Why is a constant-speed counterweight propeller normally placed in full HIGH PITCH position before the engine is stopped?

• A. To prevent oil leakage
• B. To cool the blades
• C. To reduce wear on the governor
• D. To prevent corrosion of the pitch changing mechanism

Answer: (D)

The main idea is that a hydraulically operated pitch-change system is vulnerable to moisture and seal problems when the engine isn’t running. By moving the prop to full high pitch (feather) before shutdown, the pitch actuator is placed in a position where the hydraulic chamber is more stable and better protected as oil pressure falls away. This minimizes the opportunity for moisture and air to enter the change mechanism and helps prevent corrosion of the internal parts. It’s not primarily about cooling the blades or about reducing wear on the governor, and moisture ingress leading to corrosion is the focus of why this procedure is done.