on. </div></BLOCKQUOTE>

Don't say things that are wrong and then defend them!

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Truth is you've made numerous wrong interpretations and still think they are right.
</div></BLOCKQUOTE>

While I certainly do make mistakes, none of them have been in discussions with you. Quite a number of "experts" on Ubizoo seem to think that aerodynamics is this precise thing like "Pi".

Like you in this thread, they think it is a demonstration of their knowledge to point out narrow exceptions to the general concepts.

Problem is in doing so they completely miss the concepts and cause others to draw the wrong conclusions.

How many times have we seen these wrong conclusions in twenty page threads?

Heavy airplanes can zoom higher......

It is valid to draw your own lines on engine graphs to determine supercharger power outside of design operating limits. &lt;JTD specifically&gt; http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

You did that because you saw dotted lines on an engine graph extending down. I simply did some math to try and help you out with the general concepts. I got insulted for my effort.

The excess power curve does extend both ways and is not useable for those whose L/Dmax occurs at higher speeds as a result.

That is just a few off the top of my head. There is reason why this is called “Ubizoo”.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I accept your apology, would like to apologize too and hope we can get back to debating planes and flying. </div></BLOCKQUOTE>

Yeah, Ok.

Then let's move on.

All the best,

Crumpp

JtD
04-30-2009, 04:12 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:

Why so long? </div></BLOCKQUOTE>

Because I have a life.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Aircraft performance is not as exact as "Pi" by its nature. It is a bad analogy that has no bearing to the discussion. </div></BLOCKQUOTE>

I disagree with the second sentence, but I see no point in discussing it. http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Like you in this thread, they think it is a demonstration of their knowledge to point out narrow exceptions to the general concepts. </div></BLOCKQUOTE>

I recommended you'd not use "you..." anymore. I'd like to add "they..." as well. I made my statement because I like precision. I figured some others might as well, because it could help them understand the mechanics behind it.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Problem is in doing so they completely miss the concepts and cause others to draw the wrong conclusions. </div></BLOCKQUOTE>

No, that's your approach. It seems to me that your knowledge is based on the repetition of concepts and facts you've read elsewhere and accepted as correct. My knowledge is based on understanding the physical background of things without as much factual knowledge as you have. For me it is far more important to be precise in concepts and also far easier to spot errors and simplifications than for you.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Heavy airplanes can zoom higher...... </div></BLOCKQUOTE>

Which is correct. It imho is not acceptable to omit this fact for simplification. Imho it is better to mention it and to put it into the right perspective. I understand and respect that you may have a different opinion, but mine is not wrong.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">It is valid to draw your own lines on engine graphs to determine supercharger power outside of design operating limits. &lt;JTD specifically&gt; http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

You did that because you saw dotted lines on an engine graph extending down. I simply did some math to try and help you out with the general concepts. I got insulted for my effort. </div></BLOCKQUOTE>

What did I say about "you do ..." sentences?

I did that because this it is a proper way to illustrate my point. It's not my fault that you kept arguing about parameters of a particular supercharger while missing the point I made. I've used the analogy in a pm already, but I'd like to repeat it: I'm saying that with a lever twice as long you can apply twice the force and you keep arguing that the lever isn't actually strong enough to support twice the force (without any evidence for that).
If you wish to continue discussing the point I made, you'll just need to show me a power chart of a single stage, single speed supercharger which is can not be approximated with a straight line from full throttle height down to sea level. I'd also like to see a chart of a single stage two speed supercharger where the first stage generally consumes more fuel for the same power at the same altitude than the second stage.

Kettenhunde
04-30-2009, 04:42 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> If you wish to continue discussing the point I made, you'll just need to show me a power chart of a single stage, single speed supercharger which is can not be approximated with a straight line from full throttle height down to sea level. I'd also like to see a chart of a single stage two speed supercharger where the first stage generally consumes more fuel for the same power at the same altitude than the second stage. </div></BLOCKQUOTE>

LOL,

We are not talking a single speed supercharger that is purposely designed for an application.

I already explained that, showed you how to read the charts, and did the math proving it.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Basic Aerodynamic data:

WT = 21430lbs

Wing Area = 454sqft

Span 54.16ft

b^2/S = 6.46


Power known points:

+25lbs = 1950hp

1950 x.8 x 2 = 3120THP


Speed known points:

+23.9lbs 354mph TAS x .869 = 307KTAS

q= V^2/295

q = 319.5

+25lbs 340mph TAS x .869 = 295KTAS

- This is our most important known as it is a known velocity and power point in the 2nd Gear. From here we can extrapolate performance to anywhere in the aircrafts envelope and use that to compare with our forces required at this point.

q= 295

For giggles, here is the stall speed of the aircraft used in the test.

Stall

@18,000lbs Vs1 = 91ktas

q = 28.2

CL = (18000lbs / 454 sq ft)/28.2 = 1.4

Vs2 = SQRT (295 x 21430lbs)/(1.4 x 454sqft) = 99.7ktas or 114.6mph TAS



To refine the SWAG, we will solve this is by using the difference from a known point. We know the Shaft power out at +25 lbs. We can ballpark our losses by seeing how much of that shaft power was lost in running the supercharger.
Now let's use the relationship of power at velocity in a propeller aircraft to ballpark what we need to achieve the speeds attained in the Mossie test.

Our second know point is the speed the aircraft attained in 1st Gear at +23.9lbs. Now we don't know our power available at this point. We don't need it though as this performance was not attained in the 2nd Gear, it was attained in the 1st gear!

Our engine only produces so much power so by taking the difference in power from +25 in 2nd gear, we can figure out losses if we used the same amount of power or less in this case to reach a faster speed in 1st Gear.

How do we figure out that difference? Well we have to know how much power it would take us to equal performance in the 1st Gear if we used the 2nd Gear.

Let's use our know point in the 2nd Gear to find an unknown point at the faster velocity the 1st Gear was able to attain.

First we have to do the step I left out the first time, separate the power of induced drag from parasitic. Induced drag has a direct relationship and exerts the smallest influence at high velocity. It simply is not going to change out total picture by more than a few horsepower.

Our Drag is calculated below, separated into components, and converted to THP.

Prp = 3079.4lbs x 307ktas / 325 = 2909 thp

Prp2 / 2909thp = (307KTAS / 295 KTAS)^3

Prp2 = 3271thp

3271- 2909 = 362thp Prp

3271thp / 2 engines = 1635.5 thp Prp per engine

Pri at +25lbs

Pri = (246.4lbs x 307ktas) / 325 = 232.8thp

Pri2/232.8thp = 295ktas/307ktas

Pri2 = (295/307)x232.8 = 223.7thp

232.8 - 223.7 = 9.1 thp difference due to induced drag.

223.7thp / 2 engines = 111.85 Pri per engine

3263hp + 223.7thp = 3494.7thp

3494.7thp x 1.25 = 4368 SHP required

1950hp x 2 = 3900 hp

4368 – 3900 = 468hp

That means our engine losses by using the 2nd gear supercharger at +25lbs are in the neighborhood of 468 SHP in total or 234 hp per engine.

Not very close to the 150hp JtD's nonsense line shows.

Our original estimate was 237.9 hp so we are definitely in the ballpark.

Almost done here!

Let's squash this fallacy that we are holding CL/CD fixed. That notion comes from Harri Phil's mistaking a parametric study on weight gain effects on speed in which we do hold a fixed L/D ratio. He argued for pages with a man who retired from the Skunk works in that one!

In our case here, we are dealing forces required and not just a co-efficient. We can easily calculate our Coefficients and L/D ratio.


CL = (21430lbs / 454 sq ft)/319.5 = .148 for 307ktas +25

CL = (21430lbs / 454 sq ft)/295 = .16 for 295ktas +23.9



Drag at +25 307ktas:

Drag lbs = [3120THP) x 325] / 307 ktas = 3302.9lbs

CD = (3302.9bs / 454sq ft) / 319.5 = .0228

Cdi = .318 (.16^2)/6.46x.8 = .0015

Di = .0016 x 454 x 319.5 = 232lbs

3311.4lbs - 232lbs = 3079.4lbs

Prp = 3079.4lbs x 307ktas / 325 = 2909 thp



AT +25 295ktas:

Drag lbs = [3486THP) x 325] / 295 ktas = 3840.5lbs

CD = (3840.5lbs / 454sq ft) / 295 = .0287



L/D ratio for +25lbs at 307ktas = .16/.0287 = 5.575

L/Dratio for +25 lbs at 295 ktas = .148/.0228 = 6.49


Now let's figure out where our +23.9lbs lies on the 1st Gear Supercharger power production so we can mark it on the Merlin 25 engine chart.

First let's go from a known point on the 1st Gear supercharger power line.

Power:

+18lbs = 1540hp

1540hp x .8 x 2 = 2464THP

Speed:

+18 = 332mph TAS = 288.5ktas

q = 282.4

Drag at +18 288.5ktas:

Drag lbs = [2464THP) x 325] / 288.5 ktas = 2776lbs

CD = (2776lbs / 454sq ft) / 282.4 = .0217

Cdi = .318 (.167^2)/6.46x.8 = .0017

Di = .0017 x 454 x 319.5 = 246.4lbs

2776lbs - 246.4lbs = 2530lbs

Prp = 2530lbs x 288.5ktas / 325 = 2246thp

CL = (21430lbs / 454 sq ft)/282.4 = .167 for 288.5ktas +18lbs

Now to find our forces required by the 1st Gear to reach + 23.9lbs

Prp2 / 2246thp = (307KTAS / 288.5 KTAS)^3

Prp2 = 2706thp

Pri at +23.9lbs

Pri = (246.4lbs x 307ktas) / 325 = 232.8thp

Pri2/232.8thp = 288.5ktas/307ktas

Pri2 = (288.5/307)x232.8 = 219thp

Pr at 23.9lbs = 2706thp + 219thp = 2925thp

2925thp x 1.25 = 3656hp / 2 = 1828hp on the Merlin chart is our 23.9lbs mark.

Our ballpark using PLANK/33,000 was 1864hp so it gave pretty good agreement.

So while our L/D ratio is fixed by design, it is not held fixed by the formulation. We are not doing a parametric study to examine the effects of one parameter. We are using the forces required to determine what we need to achieve a desired level of performance.

By taking the difference between the performance the engine was able to attain because of fewer losses due to the supercharger being used well outside of its design efficiency point, we can conclude that 234hp is not anywhere in the ballpark of drawing nonsense lines on an engine charts as JtD demonstrates. </div></BLOCKQUOTE>

http://forums.ubi.com/eve/foru...861000817#8861000817 (http://forums.ubi.com/eve/forums/a/tpc/f/23110283/m/8141036117?r=8861000817#8861000817)


What I can't do is change your mind. What is that saying, "You can lead a horse to water but you cannot make him drink."

Nothing I can do for you, JtD so I think it best if I just ignore you. It has become tiresome discussing it with you.

Good luck in your journey. Find someone knowledgeable whom you trust.

All the best,

Crumpp

HetzerII
04-30-2009, 04:57 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Heavy airplanes can zoom higher...... </div></BLOCKQUOTE>

When you have the same airframe and engine. But imho also thrust/weight plays an important rule here. So saying plane x zooms higher because its heavier than Y is wrong.

M_Gunz
04-30-2009, 05:04 AM
Gee, the threadlock must have worn off.

JtD
04-30-2009, 05:40 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:

LOL </div></BLOCKQUOTE> I didn't make a joke so I again have to assume you're laughing at me. Bad conduct.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">We are not talking a single speed supercharger that is purposely designed for an application. </div></BLOCKQUOTE>

This is exactly what I meant when I said this:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I'm saying that with a lever twice as long you can apply twice the force and you keep arguing that the lever isn't actually strong enough to support twice the force. </div></BLOCKQUOTE>

For this purpose there is no difference between a two speed supercharger that just uses one speed and a single speed supercharger.

The temperature problems for the abused two speed supercharger are a totally different pair of shoes.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">SWAG...we can conclude that 234hp is not anywhere in the ballpark of drawing nonsense lines on an engine charts as JtD demonstrates. </div></BLOCKQUOTE>

If I had drawn my "nonsense" lines on that chart I'd have come up with about 250hp. I'm impressed that you came so close with that unnecessary and simplified math! How you find that 234 and 250 isn't the same ballpark is beyond me, though, as is the idea that I had actually said anything regarding the Merlin.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Find someone knowledgeable whom you trust. </div></BLOCKQUOTE>

I talk to them on a daily basis. Part of the job.

JtD
04-30-2009, 05:42 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by HetzerII:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Heavy airplanes can zoom higher...... </div></BLOCKQUOTE>

When you have the same airframe and engine. But imho also thrust/weight plays an important rule here. So saying plane x zooms higher because its heavier than Y is wrong. </div></BLOCKQUOTE>

This what we've been talking about for, I don't know, 3 out of the 6 pages. http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

Kettenhunde
04-30-2009, 06:02 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Posts: 2 | Registered: Sun May 25 2008
</div></BLOCKQUOTE>

Well, I see you are on your second post, I wonder what your other username could be on these forums??

But you do illustrate my earlier point about creating confusion very well.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> When you have the same airframe and engine. But imho also thrust/weight plays an important rule here. So saying plane x zooms higher because its heavier than Y is wrong.
</div></BLOCKQUOTE>


Oops I forgot to add in the picture in case someone is dishonest and tries to claim better agreement with drawing a silly line on a chart. One picture is worth a thousand words.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">How you find that 234 and 250 isn't the same ballpark is beyond me, though, as is the idea that I had actually said anything regarding the Merlin. </div></BLOCKQUOTE>

Basic Aerodynamic data:

WT = 21430lbs

Wing Area = 454sqft

Span 54.16ft

b^2/S = 6.46


Power known points:

+25lbs = 1950hp

1950 x.8 x 2 = 3120THP


Speed known points:

+23.9lbs 354mph TAS x .869 = 307KTAS

q= V^2/295

q = 319.5

+25lbs 340mph TAS x .869 = 295KTAS

- This is our most important known as it is a known velocity and power point in the 2nd Gear. From here we can extrapolate performance to anywhere in the aircrafts envelope and use that to compare with our forces required at this point.

q= 295

For giggles, here is the stall speed of the aircraft used in the test.

Stall

@18,000lbs Vs1 = 91ktas

q = 28.2

CL = (18000lbs / 454 sq ft)/28.2 = 1.4

Vs2 = SQRT (295 x 21430lbs)/(1.4 x 454sqft) = 99.7ktas or 114.6mph TAS



To refine the SWAG, we will solve this is by using the difference from a known point. We know the Shaft power out at +25 lbs. We can ballpark our losses by seeing how much of that shaft power was lost in running the supercharger.
Now let's use the relationship of power at velocity in a propeller aircraft to ballpark what we need to achieve the speeds attained in the Mossie test.

Our second know point is the speed the aircraft attained in 1st Gear at +23.9lbs. Now we don't know our power available at this point. We don't need it though as this performance was not attained in the 2nd Gear, it was attained in the 1st gear!

Our engine only produces so much power so by taking the difference in power from +25 in 2nd gear, we can figure out losses if we used the same amount of power or less in this case to reach a faster speed in 1st Gear.

How do we figure out that difference? Well we have to know how much power it would take us to equal performance in the 1st Gear if we used the 2nd Gear.

Let's use our know point in the 2nd Gear to find an unknown point at the faster velocity the 1st Gear was able to attain.

First we have to do the step I left out the first time, separate the power of induced drag from parasitic. Induced drag has a direct relationship and exerts the smallest influence at high velocity. It simply is not going to change out total picture by more than a few horsepower.

Our Drag is calculated below, separated into components, and converted to THP.

Prp = 3079.4lbs x 307ktas / 325 = 2909 thp

Prp2 / 2909thp = (307KTAS / 295 KTAS)^3

Prp2 = 3271thp

3271- 2909 = 362thp Prp

3271thp / 2 engines = 1635.5 thp Prp per engine

Pri at +25lbs

Pri = (246.4lbs x 307ktas) / 325 = 232.8thp

Pri2/232.8thp = 295ktas/307ktas

Pri2 = (295/307)x232.8 = 223.7thp

232.8 - 223.7 = 9.1 thp difference due to induced drag.

223.7thp / 2 engines = 111.85 Pri per engine

3263hp + 223.7thp = 3494.7thp

3494.7thp x 1.25 = 4368 SHP required

1950hp x 2 = 3900 hp

4368 – 3900 = 468hp

That means our engine losses by using the 2nd gear supercharger at +25lbs are in the neighborhood of 468 SHP in total or 234 hp per engine.

Not very close to the 150hp JtD's nonsense line shows.

Our original estimate was 237.9 hp so we are definitely in the ballpark.

Almost done here!

Let's squash this fallacy that we are holding CL/CD fixed. That notion comes from Harri Phil's mistaking a parametric study on weight gain effects on speed in which we do hold a fixed L/D ratio. He argued for pages with a man who retired from the Skunk works in that one!

In our case here, we are dealing forces required and not just a co-efficient. We can easily calculate our Coefficients and L/D ratio.


CL = (21430lbs / 454 sq ft)/319.5 = .148 for 307ktas +25

CL = (21430lbs / 454 sq ft)/295 = .16 for 295ktas +23.9



Drag at +25 307ktas:

Drag lbs = [3120THP) x 325] / 307 ktas = 3302.9lbs

CD = (3302.9bs / 454sq ft) / 319.5 = .0228

Cdi = .318 (.16^2)/6.46x.8 = .0015

Di = .0016 x 454 x 319.5 = 232lbs

3311.4lbs - 232lbs = 3079.4lbs

Prp = 3079.4lbs x 307ktas / 325 = 2909 thp



AT +25 295ktas:

Drag lbs = [3486THP) x 325] / 295 ktas = 3840.5lbs

CD = (3840.5lbs / 454sq ft) / 295 = .0287



L/D ratio for +25lbs at 307ktas = .16/.0287 = 5.575

L/Dratio for +25 lbs at 295 ktas = .148/.0228 = 6.49


Now let's figure out where our +23.9lbs lies on the 1st Gear Supercharger power production so we can mark it on the Merlin 25 engine chart.

First let's go from a known point on the 1st Gear supercharger power line.

Power:

+18lbs = 1540hp

1540hp x .8 x 2 = 2464THP

Speed:

+18 = 332mph TAS = 288.5ktas

q = 282.4

Drag at +18 288.5ktas:

Drag lbs = [2464THP) x 325] / 288.5 ktas = 2776lbs

CD = (2776lbs / 454sq ft) / 282.4 = .0217

Cdi = .318 (.167^2)/6.46x.8 = .0017

Di = .0017 x 454 x 319.5 = 246.4lbs

2776lbs - 246.4lbs = 2530lbs

Prp = 2530lbs x 288.5ktas / 325 = 2246thp

CL = (21430lbs / 454 sq ft)/282.4 = .167 for 288.5ktas +18lbs

Now to find our forces required by the 1st Gear to reach + 23.9lbs

Prp2 / 2246thp = (307KTAS / 288.5 KTAS)^3

Prp2 = 2706thp

Pri at +23.9lbs

Pri = (246.4lbs x 307ktas) / 325 = 232.8thp

Pri2/232.8thp = 288.5ktas/307ktas

Pri2 = (288.5/307)x232.8 = 219thp

Pr at 23.9lbs = 2706thp + 219thp = 2925thp

2925thp x 1.25 = 3656hp / 2 = 1828hp on the Merlin chart is our 23.9lbs mark.

Our ballpark using PLANK/33,000 was 1864hp so it gave pretty good agreement.

So while our L/D ratio is fixed by design, it is not held fixed by the formulation. We are not doing a parametric study to examine the effects of one parameter. We are using the forces required to determine what we need to achieve a desired level of performance.

