NP stands for which term in propeller terminology?

• A. Net Power
• B. Nodal Pitch
• C. Neutral Position
• D. Propeller Speed

Answer: (D)

The key idea is recognizing what NP represents in propeller terminology: it denotes the propeller speed, the rotational speed of the propeller itself (propeller RPM). This is the measurement the governor controls to keep the propeller operating efficiently, even as engine speed changes during flight or propulsion.

NP is not about engine output or power, so it isn’t Net Power. It isn’t a term for a pitch setting like Nodal Pitch, and it isn’t a neutral mechanical position. Instead, NP specifically refers to how fast the propeller is turning, which is distinct from the engine’s crankshaft speed or power.

For a practical sense, imagine the propeller speed being kept at a target value, say 1800 RPM, by the governor. The engine RPM might vary, but the governor adjusts blade pitch to hold the propeller at that NP value, ensuring consistent thrust and efficiency.