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Tranie117
09-08-2008, 05:23 AM
So erm, what is it... How is it different to throttle when should I use it etc. Thanks.

Tranie117
09-08-2008, 05:23 AM
So erm, what is it... How is it different to throttle when should I use it etc. Thanks.

foxyboy1964
09-08-2008, 05:43 AM
Think of prop pitch (PP) like the gears on a car, or bike.

100% PP= 1st gear

0% PP= 6th gear, or on a bike 21st gear

If you're going uphill on a bike you would select somethimg between maybe 4th and 1st gear. If you're climbing in the aircraft you would select something between maybe 85% and 100%.

Going downhill you would select maybe 18th to 21st gear (if you want to pick up speed). In the aircraft you'd select maybe 30% to 0%.

This is a very simple way of looking at it, and all the aircraft are different, but it's a good enough description to be going on with. You should try to get used to listening to the noise the engine makes while looking at the rev counter and keeping the revs in the power band.

Uufflakke
09-08-2008, 07:19 AM
This link will help you with Complex Engine Management (CEM) including Prop Pitch, Throttle, Supercharger, Fuel Mixture, etc...

http://www.airwarfare.com/Sims/FB/fb_cem.htm#Prop%20Pitch

M_Gunz
09-09-2008, 05:22 AM
Here's just one 3 pager on the subject... (http://forums.ubi.com/eve/forums/a/tpc/f/23110283/m/1921082203?r=1921082203#1921082203)

The Search does work even though it's called Find here. Try Find --> prop +pitch
It's amazing how many threads have a post mentioning some use or asking a question about it.
A whole lot of typing just archived there for no reason whatsoever.

Zeus-cat
09-10-2008, 11:07 PM
Isn't 0% prop pitch like your bike chain has come off? I don't think you get any thrust out of the prop at 0%.

Altamov_Steppes
09-10-2008, 11:29 PM
In simple terms a CSU has two controls:
1. the throttle - which controls RPM
2. a propellor governor- which changes the pitch of the blades

Regards
KT

sw25th
09-11-2008, 12:00 AM
in the airplane i fly, if you take the prop all the way back and leave the throttle you get a higher manifold pressure but slower engine speed. So, really we only adjust the prop about 500RPM difference from full. so if 2700 RPM we never go below 2200RPM.

Now on our checklist it says take the prop to idle with engine failure, and this is so we can increase our glide distance.

when a prop has a small AOA and is windmilling it creates more drag, and when it's at a wider pitch it produces drag, just less.

In this game, you must adjust prop pitch based on engine RPM, not %.

So look at the RPM gauge in the cockpit and adjust the % based on that.

copet
09-11-2008, 12:03 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Uufflakke:
This link will help you with Complex Engine Management (CEM) including Prop Pitch, Throttle, Supercharger, Fuel Mixture, etc...

http://www.airwarfare.com/Sims/FB/fb_cem.htm#Prop%20Pitch </div></BLOCKQUOTE>

WOWOWOWOW! That is so helpful, yet intimidating. I've been playing for a month now and haven't really messed with much of that, but it seems like it can really affect my performance if I do it right. Thanks for that link!

idonno
09-11-2008, 01:10 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Altamov_Steppes:
In simple terms a CSU has two controls:
1. the throttle - which controls RPM
2. a propellor governor- which changes the pitch of the blades

Regards
KT </div></BLOCKQUOTE>

After I wrote this I noticed I'm kind of repeating sw25th, but here it is anyway.

The throttle controls manifold pressure, not rpm's. The propeller governor controls rpm's by adjusting the blade pitch.

In real life you don't adjust the prop based on a percentage, but by the rpm's. For example, climb settings for a P-47 would be something like 2700 rpm's and 52 inches of manifold pressure, and cruise settings could be 2300 and 27 inches.

It's hard on an engine to run it with low rpm's and high manifold pressure, but unfortunately that doesn't seem to be modeled in-game.

You won't go as fast with lower rpm settings, but you will burn less fuel with the right combination of rpm and manifold pressure. Also, some people use lower rpm's in the game to keep the engine cool.

M_Gunz
09-11-2008, 03:38 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Zeus-cat:
Isn't 0% prop pitch like your bike chain has come off? I don't think you get any thrust out of the prop at 0%. </div></BLOCKQUOTE>

The prop in normal operation has limits to the angle it can turn and they are not 0 to 90, more
like less than half that. Only some props will feather and that's a special step.

You can control CSP pitch with throttle. Leave the rpms steady and vary the throttle, the
pitch of the prop will change just to keep the rpms steady. You can leave throttle and rpms
set and change pitch by climbing or diving. Of course you are only getting the pitch to change
indirectly, it's some secret trick to run faster or jump higher like a pair of Keds.

