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XyZspineZyX
08-21-2003, 09:24 PM
If you have CEM enabled and fly a plane that has no auto pitch setting like LA 5 or LA7..... what Prop Pitch setting does the game launch into?

I've been flying LA7 ok with CEM on and never touching the Prop pitch.... in fact if I do try to use prop pitch I usually get into a mess.

Mark

XyZspineZyX
08-21-2003, 09:24 PM
If you have CEM enabled and fly a plane that has no auto pitch setting like LA 5 or LA7..... what Prop Pitch setting does the game launch into?

I've been flying LA7 ok with CEM on and never touching the Prop pitch.... in fact if I do try to use prop pitch I usually get into a mess.

Mark

XyZspineZyX
08-21-2003, 09:26 PM
100% is biggest thrust like in speed
0% is lowest thrust like in taxiing and works like the radiator (speed brake)


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XyZspineZyX
08-21-2003, 09:33 PM
I'll re-phrase that.


Take a non automated prop pitch plane (VVS).

In "CEM OFF" what does the sim do with prop pitch whilst you are flying. Does it alter the prop pitch for you?


In "CEM ON" what happens if you fly around without touching prop pitch settings? does the sim launch you into a random prop pitch setting or launch you into just an average joe setting.

Mark

XyZspineZyX
08-21-2003, 09:35 PM
no altering - it starts at 100% and stays there no change

low drag
hi torque - tries to turn you round

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XyZspineZyX
08-21-2003, 10:18 PM
It's a constant speed prop. Just leave it on 100%, unless your after more economy.

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XyZspineZyX
08-21-2003, 10:20 PM
lil_labbit wrote:
- 100% is biggest thrust like in speed
- 0% is lowest thrust like in taxiing and works like
- the radiator (speed brake)

Everything below considers a Constant Speed propeller at military power.

That isn't quite correct, 100% has the greatest mechanical advantage, thus requiring less torque (i.e. Force) for a given amount of work by increasing the distance over which it acts. However, the speed limitation is quite unrelated, it is limited by maximum engine output at a certain RPM, remember that many engines do not produce maximum torque, power, or range at maximum rpm.

60% Prop Lever has a smaller mechanical advantage, requiring greater particle acceleration. The torque required is much greater and the engine reaches maximum output capability. Exactly the same as 5th gear in a car, you can now load the engine until it is in the optimum rpm band for torque. You are now making the most use of your engine's power capability and this translates into speed.

The thrust really doesn't change because thrust is not associated with velocity. All prop pitch does is let you adjust the rpm at which your engine will attempt to produce maximum output. There are other large factors, like the best lift angle for the prop blades, viscosity of air, and many other aerodynamic factors, but these are left out for sake of simplicity.

It is not like a car gearbox because there is never a rev limit, at 100% Manifold Pressure, the engine is always working at full load. Compared to a manual gearbox in, say a Corvette, the aircraft's lowest pitch at 100% is no lower than about 5th gear in terms of how the engine is nearly unable to reach redline.

What you say about acting as speed brakes is quite incorrect as well, props will only slow you down when they are turning slower than their theoretical pitch rating. In this case, 100% pitch exposes the greatest prop area to the free stream. So 100% pitch at near idle throttle will slow you down more than at any other pitch. Aerobatics aircraft use this engine braking and consider it quite important to their routines.

Message Edited on 08/21/0305:33PM by Flightvector

XyZspineZyX
08-22-2003, 12:38 AM
FlightVector, your postings are alwayse extremely detailed, and inteligent, respectful, and also alwayse correct.

But I have one question (disagreement) in your above explanation. I have been under the impression that aircraft engines are designed to give maximum power (horsepower) at the rated (maximum CSP governed) engine RPM. So I believe it can be generally assumed (I'm sure there could be exceptions, there alwayse is) that putting the 'prop pitch lever full forward' (in FB, 100%) will give you maximum horsepower in all flight conditions (all flight conditions that the CSP can adjust for that is). Do you have information to the contrary?

michapma
08-22-2003, 09:17 AM
FlightVector,

I dare say you made me think hard. /i/smilies/16x16_robot-happy.gif

I have some questions about the development of power and thrust. Engine output power is rpm times torque (times 2pi). The propeller then has to translate that power to thrust. You seem to be saying that the aircraft engines are not designed to develop maximum torque at redline, but rather at lower rpms. One question for developing max engine ouput is then where does the maximum product of torque and rpm lie? Somewhere between peak-torque rpm (when the prop is loaded by a coarser pitch) and redline, or at peak torque? The question then is also does max engine output correspond to max thrust? If the propeller becomes less efficient at a coarser setting to load the engine and get peak torque, couldn't that actually reduce thrust? (The engine would be providing more power but not translating it to thrust, but of course I don't know whether the prop is actually less efficient at such a setting.)

