How is the pitch-changing mechanism of the hydromatic propeller lubricated?

How is the pitch-changing mechanism of the hydromatic propeller lubricated?

• A. Engine oil
• B. Hydraulic fluid
• C. Pitch-changing oil
• D. Mineral oil

Answer: (C)

Hydromatic propellers change blade pitch through a hydraulic system in the hub, and the fluid that powers and lubricates that movement is the oil used specifically for pitch-change actuation. This oil is what under pressure moves the pitch-change mechanism and also keeps the moving parts lubricated. While engine oil is the source of the fluid in many installations, its role here is to act as the hydraulic medium that enables pitch changes, so identifying the fluid by its function—pitch-changing oil—best reflects how the system operates.

Hydromatic propellers change blade pitch through a hydraulic system in the hub, and the fluid that powers and lubricates that movement is the oil used specifically for pitch-change actuation. This oil is what under pressure moves the pitch-change mechanism and also keeps the moving parts lubricated. While engine oil is the source of the fluid in many installations, its role here is to act as the hydraulic medium that enables pitch changes, so identifying the fluid by its function—pitch-changing oil—best reflects how the system operates.