What does the mechanical overspeed governor modulate?

• A. Fuel flow to the engine
• B. Oil pressure to the propeller pitch change piston
• C. Air intake for combustion
• D. Electrical output to the cockpit

Answer: (B)

The mechanical overspeed governor plays a crucial role in regulating the oil pressure to the propeller pitch change piston. Its primary function is to maintain the propeller's speed within safe operating limits by adjusting the pitch of the propeller blades. When the engine speed exceeds a certain threshold, the overspeed governor activates, reducing the oil pressure directed to the pitch change mechanism. This adjustment effectively alters the blade angle to decrease the propeller's speed, preventing potential damage from overspeed conditions.

By managing the oil pressure sent to the propeller's pitch change piston, the governor ensures smooth operation and optimal performance of the aircraft, as maintaining proper propeller speed is vital for flight stability and efficiency. Understanding this mechanism is essential for assessing engine and propeller interactions in aviation systems.