FAA Aviation Mechanic Powerplant (AMP)PropellersEasy
A student mechanic is asked to define the term 'blade angle' for a fixed-pitch propeller. Which statement correctly describes it?
- AThe angle between the relative wind and the blade's leading edge
- BThe angle between the propeller thrust line and the aircraft longitudinal axis
- CThe angle between the chord line of the blade and the plane of propeller rotation
- DThe angle between the leading edge and the propeller hub centerline
Show answer & explanationAnswer & explanation
Correct answer: C. The angle between the chord line of the blade and the plane of propeller rotation
Blade angle is measured between the chord line of the propeller blade section and the plane of rotation. It is typically measured at a specified blade station, such as 75% of the blade radius.
Why the other options are wrong
- A. This describes angle of attack, a related but different concept.
- B. This is unrelated to how blade angle is defined.
- D. This describes blade twist location, not blade angle.
Blade Angle
The angle formed between the chord line of a propeller blade section and the plane of rotation.
- Measured at a specified blade station (often 75% radius)
- Different from angle of attack, which includes relative wind
- Fixed-pitch props have one blade angle; constant-speed props vary it
Memory trick: Chord to rotation plane = blade angle, chord to wind = angle of attack