The constant-speed propeller range is controlled by which of the following?

• A. The governor spring tension
• B. Engine RPM
• C. Hydraulic pressure
• D. The mechanical limits in the propeller pitch range

Answer: (D)

The ability of a constant-speed propeller to hold a given RPM is limited by how far the blades can move in pitch—the mechanical stops that define the fine and coarse pitch limits. The governor adjusts blade angle by using oil pressure to maintain the set RPM, but it cannot move the blades beyond the physical limits of pitch travel. Therefore, the range over which the propeller can regulate RPM is defined by those mechanical limits in the pitch range. The other factors, like engine RPM signals or hydraulic pressure alone, don’t set the range—the stops in the pitch mechanism do.