I had assumed that you get max thrust at 100%, which corresponds to full rpm, and that the engines were designed to get max power at redline. In fact though, I recently read that to different Merlin engines (for the Spitfire? One was Rolls Royce Merlin and the other a Packard I guess.) had different power bands, the one ran like crap at low power but very smoothly at full power, whereas the other one was more broadly distributed, doing well at lower power settings but straining at high power. If that makes any sense.

I got some interesting info from this site, although there isn't enough about propeller performance (they are apparently still writing that).

http://www.epi-eng.com/index.html

Mike

<table width="100%" border="0" cellspacing="0" cellpadding="10"><tr valign="middle" bgcolor="#3e463b"><td height="40" colspan="3" align="center">The ongoing IL-2 User's Guide project (http://people.ee.ethz.ch/~chapman/il2guide/)</a></td></tr><tr bgcolor="#515e2f"><td width="40%">FB engine management:
Manifold Pressure sucks (http://www.avweb.com/news/columns/182081-1.html)
Those Marvelous Props (http://www.avweb.com/news/columns/182082-1.html)
Mixture Magic (http://www.avweb.com/news/columns/182084-1.html)
Putting It All Together (http://www.avweb.com/news/columns/182085-1.html)
Those Fire-Breathing Turbos (Part 1 of 6) (http://www.avweb.com/news/columns/182102-1.html)</td><td align="center">

‚ =69.GIAP=Chap‚

69.GIAP (http://www.baseclass.modulweb.dk/giap/)</p></td><td width="40%" align="right" valign="top">Hardware:
Flight Simulation Performance Analyzed (http://www.simhq.com/_air/air_062a.html)
Building a home-made throttle quadrant step by step (http://forums.ubi.com/messages/message_view-topic.asp?name=us_il2sturmovik_gd&id=zkavv)
Sound Can Be Hazardous for Games (http://www6.tomshardware.com/game/20030405/index.html)</td></tr></table>

XyZspineZyX
08-22-2003, 04:21 PM
Bump, in hope that a guru could clarify this. Most interested in the historic (real) context, but hope FB would be the same http://ubbxforums.ubi.com/infopop/emoticons/icon_smile.gif

XyZspineZyX
08-22-2003, 04:28 PM
BTW .. why do the Emils now maintain an RPM of about 2200 when Auto is enabled? This is pretty low ... no??

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XyZspineZyX
08-22-2003, 04:48 PM
Can someone please write the definative guide to Prop Pitch operation in FB for both VVS planes as well as Luftwaffe planes? I've taken the 109s off auto pitch, but over-revving my engine doesn't seem to translate to the greatest amount of actual power. All it seems to do is cause my engine to eventually seize. I've been flying low along the ground, and trying to maintain a fixed speed of 500kph for all my tests. While doing this, I adjust my throttle and prop pitch for different rph, let my speed build up to about 550kph, and then start climbing vertically. I figure the best settings should get me largest gain in altitude before my plane drops. I've only done this with the 109 so far, but my results seem dubious to me. If anyone has proper information on the topic, could they write a guide? I'd be glad to host it on my server space.

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XyZspineZyX
08-22-2003, 04:57 PM
I believe TailSpin wrote a good (.pdf) document that gives correct RPM settings for all Bf109's (and information on all aircraft). Unfortunately I have misplaced this web address. Also Michampa is putting together an extremely comprehensive guide to flying, though I think he isn't finished yet. For 109's you need to find out the 'optimum RPM' for that model 109 (my apologies as I don't know them), that RPM is what you should attempt to maintain to avoid engine damage and give maximum power output (I believe it is roughly 100-200 RPM over what the 'automated system' runs it at, though this is a guess). For example the FW190D9 (simlar system as 109's) runs around 3100RPM, while the Bf109E runs around 2400RPM I believe.

XyZspineZyX
08-22-2003, 05:10 PM
Is TailSpin's document about the post-patch CEM or the pre=patch CEM, because I remember that Oleg was saying something about changing the prop-pitch system since it had innacuracies.