By taking the difference between the performance the engine was able to attain because of fewer losses due to the supercharger being used well outside of its design efficiency point, we can conclude that 234hp is not anywhere in the ballpark of drawing nonsense lines on an engine charts as JtD demonstrates.

http://img259.imageshack.us/img259/2646/jtdline.jpg (http://img259.imageshack.us/my.php?image=jtdline.jpg)

125 hp is nothing even close to 234 hp…….

All the best,

Crumpp

Feathered_IV
04-30-2009, 06:13 AM
I made the headrest of my Tempest a bit smaller. Not game breaking by any means, but much better now. http://forums.ubi.com/images/smilies/16x16_smiley-happy.gif

JtD
04-30-2009, 06:50 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
125 hp is nothing even close to 234 hp…….
</div></BLOCKQUOTE>

I know, but you drew the lines. Not me.

If I drew lines I'd end up at about 250hp difference between MS and FS gear.

I recommend you sort out who said what so we won't waste time with you arguing with yourself.

For what it's worth, by now you've also labeled me dishonest and my methods silly. Just so you know you've crossed the line, again. You should read this (http://forums.ubi.com/eve/forums/a/tpc/f/23110283/m/3971030057) again.

Wurkeri
04-30-2009, 07:12 AM
JtD,
Just check FTHs in the above Merlin chart: MS gear line is shifted to the left (actually too much) due to lower speed of the tested Mosquito. However, the FS gear line is not shifted to the left at all despite it did only 369mph http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

Anyway, who cares? It does not matter at all what evidence you bring in or how many times you prove the calculations wrong...

Kettenhunde
04-30-2009, 07:39 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> how many times you prove the calculations wrong </div></BLOCKQUOTE>

I think you have to prove the math wrong at least one time for that statement to count, Gripen.

All the best,

Crumpp

HetzerII
04-30-2009, 08:08 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">This what we've been talking about for, I don't know, 3 out of the 6 pages. </div></BLOCKQUOTE>

One note for me:
First read the whole thread before writing

noted...

http://forums.ubi.com/images/smilies/crackwhip.gif

ROXunreal
04-30-2009, 10:59 AM
Excuse for not reading the whole thread but I just CAN't read all this for nothing. So if my question has already been answered here then just say so so I can look for it, if not, here is my simple question:

When BnZ-ing with the Tempest, what prop/radiator/anything else settings should I use for diving and zoom climbing? As I said I really like this plane but am put off by its rather unfavorable zoom climb characteristic, at least the way I'm flying it.

VW-IceFire
04-30-2009, 04:26 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by ROXunreal:
Excuse for not reading the whole thread but I just CAN't read all this for nothing. So if my question has already been answered here then just say so so I can look for it, if not, here is my simple question:

When BnZ-ing with the Tempest, what prop/radiator/anything else settings should I use for diving and zoom climbing? As I said I really like this plane but am put off by its rather unfavorable zoom climb characteristic, at least the way I'm flying it. </div></BLOCKQUOTE>
Unfavourable zoom climb? What are you doing to it? Zoom climb is really good in the Tempest...not the best but close.

In general I use the following settings:

WEP on 70% prop pitch for combat cruise with WEP on 90% or 95% prop pitch settings for short periods of time.

The rest of the time its rads closed with prop pitch 90% and throttle whatever I want it to be. I don't modify my settings much specifically to boom and zoom. Remember that in a Tempest and any other fighter in game using a CSP device that the prop pitch percentage setting is RPM related rather than controlling the blades. Sometimes having the RPM a bit lower will help in a dive and maybe in the zoom climb but not as much after that.

To properly zoom climb keep the angles down and avoid hard control motions.

tagert
04-30-2009, 10:04 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> how many times you prove the calculations wrong </div></BLOCKQUOTE>

I think you have to prove the math wrong at least one time for that statement to count, Gripen. </div></BLOCKQUOTE>
Been there done that..

Yet it didn't help you one bit..

Thus I can only conclude you require 'more than once' to see the light..

How many times more?

Ill let you know when..

No..

If it ever happens.

JtD
04-30-2009, 11:07 PM
I usually fly the Tempest at 90% prop pitch with WEP on and 103% power rads either 2 or 4. It's is about the maximum you can get out of it continuously without overheating. The Tempest takes time to get used to because the torque is the other way round, just like in Yaks. So you'll need a bit of training in order to fly clean maneuvers.

The Tempest does not have a great climb rate above 2000 meters so the zoom climb will suffer, too. But I'd never label the Tempest a poor zoom climber.

Kettenhunde
04-30-2009, 11:50 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Been there done that..
</div></BLOCKQUOTE>

That is not the truth.

It is pretty easy to spot a math error and so far nobody has done it.

There is quite a bit of grumbling and whining with nothing to back it up.

All the best,

Crumpp

JtD
05-01-2009, 12:33 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Been there done that..
</div></BLOCKQUOTE>

That is not the truth.

It is pretty easy to spot a math error and so far nobody has done it. </div></BLOCKQUOTE>

Your 1864hp PLANK estimate is wrong, correct is 1896hp. That has been pointed out to you already.
Your 1824hp label on the chart is wrong, you came up with 1828hp in your calculation.
Comparing 25lbs (FS) and 23.9lbs (MS) manifold pressure to find the power difference between FS and MS gear at the same manifold pressure is pointless, because manifold pressure isn't the same.

Kettenhunde
05-01-2009, 02:37 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Your 1864hp PLANK estimate is wrong, correct is 1896hp. That has been pointed out to you already. Your 1824hp label on the chart is wrong, you came up with 1828hp in your calculation.
Comparing 25lbs (FS) and 23.9lbs (MS) manifold pressure to find the power difference between FS and MS gear at the same manifold pressure is pointless, because manifold pressure isn't the same. </div></BLOCKQUOTE>

You claiming something is not a mathematical proof.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Your 1864hp PLANK estimate is wrong, correct is 1896hp </div></BLOCKQUOTE>

That is within 1.7% and certainly gives excellent agreement considering our tolerances is ~3%.

Considering we are not using test stand measured BMEP it is really good results that I am happy with.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> . Your 1824hp label on the chart is wrong, you came up with 1828hp in your calculation. </div></BLOCKQUOTE>

You are right! You can now say you found an error.

I think the width of line marking the point covers that but you can change it on your copy if you like!

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Comparing 25lbs (FS) and 23.9lbs (MS) manifold pressure to find the power difference between FS and MS gear at the same manifold pressure is pointless, because manifold pressure isn't the same </div></BLOCKQUOTE>

It certainly is applicable if we want to find out the losses in power. It is very easy to find as well as I demonstrated. Just use the forces required and we can determine the power required at our new manifold pressure!

It is simple applied physics.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> First let's go from a known point on the 1st Gear supercharger power line.

Power:

+18lbs = 1540hp

1540hp x .8 x 2 = 2464THP

Speed:

+18 = 332mph TAS = 288.5ktas

q = 282.4

Drag at +18 288.5ktas:

Drag lbs = [2464THP) x 325] / 288.5 ktas = 2776lbs

CD = (2776lbs / 454sq ft) / 282.4 = .0217

Cdi = .318 (.167^2)/6.46x.8 = .0017

Di = .0017 x 454 x 319.5 = 246.4lbs

2776lbs - 246.4lbs = 2530lbs

Prp = 2530lbs x 288.5ktas / 325 = 2246thp

CL = (21430lbs / 454 sq ft)/282.4 = .167 for 288.5ktas +18lbs

Now to find our forces required by the 1st Gear to reach + 23.9lbs

Prp2 / 2246thp = (307KTAS / 288.5 KTAS)^3

Prp2 = 2706thp

Pri at +23.9lbs

Pri = (246.4lbs x 307ktas) / 325 = 232.8thp

Pri2/232.8thp = 288.5ktas/307ktas

Pri2 = (288.5/307)x232.8 = 219thp

Pr at 23.9lbs = 2706thp + 219thp = 2925thp

2925thp x 1.25 = 3656hp / 2 = 1828hp on the Merlin chart is our 23.9lbs mark.

Our ballpark using PLANK/33,000 was 1864hp so it gave pretty good agreement. </div></BLOCKQUOTE>

All the best,

Crumpp

JtD
05-01-2009, 02:46 AM
So your summary is:
- you used a wrong concept
- made a wrong calculation within that concept
- made a typing mistake within the calculations
and all that is right. Then, of course, one has to admit that all your calculations are right.

Still, I prefer to think that the power output of naturally aspirated engines isn't zero.

Kettenhunde
05-01-2009, 02:59 AM
The analysis is correct.

Do you really attach that much significance to a transcription error of a 4 hp difference on a chart?

I surprised the concept of significant digits and agreement escapes you. You did tell me you were an aeronautical engineer, right?

That whole, "Kettenhunde is looking at things as a Pilot and JtD is looking at things as Engineer", spiel on your PM. Remember that?

In plain language, you are just looking at things wrong. The math proves it.

All the best,

Crumpp

Wurkeri
05-01-2009, 03:05 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JtD:
So your summary is:
- you used a wrong concept
- made a wrong calculation within that concept
- made a typing mistake within the calculations
and all that is right. Then, of course, one has to admit that all your calculations are right.

Still, I prefer to think that the power output of naturally aspirated engines isn't zero. </div></BLOCKQUOTE>

Well, another way to look the same issue is that at full throttle the engine did according to chart

1600hp +18lbs
1950hp +25lbs

so if someone calculates that still at full throttle it did

1824hp +23,9lbs

it means that first 5,9lbs MAP increase from +18lbs to +23,9lbs gave 224hp and last 1,1lbs increase from +23,9lbs to +25lbs gave 126hp... go figure...

Anyway, it does not matter how many times this is pointed to be wrong...

Kettenhunde
05-01-2009, 03:28 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> it means that first 5,9lbs MAP increase from +18lbs to +23,9lbs gave 224hp and last 1,1lbs increase from +23,9lbs to +25lbs gave 126hp... go figure...
</div></BLOCKQUOTE>

Funny how that works, huh?

What does that have to do with the silly assmuption we can draw a line from the MS gear to sea level to determine power loss if the MS gear was used below its FTH, anyway?

All the best,

Crumpp

JtD
05-01-2009, 03:31 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:

I surprised the concept of significant digits and agreement escapes you. </div></BLOCKQUOTE>

To omit one atmosphere of boost from a calculation is not insignificant if it means you're calculating with around two instead of around three. If you were calculating at around 299 instead of 300, then it would be insignificant. But you don't, so it isn't.

Kettenhunde
05-01-2009, 03:36 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">To omit one atmosphere of boost from a calculation is not insignificant if it means you're calculating with around two instead of around three. If you were calculating at around 299 instead of 300, then it would be insignificant. But you don't, so it isn't. </div></BLOCKQUOTE>

http://forums.ubi.com/images/smilies/disagree.gif

You guys are great at generating pure innuendo.

Just do the damn math and prove it wrong.

Personally, I don't think you even are following the calculations because you certainly do not get the concepts. That is clear from this statement:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">To omit one atmosphere of boost from a calculation </div></BLOCKQUOTE>

It is forces required, JtD.

It is not the PLANK/33,000 formula; it is just being used to confirm the validity of my earlier math from that thread using PLANK/33,000.

The formulation above does not care what the manifold pressure is set too. It only cares what force is required to achieve performance.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> First let's go from a known point on the 1st Gear supercharger power line.

Power:

+18lbs = 1540hp

1540hp x .8 x 2 = 2464THP

Speed:

+18 = 332mph TAS = 288.5ktas

q = 282.4

Drag at +18 288.5ktas:

Drag lbs = [2464THP) x 325] / 288.5 ktas = 2776lbs

CD = (2776lbs / 454sq ft) / 282.4 = .0217

Cdi = .318 (.167^2)/6.46x.8 = .0017

Di = .0017 x 454 x 319.5 = 246.4lbs

2776lbs - 246.4lbs = 2530lbs

Prp = 2530lbs x 288.5ktas / 325 = 2246thp

CL = (21430lbs / 454 sq ft)/282.4 = .167 for 288.5ktas +18lbs

Now to find our forces required by the 1st Gear to reach + 23.9lbs

Prp2 / 2246thp = (307KTAS / 288.5 KTAS)^3

Prp2 = 2706thp

Pri at +23.9lbs

Pri = (246.4lbs x 307ktas) / 325 = 232.8thp

Pri2/232.8thp = 288.5ktas/307ktas

Pri2 = (288.5/307)x232.8 = 219thp

Pr at 23.9lbs = 2706thp + 219thp = 2925thp

2925thp x 1.25 = 3656hp / 2 = 1828hp on the Merlin chart is our 23.9lbs mark.

Our ballpark using PLANK/33,000 was 1864hp so it gave pretty good agreement.
</div></BLOCKQUOTE>

The mathematical relationship holds and as long as we know the forces required for one condition of flight, we can easily determine it for others.

All the best,

Crumpp

JtD
05-01-2009, 03:39 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Wurkeri:

Well, another way to look the same issue is that at full throttle the engine did according to chart

1600hp +18lbs
1950hp +25lbs

so if someone calculates that still at full throttle it did

1824hp +23,9lbs

it means that first 5,9lbs MAP increase from +18lbs to +23,9lbs gave 224hp and last 1,1lbs increase from +23,9lbs to +25lbs gave 126hp... go figure...

Anyway, it does not matter how many times this is pointed to be wrong... </div></BLOCKQUOTE>

I think it's 1540 @ 18lbs because you best take all data from sea level, not full throttle alt. Still, the song remains the same.

JtD
05-01-2009, 03:42 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">To omit one atmosphere of boost from a calculation is not insignificant if it means you're calculating with around two instead of around three. If you were calculating at around 299 instead of 300, then it would be insignificant. But you don't, so it isn't. </div></BLOCKQUOTE>

http://forums.ubi.com/images/smilies/16x16_smiley-very-happy.gif

http://forums.ubi.com/images/smilies/disagree.gif

That's rich. </div></BLOCKQUOTE>

What part do you disagree with?

Kettenhunde
05-01-2009, 03:51 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> What part do you disagree with? </div></BLOCKQUOTE>

Manifold pressure is not even a part of those calculations JtD. Your assertion is laughable.


<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">To omit one atmosphere of boost from a calculation is not insignificant if it means you're calculating with around two instead of around three. If you were calculating at around 299 instead of 300, then it would be insignificant. But you don't, so it isn't. </div></BLOCKQUOTE>

http://forums.ubi.com/images/smilies/disagree.gif

You guys are great at generating pure innuendo.

Just do the damn math and prove it wrong.

Personally, I don't think you even are following the calculations because you certainly do not get the concepts. That is clear from this statement:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">To omit one atmosphere of boost from a calculation </div></BLOCKQUOTE>

It is forces required, JtD.

It is not the PLANK/33,000 formula; it is just being used to confirm the validity of my earlier math from that thread using PLANK/33,000.

The formulation above does not care what the manifold pressure is set too. It only cares what force is required to achieve performance.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> First let's go from a known point on the 1st Gear supercharger power line.

Power:

+18lbs = 1540hp

1540hp x .8 x 2 = 2464THP

Speed:

+18 = 332mph TAS = 288.5ktas

q = 282.4

Drag at +18 288.5ktas:

Drag lbs = [2464THP) x 325] / 288.5 ktas = 2776lbs

CD = (2776lbs / 454sq ft) / 282.4 = .0217

Cdi = .318 (.167^2)/6.46x.8 = .0017

Di = .0017 x 454 x 319.5 = 246.4lbs

2776lbs - 246.4lbs = 2530lbs

Prp = 2530lbs x 288.5ktas / 325 = 2246thp

CL = (21430lbs / 454 sq ft)/282.4 = .167 for 288.5ktas +18lbs

Now to find our forces required by the 1st Gear to reach + 23.9lbs

Prp2 / 2246thp = (307KTAS / 288.5 KTAS)^3

Prp2 = 2706thp

Pri at +23.9lbs

Pri = (246.4lbs x 307ktas) / 325 = 232.8thp

Pri2/232.8thp = 288.5ktas/307ktas

Pri2 = (288.5/307)x232.8 = 219thp

Pr at 23.9lbs = 2706thp + 219thp = 2925thp

2925thp x 1.25 = 3656hp / 2 = 1828hp on the Merlin chart is our 23.9lbs mark.

Our ballpark using PLANK/33,000 was 1864hp so it gave pretty good agreement.
</div></BLOCKQUOTE>

The mathematical relationship holds and as long as we know the forces required for one condition of flight, we can easily determine it for others.

All the best,

Crumpp

Kettenhunde
05-01-2009, 03:54 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">it means that first 5,9lbs MAP increase from +18lbs to +23,9lbs gave 224hp and last 1,1lbs increase from +23,9lbs to +25lbs gave 126hp... go figure... </div></BLOCKQUOTE>


JtD and Wurkeri, this relations is applicable to MS gear only and cannot be used to determine FS gear losses at sea level.

Notice the bottom scale of the chart is altitude!

All the best,

Crumpp

JtD
05-01-2009, 04:19 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Kettenhunde:
Manifold pressure is not even a part of those calculations JtD. Your assertion is laughable. </div></BLOCKQUOTE>

You've repeatedly stated in this topic:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Kettenhunde:
Our ballpark using PLANK/33,000 was 1864hp so it gave pretty good agreement. </div></BLOCKQUOTE>

And I said:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">JtD:
Your 1864hp PLANK estimate is wrong, correct is 1896hp. </div></BLOCKQUOTE>

Your 1864hp comes from the topic you linked, there you say:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Kettenhunde:
Using PLANK/33,000 we can fold LANK/33,000 into a value of X and estimate our power at 23.9lbs

25X = 1950hp X = 78

23.9 (78) = 1864hp </div></BLOCKQUOTE>

There it has been corrected by Wurkeri:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Wurkeri:
This part is all wrong: +25 lbs is addition to the sealavel pressure about 14,696 psi. So correct calculation will result 1896hp. About same result can be calculated from power chart knowing that at +25 lbs it did 1950hp at sealevel and 1600hp at +18 lbs FTH, this results 1895hp. </div></BLOCKQUOTE>

This is something you chose to ignore up to this very minute and you came up with this statement:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Kettenhunde:
It is pretty easy to spot a math error and so far nobody has done it. </div></BLOCKQUOTE>

This is not true. You have provided numerous calculations in the past and some contained errors, which have been pointed out to you.

In your drag calculation you make a few simplifications that have a huge impact on the result. For instance, you assume the same efficiency at both 18 and 23.9 lbs of boost. This is hardly correct and reducing efficiency from your 80% to 77% at 23.9 lbs ends up with 1900hp per engine. Very good agreement with a correct plank. However, since I don't know the specifics of the prop used, I give you the benefit of doubt and leave it as it is. There is a large amount of uncertainty in the calculation, but no mistake to my knowledge.

Your mistake is to take a result with an uncertainty in the range of 100hp and draw conclusions that require a far higher precision. But this is no error in your math.

Kettenhunde
05-01-2009, 04:41 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> You've repeatedly stated in this topic:
</div></BLOCKQUOTE>

Yes I did!

I used a rearrangement of PLANK/33,000 to ballpark the power earlier in the thread.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Using PLANK/33,000 we can fold LANK/33,000 into a value of X and estimate our power at 23.9lbs

25X = 1950hp X = 78

23.9 (78) = 1864hp
</div></BLOCKQUOTE>

I am surprised it gave that good of an agreement.

It is clear that you do not understand that the math below has nothing to do with the re-arrangement of PLANK/33,000.

It is a completely different methodology to determine aircraft performance. We don't even use manifold pressure in this methodology. For that matter we don't even use Manifold pressure in PLANK. Your obsession with it is puzzling and points to your lack of understanding what is going on.

This methodology just uses the relationship of forces required from a know point of performance.

We simple say if we are going this fast, at this altitude, we need this much power according to our engine chart.

We have our known points and can use the relationships to determine performance in any other part of the envelope.

Who cares what manifold pressure the engine is set too?

