FAA Powerplant Written Practice Test

At which pitch angle does a propeller typically produce its greatest amount of thrust?

1. 0 degrees

2. 15 degrees

3. 30 degrees

4. 45 degrees

The correct answer is: 30 degrees

A propeller typically produces its greatest amount of thrust around a pitch angle of 15 degrees. At this angle, the blades are angled to efficiently convert the rotational energy of the propeller into forward thrust, while also minimizing unnecessary drag. As the pitch angle increases beyond this optimal zone, the thrust starts to decrease due to an increase in drag and the potential for stalling of the airflow over the blades. Therefore, while an angle around 0 degrees might increase thrust at very low airspeeds, it generally would not be optimal for producing maximum thrust under typical flight conditions. Higher angles such as 30 or 45 degrees, while they might seem to offer more surface area to push against the air, can lead to decreased thrust due to stalling and increased drag. Thus, the 15 degrees pitch angle strikes a balance between thrust generation and drag management, making it the arcane choice for achieving maximum thrust in propeller-driven aircraft.