Fixed-pitch vs constant-speed propellers

A fixed-pitch propeller has one blade angle. RPM is directly related to power, so it rises and falls with the throttle. You read it on the tachometer (TP 1102).

A constant-speed propeller adds a governor that holds the RPM you select by continuously changing the blade angle. You set RPM with the propeller pitch lever and power with the throttle.

Once an RPM is set on a constant-speed prop:

• The throttle changes manifold pressure (read on the manifold pressure gauge), not the RPM.
• The pitch lever sets the RPM the governor holds. Lever fully forward = smallest blade angle (fine pitch), high RPM; pulled back = greatest angle (coarse), low RPM.

For exact RPM and manifold-pressure settings, use the POH/AFM for the aircraft.

Trap: on a constant-speed prop, expecting the throttle to change RPM. The governor holds RPM; the throttle moves manifold pressure.

Practice