We know the amount of power we must have to achieve performance.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">First let's go from a known point on the 1st Gear supercharger power line.

Power:

+18lbs = 1540hp

1540hp x .8 x 2 = 2464THP

Speed:

+18 = 332mph TAS = 288.5ktas

q = 282.4

Drag at +18 288.5ktas:

Drag lbs = [2464THP) x 325] / 288.5 ktas = 2776lbs

CD = (2776lbs / 454sq ft) / 282.4 = .0217

Cdi = .318 (.167^2)/6.46x.8 = .0017

Di = .0017 x 454 x 319.5 = 246.4lbs

2776lbs - 246.4lbs = 2530lbs

Prp = 2530lbs x 288.5ktas / 325 = 2246thp

CL = (21430lbs / 454 sq ft)/282.4 = .167 for 288.5ktas +18lbs

Now to find our forces required by the 1st Gear to reach + 23.9lbs

Prp2 / 2246thp = (307KTAS / 288.5 KTAS)^3

Prp2 = 2706thp

Pri at +23.9lbs

Pri = (246.4lbs x 307ktas) / 325 = 232.8thp

Pri2/232.8thp = 288.5ktas/307ktas

Pri2 = (288.5/307)x232.8 = 219thp

Pr at 23.9lbs = 2706thp + 219thp = 2925thp

2925thp x 1.25 = 3656hp / 2 = 1828hp on the Merlin chart is our 23.9lbs mark.

Our ballpark using PLANK/33,000 was 1864hp so it gave pretty good agreement.

</div></BLOCKQUOTE>


It hasn't been corrected by Wurkeri. He has just pointed out the relationships at sea level for MS gear. He actually confirms quite nicely my calculations.

Remember the discussion was the using the engine chart to make a valid assumption about power loss using FS gear at sea level.

To do that we have to take the aircraft to EAS and compare our power required for MS gear and FS gear.

I then compare the difference with the chart. You can see from the results drawing lines from FS gear to sea level on a chart trying to ballpark power losses of the supercharger is nonsense.

All the best,

Crumpp

JtD
05-01-2009, 05:21 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">It is clear that you do not understand that the math below has nothing to do with the re-arrangement of PLANK/33,000. </div></BLOCKQUOTE>

No, the point is that your plank estimate is wrong.

And, I am still not tired of to repeat myself, I do understand all this pretty well. So your assertion that I don't means that you don't understand what write, because if you did, you wouldn't state that I don't understand. Understood? So, if anything in my statements is not clear to you, feel free to ask and I'll happily explain. Oh, and with your lack of understanding I don't mean you don't get the subject, I think you just don't get me.

The fact that I understand is quite evident from the fact that I separated my statements regarding plank and drag by a paragraph with an empty line in between. I get the impression that structuring text does not have the same importance to you as it has to me. Please save yourself some time and leave out the "you do not understand" statements.

There's also no point in posting the calculation yet another time.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">It hasn't been corrected by Wurkeri. He has just pointed out the relationships at sea level for MS gear. He actually confirms quite nicely my calculations. </div></BLOCKQUOTE>

Yes, I know. This is why I said Wukeri has corrected the _plank_ calculation. I also said that the drag based calculation as such contains no mistake to my knowledge. This is probably a good enough reason for Wukeri not to correct it.

Since you've displayed some problems following my statements, I'll provide a simple summary:
--------------------
I am dealing with two different calculations.
a) plank calculation - technically not correct
b) drag based calculation - technically correct
--------------------
Once you get this we can go back up and discuss the details.

Kettenhunde
05-01-2009, 08:49 AM
Repetition does not make something truthful.

Cut the baloney and do the math.

All the best,

Crumpp

Wurkeri
05-01-2009, 09:30 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JtD:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Wurkeri:

Well, another way to look the same issue is that at full throttle the engine did according to chart

1600hp +18lbs
1950hp +25lbs

so if someone calculates that still at full throttle it did

1824hp +23,9lbs

it means that first 5,9lbs MAP increase from +18lbs to +23,9lbs gave 224hp and last 1,1lbs increase from +23,9lbs to +25lbs gave 126hp... go figure...

Anyway, it does not matter how many times this is pointed to be wrong... </div></BLOCKQUOTE>

I think it's 1540 @ 18lbs because you best take all data from sea level, not full throttle alt. Still, the song remains the same. </div></BLOCKQUOTE>

I wrote "at full throttle"; at sealevel the engine is in partial throttle at +18lbs, therefore the power value 1540hp is not directly comparable with +25lbs value 1950hp which is reached at full throttle. However, at 18lbs MS gear FTH (6500ft) engine is running at full throttle reaching 1600hp and because the HX809 did +23,9lbs at full throttle as well, the output can be calculated with simple linear approximation from full throttle +18lbs and +25lbs values.

Note that I calculated this both ways, plank method and FTH method, allready in the original thread the results being 1896hp and 1895hp respectively.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JtD:
Yes, I know. This is why I said Wukeri has corrected the _plank_ calculation. I also said that the drag based calculation as such contains no mistake to my knowledge. This is probably a good enough reason for Wukeri not to correct it. </div></BLOCKQUOTE>

Actually the drag calculation is still wrong but I don't care to correct it again; the errors are the same as earlier. It does not matter how many times I point out the errors, he can't get it; at that point when K posted his current version of the calculation, he was arguing alone as the moderators noted...


I reported my own calculation results with correct method allready in the original thread and these are very close the power chart values ie about 190hp difference at sealevel between MS and FS gear using polar method and 185hp difference using the chart (the error in the K's chart is actually pointed out above). Send PM if you want to know the details, I should still have the spreadsheets somewhere.

Kettenhunde
05-01-2009, 09:39 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Note that I calculated this both ways, </div></BLOCKQUOTE>

Link, I don't remember any math from you!

All I remeber is you claiming that AoA was fixed in my calculations.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Wurkeri says:

Nope, I say that your calculation assumes constant Cl/Cd relation ie Cl is assumed to be constant.
</div></BLOCKQUOTE>

http://forums.ubi.com/eve/foru...291087717#2291087717 (http://forums.ubi.com/eve/forums/a/tpc/f/23110283/m/8141036117?r=2291087717#2291087717)

I wouldn't say you have a steller record in understanding what is going on with the math.

Of course it is not essential either you have a deep understanding when you only need it for some models.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Kettenhunde says:

Let's squash this fallacy that we are holding CL/CD fixed. That notion comes from Harri Phil's mistaking a parametric study on weight gain effects on speed in which we do hold a fixed L/D ratio. He argued for pages with a man who retired from the Skunk works in that one!

In our case here, we are dealing forces required and not just a co-efficient. We can easily calculate our Coefficients and L/D ratio.


CL = (21430lbs / 454 sq ft)/319.5 = .148 for 307ktas +25

CL = (21430lbs / 454 sq ft)/295 = .16 for 295ktas +23.9



Drag at +25 307ktas:

Drag lbs = [3120THP) x 325] / 307 ktas = 3302.9lbs

CD = (3302.9bs / 454sq ft) / 319.5 = .0228

Cdi = .318 (.16^2)/6.46x.8 = .0015

Di = .0016 x 454 x 319.5 = 232lbs

3311.4lbs - 232lbs = 3079.4lbs

Prp = 3079.4lbs x 307ktas / 325 = 2909 thp



AT +25 295ktas:

Drag lbs = [3486THP) x 325] / 295 ktas = 3840.5lbs

CD = (3840.5lbs / 454sq ft) / 295 = .0287



L/D ratio for +25lbs at 307ktas = .16/.0287 = 5.575

L/Dratio for +25 lbs at 295 ktas = .148/.0228 = 6.49
</div></BLOCKQUOTE>


All the best,

Crumpp

Kettenhunde
05-01-2009, 09:49 AM
We don't have to cover all this again:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Wurkeri says:

This is unaccurate way to calculate because exhaust thrust, change on Cl and propeller efficiency is not accounted. Using basic polar analysis I got 1706,5hp for 340mph per engine ie the engines produce about 190hp less at sealevel at FS gear than at MS gear. </div></BLOCKQUOTE>

Hardly, the calculation rolls all of that into determine the power required to achieve performance, Wurkeri.

This way we don't have to make a bunch of assumptions based on what we don't know!

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Wurkeri says:

The estimated parameters used are: Exhaust thrust 100kp/engine, e=0,8, propeller efficiency 0,8. </div></BLOCKQUOTE>

We just say if it takes this much power to go this fast, then based on the relationship of power; we need this much more to make this airplane this much faster. Pretty simple, effective, and not hard to follow.

In fact it is taught in Aircraft Performance Classes, imagine that huh!

We have kind of been through this before. I was waiting for you to do the calcs but I think enough pages have passed that it is obvious you did not know how or did not realize it could be estimated with a fair degree of accuracy.

I can understand not wanting to estimate off the climbs but once that level speed data came in, it was all over but the crying.

It is accurate within the realm of significant digits. To get more accurate you would need a level of detail that is beyond these boards and one mans capability.


<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Wurkeri says:

Point here is that it's you who continously add nonsense lines. JtD just extended existing line to the sealevel to prove his point and it's supported by Allied test data on the BMW 801. </div></BLOCKQUOTE>

Well 58% is not in the realm of significant digits, it is just plain inaccurate and wrong.

The interpretation of the dotted lines on a 60 year old chart you keep pushing does not correspond to my experience in any way. Standard notation says those are unusable data points UNLESS we have a legend that explains otherwise.

The chart has no legend nor is ANY REFERENCE located in the entire report to any attempt to depict power at any other setting than those found in the captured German documents for operating the BMW801.

You are azz-U-me – ing things that do not exist in fact in the report. Assumptions will get you in trouble.

If you are comfortable making assumption without facts, then by all means do so. Just don't push it around as fact when it is just your assumption.

As for the ability to run High blower at low altitudes:

The Mosquito and Spitfire testing of the 100/150 grade boost increase is not a result of a 2nd gear supercharger being designed to operate at sea level, that is the result of technological advances outstripping the original engineering.

Otherwise, the supercharger would have been completely different in order to optimize the new knock limited performance potential!

http://forums.ubi.com/eve/foru...251085717#5251085717 (http://forums.ubi.com/eve/forums/a/tpc/f/23110283/m/8141036117?r=5251085717#5251085717)

All the best,

Crumpp

M_Gunz
05-01-2009, 12:15 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
Drag at +25 307ktas:

Drag lbs = [3120THP) x 325] / 307 ktas = 3302.9lbs

AT +25 295ktas:

Drag lbs = [3486THP) x 325] / 295 ktas = 3840.5lbs

</div></BLOCKQUOTE>

That's like a 7100 lb plane, and the engine can press ... is ktas Knots True Airspeed?

I just seems a bit odd to me that Drag is 537.6 lbs MORE at 295 than it is at 307?
I see thrust decreasing with speed (3486 @ 295 --&gt; 3120 @ 307 see note below) and each seems again
divided by speed and I am really having a hard time seeing more drag at 295 knots than at 307.
I *can* see being at +25 at 295 ktas and pouring out more thrust than at 307 but that's not drag
as long as the plane is still accelerating or climbing. 307 ktas, and what is top speed?

Note that 3486 x 295 /307 = 3350 not 3120 so it's not simple thrust=power/speed, would that be
exhaust/radiator boost in the data? That would make extrapolation and maybe interpolation just
a bit iffy?

tagert
05-01-2009, 04:33 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Wurkeri says:
Nope, I say that your calculation assumes constant Cl/Cd relation i.e. Cl is assumed to be constant. </div></BLOCKQUOTE>

http://forums.ubi.com/eve/foru...291087717#2291087717 (http://forums.ubi.com/eve/forums/a/tpc/f/23110283/m/8141036117?r=2291087717#2291087717)

I wouldn't say you have a steller record in understanding what is going on with the math. </div></BLOCKQUOTE>
Well..

I wouldn't say you have a stellar record in understanding what is going on with the math either!

Remember when you got <span class="ev_code_yellow">Total Mechanical Energy Equation (TME)</span> and <span class="ev_code_red">Conservation of Energy Concept</span> confused, i.e.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde Tue August 21 2007 07:48: :
http://forums.ubi.com/eve/foru...283/m/8521039185/p/9 (http://forums.ubi.com/eve/forums/a/tpc/f/23110283/m/8521039185/p/9)
It is very clear Tagert you have no clue how to use Total Energy concepts to predict aircraft performance.

http://img179.imagevenue.com/i..._of_TE_122_575lo.JPG (http://img179.imagevenue.com/img.php?image=07270_Conservation_of_TE_122_575lo.J PG)

<span class="ev_code_yellow">TE energy cannot change</span> IAW the <span class="ev_code_red">law of conservation of energy.</span> </div></BLOCKQUOTE>

When in fact TE can and does change..

As a mater of FACT..

The definition of WORK is that it is equal to the CHANGE in the TME..
The definition of POWER is that it is equal to the RATE of CHANGE in the TME..

It is knowing that energy can not be created or destroyed (conservation of energy) in conjunction with the TME that tells you the CHANGE is due to things like THRUST and DRAG.

SAVVY?

JtD
05-01-2009, 05:03 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
Repetition does not make something truthful. </div></BLOCKQUOTE>

Coming from you this is gold, http://forums.ubi.com/images/smilies/16x16_smiley-very-happy.gif.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Cut the baloney and do the math. </div></BLOCKQUOTE>

I take it you again haven't read what I wrote, or in case you did you haven't processed it yet, so I leave it up to you to go back to my post any time you like. It's there, it won't run away. I'll be around, too, so if you have any questions don't hesitate to ask.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Wurkeri:

Actually the drag calculation is still wrong but I don't care to correct it again; the errors are the same as earlier. It does not matter how many times I point out the errors, he can't get it; at that point when K posted his current version of the calculation, he was arguing alone as the moderators noted... </div></BLOCKQUOTE>

I called it simplifications, not mistakes. I still think that's ok. The mistake is to use the rather vague result of the simplified calculation for the precise statements Kettenhunde is trying to make.

M_Gunz
05-01-2009, 06:10 PM
LOL!
Good ole half a sentence;
still can't get the part about predicting AC performance...
still can't figure out why that's important when trying to put values on data.
still stuck ignoring half of what goes on while attention is fixed on the agenda.
small, round, and very ex-clusive view and warm ears in part-context-land.

Kettenhunde
05-01-2009, 08:23 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> That's like a 7100 lb plane, and the engine can press ... is ktas Knots True Airspeed? </div></BLOCKQUOTE>

It is a twin engine Mosquito. Yes that is Knots True Airspeed as per standard BGS system.

Two engines produces twice the power!

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> I just seems a bit odd to me that Drag is 537.6 lbs MORE at 295 than it is at 307?
</div></BLOCKQUOTE>

Exactly and good eye! That is what made this test unique.

That is because the measured aircraft is traveling slower on more power.

This was a measured flight test of Mosquito running FS gear at sea level.

The engine is outside its normal operating parameters on the +25 as it is being operated in the wrong gear.

It is producing tons of power but very little of it is going to propel the aircraft. Most of it just heat loss from running the supercharger outside of its design parameters.

That is the whole point of the calculation is to measure the actual forces required if we ran our FS gear at a sea Level and compare it with a silly line drawn on a chart.

Until that report of the Mosquito was posted, the data was not very good for calculating the power loss to compare. Once that report came up and I had the data, the rest was easy.

Notice the manifold pressure settings and speed from the measured results:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Speed known points:

+23.9lbs 354mph TAS x .869 = 307KTAS

q= V^2/295

q = 319.5

+25lbs 340mph TAS x .869 = 295KTAS
</div></BLOCKQUOTE>

All the best,

Crumpp

M_Gunz
05-01-2009, 11:03 PM
Yeah but the DRAG should not be more at lower speed for the same plane up at those speeds!
Heat loss in supercharger is DRAG now? Or just more power used and not the drag?

Sure down at the backside of the power curve but not at any 300 knots!
And those numbers are both top speeds. But you've already stated that there was more waste at +25
so the THP used for drag calculation should not include the losses.


I just think there's a problem with the labels used, makes things confusing at best with luck.

If drag at 307 is 3120 lbs then I would expect drag at 295 to be more like 3058 lbs = sqrt(295/307) x 3120.

Wurkeri
05-01-2009, 11:08 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JtD:
I called it simplifications, not mistakes. I still think that's ok. The mistake is to use the rather vague result of the simplified calculation for the precise statements Kettenhunde is trying to make. </div></BLOCKQUOTE>

Well, all his calculation proves is that he simply can't get correct results with his calculation; a simple graphical estimation gives much more accurate results as can be seen below:

http://img73.imageshack.us/img73/4369/jtdllines.jpg

Kettenhunde
05-02-2009, 12:44 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> a simple graphical estimation gives much more accurate results as can be seen below:
</div></BLOCKQUOTE>

http://forums.ubi.com/images/smilies/16x16_smiley-very-happy.gif

You keep referring too the “correct” PLANK but where is your math Wurkeri?

Facts are it is not correct and I will bet you already know why. Probably best not to have full disclosure in this case, huh?

You have made all kinds of claims which have proven to been untrue and are pretty short on actually presenting any of the math to back up your claim.

Of course we can move the lines at random to be where you need them to be to prove a point. Moving them where the math dictates has a different outcome.

I think this conversation is about done if all you can do is present graphs without proof.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Yeah but the DRAG should not be more at lower speed for the same plane up at those speeds!
</div></BLOCKQUOTE>

Sure it will if it takes more power to go the slower speed. These are measured points from a flight test in which FS gear was used at sea level. FS gear will produce more manifold pressure at a lower altitude but the airplane does not fly as fast. You can see though that it does not translate into more usable power.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Speed known points:

+23.9lbs 354mph TAS x .869 = 307KTAS =
MS Gear Performance at sea level </div></BLOCKQUOTE>

Less power at a faster speed means lower drag forces are required to achieve this in flight.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">+25lbs 340mph TAS x .869 = 295KTAS = FS Gear performance at sea level
</div></BLOCKQUOTE>

Higher power for less speed means our drag forces required must increase. In standard conditions our fluid is considered dry so the adiabatic law applies and no heat transfer can take place. Instead of being lost to the atmosphere, it translates into drag on the aircraft.

This allows us to measure the work being performed on the airplane. The engine is performing much more work at the higher manifold pressure for less speed when operating in FS gear at sea level.

We have our forces required and can determine rather nicely what our power loss is for running FS gear at sea level.

All the best,

Crumpp

JtD
05-02-2009, 12:57 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
You keep referring too the “correct” PLANK but where is your math Wurkeri? </div></BLOCKQUOTE>

It's the one I referred to and quoted in this topic. If you bother to read other people statements, you'll find it.

Kettenhunde
05-02-2009, 01:12 AM
I see where he makes the claim that because of the 14.7 to absolute his PLANK estimation is more accurate.

That seems to be the crux of the issue? Right?

Let me see the math please! Let's quit screwing around and get it resolved.

All the best,

Crumpp

Feathered_IV
05-02-2009, 01:55 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
Repetition does not make something truthful.
Crumpp </div></BLOCKQUOTE>

That perfectly sums up all these bullsh*t 12-pager circular arguments.

Kurfurst__
05-02-2009, 03:52 AM
Another typical Wurkeri show, LOL. http://forums.ubi.com/images/smilies/88.gif

Xiolablu3
05-02-2009, 04:33 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kurfurst__:
Another typical Wurkeri show, LOL. http://forums.ubi.com/images/smilies/88.gif </div></BLOCKQUOTE>

Actually I think people are learning stuff and JTD and Crummp are deabting something about which I have no idea. WOuld be a shame to lock it...it has some good info in the thread.

Wurkeri
05-02-2009, 04:39 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JtD:
It's the one I referred to and quoted in this topic. If you bother to read other people statements, you'll find it. </div></BLOCKQUOTE>

I don't know what is the deal here, calculation it self is very simple:

+23,9lbs corresponds total pressure of 38,6 lbs (14,7+23,9) and +25lbs corresponds 39,7 lbs total.

