Prop Pitch question...

[41Sqn_Banks]

Thats wrong. Your comparison with a manual transmission in a car is only valid when having a manual pitch control, but not for constant speed. A csp is a car with automatic transmission where 100% rpm is for "sporty" driving and everything below 100% rpm is for economical driving.

Top Speed is at maximum rpm and maximum boost, just look at historic performance tests, for top speed they always were at maximum rpm and maximum boost. Why would they do this when there was more speed at lower rpm

[Codex]

Have read here: http://people.ee.ethz.ch/~chapman/il.../proppitch.htm

Be patient with it, read it over a few times if you have to...you'll get it eventually.

[Flyby]

I think I understand a little of the prop pitch article, but I'm not all that clear on it as I think I should be. Someone check me out, please. I'm thinking of altitude, and speed situations where I need to adjust prop pitch to either achieve, or maintain performance. For instance:
* I think I need more pitch at higher altitude for biting into the thinner air, and less drag on the airfoils (wings, and propeller blades), especially if speed has fallen off like during a long climb.
* I think I need to decrease prop pitch when I dive from high altitude, as speed builds up, and engine rpm rises ( I'd have to watch, and adjust pitch to keep rpms from over-reving the engine).
* I think I don't need as much "bite", in general, from the prop at lower altitudes where the air is more dense.
* I think all of the above are dependant on tactical power requiremens. That is, whatever it takes to keep the engine in the desired performance regime: Max aircraft speed at low altitude versus max aircraft speed at high altitude: increasing diving speed: takeoff: landing: cruising.
I guess it all depends on the individual aircraft, and knowing your plane, or watching the engine revs. Anyway, that's my thinking. Am I on the right track anywhere here?
thanks!
Flyby out

[41Sqn_Banks]

I really don't understand why so many people have problems with that topic. In fact you can reduce it to some basic rules:

If you have a CSP you don't need to care about the angle of the blades or something, all this is done by the CS governor. The only thing you need to think about is the engine RPM. And there the rule is simple:
High RPM = high acceleration, high speed, high temperature, high fuel consumption
Low RPM = low acceleration, low speed, low temperature, low fuel consumption

When diving you can make a "power dive" which is with high RPM and high Boost, or you can do a "low drag dive" with low RPM and low Boost, or you can do a "high drag dive" with high RPM and low Boost.

Thats all ... Same rules for a manual propeller, only that you need to maintain the RPM yourself at the high or low level.

[Flyby]

I wonder how many planes in IL2 have a cps? At least Banks is honest when he says he doesn't understand why so many people have a problem understanding with this topic. Now I wonder how many people actually DO have a problem understanding the topic. I think I'm at least one who is/was not perfectly clear on it.
Flyby

[Bearcat]

Most of the American ones do... and as far as a CSP prop goes.... think throttle = Manifold pressure prop pitch = RPM.. If you do not let your RPM redline you will get more out of the engine.

[BSS_Sniper]

Originally Posted by 41Sqn_Banks

Thats wrong. Your comparison with a manual transmission in a car is only valid when having a manual pitch control, but not for constant speed. A csp is a car with automatic transmission where 100% rpm is for "sporty" driving and everything below 100% rpm is for economical driving.

Top Speed is at maximum rpm and maximum boost, just look at historic performance tests, for top speed they always were at maximum rpm and maximum boost. Why would they do this when there was more speed at lower rpm

CEM is so messed up in this game, I mean, he never really had it modeled.

I believe you got things mixed up a bit. Manual pitch control and constant speed propellers are the same thing. When you set a RPM with your prop lever you are doing two things, changing the angle of the blade AND setting a particular RPM. Neither change with power (manifold pressure) inputs.

If you're confused in game about how to use these things, its understandable since it isn't modeled correctly. Each aircraft has a chart in the pilot operating handbook that shows manifold pressure and prop settings for different phases of flight ie; takeoff, climb, cruise climb, cruise, decent, approach and landing. For full power and speed its always full MP and full Prop. Again, this game doesn't model it correctly and the little tricks learned to do different things in here (concerning CEM) would not work in a real plane, it would destroy the engine.

