In which scenario is the blade angle of a constant-speed propeller expected to be greatest?

• A. during takeoff
• B. during taxiing
• C. during high-speed cruise
• D. during approach

Answer: (C)

Constant-speed propellers use a governor to keep engine RPM steady by changing the blade angle to match the engine’s load at different airspeeds. When you fly fast, you want the prop to convert the engine power into forward thrust efficiently, which means using a coarser (greater) blade angle. The governor increases pitch to reduce the propeller’s load and keep RPM from dropping, so the blade angle ends up largest during high-speed cruise. In takeoff or approach, you need maximum thrust at low speed, so the pitch is kept finer (smaller angle) to allow higher RPM and more available power. Taxiing involves light load at low speed, resulting in a smaller blade angle than cruise.