=&gt;38,6/39,7=0,9723

=&gt; 1950hp * 0,9723 = 1896hp

Another way to reach about same value is to use FTH values as described above

+18lbs 1600hp
+25lbs 1950hp

Pressure difference 7lbs and power difference 350hp so power increase per lbs is

350 / 7 = 50hp

The pressure difference between +18 lbs and +23,9lbs is 5,9lbs so at +23,9lbs (full throttle) the engine will do

1600 + 5,9*50 = 1895hp

or the other way

1950 - 1,1*50 = 1895hp

But as will be seen, the show will go on...

JtD
05-02-2009, 04:41 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
I see where he makes the claim that because of the 14.7 to absolute his PLANK estimation is more accurate.

That seems to be the crux of the issue? Right?

Let me see the math please! Let's quit screwing around and get it resolved. </div></BLOCKQUOTE>

1950*(23.9+14.7)/(25+14.7)=1896

Kurfurst__
05-02-2009, 06:04 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Xiolablu3:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kurfurst__:
Another typical Wurkeri show, LOL. http://forums.ubi.com/images/smilies/88.gif </div></BLOCKQUOTE>

Actually I think people are learning stuff and JTD and Crummp are deabting something about which I have no idea. Would be a shame to lock it...it has some good info in the thread. </div></BLOCKQUOTE>

I do hope that for some of us there is something to learn from it; but OTOH I am pretty sure that part is not an important consideration for some of the participants, who merely came to this board to bash some old 'enemies', re-fighting 'battles' of the past over and over again. I have seen it enough times.

Kettenhunde
05-02-2009, 09:38 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Another way to reach about same value is to use FTH values as described above
</div></BLOCKQUOTE>

You mean just read the engine chart and assume a linear relationship over different altitudes??

It does not work.

Engine performance charts only tell us very specific information that is applicable only to the terms listed on the chart.

http://img392.imageshack.us/img392/3708/enginepowercharts.jpg (http://img392.imageshack.us/my.php?image=enginepowercharts.jpg)



Your second method is a little better but does not have near the accuracy you are claiming it to have, Gripen.

While the relationship of power to manifold pressure is linear the slope is determined by rpm.

http://img392.imageshack.us/img392/599/rpmandslope.jpg (http://img392.imageshack.us/my.php?image=rpmandslope.jpg)

Your SWAG will put you in a very rough ballpark for a 1/1 slope. Unfortunately, there is no element of rpm to gauge your initial slope.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> I don't know what is the deal here, calculation it self is very simple:

+23,9lbs corresponds total pressure of 38,6 lbs (14,7+23,9) and +25lbs corresponds 39,7 lbs total.

=&gt;38,6/39,7=0,9723

=&gt; 1950hp * 0,9723 = 1896hp
</div></BLOCKQUOTE>


That is why I worked the PLANK/33000 estimate like I did. We don't know the slope and pressure is not "manifold pressure" but rather Brake Mean Effective Pressure (BMEP).

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Using PLANK/33,000 we can fold LANK/33,000 into a value of X and estimate our power at 23.9lbs

25X = 1950hp X = 78

23.9 (78) = 1864hp

2 engines = 2 x 1864 = 3728hp
</div></BLOCKQUOTE>

By lumping LANK into a value of X I was able to approximate the slope and since the manifold pressure realtionship is linear, we are only looking for the "change in" manifold pressure.

Length of stroke, Area of the piston, and K being the number of cylinders are all fixed by engine design. Our N being the power strokes or RPM/2 can change but in this case we hold it constant with the value adding our slope.

I was really surprised at how good of an agreement I got with the forces required calculations. Force required from known points of measured points is the most accurate method and does not give very good agreement with your estimate.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">First let's go from a known point on the 1st Gear supercharger power line.

Power:

+18lbs = 1540hp

1540hp x .8 x 2 = 2464THP

Speed:

+18 = 332mph TAS = 288.5ktas

q = 282.4

Drag at +18 288.5ktas:

Drag lbs = [2464THP) x 325] / 288.5 ktas = 2776lbs

CD = (2776lbs / 454sq ft) / 282.4 = .0217

Cdi = .318 (.167^2)/6.46x.8 = .0017

Di = .0017 x 454 x 319.5 = 246.4lbs

2776lbs - 246.4lbs = 2530lbs

Prp = 2530lbs x 288.5ktas / 325 = 2246thp

CL = (21430lbs / 454 sq ft)/282.4 = .167 for 288.5ktas +18lbs

Now to find our forces required by the 1st Gear to reach + 23.9lbs

Prp2 / 2246thp = (307KTAS / 288.5 KTAS)^3

Prp2 = 2706thp

Pri at +23.9lbs

Pri = (246.4lbs x 307ktas) / 325 = 232.8thp

Pri2/232.8thp = 288.5ktas/307ktas

Pri2 = (288.5/307)x232.8 = 219thp

Pr at 23.9lbs = 2706thp + 219thp = 2925thp

2925thp x 1.25 = 3656hp / 2 = 1828hp on the Merlin chart is our 23.9lbs mark.

Our ballpark using PLANK/33,000 was 1864hp so it gave pretty good agreement. </div></BLOCKQUOTE>

1864hp is an overestimate but it is much closer to the 1824hp as determined by Forces required.

That is a 2% error over the Forces Required calculations when we account for rpm slope versus a 4% error when we do not.

That is a 100% increase in error using a simple linear relationship assuming a 1/1 slope.

All the best,

Crumpp

tagert
05-02-2009, 10:01 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
Let me see the math please! Let's quit screwing around and get it resolved. </div></BLOCKQUOTE>
By the way..

Still waiting on that 'math' and/or 'rule'..

That you and yours says I calculated wrong and/or broke respectfully..

When applying the TME equation to measure the energy change of a plane during a ZOOM..

So..

As you yourself said..

Let me see the math/rule please!

Let's quit screwing around and get it resolved. http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

Kettenhunde
05-02-2009, 10:10 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Let me see the math/rule please!
</div></BLOCKQUOTE>

http://img7.imageshack.us/img7/5237/adiabaticlawinsubsonicf.jpg (http://img7.imageshack.us/my.php?image=adiabaticlawinsubsonicf.jpg)

tagert
05-02-2009, 10:12 AM
Pressure equations are neat and all..

But please explain what those have to do with the application of the TME equation to measure the change in energy of a plane?

If you can..

Kettenhunde
05-02-2009, 10:26 AM
Tagert,

I will respond to you this once. Do not screw it up or you will go right back to being ignored.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> In standard conditions our fluid is considered dry so the adiabatic law applies and no heat transfer can take place. Instead of being lost to the atmosphere, it translates into drag on the aircraft.

This allows us to measure the work being performed on the airplane. </div></BLOCKQUOTE>

http://forums.ubi.com/eve/foru...891050457#5891050457 (http://forums.ubi.com/eve/forums/a/tpc/f/23110283/m/1171014947?r=5891050457#5891050457)

tagert
05-02-2009, 10:29 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
Tagert,

I will respond to you this once. Do not screw it up or you will go right back to being ignored.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> In standard conditions our fluid is considered dry so the adiabatic law applies and no heat transfer can take place. Instead of being lost to the atmosphere, it translates into drag on the aircraft.

This allows us to measure the work being performed on the airplane. </div></BLOCKQUOTE>

http://forums.ubi.com/eve/foru...891050457#5891050457 (http://forums.ubi.com/eve/forums/a/tpc/f/23110283/m/1171014947?r=5891050457#5891050457) </div></BLOCKQUOTE>

So your saying the TME equation can NOT be used to measure the change in energy of a plane?

Well..

You should get on the phone and contact NASA and every other air force in the world and let them know that the energy height and specific energy equations (that are nothing more than the TME equation divided by the weight of the plane) are in error..

Because those two equations are based on the notion that the TME equation CAN be used to measure the change of energy of a plane.

As for your quote..

Where did it come from?

Reason I ask is it actully supports what I have been saying all along (see the yellow part), i.e.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">In standard conditions our fluid is considered dry so the adiabatic law applies and no heat transfer can take place. Instead of being lost to the atmosphere, <span class="ev_code_yellow">it translates into drag on the aircraft</span> </div></BLOCKQUOTE>

So could you provide me the link and or the book you got it from?

In that I would like to use it in future posts about the application of the TME equation to measure the change in energy of a plane.

SAVVY?

Kettenhunde
05-02-2009, 10:43 AM
Your issue was not treating the aircraft as a closed system in an adiabatic fluid.

I tried to explain that to you and how it was violating the formulation rules to determine aircraft performance.

I tried to help you and was met with a barrage of insults for my efforts.

As you know this to be true but insist on altering your reality, you can go back to being ignored.

All the best,

Crumpp

tagert
05-02-2009, 10:46 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
Your issue was not treating the aircraft as a closed system in an adiabatic fluid. </div></BLOCKQUOTE>
Neither does the Energy Height or Specific Energy equations

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
I tried to explain that to you and how it was violating the formulation rules to determine aircraft performance. </div></BLOCKQUOTE>
Well as noted above..

You better get on the phone ASAP and tell NASA and the like they are doing it all wrong!

In that the Energy Height and Specific Energy are not treating the aircraft as a closed system..

If they were treating the aircraft as a closed system there would be no change in the TME equation, thus no change in the Energy Height equations, thus no change in the Specified Energy equation and thus no way to calculate the performance.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
I tried to help you and was met with a barrage of insults for my efforts. </div></BLOCKQUOTE>
Well..

You tried..

But you failed..

Now I am the one trying to help you here!!

Take pause here..

Count to 10..

And than note that if you consider the plane as a close system there would be no change..

Thus no way to calculate performance..

Let that settle in for a moment before you reply..

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
As you know this to be true but insist on altering your reality, you can go back to being ignored. </div></BLOCKQUOTE>
Only true in your world..

The world where you have a very hard time admitting you made a big mistake

Insuber
05-02-2009, 10:49 AM
Hey pilots keep it cool it's a game, isn'it ? http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

Kettenhunde
05-02-2009, 11:03 AM
Repost so it does not get buried:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Wurkeri says:
Another way to reach about same value is to use FTH values as described above
</div></BLOCKQUOTE>

You mean just read the engine chart and assume a linear relationship over different altitudes??

It does not work.

Engine performance charts only tell us very specific information that is applicable only to the terms listed on the chart.

http://img392.imageshack.us/img392/3708/enginepowercharts.jpg (http://img392.imageshack.us/my.php?image=enginepowercharts.jpg)



Your second method is a little better but does not have near the accuracy you are claiming it to have, Gripen.

While the relationship of power to manifold pressure is linear the slope is determined by rpm.

http://img392.imageshack.us/img392/599/rpmandslope.jpg (http://img392.imageshack.us/my.php?image=rpmandslope.jpg)

Your SWAG will put you in a very rough ballpark for a 1/1 slope. Unfortunately, there is no element of rpm to gauge your initial slope.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Wurkeri says:
I don't know what is the deal here, calculation it self is very simple:

+23,9lbs corresponds total pressure of 38,6 lbs (14,7+23,9) and +25lbs corresponds 39,7 lbs total.

=&gt;38,6/39,7=0,9723

=&gt; 1950hp * 0,9723 = 1896hp
</div></BLOCKQUOTE>


That is why I worked the PLANK/33000 estimate like I did. We don't know the slope and pressure is not "manifold pressure" but rather Brake Mean Effective Pressure (BMEP).

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Crumpp says:
Using PLANK/33,000 we can fold LANK/33,000 into a value of X and estimate our power at 23.9lbs

25X = 1950hp X = 78

23.9 (78) = 1864hp

2 engines = 2 x 1864 = 3728hp
</div></BLOCKQUOTE>

By lumping LANK into a value of X I was able to approximate the slope and since the manifold pressure realtionship is linear, we are only looking for the "change in" manifold pressure.

Length of stroke, Area of the piston, and K being the number of cylinders are all fixed by engine design. Our N being the power strokes or RPM/2 can change but in this case we hold it constant with the value adding our slope.

I was really surprised at how good of an agreement I got with the forces required calculations. Force required from known points of measured points is the most accurate method and does not give very good agreement with your estimate.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Crumpp says:
First let's go from a known point on the 1st Gear supercharger power line.

Power:

+18lbs = 1540hp

1540hp x .8 x 2 = 2464THP

Speed:

+18 = 332mph TAS = 288.5ktas

q = 282.4

Drag at +18 288.5ktas:

Drag lbs = [2464THP) x 325] / 288.5 ktas = 2776lbs

CD = (2776lbs / 454sq ft) / 282.4 = .0217

Cdi = .318 (.167^2)/6.46x.8 = .0017

Di = .0017 x 454 x 319.5 = 246.4lbs

2776lbs - 246.4lbs = 2530lbs

Prp = 2530lbs x 288.5ktas / 325 = 2246thp

CL = (21430lbs / 454 sq ft)/282.4 = .167 for 288.5ktas +18lbs

Now to find our forces required by the 1st Gear to reach + 23.9lbs

Prp2 / 2246thp = (307KTAS / 288.5 KTAS)^3

Prp2 = 2706thp

Pri at +23.9lbs

Pri = (246.4lbs x 307ktas) / 325 = 232.8thp

Pri2/232.8thp = 288.5ktas/307ktas

Pri2 = (288.5/307)x232.8 = 219thp

Pr at 23.9lbs = 2706thp + 219thp = 2925thp

2925thp x 1.25 = 3656hp / 2 = 1828hp on the Merlin chart is our 23.9lbs mark.

Our ballpark using PLANK/33,000 was 1864hp so it gave pretty good agreement. </div></BLOCKQUOTE>

1864hp is an overestimate but it is much closer to the 1824hp as determined by Forces required.

That is a 2% error over the Forces Required calculations when we account for rpm slope versus a 4% error when we do not.

That is a 100% increase in error using a simple linear relationship assuming a 1/1 slope.

All the best,

Crumpp

tagert
05-02-2009, 11:06 AM
Repost so it does not get buried:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by tagert:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
Let me see the math please! Let's quit screwing around and get it resolved. </div></BLOCKQUOTE>
By the way..

Still waiting on that 'math' and/or 'rule'..

That you and yours says I calculated wrong and/or broke respectfully..

When applying the TME equation to measure the energy change of a plane during a ZOOM..

So..

As you yourself said..

Let me see the math/rule please!

Let's quit screwing around and get it resolved. http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif </div></BLOCKQUOTE>

deepo_HP
05-02-2009, 05:32 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by tagert:
Let me see the math/rule please! </div></BLOCKQUOTE>since you asked so often already:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by tagert:
the TME equation divided by the weight of the plane </div></BLOCKQUOTE>you can't divide an equation! you want to use the quantity described by&lt; the equation.
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by tagert:
the TME equation CAN be used to measure the change of energy of a plane. </div></BLOCKQUOTE>you can't use an equation to measure a quantity, and less the change of a quantity. you want to use sensors to measure. to calculate the change of a scalar, you want to measure over time at least twice.

not that i want to make fun here, but perhaps it prevents further<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by tagert:
Repost so it does not get buried: </div></BLOCKQUOTE>see, 'reposting' makes sense, if there is new or different content. 'reposting' of repeatedly asking the same and quoting the same lines, is in my opinion neither on topic nor is any possible result to be expected. i also doubt, that you would like to have your rhetorical questions being answered, but rather want them open to be repeated more often...
an unanswered question will make the reader probably think about your point. asking the same many times surely won't!


the tone in this forum is sometimes quite sublevel, and perhaps you have been provoked. however, that doesn't bother me as an interested reader. what bothers me more is, that i lose topic every time, i have to scroll over your lengthy posts of repetitive phrases.

i am sorry for having been off-topic and lengthy here. won't happen anymore.

M_Gunz
05-02-2009, 06:19 PM
Engine power is in units of energy per second. Multiply by the number of seconds run and you have energy quantity.
And here's the best part... the result has NO time in it. None.
No excuse needed there is no time in energy as seems to be at least partly understood.
The motor adds energy.
You can account for engine input and you end up with energy only. It's not verboten to work with time, only to end
up with time-units. That's not a problem since the end value is energy which has no time.

It's there, it's part of the result, it counts.
When one motor runs longer than the other and your weights are normalized and so is power, the one that ran longer
added more energy to its end result. If you can't use that number because you can't measure the drag then guess what,
your test is inaccurate in itself and ignoring any of that doesn't make it good.

You can compare two tests of equal length and cancel engine input of one to the other because they are equal length.
Go ask NASA.

Insuber
05-02-2009, 06:29 PM
I have tried extensively online the Tempest tonight and found it deadly as an energy fighter, with the 4 hispanos grinding and stripping big chunks out of adversaries. It is a very stable platform and retains a good agility at high speeds. I broke it once, in a dive, at 740 IAS, quite low compared to the 900 kmh or Vne in game. No problems with FWs and 109s, the only real adversary was the Do335. At medium heigh,
IMHO it is one or the top 5 planes of this sim.

Regards,
Insuber

tagert
05-02-2009, 06:58 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by deepo_HP:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by tagert:
Let me see the math/rule please! </div></BLOCKQUOTE>
since you asked so often already: </div></BLOCKQUOTE>
Finally..

Someone willing to state the math/rule I am told I broke!

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by deepo_HP:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by tagert:
the TME equation divided by the weight of the plane </div></BLOCKQUOTE>you can't divide an equation! you want to use the quantity described by&lt; the equation. </div></BLOCKQUOTE>
Ah..

I see your error here..

Allow me..

It is not 'I' who said you divide the TME equation by the weight to obtain the Energy Height equation..

It is the likes of NASA and air forces around the world that divide the TME equation to obtain the Energy Height equation..

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by deepo_HP:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by tagert:
the TME equation CAN be used to measure the change of energy of a plane. </div></BLOCKQUOTE>
you can't use an equation to measure a quantity, and less the change of a quantity. you want to use sensors to measure. to calculate the change of a scalar, you want to measure over time at least twice. </div></BLOCKQUOTE>
Ah..

I see your error here..

Allow me..

It is not 'I' who said you can use the TME equation to measure the change in energy of a plane..

It is the likes of NASA and air forces around the world that say you can..

In that the Energy Height equation is nothing more than the TME equation divided by the weight..

So if you cant use the TME equation to measure the change in energy..

Than you couldn't use the Energy Height equation to measure the change in energy height..

Than you couldn't use the Specific Power equation to measure the rate of change in energy height..

HINT..

The reason they divide by the weight is to 'normalize' the result..

Which allows you to make direct comparisons between planes..

In English..

Measure and compare the performance of different planes..

As for wanting to use a sensor to measure..

They do!

The sensor is an altitude gauge (corrected) and a velocity gauge (corrected and converted to tas)..

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by deepo_HP:
not that i want to make fun here, </div></BLOCKQUOTE>
Trust me thus far you haven't!

Unless you consider making fun of yourself making fun?

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by deepo_HP:
but perhaps it prevents further
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by tagert:
Repost so it does not get buried: </div></BLOCKQUOTE>
see, 'reposting' makes sense, if there is new or different content. 'reposting' of repeatedly asking the same and quoting the same lines, is in my opinion neither on topic nor is any possible result to be expected. </div></BLOCKQUOTE>
Ok sorry..

I just figured if it was ok for Crump to do it..

It would be ok for me to do it..

Sorry I didn't realize the double standard was in play.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by deepo_HP:
i also doubt, that you would like to have your rhetorical questions being answered, but rather want them open to be repeated more often...
an unanswered question will make the reader probably think about your point. asking the same many times surely won't! </div></BLOCKQUOTE>
So is that your way of saying you promise not to reply anymore?

