[II./JG1_Krupinski]

This is always a source of confusion for many reasons. First, there is many types of prop pitch setups in IL-2, as there were in the real planes. Second, people have a misconception about the idea of changing the pitch of a prop.

After reading the first page and a half, I just have to post and hopefully clear the air.

First, adjustable pitch props are just like transmissions in a car. BUT, this is in the sense of ALLOWING the driver or pilot to set the engine RPM. In a race car, the transmission is geared to put the RPMs at or close to where the engine produces maximum power.

In a sedan, the transmission is not geared the same way, and a balance between power and efficiency is made.

When an engine is producing power, it doesn't do so linearly across the RPM and power output doesn't just keep going up with RPM. There is a curve where at low RPMs its producing a low amount of power, at higher RPM the engine will be producing more power; BUT at max RPM the engine MAY NOT be producing max power. However, power output is directly related to RPM. There is a POWER CURVE related to RPM.

Since the above paragraph is true, you want some tool to allow the pilot to set the RPM of the engine. In combat situations, he would want to set the RPMs where ever the engine produces most power, at the peak of the power curve. In cross country situations, the pilot would favor efficiency over power output so he may set the engine RPMs lower than peak so to save on fuel and engine life.

There are a handful of types of adjustable props in the game. The best is a CONSTANT SPEED PROP. This term is misleading as it really dictates the speed of the engine, not the speed of the prop. This type is found mostly on the US birds such as the P51. What happens is the pilot finds the RPM he wants to use (ie 2500) and sets the pitch to keep the engine @ 2500 rpms. The neat part now is, no matter what throttle settings he uses the governor will dynamically adjust the pitch of the prop so the engine maintains a constant speed of 2500 RPM. Now, at really power settings, the engine just can't produce enough power and the governor is set to NOT go to a 0° propeller AoA, so the RPMs will drop at low settings. The big payoff with this system, is the RPMs will be constant at all airspeeds, without intervention from the pilot.

The next type of adjustable pitch propeller is just that; The Adjustable Pitch Propeller or Variable Pitch Propeller. The german fighters are built like this, IN GENERAL! (I say in general because 190 & 109 prop systems are similar they are really different) In this system, the pilot has direct control over the pitch of the prop. But again, the pilot would want to set the pitch to dictate the engine RPM's for he given situation. BUT... BUT... BUT... He must constantly change the pitch as his airspeed changes. In a climb, he has to apply a finer setting (closer to 100%), in a dive he has to apply a coarser setting (closer to 0%). Else in the former case he'll stall out or in the latter burn his engine up due to the high RPMs. Even straight and level flight needs attention as generally the airspeed increases so therefore you must use a coarser setting to maintain the same RPMs. In this system the RPMs will change also with throttle setting. Its a relationship between throttle, pitch setting and air speed; if any of these change, so does the RPMs. Therefore the pilot must constantly manually change the pitch setting.

NOTE: 100% PITCH DOES NOT EQUAL 100% POWER AT ANY THROTTLE SETTING! More RPMs does not mean go faster. It's all about setting the engine to the RPM at which it produces the maximum power for any throttle setting*.

*Even if the throttle isn't @ 100% or above, the engine still has a power curve, it's peak is the same RPM at max power, but it's just not putting out max power.

Note: 190 is NOT a Constant Speed Propeller.
Petition to get power curves published!