What happens to the propeller pitch if oil pressure is lost?

When oil pressure is lost in the propeller system, the propeller pitch automatically feathers. Feathering refers to the adjustment of the propeller blades to a position that minimizes aerodynamic drag and maximizes the efficiency of the propeller when the engine is not producing power, such as in the event of an engine failure.

In a typical constant-speed propeller system, oil pressure is required to adjust the blade pitch from a low pitch (which provides maximum thrust) to a high pitch (which is more aerodynamically efficient). If oil pressure is lost, the pitch will not remain unchanged; instead, the blades will move toward the feathered position. This occurs because the counterweights in the propeller are designed to take over when oil pressure is absent, allowing the blades to align with the airflow to reduce drag significantly.

Therefore, automatic feathering is a crucial safety feature in multi-engine aircraft, as it helps to prevent additional drag and allows the aircraft to maintain control after an engine failure. This mechanism highlights the importance of oil pressure in ensuring that the propeller operates effectively during normal and emergency situations.