FAA Aircraft Dispatcher Practice Exam

What is the primary use of an APU?

1. To provide thrust during takeoff

2. To supply electricity and air conditioning on the ground

3. To assist in engine maintenance

4. To increase cruising speed

The correct answer is: To supply electricity and air conditioning on the ground

The primary use of an Auxiliary Power Unit (APU) is to supply electricity and air conditioning on the ground. An APU is a small engine located on the aircraft that provides power to electrical systems when the main engines are not running. This is particularly important during pre-flight checks or when the aircraft is parked at the gate, as it allows for the operation of essential systems such as lighting, avionics, and environmental control systems like air conditioning without needing to have the main engines running. This capability enhances efficiency and reduces fuel consumption, allowing the aircraft to remain ready for flight while minimizing the environmental impact of ground operations. While thrust management during takeoff is crucial, the APU’s role is not related to providing thrust; instead, it supports ground operations. The idea of assisting in engine maintenance or increasing cruising speed doesn’t align with the APU’s function either, as it is not designed for those purposes. Understanding the APU's role helps aircraft dispatchers manage ground operations effectively and ensure passenger comfort prior to departure.