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by deepo_HP:
the tone in this forum is sometimes quite sublevel, and perhaps you have been provoked. however, that doesn't bother me as an interested reader. what bothers me more is, that i lose topic every time, i have to scroll over your lengthy posts of repetitive phrases. </div></BLOCKQUOTE>
Well than I give you permission to skip over my posts..

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by deepo_HP:
i am sorry for having been off-topic and lengthy here. won't happen anymore. </div></BLOCKQUOTE>
Promise?

For you own sake..

That is to save face..

I hope you don't!!

I really don't want to have to point out your mistakes more than once!

So in summary..

You didn't post the rule or math I an told I broke..

As a mater of FACT you showed how little you know about the subject..

In that your saying NASA is wrong for dividing by the weight to obtain the Energy Height equation from the TME equation.

Now, if you have an issue with that..

Can I suggest you take it up with NASA?

In that I don't make the rules they set up..

I only abide by them!

SAVVY?

Swivet
05-03-2009, 12:50 AM
There's a reason it's underrated

WTE_Ibis
05-03-2009, 02:30 AM
aah, Tagert at his annoying best, isn't he a sweetie, god I missed you while you were on holidays.
http://forums.ubi.com/images/smilies/compsmash.gif



.

Bremspropeller
05-03-2009, 06:55 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">So if you cant use the TME equation to measure the change in energy.. </div></BLOCKQUOTE>

Nope.

No change of fuel taken into account.
Thus, your TME equation is flawed.

tagert
05-03-2009, 07:12 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">So if you cant use the TME equation to measure the change in energy.. </div></BLOCKQUOTE>

Nope.

No change of fuel taken into account.
Thus, your TME equation is flawed. </div></BLOCKQUOTE>
That is your opinion..

Thus your wecome to it..

But know this..

The Energy Height equation is nothing more than the TME equation divided by the weight of the plane..

Therefore if the use of the TME equation is 'flawed'..

Than the use of the Energy Height equation is 'flawed'..

As you know the likes of NASA and air forces around the world use the Energy Height equation as a way to measure the performance of planes..

And they don't take into account the energy added by the fuel..

So if you have an issue with that..

And think you know better than them..

May I sugest you take it up with the likes of NASA?

In that I don't make the rules..

I just abide by them..

SAVVY?

tagert
05-03-2009, 07:23 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by WTE_Ibis:
aah, Tagert at his annoying best, </div></BLOCKQUOTE>
Well..

The FACTS only annoy those who are in conflit with them.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by WTE_Ibis:
isn't he a sweetie, god I missed you while you were on holidays. http://forums.ubi.com/images/smilies/compsmash.gif </div></BLOCKQUOTE>
I missed you too Ibis!

Now with that out of the way..

Do you care to weight in on the current topic?

Be interesting to know if you too think the likes of NASA are wrong.

tagert
05-03-2009, 07:35 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Swivet:
There's a reason it's underrated </div></BLOCKQUOTE>
Really?

I am all ears!

Why is it underrated?

For the same reasons the P38 is underrated? http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

tagert
05-03-2009, 07:54 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
Engine power is in units of energy per second. Multiply by the number of seconds run and you have energy quantity.
And here's the best part... the result has NO time in it. None.
No excuse needed there is no time in energy as seems to be at least partly understood. </div></BLOCKQUOTE>
Bravo Gunz!!

I think your finally getting it!

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
The motor adds energy. </div></BLOCKQUOTE>
Yes.. In conjunction with the fuel.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
You can account for engine input and you end up with energy only. It's not verboten to work with time, only to end
up with time-units. That's not a problem since the end value is energy which has no time.
It's there, it's part of the result, it counts. </div></BLOCKQUOTE>
Finally!

I can not tell you how proud I am of you!

You are making real progress here!

Keep it up!

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
When one motor runs longer than the other and your weights are normalized and so is power, the one that ran longer
added more energy to its end result. If you can't use that number because you can't measure the drag then guess what,
your test is inaccurate in itself and ignoring any of that doesn't make it good.

You can compare two tests of equal length and cancel engine input of one to the other because they are equal length.
Go ask NASA. </div></BLOCKQUOTE>
This notion of how long (read time) the engine runs or the plane flys is your only mistake left!

Allow me..

Lets take a look at the Specific Power (Ps) equation (read derivative of the Energy Height (Es) equation) and how it is used..

One method to calculate Ps is to do level accelerations..

Where the plane flys at max power 'until' it reaches its max velocity (read acc = 0) at that altitude..

From such a run the max Ps can be found..

Now..

Try and apply your 'time limit' theory here..

You do realize that each plane is going to take a different amount of time to reach it's max velocity..

Right?

Yet you want to limit how long the plane can fly (read how long the engines run)?

If you picked some arbitrary 'time limit'..

You stand the chance of stopping the test before some of the planes reach thier max Ps..

Is that fair?

Don't you wish we had an equation that was NOT depended on time?

Guess what..

WE DO!

The TME equation!!

So do you now see why you shouldn't apply any 'time limits' to such a test?

If not..

Stick around..

If you keep reading, I know this too will become clear to you with 'time'

Pun intended! http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

JtD
05-03-2009, 08:40 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:

That is why I worked the PLANK/33000 estimate like I did. We don't know the slope and pressure is not "manifold pressure" but rather Brake Mean Effective Pressure (BMEP). </div></BLOCKQUOTE>

Please make your approximation again for a suction engine with an manifold pressure of 0. Since it will result in 0 power, you may finally spot your error.

All the numbers you post do not change the fact that your basic approach to the solution is wrong. It just becomes harder to spot. It's not insignificant, it's a reduction of power of 86 hp instead of 54hp, so it's a 59% error. So please do it right:

1950*(23.9+14.7)/(25+14.7)=1896

Bremspropeller
05-03-2009, 08:59 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> As you know the likes of NASA and air forces around the world use the Energy Height equation as a way to measure the performance of planes.. </div></BLOCKQUOTE>

NASA does not exclude the rather major fact that their rockets DO burn fuel at astronomic rates.

I didn't say THE tme-equations is flawed.
I said YOUR tme-euation is flawed.

People are discussing airplanes here, not point-masses in vacuum.

Therefore the approach Ekin + Epot = E is a bit simplistic when not considering ALL factors, but only some.

Kettenhunde
05-03-2009, 09:27 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">1950*(23.9+14.7)/(25+14.7)=1896 </div></BLOCKQUOTE>


Force required from known points of measured data is the most accurate method and does not give very good agreement with your estimate.

It is clear to me that no matter what you are presented with, your mind is not going to be changed.

Good luck on your journey.

If anyone would like a copy of the report I posted from the AIAA library on estimating piston engine performance, just PM me.

http://www.aiaa.org/index.cfm

To help Feathered get another page, LOL!

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Repost so it does not get buried:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Wurkeri says:
Another way to reach about same value is to use FTH values as described above
</div></BLOCKQUOTE>

You mean just read the engine chart and assume a linear relationship over different altitudes??

It does not work.

Engine performance charts only tell us very specific information that is applicable only to the terms listed on the chart.

http://img392.imageshack.us/img392/3708/enginepowercharts.jpg (http://img392.imageshack.us/my.php?image=enginepowercharts.jpg)



Your second method is a little better but does not have near the accuracy you are claiming it to have, Gripen.

While the relationship of power to manifold pressure is linear the slope is determined by rpm.

http://img392.imageshack.us/img392/599/rpmandslope.jpg (http://img392.imageshack.us/my.php?image=rpmandslope.jpg)

Your SWAG will put you in a very rough ballpark for a 1/1 slope. Unfortunately, there is no element of rpm to gauge your initial slope.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Wurkeri says:
I don't know what is the deal here, calculation it self is very simple:

+23,9lbs corresponds total pressure of 38,6 lbs (14,7+23,9) and +25lbs corresponds 39,7 lbs total.

=&gt;38,6/39,7=0,9723

=&gt; 1950hp * 0,9723 = 1896hp
</div></BLOCKQUOTE>


That is why I worked the PLANK/33000 estimate like I did. We don't know the slope and pressure is not "manifold pressure" but rather Brake Mean Effective Pressure (BMEP).

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Crumpp says:
Using PLANK/33,000 we can fold LANK/33,000 into a value of X and estimate our power at 23.9lbs

25X = 1950hp X = 78

23.9 (78) = 1864hp

2 engines = 2 x 1864 = 3728hp
</div></BLOCKQUOTE>

By lumping LANK into a value of X I was able to approximate the slope and since the manifold pressure realtionship is linear, we are only looking for the "change in" manifold pressure.

Length of stroke, Area of the piston, and K being the number of cylinders are all fixed by engine design. Our N being the power strokes or RPM/2 can change but in this case we hold it constant with the value adding our slope.

I was really surprised at how good of an agreement I got with the forces required calculations. Force required from known points of measured points is the most accurate method and does not give very good agreement with your estimate.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Crumpp says:
First let's go from a known point on the 1st Gear supercharger power line.

Power:

+18lbs = 1540hp

1540hp x .8 x 2 = 2464THP

Speed:

+18 = 332mph TAS = 288.5ktas

q = 282.4

Drag at +18 288.5ktas:

Drag lbs = [2464THP) x 325] / 288.5 ktas = 2776lbs

CD = (2776lbs / 454sq ft) / 282.4 = .0217

Cdi = .318 (.167^2)/6.46x.8 = .0017

Di = .0017 x 454 x 319.5 = 246.4lbs

2776lbs - 246.4lbs = 2530lbs

Prp = 2530lbs x 288.5ktas / 325 = 2246thp

CL = (21430lbs / 454 sq ft)/282.4 = .167 for 288.5ktas +18lbs

Now to find our forces required by the 1st Gear to reach + 23.9lbs

Prp2 / 2246thp = (307KTAS / 288.5 KTAS)^3

Prp2 = 2706thp

Pri at +23.9lbs

Pri = (246.4lbs x 307ktas) / 325 = 232.8thp

Pri2/232.8thp = 288.5ktas/307ktas

Pri2 = (288.5/307)x232.8 = 219thp

Pr at 23.9lbs = 2706thp + 219thp = 2925thp

2925thp x 1.25 = 3656hp / 2 = 1828hp on the Merlin chart is our 23.9lbs mark.

Our ballpark using PLANK/33,000 was 1864hp so it gave pretty good agreement. </div></BLOCKQUOTE>

1864hp is an overestimate but it is much closer to the 1824hp as determined by Forces required.

That is a 2% error over the Forces Required calculations when we account for rpm slope versus a 4% error when we do not.

That is a 100% increase in error using a simple linear relationship assuming a 1/1 slope.

All the best,

Crumpp </div></BLOCKQUOTE>

Feathered_IV
05-03-2009, 09:32 AM
Almost twelve pages. Wipe your chins and adjust your helmets lads. You're nearly there. http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

JtD
05-03-2009, 09:57 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:

Force required from known points of measured data is the most accurate method and does not give very good agreement with your estimate. </div></BLOCKQUOTE>

It does. I cut out the rest because you've posted it half a dozen times already. Doesn't make it right, though.

1864hp is a wrong plank estimate.

1828hp is a very rough drag based estimate. I've shown you how little it takes to end up at 1900hp (and claim "a very good agreement!").

It's 1896hp plank, Kettenhunde. Do the math for an unsupercharged engine (0 lbs boost). Or have an engineer do it for you. Then fix your method.

Swivet
05-03-2009, 10:36 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by tagert:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Swivet:
There's a reason it's underrated </div></BLOCKQUOTE>
Really?

I am all ears!

Why is it underrated?

For the same reasons the P38 is underrated? http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif </div></BLOCKQUOTE>



If you've flown it then you know right?.........right.

M_Gunz
05-03-2009, 10:53 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by tagert:
Try and apply your 'time limit' theory here..

You do realize that each plane is going to take a different amount of time to reach it's max velocity..

Right?

Yet you want to limit how long the plane can fly (read how long the engines run)?

If you picked some arbitrary 'time limit'..

You stand the chance of stopping the test before some of the planes reach thier max Ps..

Is that fair?

Don't you wish we had an equation that was NOT depended on time?

Guess what..

WE DO!

The TME equation!!

So do you now see why you shouldn't apply any 'time limits' to such a test?

If not..

Stick around..

If you keep reading, I know this too will become clear to you with 'time'

Pun intended! http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif </div></BLOCKQUOTE>

There is such a use but that is not what you do when you compare the final heights of the different planes directly
as energy retention.

Can you predict how the planes will perform relative to each other in anything but the test conditions just based on
the changes in height from start to end of the test? Hmmmm? Do your results have a non-trivial meaning?

tagert
05-03-2009, 10:58 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
There is such a use but that is not what you do when you compare the final heights of the different planes directly
as energy retention. </div></BLOCKQUOTE>
True..

My ZOOM testing is a different application of the TME equation..

But as I have shown here..

The use of the TME equation to measure the change in energy is valid..

In that the likes of NASA and air forces around the world use the TME equation to measure the change in energy..

The only reason they divide by the weight (read normalize) is so they can compare the change between two different planes, or the same plane with a different configuration.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
Can you predict how the planes will perform relative to each other in anything but the test conditions just based on the changes in height from start to end of the test? </div></BLOCKQUOTE>
Yes!

The ZOOM climb was a WWII way of getting a 'feel' for the performance of the plane..

The purpose of my ZOOM testing was to see how well the in-game planes matched those WWII descriptions of a good ZOOMING plane..

Is it the best way?

That is debatable..

But it is a way..

A way that better men than you and I found valid to do back in WWII..

Thus if you have a problem with it..

You have a problem with them not I..

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
Hmmmm? Do your results have a non-trivial meaning? </div></BLOCKQUOTE>
I think so..

And so did the test pilots/engineers of WWII who did ZOOM testing..

Especially in light of the FACT that I have shown it valid to use the TME equation to measure the energy change..

Something you and yours initially said was not possible..

As a mater of FACT Crummp is still saying that..

Well he was until I pointed it out to him that it is wrong to say the plane has to be treated as a closed system..

In that if you did that, there would be no change in the total energy..

Thus the Energy Height (Es) and Specific Power (Ps) equations would not change either..

It is a subtle point that he has not come to grips with yet..

But I have high hopes for him that one day he will realize the error in his statement.

tagert
05-03-2009, 11:13 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Swivet:
If you've flown it then you know right?.........right. </div></BLOCKQUOTE>
I have flown it and the 38..

I am just not sure what you mean by underrated?

As in it is thought of as an easy kill?

If so than I agree..

In that a lot of peeps don't give the 38 the respect it deserves online..

Which is a good thing for the 38 pilot..

In that the newb 109 pilot will see a 38, think it is an easy 200points, slide in and if it is I he slid into, he will soon find my 38 on his six and colorful tracers passing by his canopy and the lovely sound of 20mm knocking on his back door! http://forums.ubi.com/images/smilies/16x16_smiley-very-happy.gif

tagert
05-03-2009, 11:14 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> As you know the likes of NASA and air forces around the world use the Energy Height equation as a way to measure the performance of planes.. </div></BLOCKQUOTE>

NASA does not exclude the rather major fact that their rockets DO burn fuel at astronomic rates. </div></BLOCKQUOTE>
Just to be crystal..

I never said NASA is not interested in how much fuel it will take for a rocket to fly to a certain height..

But that is a different topic all together..

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
I didn't say THE tme-equations is flawed.
I said YOUR tme-equation is flawed. </div></BLOCKQUOTE>
Ah..

I see your mistake here..

Allow me..

I don't have any personal TME equation..

I use the same TME equation that the likes of NASA and air forces around the world use..

The only difference is I normalize it by the magnitude of the mass of the plane and the Energy Height equation normalizes it by the weight of the plane..

Now before you say anything know this..

You don't have to normalize it!

In both cases the TME equations measure the 'change in energy'

The only reason you normalize it is so you can compare the results of two different planes or the same plane with a different configuration.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
People are discussing airplanes here, not point-masses in vacuum. </div></BLOCKQUOTE>
Ah..

I see your mistake here..

Allow me..

You have me confused with Crummp..

He was the one that said energy has to remain constant (read no change in energy)

Not I!

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
Therefore the approach Ekin + Epot = E is a bit simplistic when not considering ALL factors, but only some. </div></BLOCKQUOTE>
Ah..

I see your mistake here..

Allow me..

You think the likes of NASA and air forces around the world are wrong whne they use the Energy Height equation?

In that it does NOT..

How did you say it?

"consider 'ALL' the factors"

You have the same problem Gunz is having..

He keeps trying to make 'time' and input..

When 'time' is actually a result you can get from the test..

Not an input or limit imposed on the test.

SAVVY?

Bremspropeller
05-03-2009, 12:05 PM
I'm not mistaken, you are.

Go and ask NASA about E-conservation, you might be surprised big time. http://forums.ubi.com/images/smilies/16x16_smiley-very-happy.gif

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">But that is a different topic all together.. </div></BLOCKQUOTE>

It ain't.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> The only difference is I normalize it by the magnitude of the mass of the plane and the Energy Height equation normalizes it by the weight of the plane.. </div></BLOCKQUOTE>

Which is wrong as you don't take lift and thus drag into account.
Where is your thrust-figure?

Do you consider fuel as a form of energy?
Because that's what it is.


So much for comparing aircraft, not point-masses.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">The only reason you normalize it is so you can compare the results of two different planes or the same plane with a different configuration. </div></BLOCKQUOTE>

You can't for reasons stated above.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Ah..

I see your mistake here..

Allow me..

You think the likes of NASA and air forces around the world are wrong whne they use the Energy Height equation? </div></BLOCKQUOTE>

No, I'm just stating you're having trouble using the equation without using factors that impact performance.
NASA and numerous air-forces (btw: who told you that BS?) are a bit more sophisticated in their approaches than you claim to be, armchair aero-engineer http://forums.ubi.com/groupee_common/emoticons/icon_rolleyes.gif

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">You have the same problem Gunz is having.. </div></BLOCKQUOTE>

Really?
Who's ever repeating his lil record?
It's you, right?

You'd better go back "testing" and drawing fancy graphs whereas leaving the talk to people that do - remotely - know what they're talking about.

Hint: that does not include you http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

Kettenhunde
05-03-2009, 12:05 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
1950*(23.9+14.7)/(25+14.7)=1896 </div></BLOCKQUOTE>

JtD,

Do you understand it is not manifold pressure that even goes into the formula?

It is BMEP!

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Brake Mean Effective Pressure (BMEP) is another very effective yardstick for comparing the performance of one engine to another, and for evaluating the reasonableness of performance claims or requirements.

</div></BLOCKQUOTE>

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> BMEP = 150.8 x TORQUE (lb-ft) / DISPLACEMENT (ci)

</div></BLOCKQUOTE>

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">This tool is extremely handy to evaluate the performance which is claimed for any particular engine. For example, the 200 HP IO-360 (360 CID) and 300 HP IO-540 (540 CID) Lycomings make their rated power at 2700 RPM. At that RPM, the rated power requires 389 lb-ft and 584 lb-ft of torque respectively. (If you don't understand that calculation, CLICK HERE)

From those torque values, it is easy to see (from Equation 8 above) that both engines operate at a BMEP of about 163 PSI. (1.08 lb-ft of torque per cubic inch) at peak power. The BMEP at peak torque is slightly greater.

For a long-life, naturally-aspirated, gasoline-fueled, two-valve-per-cylinder, pushrod engine, a BMEP over 200 PSI is difficult to achieve and requires a serious development program and very specialized components.

</div></BLOCKQUOTE>

http://www.epi-eng.com/piston_...rmance_yardstick.htm (http://www.epi-eng.com/piston_engine_technology/bmep_performance_yardstick.htm)

That has nothing to do with manifold pressure and is not even close in terms of absolute value. BMEP is theoretical pressure measured at the crankshaft with a special instrument. It is much higher than manifold pressure in fact.

On my airplanes Lycoming O-360 A1A, when the manifold pressure is 21inHG, the BMEP is ~160(+)!