Altamov_Steppes
09-11-2008, 06:18 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by idonno:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Altamov_Steppes:
In simple terms a CSU has two controls:
1. the throttle - which controls RPM
2. a propellor governor- which changes the pitch of the blades

Regards
KT </div></BLOCKQUOTE>

After I wrote this I noticed I'm kind of repeating sw25th, but here it is anyway.

The throttle controls manifold pressure, not rpm's. The propeller governor controls rpm's by adjusting the blade pitch.

<span class="ev_code_YELLOW">true!...however, to be more in depth about it: throttle increases the fuel/air flow to give rise to a certain manifold pressure which in turn determines the RPM at that throttle setting. The variable pitch prop is intended to keep the RPMS in rough synch with the manifold pressure. Therefore the variable pitch propellor contols both prop and engine.
Oil pressure it is that actually operates the prop pitch mechanism. For this reason if there is a critically reduced oil pressure the pitch of the prop in single engined aircraft will bounce back to fine pitch and blow the engine if the engine RPM is not in a certain ratio with with Manifold Pressure (I believe I've found this modelled in the 109). By contrast, multi-engined aircraft go to c-o-a-r-s-e pitch at critically reduced oil pressure and 'feather' the props.
It is for these reasons that the danger of blowing an engine is more risky when going down hill. It is for these reasons that lowered prop pitch is used for low power settings such as cruise and descent and high prop pitch settings for high power operations such as climb and takoff. To be noted is the fact of fixed pitch propellored aircraft blowing their engines when their engine speed exceeds the useful absorption of power that that particular fixed pitch propellor can achieve from its engine. Regards KT </span>

In real life you don't adjust the prop based on a percentage, but by the rpm's. For example, climb settings for a P-47 would be something like 2700 rpm's and 52 inches of manifold pressure, and cruise settings could be 2300 and 27 inches.

<span class="ev_code_YELLOW">The procedure of matching the Manifold Pressure with RPM in a certain ratio does not apply to turbo-supercharged engines such as the Allison in the P-47. Regards KT</span>

It's hard on an engine to run it with low rpm's and high manifold pressure, but unfortunately that doesn't seem to be modeled in-game.

You won't go as fast with lower rpm settings, but you will burn less fuel with the right combination of rpm and manifold pressure. Also, some people use lower rpm's in the game to keep the engine cool. </div></BLOCKQUOTE>

idonno
09-11-2008, 06:49 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Altamov_Steppes:
<span class="ev_code_YELLOW">... throttle increases the fuel/air flow to give rise to a certain manifold pressure which in turn determines the RPM at that throttle setting.</span> </div></BLOCKQUOTE>

That is incorrect. The RPM's (while they may fluctuate momentarily) do not follow changes in manifold pressure. As you raise and lower the MP, the pitch of the blades will adjust to whatever angle is necessary (within the mechanism's physical limits) to maintain the set RPM's. If you reduce MP, the blades will go to their finest pitch if necessary. If you increase MP, the blades will adjust to take a bigger bite. Either way, the RPM's will remain constant.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Altamov_Steppes:
<span class="ev_code_YELLOW">The procedure of matching the Manifold Pressure with RPM in a certain ratio does not apply to turbo-supercharged engines such as the Allison in the P-47. Regards KT</span> </div></BLOCKQUOTE>

Yes it does. The settings I presented were taken from a P-47 power settings chart.

idonno
09-11-2008, 07:01 PM
Altamov_Steppes,

After reading your last post again, I realized that you are talking about an automatic system like the ones found on the 109 and 190. As far as those systems go, you are correct.

WTE_Galway
09-11-2008, 08:13 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by idonno:
Altamov_Steppes,

After reading your last post again, I realized that you are talking about an automatic system like the ones found on the 109 and 190. As far as those systems go, you are correct. </div></BLOCKQUOTE>

yeah, its kinda important to remember that 109 auto pitch is not the same as the modern Constant Speed Prop.

Else confusion will result. Be sure.

Altamov_Steppes
09-11-2008, 09:02 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by idonno:
Altamov_Steppes,

After reading your last post again, I realized that you are talking about an automatic system like the ones found on the 109 and 190. As far as those systems go, you are correct. </div></BLOCKQUOTE>

Just check whether the ratio MP/Hg you quoted is from a P-47-10. I'm not sure if the 10 was turbo-supercharged or not. I believe not. I think it was the P-47D-27 that first introduced the turbo-supercharged engine.

If this is so then the 10 would require monitoring of the MP/Hg ratio whereas the 27 would not because it was turbo-charged.

As a rule of thumb the Hg in units should match RPM in 1000's. So, for example if cruise RPM is 2200 then there should be about 22 Hg to minimise risk of damage.

