FAA Powerplant Written Practice Test

Blade angle is formed by which two lines?

1. Chord of the blade and relative motion

2. Perpendicular to the crankshaft and chord of the blade

3. Leading edge and trailing edge of the blade

4. Plane of rotation and center of the hub

The correct answer is: Perpendicular to the crankshaft and chord of the blade

Blade angle is defined as the angle between the chord line of a propeller blade and the plane of rotation. In this context, the chord line of the blade is a straight line that runs from the leading edge to the trailing edge of the blade, representing the profile of the blade as it moves through the air. The plane of rotation, on the other hand, is essentially the circle traced by the tips of the blades when the propeller spins. The angle formed between the chord of the blade and the plane of rotation is critical in determining the aerodynamic efficiency of the blade during operation. It affects how much thrust the propeller generates at a given rotational speed and is a vital parameter in propeller design and performance analysis. The other options do not accurately define the relationship between the two lines that form the blade angle. Therefore, the definition that focuses on the chord of the blade and its relationship to the plane of rotation is the most pertinent and correct in the context of how blade angle is determined.