FAA Powerplant Written Practice Test

How do small feathering propellers prevent themselves from feathering when the engine is turned off?

1. By using springs to hold the pitch.

2. By latches locking the propeller in low pitch.

3. Through a hydraulic lock mechanism.

4. By electronic control systems.

The correct answer is: By latches locking the propeller in low pitch.

Small feathering propellers are designed with latches that secure the blades in a low-pitch position when the engine is not operating. This mechanism is crucial because, in the event of an engine failure, feathering the propeller can significantly reduce drag and improve aerodynamic performance. However, if the propeller were to feather accidentally while the engine is shut down, it could lead to operational issues or unexpected behavior during recovery efforts. The latches act as a safety feature, ensuring that the propeller remains in a low-pitch, non-feathered orientation. This is particularly relevant for small aircraft or those where feathering is not required when the engine is not running. The use of latches provides a mechanical solution that is both reliable and straightforward, making it an effective way to keep the propeller from feathering unintentionally. Alternative methods, such as using springs or hydraulic mechanisms, serve different functions in other systems but are not specifically designed to prevent feathering in the case of small feathering propellers.