This means your quoted figues for the P-47 for cruise matches this general rule while the figures for climb gives Hg twice as much than the general rule. I would check if it's a 10 Thunderbolt. If it's a 27 Thunderbolt the figures are automatic and result from the Turbo RPM gauge and not the normal RPM gauge.

Regards KT

idonno
09-11-2008, 10:27 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Altamov_Steppes:

Just check whether the ratio MP/Hg you quoted is from a P-47-10. I'm not sure if the 10 was turbo-supercharged or not. I believe not. I think it was the P-47D-27 that first introduced the turbo-supercharged engine.

If this is so then the 10 would require monitoring of the MP/Hg ratio whereas the 27 would not because it was turbo-charged.

As a rule of thumb the Hg in units should match RPM in 1000's. So, for example if cruise RPM is 2200 then there should be about 22 Hg to minimise risk of damage.

This means your quoted figues for the P-47 for cruise matches this general rule while the figures for climb gives Hg twice as much than the general rule. I would check if it's a 10 Thunderbolt. If it's a 27 Thunderbolt the figures are automatic and result from the Turbo RPM gauge and not the normal RPM gauge.

Regards KT </div></BLOCKQUOTE>


P-47N Pilot Training Manual (http://www.tailwheel.nl/downloads/p47trainingmanualsmall.pdf)

M_Gunz
09-11-2008, 11:31 PM
The P-47 we know, from the redesign of the XP-47A to the XP-47B was built around the turbocharger.

Every production P-47 had a turbocharger. Every IL2 P-47 model has one modeled.

Curtiss-Wright came out with an electric CSP around 1930. At least some P-39's and P-40's had it.
Hamilton-Standard came out with a hydraulic CSP later on. It was used on many heavy planes.
Rotol had one and I don't know who else.

They all work on adjusting blade pitch finer to let the prop turn to speed and co****r to slow
it down. Examine automatic valves on steam engines and you'll find some of the same principles
at work, it was not unprecedented engineering at the time and surely some twisting was done to
avoid paying patent rights was involved in how many designs were used.

Altamov_Steppes
09-11-2008, 11:51 PM
From reading the relevant parts of the manual (pages in the 20's) it appears the N series was the first to install an Automated Engine Control.
Before that there was a turbo control lever or 'B' lever (if the game is correct we should see that in game). It seems to me that the game could possibly simulate the automatic engine control (just press the WEP button and move the throttle simultaneously ?). Similarly, it appears we can, in game, simulate a decouple of the throttle and PP levers levers and go real for those P-47 series below the N series (unlatched for takeoff, cruise etc and latched for WEP) by advancing RPM (prop pitch) before manifold pressure and decrease manifold pressure (throttle) before RPM. Just an observation.
Regards KT

Altamov_Steppes
09-11-2008, 11:57 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:

...They all work on adjusting blade pitch finer to let the prop turn to speed and co****r to slow it down. Examine automatic valves on steam engines and you'll find some of the same principles at work, it was not unprecedented engineering at the time and surely some twisting was done to
avoid paying patent rights was involved in how many designs were used. </div></BLOCKQUOTE>

yes...pre flight check of turbo-charged aircraft includes (if there is airmanship in the pilot) checking the valves that allow the oil to work the pitch change. They must allow the oil to flow evenly.

No41Sqn_Banks
09-12-2008, 01:44 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Altamov_Steppes:
From reading the relevant parts of the manual (pages in the 20's) it appears the N series was the first to install an Automated Engine Control.
Before that there was a turbo control lever or 'B' lever (if the game is correct we should see that in game). It seems to me that the game could possibly simulate the automatic engine control (just press the WEP button and move the throttle simultaneously ?). Similarly, it appears we can, in game, simulate a decouple of the throttle and PP levers levers and go real for those P-47 series below the N series (unlatched for takeoff, cruise etc and latched for WEP) by advancing RPM (prop pitch) before manifold pressure and decrease manifold pressure (throttle) before RPM. Just an observation.
Regards KT </div></BLOCKQUOTE>

Ok now I unterstand the confusion in this thread (after reading is several times). We only have a "throttle" which controls the "manifold preasure" and a "rpm lever" which controls the "engines rpm" (the rpm of the crankshaft).
There is no spererated "b" (boost) turbo-lever that controls the "turbo rpm" (the rpm of the turbine). Ingame the "throttle" controls the "butterfly valve of carburator" and the "turbo waste gate" (which regulates the "turbo rpm"), hence in game we have only the automatic engine control system.

What you are doing is mixing "eninge rpm" and "tubo rpm", you should not do this they are different things.
If "throttle" is increased the "turbo rpm" is increased to give a higher manifold preasure, but the "engine rpm" remains constant due to the constant speed coverner which regulated the pitch of the propeller blades. However if you decrease "engine rpm" the manifold preasure remains the same and "turbo rpm" doesn't change.