So how you can look at the basic formula for engine power:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> POWER is CALCULATED from torque and RPM, by the following equation:

HP = Torque x RPM ÷ 5252

</div></BLOCKQUOTE>

How you can claim to be precisely accurate without considering the RPM/slope of the line?

Do understand this and are just playing, Ubizoo theater?

Facts are the most accurate gauge we can do is calculations from know points of performance using the forces required. That has been done and often repeated in this thread.

That gauge does not give very good agreement with estimating power off the linear relationship of manifold pressure without a defined slope to that line. That is a fact!

I was really surprised at the agreement I got off the plank formula.

http://img206.imageshack.us/img206/5392/enginepower.jpg (http://img206.imageshack.us/my.php?image=enginepower.jpg)

http://img206.imageshack.us/img206/599/rpmandslope.jpg (http://img206.imageshack.us/my.php?image=rpmandslope.jpg)


All the best,

Crumpp

JtD
05-03-2009, 12:37 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:

Do you understand it is not manifold pressure that even goes into the formula? </div></BLOCKQUOTE>

That's something I know.

However, _you_ chose to use manifold pressure for a power estimate. Which can be done, as a linear relationship between manifold pressure and mean effective pressure can be approximated for the small range we use it at and for the accuracy we seek. Now if you come back telling me that manifold pressure should not be used, then I wonder why _you_ chose to do so in the first place!

You basic error remains, though. You omitted 1 bar pressure, meaning a suction engine in your calculation runs on vacuum and produces no power whatsoever. Likewise, applying the calculation for supercharged engines with just 1.5-2 bar boost will give wrong results. So, the correct version of your calculation remains:

1950*(23.9+14.7)/(25+14.7)=1896

Or you use Wurkeris second approach where he estimates "the slope" from two datapoints we have and gets to 1895hp.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Facts are the most accurate gauage we can do is calculations from know points of performance using the forces required. That has been done and often repeated in this thread. </div></BLOCKQUOTE>

There is more uncertainty to your drag based calculation than to the plank based calculation. You've assumed constants that just aren't there, and small changes have a huge effect! So I very much disagree with your opinion that it is the better way - unless you're using a complex calculation that goes far beyond the reasonable effort for a discussion in an internet game forum.

Kettenhunde
05-03-2009, 01:17 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Wurkeris second approach where he estimates "the slope" from two datapoints we have and gets to 1895hp.
</div></BLOCKQUOTE>

There is not two data points. There is ONE known power point and TWO known manifold pressure points being used to estimate power at an UNKNOWN power point.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">1950*(23.9+14.7)/(25+14.7)=1896 </div></BLOCKQUOTE>

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> There is more uncertainty to your drag based calculation than to the plank based calculation. </div></BLOCKQUOTE>

Well I certainly think using measured points of performance and determine the forces required to achieve that performance is more accurate than a power estimate based on half a relationship without the correct values of BMEP.

We have good flight tested data gathered under known conditions to calculate forces required for both points in question.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Speed known points:

+23.9lbs 354mph TAS x .869 = 307KTAS

q= V^2/295

q = 319.5

+25lbs 340mph TAS x .869 = 295KTAS

- This is our most important known as it is a known velocity and power point in the 2nd Gear. From here we can extrapolate performance to anywhere in the aircrafts envelope and use that to compare with our forces required at this point.
</div></BLOCKQUOTE>


All the best,

Crumpp

Kettenhunde
05-03-2009, 01:26 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">However, _you_ chose to use manifold pressure for a power estimate </div></BLOCKQUOTE>


<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Crumpp says:
I was really surprised at the agreement I got off the plank formula. </div></BLOCKQUOTE>

tagert
05-03-2009, 01:31 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
I'm not mistaken, you are. </div></BLOCKQUOTE>
I beg to differ

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
Go and ask NASA about E-conservation, you might be surprised big time. http://forums.ubi.com/images/smilies/16x16_smiley-very-happy.gif </div></BLOCKQUOTE>
What part of the TME equation measuring the change in energy are you saying is not valid?

Please post it here for all to see..

Than I can help you out

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> The only difference is I normalize it by the magnitude of the mass of the plane and the Energy Height equation normalizes it by the weight of the plane.. </div></BLOCKQUOTE>
Which is wrong as you don't take lift and thus drag into account.
Where is your thrust-figure? </div></BLOCKQUOTE>
Ah..

I see your mistake here..

Allow me..

It is true that the I don't have to take lift or drag into account..

But know this..

Neither does the Energy Height (Es) equation!

You know the Es equation used by the likes of NASA and air forces around the world to measure the change in energy of a plane in flight..

So your issue is not with me..

It is with the likes of NASA..

I don't make the rules..

I just abide by them..

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
Do you consider fuel as a form of energy?
Because that's what it is. </div></BLOCKQUOTE>
Yes fuel in conjunction with the engine produces thrust..

The combination of thrust and drag is what determines the performance of the plane..

And the change in energy due to those two things is a majority of what the TME and Es equations are measuring

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
So much for comparing aircraft, not point-masses. </div></BLOCKQUOTE>
Ah..

I see your mistake here..

Allow me..

You have me confused with Crummp..

He is the one that said the plane has to considered a closed system..

Problem with is there would be no change in energy..

Thus no change in the TME
Thus no change in the Es
Thus no change in the Ps

Thus no way to measure the performance of the plane..

The two main things that define the performance of the plane is the thrust and drag combination..

Those are the two main things the TME, Es, and Ps are showing you.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">The only reason you normalize it is so you can compare the results of two different planes or the same plane with a different configuration. </div></BLOCKQUOTE>
You can't for reasons stated above. </div></BLOCKQUOTE>
Ah..

I see your mistake here..

Allow me..

It is not 'I' who says you can..

It is the likes of NASA and air forces around the world that say you can..

So if you think you found an error in the use of the TME equation to measure the change in energy..

May I recommend you take it up with the likes of NASA?

I don't make the rules..

I just abide by them..

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
No, I'm just stating you're having trouble using the equation without using factors that impact performance.
NASA and numerous air-forces (btw: who told you that BS?) are a bit more sophisticated in their approaches than you claim to be, armchair aero-engineer http://forums.ubi.com/groupee_common/emoticons/icon_rolleyes.gif </div></BLOCKQUOTE>
Ah..

I see your mistake here..

Allow me..

You should read up on the use of the TME before you make silly comments like that..

Here is a link that I think will help you out with that regard

http://www.aviation.org.uk/doc...ricted-FTM108/c5.pdf (http://www.aviation.org.uk/docs/flighttest.navair.navy.milunrestricted-FTM108/c5.pdf)

And pay close att to the FACT that you do NOT have to take 'other factors' like 'lift' or 'drag' into account when using the Es or Ps equation..

Enjoy!

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">You have the same problem Gunz is having.. </div></BLOCKQUOTE>

Really? </div></BLOCKQUOTE>
Really!

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
Who's ever repeating his lil record?
It's you, right? </div></BLOCKQUOTE>
Ah..

I see your problem here

Allow me..

Reposting something someone said is not the same as having the problem they have..

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
You'd better go back "testing" and drawing fancy graphs whereas leaving the talk to people that do - remotely - know what they're talking about.

Hint: that does not include you http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif </div></BLOCKQUOTE>
Again

That is your opinion

and your welcome to it

But you really should read that link I provided you..

After which I think even you will realize the mistakes in your statements above..

Or who knows..

Maybe you will find something and teach NASA a thing or two..

But I wouldn't put any money on that! http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

M_Gunz
05-03-2009, 01:41 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by tagert:
The use of the TME equation to measure the change in energy is valid..

In that the likes of NASA and air forces around the world use the TME equation to measure the change in energy.. </div></BLOCKQUOTE>

Sure but they don't use it the same way you do. I can buy a scalpel, that doesn't make me a surgeon.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">The only reason they divide by the weight (read normalize) is so they can compare the change between two different planes, or the same plane with a different configuration. </div></BLOCKQUOTE>

They take the difference in weight out of the comparison and the weights of the planes cancel out.

Power can be normalized in the same way, each adds 1 energy per second, and when the planes fly zoom tests for the
same amount of time then the energy added by each plane's engine is the same and they cancel out.
It also made it easier to compare the relative positions of the planes always as simultaneous events.
That's historic.

There are performance comparisons where time is open, like time to reach 20,000 ft. And those have appropriate
comparisons that may be drawn from them.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"><BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
Can you predict how the planes will perform relative to each other in anything but the test conditions just based on the changes in height from start to end of the test? </div></BLOCKQUOTE>
Yes!

The ZOOM climb was a WWII way of getting a 'feel' for the performance of the plane..

The purpose of my ZOOM testing was to see how well the in-game planes matched those WWII descriptions of a good ZOOMING plane..

Is it the best way?

That is debatable..

But it is a way..

A way that better men than you and I found valid to do back in WWII.. </div></BLOCKQUOTE>

For the kind of conclusions YOU'VE drawn? You're full of it.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Thus if you have a problem with it..

You have a problem with them not I..

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
Hmmmm? Do your results have a non-trivial meaning? </div></BLOCKQUOTE>
I think so..

And so did the test pilots/engineers of WWII who did ZOOM testing.. </div></BLOCKQUOTE>

What a bunch of puff and bluff. Comparative zoom test procedures that have been shown here run the planes together,
equal time. Other tests for other purposes do not substitute for those.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Especially in light of the FACT that I have shown it valid to use the TME equation to measure the energy change.. </div></BLOCKQUOTE>

It sure is. You want to get VALID results then you need to account for ALL the energy and not hide differences
away under inaccurate labels, which you have done.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Something you and yours initially said was not possible.. </div></BLOCKQUOTE>

You can play your little parts of sentences turned into BS all you want, you are lying right there.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">As a mater of FACT Crummp is still saying that..

Well he was until I pointed it out to him that it is wrong to say the plane has to be treated as a closed system..

In that if you did that, there would be no change in the total energy..

Thus the Energy Height (Es) and Specific Power (Ps) equations would not change either..

It is a subtle point that he has not come to grips with yet.. </div></BLOCKQUOTE>

LOL! You don't a CLUE do you? Of course the energy of the plane changes! It's the Total System that does not.
You got about _half_ way there, I'll give you that.

If you can't account for the changes of energy within the Total System then you can't put accurate numbers on
those changes. When you violate the connection between data and meaning (label) then you lose the meaning.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">But I have high hopes for him that one day he will realize the error in his statement. </div></BLOCKQUOTE>

I've got no hope with you. You can't even take in whole ideas, or can't admit any that show you wrong.
You cling to crediting myself and others with statements we never made. You won't answer a point as presented.
No hope for you.

tagert
05-03-2009, 01:57 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
Sure but they don't use it the same way you do. I can buy a scalpel, that doesn't make me a surgeon. </div></BLOCKQUOTE>
So what part of me saying..

"My ZOOM testing is a different application of the TME equation"

Did you not understand?

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">The only reason they divide by the weight (read normalize) is so they can compare the change between two different planes, or the same plane with a different configuration. </div></BLOCKQUOTE>
They take the difference in weight out of the comparison and the weights of the planes cancel out. </div></BLOCKQUOTE>
Is what I said

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
Power can be normalized in the same way, each adds 1 energy per second, and when the planes fly zoom tests for the same amount of time then the energy added by each plane's engine is the same and they cancel out. It also made it easier to compare the relative positions of the planes always as simultaneous events. That's historic. </div></BLOCKQUOTE>
Ah..

I see your mistake here..

Allow me..

The TME equation does not use 'time' as an input..

Only the position and velocity..

That is why you will not see any length of time the engine ran in my ZOOM testing.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
There are performance comparisons where time is open, like time to reach 20,000 ft. And those have appropriate comparisons that may be drawn from them. </div></BLOCKQUOTE>
Ah..

I see your mistake here..

Allow me..

Your operating under the impression that I am saying the TME, Es, and Ps are the only methods to judge the performance of a plane..

I a not!

As a mater of fact in WWII they use to do a separate ROC and Top Speed per Altitude testing to judge the performance of a plane..

It wasn't until after WWII they stop doing two separate tests and switch to the one Energy method of testing.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
For the kind of conclusions YOU'VE drawn? You're full of it. </div></BLOCKQUOTE>
Hardly!

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
You have a problem with them not I.. </div></BLOCKQUOTE>
Clearly that is not true..

You and yours are the ones that have been saying for years the TME equation can not be used to measure the change in energy..

Not I..

Thus my statement stands

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
What a bunch of puff and bluff. Comparative zoom test procedures that have been shown here run the planes together, equal time. Other tests for other purposes do not substitute for those. </div></BLOCKQUOTE>
Ah..

I see your mistake here..

Allow me..

Go back and read the level accelerating example I gave you..

Maybe on the second read you will realize 'time' is not and should not be a factor

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
It sure is. You want to get VALID results then you need to account for ALL the energy and not hide differences
away under inaccurate labels, which you have done. </div></BLOCKQUOTE>
Ah..

I see your mistake here..

Allow me..

You, like your friend Crump, are referring to a close system when you say you have to account for all the energy..

That is just not the case..

If you accounted for all the energies than there would be no change..

Thus no change in the TME
Thus no change in the Es
Thus no change in the Ps

Thus no way to judge the performance of the plane.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Something you and yours initially said was not possible.. </div></BLOCKQUOTE>
You can play your little parts of sentences turned into BS all you want, you are lying right there. </div></BLOCKQUOTE>
Ah..

I see your mistake here..

Allow me..

Got back a few pages in this thread and click on the link I provided Crump where he said that the energy has to remain constant..

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
LOL! You don't a CLUE do you? Of course the energy of the plane changes! It's the Total System that does not.
You got about _half_ way there, I'll give you that. </div></BLOCKQUOTE>
Ah..

I see your mistake..

Allow me..

You think that you saying now 'of course' some how excuses you from the fact that is not what you and yours originally said..

It doesn't

But I am glad to see that you are finally admitting your mistake!

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
If you can't account for the changes of energy within the Total System then you can't put accurate numbers on those changes. When you violate the connection between data and meaning (label) then you lose the meaning. </div></BLOCKQUOTE>
Ah..

I see your mistake here..

Allow me..

You think it is I who says you don't have to account for 'all' the changes in energy when using the TME, Es, or Ps equations..

It is not I, it is the likes of NASA and air forces around the world that say that..

Thus if you think you found some error in that..

May I suggest you constant them?

In that I don't make the rules..

I just abide by them

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
I've got no hope with you. </div></BLOCKQUOTE>
None needed here..

In that I am on the side of the likes of NASA here..

Where as you are on the side of Crump..

Given the choice I choose to remain where I am

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
You can't even take in whole ideas, or can't admit any that show you wrong. </div></BLOCKQUOTE>
So what is it your saying Gunz?

Are you reversing here?

Are you going back to the notion that the TME equation can not be used to measure the change in energy?

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
You cling to crediting myself and others with statements we never made. You won't answer a point as presented. No hope for you. </div></BLOCKQUOTE>
Well..

I still have hope for you Gunz!

I know you can do it!

Good Luck!

tagert
05-03-2009, 02:26 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
Yawn, ole tagert...same ole BS ever since. </div></BLOCKQUOTE>
Trust me Brem..

I can help you here!

Simply look at that link I gave you and see for yourself..

They don't take 'lift' or 'drag' into account when using the TME equation!

Thus proving your wrong when you say you have to!

JtD
05-03-2009, 02:41 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:

There is not two data points. There is ONE known power point and TWO known manifold pressure points being used to estimate power at an UNKNOWN power point. </div></BLOCKQUOTE>

There are several known power points with several know manifold pressures and we take TWO to interpolate to a THIRD. That's very simple math. It should also be noted that the relation between manifold pressure and mean effective pressure can be approximated as linear with no big error as long as the manifold pressure changes by as small amounts as 3% like in our case. This is evident from the fact that you can get to the 23.9lbs performance from the 25lbs figure of 1950hp and the 18lbs figure of 1600hp and get a difference of only 7hp (1896hp or 1889hp respectively)! We can be rather confident that the true figure is between these two numbers because we approached it from both ways.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Well I certainly think using measured points of performance and determine the forces required to achieve that performance is more accurate than a power estimate based on half a relationship without the correct values of BMEP.

We have good flight tested data gathered under known conditions to calculate forces required for both points in question. </div></BLOCKQUOTE>

Yes, you have a very good estimate of the force in flight, but you have no clue about how to relate them to engine power, which is what we want to know. What do you base your constant efficiency of 80%? That's certainly a figure that has no relationship with the real word and yet has a huge impact on the result. I say it's 80% at 332 mph and 77% at 354 mph. Got it from the same place you got yours from, pulled it out of my behind. Makes 1900hp @ 23.9lbs.

It's more accurate to calculate the engine than to calculate the plane if you want to know something about the engine.

Bremspropeller
05-03-2009, 03:36 PM
Sorry for deleting the other message - I actually wanted to edit it... http://forums.ubi.com/images/smilies/compsmash.gif


Well, as Crumpp stated, TE never changes.

Otherwise, your "friends" at NASA would have had a pretty rough job, sending a rocket into space.

According to you, tagert, a rocket had a TE of zero on the launchpad.

It does, however have the same energy as if it was travelling in orbit.
It's all conserved in the propellant.

BTW: your fancy PDF shows that drag, lift and weight are taken into consideration, despite you telling the opposite.

Just writing down a different expression doesn't cancel out the meaning of the forces included.

Mr_Zooly
05-03-2009, 03:47 PM
Are we talking about in game or reality? If its in game performance then surely the whole discussion point is moot, if not then pure physics and mathematics (real world stuff) dont take into account possible imperfections in build quality (wartime conditions) and fuel consistency let alone the fact that airframes werent built to last more than a few hours of high stress combat which would have an effect on metal fatigue etc..
Just my 2 cents/pence

tagert
05-03-2009, 04:40 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
Sorry for deleting the other message - I actually wanted to edit it... http://forums.ubi.com/images/smilies/compsmash.gif </div></BLOCKQUOTE>
NP!

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
Well, as Crumpp stated, TE never changes. </div></BLOCKQUOTE>
Ah..

I see your mistake here..

Allow me..

It depends on your definition of TE..

You appear to have the same problem Crummp had..

Till I cleared it up for him..

Where he was confusing the 1st law of thermodynamics with the total mechanical energy (TME) equation..

They are often used in conjunction with each other in high school physics classes..

So much so that some people incorrectly begin to think the TME equation must allways remain constant..

I think it stems from the fact that most high school physics classes consist of the examples where the TME does remains constant..

But in the real world that is hardly ever the case!

About the only time you will see TME remain constant is on the chalk board of a high school physics class..

Where the assume a point mass in a vacuum or an object where they assume friction is so small it can be ignored..

Thus if someone never took any physics classes past high school..

It is not suprising they 'feel' that TME must allways remain constant!

It is knowing the 1st law of thermodynamics in conjunction with the TME equation that when TME changes..

It is due to other forces acting..

Other than PE or KE..

In that the TME equation only 'accounts' for PE and KE..

In the case of an airplane in flight..

Those other forces are Drag and Thrust..

Not the only other forces..

But the main other forces..

So it should be clear to you now that in the real world the TME equation is typically changing..

Especially when you consider the FACT that the definition of WORK is that it is equal to the CHANGE in TME..

And that POWER is equal to the RATE OF CHANGE of TME.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
Otherwise, your "friends" at NASA would have had a pretty rough job, sending a rocket into space.

According to you, tagert, a rocket had a TE of zero on the launchpad.

It does, however have the same energy as if it was travelling in orbit.
It's all conserved in the propellant. </div></BLOCKQUOTE>
See above..

Your statements are based on a rocky foundation!

TME does not have to and hardly ever does remain constant!

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
BTW: your fancy PDF shows that drag, lift and weight are taken into consideration, despite you telling the opposite.
Just writing down a different expression doesn't cancel out the meaning of the forces included. </div></BLOCKQUOTE>
Ah..

