What is the alpha range of a variable pitch propeller?

The alpha range of a variable pitch propeller refers to the range of blade angles through which the propeller can be adjusted for optimal performance under different flight conditions. The correct response, indicating the alpha range consists of the feather and flight fine pitch stop, is appropriate because it encompasses the full operational spectrum for flight modes.

Feathering allows the blades to be aligned with airflow to reduce drag when the propeller is not needed, particularly in scenarios like engine failure. The flight fine pitch stop, on the other hand, refers to the lowest pitch angle where the propeller is efficient for flight, providing maximum thrust and responsiveness during normal operations.

The incorrect options fail to accurately represent the range pertaining to typical flight operations. For instance, ground fine pitch stops are not relevant during flight as they are designed for takeoff or landing scenarios, where the propeller blade angle is optimized for maximizing thrust on the ground, rather than in the air. Similarly, reverse pitch is used strictly for deceleration and maneuverability on the ground, also not applicable in normal flight conditions. Thus, the alpha range specifically caters to the conditions relevant for flight, highlighting the importance of both feathering and the flight fine pitch settings.