What function does a universal propeller protractor serve?

The universal propeller protractor is primarily used to determine the pitch angle of a propeller or to measure the degrees of flap travel. This tool is essential for ensuring that the propeller is set to the correct pitch, which can significantly affect the performance and efficiency of the aircraft. The pitch angle is the angle between the chord line of the propeller blade and the plane of rotation. By accurately measuring this angle, pilots and mechanics can optimize the propeller's performance for various flight conditions.

In addition, the usage of a universal propeller protractor to measure degrees of flap travel is closely related. Flaps, which increase the wing's lift during takeoff and landing, also rely on precise angle measurements to function effectively. The protractor helps ensure that the flaps are deployed to the intended angle, enhancing safety and performance during critical phases of flight.

In contrast, measuring wing span, tracking engine RPM, and other functions fall outside the specific capabilities of a universal propeller protractor. These functions require different tools and instruments tailored for those specific tasks.