FAA Powerplant Written Practice Test

What does the angle of attack of a propeller blade refer to?

1. The angle between the blade and the engine

2. The angle between the chord and the relative wind

3. The angle between the blade and the airfoil

4. The angle at which the propeller enters the wind

The correct answer is: The angle between the chord and the relative wind

The angle of attack of a propeller blade refers to the angle between the chord line of the blade and the relative wind or airflow. This angle is critical because it directly impacts the lift and thrust produced by the propeller. A higher angle of attack generally increases the amount of lift generated up to a certain point before airflow begins to separate from the blade, which can lead to a loss of lift or stall. Understanding the angle of attack is essential for optimizing propeller performance as it influences the efficiency of the conversion of engine power into thrust. The relative wind is defined as the direction of the airflow relative to the propeller blade as the aircraft moves through the air, making this definition accurate and relevant to the function of the propeller. The other options do not accurately define the angle of attack in the context of propeller blades. The angle between the blade and the engine does not pertain to aerodynamic principles and is not how the angle of attack is typically described. The angle between the blade and the airfoil is not a standard term used in aerodynamics for propeller operation. The angle at which the propeller enters the wind is vague and does not capture the specifics of how the airflow interacts with the blade's geometry. Thus, defining the angle