FAA Powerplant Written Practice Test

What assists the starter jaw in retracting after the starter motor is disengaged?

1. Weight balance mechanism

2. Return spring

3. Pneumatic actuator

4. Magnetic coil

The correct answer is: Return spring

The return spring is key in aiding the starter jaw's retraction once the starter motor is disengaged. When the starter motor is engaged, the jaw operates to engage with the engine's flywheel or starter ring gear to crank the engine. After the engine starts and the starter motor is no longer needed, the disengagement process occurs. At this moment, the return spring pulls the jaw back into its original position. The use of a spring in this context is vital because it provides a reliable and efficient means of retracting the jaw without the need for an external mechanism or additional energy source. This contributes to the overall reliability and simplicity of the starting system in an aircraft powerplant, ensuring that the starter mechanism can quickly return to its idle state, ready for the next starting cycle. Other mechanisms like pneumatic actuators or magnetic coils generally serve different functions, such as providing torque or engaging other components, and would not be suitable for this specific task of retracting the starter jaw.