What instrument is used to measure the blade angle of a propeller?

• A. Dial indicator
• B. A universal propeller protractor
• C. Calipers
• D. A transit gauge

Answer: (B)

Measuring blade angle requires a tool that can read the angle of a propeller blade relative to the plane of rotation directly on the blade itself. The universal propeller protractor is designed for this purpose: it clamps or sits on the blade and provides a direct degree reading of the blade’s pitch at a specified station, accommodating different blade shapes and hub configurations. This makes it the most accurate and practical instrument for setting or verifying blade angle.

Dial indicators measure small linear movements and aren’t used to read the angle of a blade by itself. Calipers are for measuring dimensions, not angles. A transit gauge is a general angle-measuring tool for structures, but it isn’t tailored to the practical, direct measurement of propeller blade pitch and can’t match the convenience and accuracy of a specialized propeller protractor.