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michapma
08-26-2003, 04:09 PM
According to the manual from bf109.com the Emil has the following specific power settings:

d. Betriebsdaten (operational data)

Motordrehzahl and Ladedruck (RPM and manifold pressure)

<table width=50%><tr><td>‚ </td><td>Drehzahl
U/min</td><td>Ladedruck
ata</td></tr><tr><td valign="top">Erh√¬∂hte Kurzleistung
(increased short-term power)</td><td align="center">2468</td><td align="center">1,45</td></tr><tr><td valign="top">Kurzleistung
(short-term power)</td><td align="center">2368</td><td align="center">1,35</td></tr><tr><td valign="top">Erh√¬∂hte Dauerleistung
(increased long-term power)</td><td align="center">2326</td><td align="center">1,30</td></tr></table>


Imprecise translation is my fault. I am not 100% sure of the exact meaning of erh√¬∂ht in this sense, but it is clear that the first one is not meant to be exceeded, and fairly clear that the bottom one can be prolonged for quite some while.

Bumping in the hopes of a guru for the above questions.

Mike

Edit: making the table look right

<table width="100%" border="0" cellspacing="0" cellpadding="10"><tr valign="middle" bgcolor="#3e463b"><td height="40" colspan="3" align="center">The ongoing IL-2 User's Guide project (http://people.ee.ethz.ch/~chapman/il2guide/)</a></td></tr><tr bgcolor="#515e2f"><td width="40%">FB engine management:
Manifold Pressure sucks (http://www.avweb.com/news/columns/182081-1.html)
Those Marvelous Props (http://www.avweb.com/news/columns/182082-1.html)
Mixture Magic (http://www.avweb.com/news/columns/182084-1.html)
Putting It All Together (http://www.avweb.com/news/columns/182085-1.html)
Those Fire-Breathing Turbos (Part 1 of 6) (http://www.avweb.com/news/columns/182102-1.html)</td><td align="center">

‚ =69.GIAP=Chap‚

69.GIAP (http://www.baseclass.modulweb.dk/giap/)</p></td><td width="40%" align="right" valign="top">Hardware:
Flight Simulation Performance Analyzed (http://www.simhq.com/_air/air_062a.html)
Building a home-made throttle quadrant step by step (http://forums.ubi.com/messages/message_view-topic.asp?name=us_il2sturmovik_gd&id=zkavv)
Sound Can Be Hazardous for Games (http://www6.tomshardware.com/game/20030405/index.html)</td></tr></table>

Message Edited on 08/26/0305:15PM by michapma

michapma
08-27-2003, 10:52 AM
The link to Tailspin's fbengines.pdf can be found in Vulgar's CEM guide:
http://mywebpages.comcast.net/Tailspin/documents/CEM_IL2FB.htm

Direct link:
http://mywebpages.comcast.net/Tailspin/fbengines.pdf


<table width="100%" border="0" cellspacing="0" cellpadding="10"><tr valign="middle" bgcolor="#3e463b"><td height="40" colspan="3" align="center">The ongoing IL-2 User's Guide project (http://people.ee.ethz.ch/~chapman/il2guide/)</a></td></tr><tr bgcolor="#515e2f"><td width="40%">FB engine management:
Manifold Pressure sucks (http://www.avweb.com/news/columns/182081-1.html)
Those Marvelous Props (http://www.avweb.com/news/columns/182082-1.html)
Mixture Magic (http://www.avweb.com/news/columns/182084-1.html)
Putting It All Together (http://www.avweb.com/news/columns/182085-1.html)
Those Fire-Breathing Turbos (Part 1 of 6) (http://www.avweb.com/news/columns/182102-1.html)</td><td align="center">

‚ =69.GIAP=Chap‚

69.GIAP (http://www.baseclass.modulweb.dk/giap/)</p></td><td width="40%" align="right" valign="top">Hardware:
Flight Simulation Performance Analyzed (http://www.simhq.com/_air/air_062a.html)
Building a home-made throttle quadrant step by step (http://forums.ubi.com/messages/message_view-topic.asp?name=us_il2sturmovik_gd&id=zkavv)
Sound Can Be Hazardous for Games (http://www6.tomshardware.com/game/20030405/index.html)</td></tr></table>

XyZspineZyX
08-27-2003, 03:34 PM
Aero engines differ from car engines in that maximum RPM, torque and power all come pretty much at the same point. Anything else would mean lugging around more hardware than necessary to transfer the maximum power at an RPM lower than maximum.

Overrevving will indeed likely mean loss of power and will not do your engine, transmission and prop much good. Your ground crews will hate you.

Cheers,
Fred

"If we are an arrogant nation, they will resent us. If we are a humble nation, but strong, they will welcome us."
- George W. Bush, during his campaign. No comment.

(Quote brought back by popular demand - RBJ missed it so much he mailed me about it)