I fly aircraft with constant speed propellers daily for work, turbines included. My boss would kill me if I pulled my pp back to 50% (as it is in game) and had full power. lol

Here's an example that explains a bit of what you shouldn't do, generally. It puts it into words better than I can.

"For any given RPM, there is a
manifold pressure that should not be exceeded. Manifold
pressure is excessive for a given RPM when the cylinder
design pressure is exceeded, placing undue stress on them.
If repeated or extended, the stress would weaken the
cylinder components and eventually cause engine failure."

http://www.coryat.com/faa-pp-written/index11.html

Read the Q & A there. It should help explain things a bit. The short answer to someone about pulling your PP back for more speed isn't correct. Again, before you even begin to pull your prop back you have to pull your throttle back or you will damage your engine, just not in game because it isn't modeled.

One last thing, that info is for real world aircraft/flying. In game you can do whatever and have different results, none of which are correct in the real world.

[Rama]

Originally Posted by BSS_Sniper

I believe you got things mixed up a bit. Manual pitch control and constant speed propellers are the same thing. When you set a RPM with your prop lever you are doing two things, changing the angle of the blade AND setting a particular RPM. Neither change with power (manifold pressure) inputs.

Sorry, but you're wrong.
With CSP, inside the CS governor limits, the blade angle WILL change with speed and attitude variations.
Since Speed and attitude will change il you change power (manifold pressure), then blade angle WILL change.... and same if you use elevator input to climb or dive.

Manual pitch control is different: The pitch angle is directly controlled by the pitch lever.

With IL2, almost all planes are CSP equiped when they don't have fixed pitch.
Only Bf109 (and maybe Bf110... don't remenber...) use manual prop pitch when automatized control is off.
Even FW190 never use manual controlled pitch, but CSP when Kommandogerät is off.

[BSS_Sniper]

Originally Posted by Rama

Sorry, but you're wrong.
With CSP, inside the CS governor limits, the blade angle WILL change with speed and attitude variations.
Since Speed and attitude will change il you change power (manifold pressure), then blade angle WILL change.... and same if you use elevator input to climb or dive.

Manual pitch control is different: The pitch angle is directly controlled by the pitch lever.

With IL2, almost all planes are CSP equiped when they don't have fixed pitch.
Only Bf109 (and maybe Bf110... don't remenber...) use manual prop pitch when automatized control is off.
Even FW190 never use manual controlled pitch, but CSP when Kommandogerät is off.

I think you misunderstood me or vice versa. The RPM's remain the same after you set them with the prop lever is what I was trying to convey. Either way, this sim does not model anything even close to what should happen other than the RPM you see on the gauge.

I see you were refering to an old system "manual pitch" otherwise known as controllable pitch. Most aircraft are CSP if they have a prop lever today. That threw me off.

In any of the convention constant speed aircraft, for example the P51 or F6F Hellcat. If you have run low rpm settings with a high manifold pressure, you will/can damage the engine. The way you explained it makes it sound as if the blade angle will adjust for the MP change and it will not. In the 190's and 109's, its automatic.

[Rama]

Originally Posted by BSS_Sniper

In any of the convention constant speed aircraft, for example the P51 or F6F Hellcat. If you have run low rpm settings with a high manifold pressure, you will/can damage the engine. The way you explained it makes it sound as if the blade angle will adjust for the MP change and it will not. In the 190's and 109's, its automatic.

The blade angle will adjust for the MP change, until the the CS governor limit is reached, then blade angle will stay fixed and MP will change. (when low stop limit or high stop limit is reached)
This is actually modelled in the game, and with most of the planes, if you set RPM very low and Boost at max, engine will heat, then breake (so you can overtorque)
Overrev is modelled only for some planes, so with most off them you can dive with high RPM without risking overreving (which isn't realistic)

So I agree the game is much more tolerant to overreving and overtorque than reality..

For Bf109, the automatic control can be switched off, and then you get manual prop pitch (not CSP, but pitch direct input). This is correct in real and correctly modelized.
For FW190, when automatic control (Kommandogerät) is switched off, then you get the standard CSP for pitch control.