PDA

View Full Version : some questions about propeller pitch



raaaid
11-11-2004, 03:43 PM
first when you increase pp the propeller wings have less or more contact with the air?

2nd why when i put propeller pitch to 0 the engine almost stops and if i put it to 10 it burns the engine out?

thanks in advance

-HH- Beebop
11-11-2004, 04:34 PM
"Pitch" refers to the angle of the blades to the air. At 100% prop pitch they are almost flat. As you decrease the prop pitch the blades cut into more air. Theroeticly this should increase your speed at the cost of engine RPM's. However in FB, with the exception of the Messerschmidts, prop pitch is not really prop pitch, it's an engine RPM govener. Many late war aircraft had "automatic" pitch.

As for PF, I'm not sure but I believe that prop pitch is only an RPM govener. What I do know is if I'm approaching the carrier too fast I lower the prop pitch to -0- and effectively slow the plane. Of course if I fail to land and get a 'wave off' I have to remember to return to 100% pitch or I go swimming.

For a good tutorial (IMO) on prop pitch and Complex Engine Management in general, try this:
http://people.ee.ethz.ch/~chapman/il2guide/cemguide/intro.htm

Fliger747
11-11-2004, 05:30 PM
The type of prop used is called a 'Constant Speed'. By this the prop govenor controls the prop pitch to maintain engine RPM at a constant (set) value. By moving the prop control, one changes the desired value and the blades will adjust their angles, depending on engine load and airspeed, to maintain that set value.

In actuality with the engine at or near idle, in flight, a very fine pitch (high RPM) will act as a much more effective airbrake than a low RPM setting. A bit like going downhill in a low automobile gear.

High throttle settings and low RPM cause detonation in the cylinders and is quite harmfull to the engine, high RPM causes excessive oil temperature and cylinder wear (and fuel consumption). Kind of like driving around in first gear all day in your car....