I see your mistake here..

Allow me..

It is not that they are taken into account by the TME equaiton..

They are derived from it!

Your close here!!

Stay with me for a moment and what you just said..

In that you are very close to seeing the light here..

My..

How did you say it?

fancy PDF graphs?

They are showing you the CHANGE in the TME equation..

The majority of that CHANGE is due to the combination of THRUST and DRAG..

From which you can get a good feel for the performance of the plane!

SAVVY?

Bremspropeller
05-03-2009, 05:42 PM
You certainly have to have a degree in BSing.

BTW: I'm talking of TE, not TME.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> It is not that they are taken into account by the TME equaiton..

They are derived from it! </div></BLOCKQUOTE>

Have a closer look.
The equation looks different, but it says the same thing.
Ps is Ps, aight?

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">The majority of that CHANGE is due to the combination of THRUST and DRAG.. </div></BLOCKQUOTE>

So, surprise surprise, you've discovered there's a drag-figure?

Congrats, you're on the right way http://media.ubi.com/us/forum_images/gf-glomp.gif

Another 10 pages and you'll finally get it.
There's hope for ya http://forums.ubi.com/images/smilies/25.gif

Insuber
05-03-2009, 05:58 PM
HEY! For this kind of "communication" the telephone is much more efficient. Had you thought or exchanging your telephone numbers and continue your debate elsewhere?

Ins

deepo_HP
05-03-2009, 06:54 PM
hi tagert,

you gave bremspropeller this advice:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by tagert:
You should read up on the use of the TME before you make silly comments like that..

Here is a link that I think will help you out with that regard

http://www.aviation.org.uk/doc...ricted-FTM108/c5.pdf (http://www.aviation.org.uk/docs/flighttest.navair.navy.milunrestricted-FTM108/c5.pdf) </div></BLOCKQUOTE>i took it and read the paper.

it describes present test-techniques and data-analysis to
1. Derive climb schedules to optimize time to height, energy gain, or to minimize fuel consumption.
2. Predict sustained turn performance envelopes.
3. Define mission suitability and enable operational comparisons to be made.

in a historical note, it says that in the 50's it was realised, that aircraft performance is based on
the balance that must exist between the kinetic and potential energy exchange of the aircraft, the energy dissipated against the drag, and the energy derived from the fuel.
and that 'excess power characteristics' (using the total energy concept) can be tested and analysed for aircraft performance and tactical comparison.

later on there is a 'dynamic-test' described, called
Push-Over Pull-Up Maneuver
which looks to me like a 'dive 'n' zoom' test, just with the pre- and post-condition of the same (unchanged) TE.


however, i think (quite a lot written there), that the main topic is how to use data-reduction to calculate the performance given by 'specific excess power', for example:
input data are: weight, speed, altitude, temp, fuel-flow and time
for level-acceleration, output is plotted energy-height vs. time
for climb, the output is fuel, time and distance


i won't say, i have it all understood... but crumpp said in another thread:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
Eh does not tell us the rate of change [of TE] and all aircraft under the same condition of flight will have exactly the same Eh.
To get that we need Ps or specific excess power or our rate of change over time. When Ps is calculated THEN we factor our thrust and drag. </div></BLOCKQUOTE>
i was wondering, if that is not the same as the paper says?

Kettenhunde
05-03-2009, 10:36 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> JtD says:
There are several known power points with several know manifold pressures and we take TWO to interpolate to a THIRD. That's very simple math. </div></BLOCKQUOTE>


It is very simple math that reflects only part of the relationship.

That is why using forces required is much more accurate.


<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">JtD says:

Yes, you have a very good estimate of the force in flight, but you have no clue about how to relate them to engine power, which is what we want to know. </div></BLOCKQUOTE>

This statement speaks to the extent of your knowledge. It is probably why you "fear" using forces required. You simply do not understand what is going on with it.

Thrust = drag in steady level flight, remember?

Thrust is force but when combine with a component of velocity, it gives us power. Then it is a simple matter of unit conversion.

Using the proper mathmatical relationships, If we know our power required in one condition of flight we can quite accurately determine it for any other condition of flight.

Using the forces required is the most accurate method to determine the power the aircraft must generate to achieve a given condition of flight.

In fact if we could not accurately gauge engine power then we have no basis to determine any performance in propeller aircraft.

That is why props are termed "power producers."


All the best,

Crumpp

JtD
05-03-2009, 11:43 PM
If everything is so clear for you, then please tell me where you got your 80% efficiency from and why it should remain constant at both 332mph and 354mph.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">1950 x.8 x 2 = 3120THP </div></BLOCKQUOTE>
and
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">3494.7thp x 1.25 = 4368 SHP </div></BLOCKQUOTE>

This bears no resemblance to the real relationship.

Kettenhunde
05-04-2009, 12:49 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> If everything is so clear for you, then please tell me where you got your 80% efficiency </div></BLOCKQUOTE>

I would be glad to help you to understand it.

As a general rule, we hold Horsepower available constant over a constant altitude in power producers. Simply put, power is how we determine our performance. In this case we are using Brake Horsepower.

In higher level calculations our propeller efficiency would change. However when we converted back, our brake horsepower available would still be held constant. While you can make better prediction of aerodynamic characteristics such as exhaust thrust, you will not change the overall conclusion or the performance prediction results.

Why? All we are doing is holding two things or power and propeller efficiency constant and allowing the other variables to compensate.

In the end, when we reconvert back our original baseline value of power, we have the power force required to achieve that performance under the new conditions.

All the best,

Crumpp

jamesblonde1979
05-04-2009, 01:14 AM
I'll remeber this thread whenever I encounter a Tempest on line.

I can see it now, instead of blowing me away he will pull up alongside me and shout "E=mc^2".

JtD
05-04-2009, 01:42 AM
But propeller efficiency is _not_ constant. The extra power we have for the higher speed requires a higher torque at the prop because the rpm remain constant. The higher torque however can only be achieved by a higher angle of attack of the prop blades which will create higher lift at the expense of higher drag, thus increasing forward momentum as well as torque. It is against all basic aerodynamic laws that the lift-drag relation of an airfoil / propeller blade can be estimated as a constant, in particular at the high speeds involved (0.87 mach at the prop tips).

If you do your math again for a Spitfire, increasing speed from 335mph @ sea level @ 1570hp to 358 mph @ sea level, what would your power estimate say if you use exactly the same method as with the Mosquito?

Kettenhunde
05-04-2009, 02:03 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">If you do your math again for a Spitfire, increasing speed from 335mph @ sea level @ 1570hp to 358 mph @ sea level, what would your power estimate say if you use exactly the same method as with the Mosquito? </div></BLOCKQUOTE>

What is the weight of the aircraft and under what conditons is the data flown? Give me the information I need and we can find it.

The Mosquito gave us a complete flight test with measure performance gathered under controlled conditions.

This allowed us to view the aircraft as a system and use the relationship of the forces required to determine performance.

All the best,

Crumpp

Feathered_IV
05-04-2009, 02:04 AM
Almost there! And remember, the first one to hit twelve pages is a ******. http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

JtD
05-04-2009, 02:31 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:

What is the weight of the aircraft and under what conditons is the data flown? Give me the information I need and we can find it. </div></BLOCKQUOTE>

The weight of the aircraft is 7234lbs. The original test can be found here (http://www.spitfireperformance.com/jl165rr.html).

What other conditions would you need to know?

na85
05-04-2009, 02:42 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Feathered_IV:
Almost there! And remember, the first one to hit twelve pages is a ******. http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif </div></BLOCKQUOTE>

If you don't like the thread, then don't click the link. Kindly stfu. Some of us are enjoying this thread.

Kettenhunde
05-04-2009, 02:49 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> What other conditions would you need to know? </div></BLOCKQUOTE>

I will work the formulas and post the results for you.

Only thing that raises some concern is the fact propeller is not correctly matched to the aircraft.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> It appears that the propeller has insufficient blade area to absorb the increased power of the engine with a resultant loss of efficiency, especially noticable on the climb performance. A propeller of greater diameter or increased blade area, such as a 5 blade type, should improve the rate of climb by some 300 feet per minute. </div></BLOCKQUOTE>

http://www.spitfireperformance.com/jl165rr.html

All the best,

Crumpp

M_Gunz
05-04-2009, 03:56 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Mr_Zooly:
Are we talking about in game or reality? If its in game performance then surely the whole discussion point is moot, if not then pure physics and mathematics (real world stuff) dont take into account possible imperfections in build quality (wartime conditions) and fuel consistency let alone the fact that airframes werent built to last more than a few hours of high stress combat which would have an effect on metal fatigue etc..
Just my 2 cents/pence </div></BLOCKQUOTE>

Actually IRL they do by printing qualifiers like 5% tolerance for manufacturing differences. Complete test documents do
contain or refer to the qualifiers and caveats. The curves on the charts are only best-fits of the actual data, not
physical law.

JtD
05-04-2009, 04:45 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:

I will work the formulas and post the results for you.

Only thing that raises some concern is the fact propeller is not correctly matched to the aircraft. </div></BLOCKQUOTE>

The same is true for the tested Mosquito, though, a 3-bladed 12" prop can't take much more than a 4-bladed 10.9" prop.

Kettenhunde
05-04-2009, 05:59 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> The same is true for the tested Mosquito, though, a 3-bladed 12" prop can't take much more than a 4-bladed 10.9" prop </div></BLOCKQUOTE>

One has nothing to do with the other. If the propeller was mismatched, the engineers would have noted it in the report.

It is painfully obvious when this occurs.

Before we get into that Spitfire with the mismatched propeller, let’s see how well the formula's gives agreement to the actual relationships and real world measured results.

We can take CAFE foundations Aircraft Performance Report. The CAFE foundation pioneered zero thrust glide testing to derive the drag curve. Their Aircraft Performance Reports are very well done and leave us with no stone unturned or aerodynamic questions about the aircraft.

The perfect test to see how our formulas agrees with real world measured results.

http://img142.imageshack.us/img142/6058/cafetestt182.jpg (http://img142.imageshack.us/my.php?image=cafetestt182.jpg)

http://cafefoundation.org/v2/pdf_apr/Thorp.pdf

Basic Aerodynamic data:

WT = 1600lbs

Wing Area = 86sqft

Span 20.8ft

b^2/S =5.03

Brake Horsepower Available - Lycoming O-360 A1B generating 180 bhp.

Propeller efficiency used in CAFÉ Performance Testing = 135 thp / 180 bhp = .75

This is well within the normal range for propeller efficiency which is usually between .75 and .85 with .8 being the median.

It does not matter what value we use as long as our value remains the same. We have to start form the same point to build our Thrust Horsepower Curve. This one is already built for us and everyone can see to the results to confirm the formula relationships work.

A quick word of caution on using propeller efficiencies outside the normal ranges is in order. Keep in mind the farther we get from our range of normal efficiency for a propeller, the farther off our calculated force relationships will be within the methodology. Our end result will remain the same but analyzing our components will not be as accurate.

Power known points:

150mph EAS = 70thp

@ 150mph CAS = 150mph EAS at Sea level on a standard day

Speed known points:

150 mph EAS * .869 = 130.35 KEAS

q= V^2/295

q = 57.6

198mph CAS = 198mph EAS * .869 = 172KEAS

Power of Induced drag @ 130.35KTAS

CL = 1600lbs/(57.6 * 86sqft) = .323

Cdi = .318 * {.323^2/.85*5.03) = .0078

Di = .0078*57.6*86 = 38.63lbs

Pri = (38.63lbs*130.35KTAS)/325 = 15.5thp

Prp = 70thp – 15.5thp = 54.6thp


AT 172KEAS

Prp = Prp2/54.6thp = (172KEAS / 130.35KEAS)^3

Prp = 125thp
Pri = Pri2/15.5thp = 130.5KEAS/172KEAS = 11.8


Pr = 125 + 12 = 137thp

137thp / .75 = 183BHP

A 1.6% error in our predication!

I have to do the Spitfire but I suspect we will not learn much about the accuracy of using force required equations because most likely, this type of predictions is what clued the RAE engineers into realizing the propeller was mismatched for the engine.

When they noticed a large discrepancy between predicted power and measured results, the light bulb went on.

All the best,

Crumpp

M_Gunz
05-04-2009, 06:00 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JtD:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:

I will work the formulas and post the results for you.

Only thing that raises some concern is the fact propeller is not correctly matched to the aircraft. </div></BLOCKQUOTE>

The same is true for the tested Mosquito, though, a 3-bladed 12" prop can't take much more than a 4-bladed 10.9" prop. </div></BLOCKQUOTE>

12" prop. Is that blade width? Otherwise, " is for inches, about 2.54mm each.

Was the 13 foot prop of the Corsair not a fair match for the engine and speed of the plane?
The longer the prop, the bigger the thrust producing area.

Would I be wrong in thinking that the load of weight and drag of the plane would affect what is a better prop
for any purpose, like climb or speed?

Kettenhunde
05-04-2009, 06:10 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
Was the 13 foot prop of the Corsair not a fair match for the engine and speed of the plane?
The longer the prop, the bigger the thrust producing area.

Would I be wrong in thinking that the load of weight and drag of the plane would affect what is a better prop for any purpose, like climb or speed? </div></BLOCKQUOTE>

You are definitely thinking on the right track. Blade width, airfoil selection, disc size, blade material, and resonance of the engine are just a few of the factors effecting propeller design.

Propellers are matched to absorb and use power for specific installations not engines.

What works or does not work for one installation is not applicable to a different installation unless specified by the manufacturer. This means they went back and tested the same propeller all over again in a different installation.

All the best,

Crumpp

JtD
05-04-2009, 06:49 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:

12" prop. Is that blade width? Otherwise, " is for inches, about 2.54mm each. </div></BLOCKQUOTE>

Not, it's feet. Sorry. Apparently I've been doing to much battleship guns thinking lately. It should be 12' and 10.9'.

M_Gunz
05-04-2009, 06:56 AM
I kind of figured that you don't normally think in English system units.
I learned both and prefer the Metric.

Babylonian number system is base 60, works very well at fractional math solutions used in algorithmic ways.
They count by 12 knuckles of one hand times 5 fingers of the other. A very workable pre-decimal business math.

JtD
05-04-2009, 07:15 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:

Propellers are matched to absorb and use power for specific installations not engines. </div></BLOCKQUOTE>

This might be true for today, but back in WW2 they were still gaining experience with the subject. This resulted in a lot of constellations you wouldn't find today. The Spitfire started off with a two bladed fixed pitch wooden prop, and ended with two three bladed counter rotating variable pitch props. This is just to illustrate how much folks had to learn at that time.

In addition, the report says nothing about "mismatched". The propeller was one of the standard Spitfire propellers of that time and proven in combat. The only suspected problem was that it might not be able to cope with the extra power, in particular in climb. To deal with that, you can either increase the prop disc area by using a larger prop or increase the prop disc density by adding another prop blade. Both actions result in a very roughly linear increase in maximum thrust.

It should be noted that the same aircraft was tested again with another 4-bladed prop, achieved slightly worse results and no comment was made on the suitability of the prop.

Kettenhunde
05-04-2009, 07:29 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> The same is true for the tested Mosquito, though, a 3-bladed 12" prop can't take much more than a 4-bladed 10.9" prop.
</div></BLOCKQUOTE>

One has nothing to do with the other. If the propeller was mismatched, the engineers would have noted it in the report.

It is painfully obvious when this occurs.


Generally speaking, the larger the disc area, the more power the propeller can absorb. The fewer number of blades, the more efficent the propeller.

All the best,

Crumpp

Kettenhunde
05-04-2009, 07:51 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">This might be true for today, but back in WW2 they were still gaining experience with the subject. </div></BLOCKQUOTE>

That is not correct. They had more experience with and more knowledge about high perfomance piston engine propeller aircraft than we do.

There simply is not much call for 2000 hp piston engine designs since the Jet age began.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> In addition, the report says nothing about "mismatched". </div></BLOCKQUOTE>

Sure it does!

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> It appears that the propeller has insufficient blade area to absorb the increased power of the engine with a resultant loss of efficiency </div></BLOCKQUOTE>

http://www.spitfireperformance.com/jl165rr.html


The propeller design could not handle the increase in power for the engine. They became mismatched at that point and the aircraft required a different propeller to absorb the additional power. The efficiency is not within normal design limits and the aircraft needs a new propeller.

Hence:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Crumpp Says:

I suspect we will not learn much about the accuracy of using force required equations because most likely, this type of predictions is what clued the RAE engineers into realizing the propeller was mismatched for the engine.

When they noticed a large discrepancy between predicted power and measured results, the light bulb went on.
</div></BLOCKQUOTE>

That is why I did this analysis:

Before we get into that Spitfire with the mismatched propeller, let’s see how well the formula's gives agreement to the actual relationships and real world measured results.

We can take CAFE foundations Aircraft Performance Report. The CAFE foundation pioneered zero thrust glide testing to derive the drag curve. Their Aircraft Performance Reports are very well done and leave us with no stone unturned or aerodynamic questions about the aircraft.

The perfect test to see how our formulas agrees with real world measured results.

http://img142.imageshack.us/img142/6058/cafetestt182.jpg (http://img142.imageshack.us/my.php?image=cafetestt182.jpg)

http://cafefoundation.org/v2/pdf_apr/Thorp.pdf

Basic Aerodynamic data:

WT = 1600lbs

Wing Area = 86sqft

Span 20.8ft

b^2/S =5.03

Brake Horsepower Available - Lycoming O-360 A1B generating 180 bhp.

Propeller efficiency used in CAFÉ Performance Testing = 135 thp / 180 bhp = .75

This is well within the normal range for propeller efficiency which is usually between .75 and .85 with .8 being the median.

It does not matter what value we use as long as our value remains the same. We have to start form the same point to build our Thrust Horsepower Curve. This one is already built for us and everyone can see to the results to confirm the formula relationships work.

A quick word of caution on using propeller efficiencies outside the normal ranges is in order. Keep in mind the farther we get from our range of normal efficiency for a propeller, the farther off our calculated force relationships will be within the methodology. Our end result will remain the same but analyzing our components will not be as accurate.

Power known points:

150mph EAS = 70thp

@ 150mph CAS = 150mph EAS at Sea level on a standard day

Speed known points:

150 mph EAS * .869 = 130.35 KEAS

q= V^2/295

q = 57.6

198mph CAS = 198mph EAS * .869 = 172KEAS

Power of Induced drag @ 130.35KTAS

CL = 1600lbs/(57.6 * 86sqft) = .323

Cdi = .318 * {.323^2/.85*5.03) = .0078

Di = .0078*57.6*86 = 38.63lbs

Pri = (38.63lbs*130.35KTAS)/325 = 15.5thp

Prp = 70thp – 15.5thp = 54.6thp


AT 172KEAS

Prp = Prp2/54.6thp = (172KEAS / 130.35KEAS)^3

Prp = 125thp
Pri = Pri2/15.5thp = 130.5KEAS/172KEAS = 11.8


Pr = 125 + 12 = 137thp

137thp / .75 = 183BHP

A 1.6% error in our predication!

All the best,

Crumpp

JtD
05-04-2009, 08:10 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:

One has nothing to do with the other. If the propeller was mismatched, the engineers would have noted it in the report. </div></BLOCKQUOTE>

Like I said, the same Spitfire had been tested in again, with slightly worse results, and no mention was made of the propeller. It were the same guys that tested the Mosquito.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Generally speaking, the larger the disc area, the more power the propeller can absorb. The fewer number of blades, the more efficent the propeller. </div></BLOCKQUOTE>

...and the more blades, the more power the propeller can absorb. Like I said already.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">That is not correct. They had more experience with and more knowledge about high perfomance piston engine propeller aircraft than we do. </div></BLOCKQUOTE>

From what? There were very few aircraft engines with the power in the range of 2000hp around, data acquisition, data processing and methology were just being worked out! There is very little chance that they made a dynamic analysis of engine-aircraft-propeller interference to match the prop to the rest. They mostly went by experience and guts, but neither does work very well in complex dynamic situations.

