FAA Powerplant Written Practice Test

In the event of engine failure, what mechanism holds a feathering propeller in the feathered position during flight?

1. Mechanical locks on the pitch control.

2. Hydraulic pressure within the propeller system.

3. Aerodynamic force.

4. Weight of the counterweights in the propeller hub.

The correct answer is: Aerodynamic force.

In the event of engine failure and the need to feather the propeller, aerodynamic force plays a crucial role. When a propeller is feathered, the blades are aligned in a position that minimizes drag. This alignment occurs due to the aerodynamic forces acting on the blades as the aircraft continues to move forward through the air, which helps maintain the feathered position. Feathering typically involves the pitch of the blades being adjusted to a high angle, reducing the amount of lift generated by the blades while significantly decreasing drag. In the absence of engine power, it’s the aerodynamic forces that keep the propeller blades in this optimal, drag-reducing position. While mechanical locks, hydraulic pressure, and counterweights may contribute to the overall propeller system's functioning, the primary mechanism holding a feathering propeller in the feathered position during flight, particularly after an engine failure, is a result of the aerodynamic forces at play.