Oh and this only applies to aircraft with turbo-supercharger like the P-47. Other aircraft with only a supercharger (Spitfire, Mustang, ...) don't have a "turbo rpm" as they don't have a turbo http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif Here the "throttle" controls the manifold preasure only by adjusting the "butterfly valve of carburator". But again the "rpm lever" controls the engines rpm.

Altamov_Steppes
09-14-2008, 06:01 PM
I had earlier differentiated turbo rpm from from the engine rpm gauge.

The turbo rpm allows a higher input of Hg to boost performance while the manifold pressure gauge measures pressure at the exhaust outlets (which is the measure of POWER being put out by the engine; while the PP regulates the THRUST developed by the particular propellor's useful absorption of the engine power at a certain RPM)

The point I tried to put across is that non-turbo-charged engines are restricted to a risk management strategy of appropriately matching the manifold pressure with the RPM in a certain ratio. This 'rule' does not apply to turbo-supercharged engines.

With this knowledge it is quite possible to fly the touchy 109 for example out of its automatic variable pitch system (Shift 0). But why bother unless there is reason (such as other performance envelopes or damage to the oil pressure system)?

Regards KT

M_Gunz
09-14-2008, 06:25 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Altamov_Steppes:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:

...They all work on adjusting blade pitch finer to let the prop turn to speed and co****r to slow it down. Examine automatic valves on steam engines and you'll find some of the same principles at work, it was not unprecedented engineering at the time and surely some twisting was done to
avoid paying patent rights was involved in how many designs were used. </div></BLOCKQUOTE>

yes...pre flight check of turbo-charged aircraft includes (if there is airmanship in the pilot) checking the valves that allow the oil to work the pitch change. They must allow the oil to flow evenly. </div></BLOCKQUOTE>

That would be pre-flighting any plane with Hamilton Standard or other hydraulic prop.
P-47 just happens to have both the prop and the turbo. Not all do.

Manifold pressure is measured between the throttle plate and venturi -and- the engine.
It tells the pressure of the air going into the engine.

In normally aspirated engines. (http://www.warmkessel.com/jr/flying/td/jd/15.jsp)
It's the same for turbos. (http://www.warmkessel.com/jr/flying/td/jd/31.jsp)

Unless perhaps someone wants to say that John Deakin doesn't know his stuff. These are the old
Pelican's Perch columns from AVweb, a serious Pilot site.

R_Target
09-14-2008, 08:15 PM
P-47 doesn't have an Allison engine.

Altamov_Steppes
09-14-2008, 08:23 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:
Manifold pressure is measured between the throttle plate and venturi -and- the engine.
It tells the pressure of the air going into the engine.
</div></BLOCKQUOTE>

That definition limits the use of the Manifold Pressure Gauge...enough said.

Regards KT

idonno
09-14-2008, 10:18 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Altamov_Steppes:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
Manifold pressure is measured between the throttle plate and venturi -and- the engine.
It tells the pressure of the air going into the engine.
</div></BLOCKQUOTE>

That definition limits the use of the Manifold Pressure Gauge...enough said.

Regards KT </div></BLOCKQUOTE>

What's your point?

M_Gunz
09-14-2008, 10:31 PM
What pilots know as the Manifold Pressure Gauge and engineers know as the same, where it is
located and how it works is now a matter of definition that somehow limits its use or can
be changed to something else to enhance the same?

I guess that when someone invents something else and it gets used then there will be a name.
It's been that way for a long time now. But the usual practice is not to use a name already
for something else, just to keep the confusion down as some kind of courtesy I suppose.

I wonder if anyone measures exhaust pressure on something other than a jet or rocket, at least
during normal operation and not while in the shop? Does anyone measure EPR on piston engines?

Altamov_Steppes
09-14-2008, 10:40 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:
What pilots know as the Manifold Pressure Gauge and engineers know as the same, where it is
located and how it works is now a matter of definition that somehow limits its use or can
be changed to something else to enhance the same?

I guess that when someone invents something else and it gets used then there will be a name.
It's been that way for a long time now. But the usual practice is not to use a name already
for something else, just to keep the confusion down as some kind of courtesy I suppose.

I wonder if anyone measures exhaust pressure on something other than a jet or rocket, at least
during normal operation and not while in the shop? Does anyone measure EPR on piston engines? </div></BLOCKQUOTE>

The Manifold Pressure Gauge can be used for measuring a number of things when the engine is not running. This is in fact modelled in il-2. Check it out in game.

Tranie117
09-15-2008, 11:40 AM
I probably should've mentioned this at the begining of the discussion but I'm pretty new to Il-2 &lt;--- Rhym! So alot of that was a tad over my head, but I'm reading through the varrious articals and responses you guys have posted and I think I'm begining to get to grips with this prop pitch stuff! thanks