For what it's worth, there's plenty of prop aircraft around, though many are driven by turbines.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">It appears that the propeller has insufficient blade area to absorb the increased power of the engine with a resultant loss of efficiency </div></BLOCKQUOTE>

There is no mention of "mismatched". It just _may_ have a somewhat lower "efficiency" and _may_ be "insufficient". Both of which is not mismatched. Well, maybe it's just our definition of "mismatched" that differs.

Anyway, I'm waiting for the math and expect results similar to what you got for the Mossie, like 1860hp. Any progress, yet?

JtD
05-04-2009, 08:17 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:

That is why I did this analysis:... </div></BLOCKQUOTE>

Yes, I've read it. I don't know where you're from, but around my place it is enough to write something once. Otoh, repeating the same thing over and over again is just considered annoying.

With some restrictions, the method is alright.

Kettenhunde
05-04-2009, 08:27 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Like I said, the same Spitfire had been tested in again, with slightly worse results, and no mention was made of the propeller. It were the same guys that tested the Mosquito.
</div></BLOCKQUOTE>

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Both of which is not mismatched.
</div></BLOCKQUOTE>

Well they tried or did change the propeller!

Since it was not mentioned then it very well might not have even been a factor with the new propeller.

Looking at the test would be the best thing. Not making silly assumption based on thin air speculation.'

You got into this making a bunch silly speculations and not just taking the information as it was presented.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">It should be noted that the same aircraft was tested again with another 4-bladed prop, achieved slightly worse results and no comment was made on the suitability of the prop. </div></BLOCKQUOTE>

Well facts are they mention it in this one and I tend to think it is probably valid.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> though many are driven by turbines.
</div></BLOCKQUOTE>

Turbo props are not the same as piston engine propeller aircraft and are handled somewhat differently in determining performance.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> There is very little chance that they made a dynamic analysis of engine-aircraft-propeller interference to match the prop to the rest. </div></BLOCKQUOTE>

They most certainly did match engines and propellers. Not doing so is fatal; you do know that, right???

All the best,

Crumpp

JtD
05-04-2009, 09:01 AM
And there have been no fatalities in the history of powered flight?

Kettenhunde
05-04-2009, 09:10 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">And there have been no fatalities in the history of powered flight? </div></BLOCKQUOTE>

Sure they have been.

What does that have to do with the fact they were very aware of propeller and engine compatibility?

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> With some restrictions, the method is alright. </div></BLOCKQUOTE>

Let's move on then.

I am much more interested in discovering if they changed the Spitfires propeller. I don’t see why wouldn’t as this is not a hard fix.

It would mean a significant increase in the type’s performance.

Question just becomes which route did they choose and when?

All the best,

Crumpp

JtD
05-04-2009, 09:24 AM
Can you do the math for the Spit please? Around 1860hp? Yes - no?

Late war Spitfires sometimes had 5-bladed props but there is no test result for MkIX with 25lbs boost.

uppurrz
05-04-2009, 09:45 AM
Sure they change the Spitfires prop. It went from a wooden one of fixed pitch to a 3 bladed contra rotating one of variable pitch.

Kettenhunde
05-04-2009, 09:46 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Can you do the math for the Spit please? Around 1860hp? Yes - no?
</div></BLOCKQUOTE>

Yes

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Late war Spitfires sometimes had 5-bladed props but there is no test result for MkIX with 25lbs boost. </div></BLOCKQUOTE>

It probably was not worth it with the Spitfire Mk IX's replacements already in production.

It makes more sense to just concentrate on the newer aircraft.

All the best,

Crumpp

Kettenhunde
05-04-2009, 09:47 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">3 bladed contra rotating one of variable pitch. </div></BLOCKQUOTE>

AFAIK, great in theory but awful in practice.

All the best,

Crumpp

JtD
05-04-2009, 10:15 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">3 bladed contra rotating one of variable pitch. </div></BLOCKQUOTE>

AFAIK, great in theory but awful in practice. </div></BLOCKQUOTE>

It made the aircraft easier to fly and is still working today.

uppurrz
05-04-2009, 10:53 AM
http://www.flymig.com/maks_pictures/images/TU-95.2.jpg

na85
05-04-2009, 10:54 AM
An aircraft so loud, the americans can track it using underwater sonar stations.

JtD
05-04-2009, 10:55 AM
Then it's probably best to use it in order to cover submarines...

Kettenhunde
05-04-2009, 11:00 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> It made the aircraft easier to fly and is still working today. </div></BLOCKQUOTE>

On some of the late post warfare Seafires, I understand it was essential to the safe operation of the aircraft at sea.

A go around from a carrier landing propeller effects could put you into the island without them.

Greater efficiency, thrust gains, absorbs tons of power, and neutralized propeller effects all at the expense of being very heavy with a complicated gearbox that made it a nightmare to maintain.

All the best,

Crumpp

Kettenhunde
05-04-2009, 11:03 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Then it's probably best to use it in order to cover submarines... </div></BLOCKQUOTE>

Other way around, the Soviet Submarines were used to cover the airplane.

JtD
05-04-2009, 01:15 PM
To sum up the current state of affairs, we have a

- Mosquito that increases boost from 18 to 23.9 lbs and increases speed 332 to 354 mph
- Spitfire that increases boost from 18 to 25 lbs and increases speed from 335 to 358 mph.

The powers at 18lbs boost are 1540 and 1570 hp respectively. Based on that, Kettenhundes calculation estimates the power of the engines to be 1830 and 1860 hp respectively at 23.9/25lbs boost. The first one is said to be too low, the second one is documented to be too low. For both planes engineers say the efficiency of the propeller decreased, which is not covered by Kettenhundes math. Thus everything makes perfect sense.

HellToupee
05-04-2009, 07:40 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> It made the aircraft easier to fly and is still working today. </div></BLOCKQUOTE>

On some of the late post warfare Seafires, I understand it was essential to the safe operation of the aircraft at sea.

A go around from a carrier landing propeller effects could put you into the island without them.

Greater efficiency, thrust gains, absorbs tons of power, and neutralized propeller effects all at the expense of being very heavy with a complicated gearbox that made it a nightmare to maintain.

All the best,

Crumpp </div></BLOCKQUOTE>

Does not make contra props awful tho does it, brits produced many successful aircraft with contra props, the Tu-95 is the fastest prop plane ever built, an70 GE36...

Viper2005_
05-04-2009, 08:05 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by na85:
An aircraft so loud, the americans can track it using underwater sonar stations. </div></BLOCKQUOTE>

I suspect that they can probably track other aeroplanes too...

It's certainly loud, but then again why spend huge amounts of time and money to make it quiet?

Kettenhunde
05-04-2009, 08:39 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Does not make contra props awful tho does it, </div></BLOCKQUOTE>

IMHO it does!

They are heavy, complex, and a maintenance nightmare. With the exception of a tiny handful of post war piston engines that saw very limited application, there is nothing that can take advantage of their power absorption.

I think there are other design alternatives that do the job just as well without the added hassles.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> the Tu-95 is the fastest prop plane ever built, </div></BLOCKQUOTE>

Turboprop.......Not the same thing as a piston engine aircraft. There is some use for Contra-rotating rotating props in turboprop applications. Modern blade design though is limiting these as well.

All the best,

Crumpp

Kettenhunde
05-04-2009, 09:03 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">For both planes engineers say the efficiency of the propeller decreased, which is not covered by Kettenhundes math. </div></BLOCKQUOTE>

This is not true so do not make things up that do not exist. Just read what is in the reports.

The engineers at the RAE were much smarter than you or I on their own aircraft. They were very capable and knew what they were doing.

The Mosquito’s report's only issue was that exhaust manifold on one aircraft and they felt that aircraft was on the low end of the performance range.

Neither issue affects the prediction as drag force required compensates because our power transmission is within normal limits.

The report represents several aircraft flown on mulitple flights.

http://www.wwiiaircraftperform...g/mosquito/hx809.pdf (http://www.wwiiaircraftperformance.org/mosquito/hx809.pdf)

The prediction for the Mosquito works quite well and gives very good agreement with the Merlin power chart.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Basic Aerodynamic data:

WT = 21430lbs

Wing Area = 454sqft

Span 54.16ft

b^2/S = 6.46


Power known points:

+25lbs = 1950hp

1950 x.8 x 2 = 3120THP


Speed known points:

+23.9lbs 354mph TAS x .869 = 307KTAS

q= V^2/295

q = 319.5

+25lbs 340mph TAS x .869 = 295KTAS

- This is our most important known as it is a known velocity and power point in the 2nd Gear. From here we can extrapolate performance to anywhere in the aircrafts envelope and use that to compare with our forces required at this point.

q= 295

For giggles, here is the stall speed of the aircraft used in the test.

Stall

@18,000lbs Vs1 = 91ktas

q = 28.2

CL = (18000lbs / 454 sq ft)/28.2 = 1.4

Vs2 = SQRT (295 x 21430lbs)/(1.4 x 454sqft) = 99.7ktas or 114.6mph TAS



To refine the SWAG, we will solve this is by using the difference from a known point. We know the Shaft power out at +25 lbs. We can ballpark our losses by seeing how much of that shaft power was lost in running the supercharger.
Now let's use the relationship of power at velocity in a propeller aircraft to ballpark what we need to achieve the speeds attained in the Mossie test.

Our second know point is the speed the aircraft attained in 1st Gear at +23.9lbs. Now we don't know our power available at this point. We don't need it though as this performance was not attained in the 2nd Gear, it was attained in the 1st gear!

Our engine only produces so much power so by taking the difference in power from +25 in 2nd gear, we can figure out losses if we used the same amount of power or less in this case to reach a faster speed in 1st Gear.

How do we figure out that difference? Well we have to know how much power it would take us to equal performance in the 1st Gear if we used the 2nd Gear.

Let's use our know point in the 2nd Gear to find an unknown point at the faster velocity the 1st Gear was able to attain.

First we have to do the step I left out the first time, separate the power of induced drag from parasitic. Induced drag has a direct relationship and exerts the smallest influence at high velocity. It simply is not going to change out total picture by more than a few horsepower.

Our Drag is calculated below, separated into components, and converted to THP.

Prp = 3079.4lbs x 307ktas / 325 = 2909 thp

Prp2 / 2909thp = (307KTAS / 295 KTAS)^3

Prp2 = 3271thp

3271- 2909 = 362thp Prp

3271thp / 2 engines = 1635.5 thp Prp per engine

Pri at +25lbs

Pri = (246.4lbs x 307ktas) / 325 = 232.8thp

Pri2/232.8thp = 295ktas/307ktas

Pri2 = (295/307)x232.8 = 223.7thp

232.8 - 223.7 = 9.1 thp difference due to induced drag.

223.7thp / 2 engines = 111.85 Pri per engine

3263hp + 223.7thp = 3494.7thp

3494.7thp x 1.25 = 4368 SHP required

1950hp x 2 = 3900 hp

4368 – 3900 = 468hp

That means our engine losses by using the 2nd gear supercharger at +25lbs are in the neighborhood of 468 SHP in total or 234 hp per engine.

Not very close to the 150hp JtD's nonsense line shows.

Our original estimate was 237.9 hp so we are definitely in the ballpark.

Almost done here!

Let's squash this fallacy that we are holding CL/CD fixed. That notion comes from Harri Phil's mistaking a parametric study on weight gain effects on speed in which we do hold a fixed L/D ratio. He argued for pages with a man who retired from the Skunk works in that one!

In our case here, we are dealing forces required and not just a co-efficient. We can easily calculate our Coefficients and L/D ratio.


CL = (21430lbs / 454 sq ft)/319.5 = .148 for 307ktas +25

CL = (21430lbs / 454 sq ft)/295 = .16 for 295ktas +23.9



Drag at +25 307ktas:

Drag lbs = [3120THP) x 325] / 307 ktas = 3302.9lbs

CD = (3302.9bs / 454sq ft) / 319.5 = .0228

Cdi = .318 (.16^2)/6.46x.8 = .0015

Di = .0016 x 454 x 319.5 = 232lbs

3311.4lbs - 232lbs = 3079.4lbs

Prp = 3079.4lbs x 307ktas / 325 = 2909 thp



AT +25 295ktas:

Drag lbs = [3486THP) x 325] / 295 ktas = 3840.5lbs

CD = (3840.5lbs / 454sq ft) / 295 = .0287



L/D ratio for +25lbs at 307ktas = .16/.0287 = 5.575

L/Dratio for +25 lbs at 295 ktas = .148/.0228 = 6.49


Now let's figure out where our +23.9lbs lies on the 1st Gear Supercharger power production so we can mark it on the Merlin 25 engine chart.

First let's go from a known point on the 1st Gear supercharger power line.

Power:

+18lbs = 1540hp

1540hp x .8 x 2 = 2464THP

Speed:

+18 = 332mph TAS = 288.5ktas

q = 282.4

Drag at +18 288.5ktas:

Drag lbs = [2464THP) x 325] / 288.5 ktas = 2776lbs

CD = (2776lbs / 454sq ft) / 282.4 = .0217

Cdi = .318 (.167^2)/6.46x.8 = .0017

Di = .0017 x 454 x 319.5 = 246.4lbs

2776lbs - 246.4lbs = 2530lbs

Prp = 2530lbs x 288.5ktas / 325 = 2246thp

CL = (21430lbs / 454 sq ft)/282.4 = .167 for 288.5ktas +18lbs

Now to find our forces required by the 1st Gear to reach + 23.9lbs

Prp2 / 2246thp = (307KTAS / 288.5 KTAS)^3

Prp2 = 2706thp

Pri at +23.9lbs

Pri = (246.4lbs x 307ktas) / 325 = 232.8thp

Pri2/232.8thp = 288.5ktas/307ktas

Pri2 = (288.5/307)x232.8 = 219thp

Pr at 23.9lbs = 2706thp + 219thp = 2925thp

2925thp x 1.25 = 3656hp / 2 = 1828hp on the Merlin chart is our 23.9lbs mark.

Our ballpark using PLANK/33,000 was 1864hp so it gave pretty good agreement.

So while our L/D ratio is fixed by design, it is not held fixed by the formulation. We are not doing a parametric study to examine the effects of one parameter. We are using the forces required to determine what we need to achieve a desired level of performance.

By taking the difference between the performance the engine was able to attain because of fewer losses due to the supercharger being used well outside of its design efficiency point, we can conclude that 234hp is not anywhere in the ballpark of drawing nonsense lines on an engine charts as JtD demonstrates.

http://img259.imageshack.us/img259/2646/jtdline.jpg (http://img259.imageshack.us/my.php?image=jtdline.jpg)

125 hp is nothing even close to 234 hp……. </div></BLOCKQUOTE>

Using forces required works fine and gives very good agreement with measured results:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Before we get into that Spitfire with the mismatched propeller, let’s see how well the formula's gives agreement to the actual relationships and real world measured results.

We can take CAFE foundations Aircraft Performance Report. The CAFE foundation pioneered zero thrust glide testing to derive the drag curve. Their Aircraft Performance Reports are very well done and leave us with no stone unturned or aerodynamic questions about the aircraft.

The perfect test to see how our formulas agrees with real world measured results.

http://img142.imageshack.us/img142/6058/cafetestt182.jpg (http://img142.imageshack.us/my.php?image=cafetestt182.jpg)

http://cafefoundation.org/v2/pdf_apr/Thorp.pdf

Basic Aerodynamic data:

WT = 1600lbs

Wing Area = 86sqft

Span 20.8ft

b^2/S =5.03

Brake Horsepower Available - Lycoming O-360 A1B generating 180 bhp.

Propeller efficiency used in CAFÉ Performance Testing = 135 thp / 180 bhp = .75

This is well within the normal range for propeller efficiency which is usually between .75 and .85 with .8 being the median.

It does not matter what value we use as long as our value remains the same. We have to start form the same point to build our Thrust Horsepower Curve. This one is already built for us and everyone can see to the results to confirm the formula relationships work.

A quick word of caution on using propeller efficiencies outside the normal ranges is in order. Keep in mind the farther we get from our range of normal efficiency for a propeller, the farther off our calculated force relationships will be within the methodology. Our end result will remain the same but analyzing our components will not be as accurate.

Power known points:

150mph EAS = 70thp

@ 150mph CAS = 150mph EAS at Sea level on a standard day

Speed known points:

150 mph EAS * .869 = 130.35 KEAS

q= V^2/295

q = 57.6

198mph CAS = 198mph EAS * .869 = 172KEAS

Power of Induced drag @ 130.35KTAS

CL = 1600lbs/(57.6 * 86sqft) = .323

Cdi = .318 * {.323^2/.85*5.03) = .0078

Di = .0078*57.6*86 = 38.63lbs

Pri = (38.63lbs*130.35KTAS)/325 = 15.5thp

Prp = 70thp – 15.5thp = 54.6thp


AT 172KEAS

Prp = Prp2/54.6thp = (172KEAS / 130.35KEAS)^3

Prp = 125thp
Pri = Pri2/15.5thp = 130.5KEAS/172KEAS = 11.8


Pr = 125 + 12 = 137thp

137thp / .75 = 183BHP

A 1.6% error in our predication! </div></BLOCKQUOTE>


All the best,

Crumpp

Viper2005_
05-04-2009, 09:41 PM
Why don't you just go straight to "The Performance of a Supercharged Aero Engine", take the original Rolls-Royce performance model and have done with it?

It's relatively trivial to re-create the model in excel, and the results are in excellent agreement with published performance data (surprise surprise).

http://www.rolls-royce.com/abo...rged_aero_engine.jsp (http://www.rolls-royce.com/about/heritage/publications/technical-series/supercharged_aero_engine.jsp)

You'll need to do a little work to extend the model to handle 2 stage superchargers and intercoolers if you want to go down that path, but it isn't especially difficult stuff, especially since there is quite a lot of data available.

Very roughly (since my copy of the book is at home), basic thermodynamic relationships may be used to estimate the power demand of the supercharger.

We can easily calculate the pressure ratio:

P2 = 25+14.7psi absolute.

P2 = 273646 Pa

P1 = 8000 feet plus 400 mph ram.

P1 ~ 91824 Pa according to http://www.aerospaceweb.org/de.../scripts/atmosphere/ (http://www.aerospaceweb.org/design/scripts/atmosphere/)

P2/P1 = 2.98

Assuming gamma = 1.4:

T2/T1 = 2.98^(0.4/1.4)

T2/T1 = 1.36

T1 (total temperature in this context) = 288 K (same calculator).

288*1.36 ~392 K.

Work = mass flow * Cp * delta T

Delta T = 392-288 = 104 K.

Cp ~ 1005 J/kg/K

Mass flow is a little more complex. We can't use the ideal gas law because conditions aren't ideal.

However, if we assume that the engine burns stoichiometrically, the energy of the charge is going to be about 6 MJ/kg.

If we assume that the thermal efficiency will come out at about 33%, 1800 bhp ~ 1.342 MW. So the mass flow may be expected to be in the ballpark of 0.671 kg/s.

0.671*1005*104 ~ 94 horsepower.

Assuming 75% isentropic efficiency, the supercharger will therefore draw about 125 bhp, which is in surprisingly good agreement with Jtd's result.

uppurrz
05-04-2009, 09:59 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
IMHO it does!

They are heavy, complex, and a maintenance nightmare. With the exception of a tiny handful of post war piston engines that saw very limited application, there is nothing that can take advantage of their power absorption.

I think there are other design alternatives that do the job just as well without the added hassles.

All the best,

Crumpp </div></BLOCKQUOTE>

Yes two engines could replace the contra prop.