FAA Aircraft Dispatcher Practice Exam

What backup system is available if all generators fail in an aircraft?

1. A backup battery

2. An auxiliary power unit

3. A ground power unit

4. A ram air turbine

The correct answer is: A ram air turbine

In the case of total generator failure on an aircraft, the ram air turbine (RAT) serves as a critical backup system. It is a device that can automatically deploy when the aircraft's primary electrical power sources become unavailable. The RAT harnesses airflow as the aircraft moves through the air, generating power that is then used to supply essential systems, such as flight instruments and hydraulic systems, allowing the aircraft to maintain some level of control and functionality. RATs are typically used in commercial transport aircraft specifically for emergency scenarios where maintaining essential operations becomes vital. They are designed to be a failsafe method for emergency power that tends to be deployed during critical situations, ensuring that vital systems remain operational, increasing the safety of the aircraft and its passengers. Other options, while they serve important roles in aircraft operation, do not fulfill the same immediate emergency power provision in the event of total generator failure. A backup battery can provide temporary power but may not be sufficient for all critical systems, an auxiliary power unit (APU) is intended for ground operation and may not activate during flight emergencies, and a ground power unit is used only when the aircraft is stationary and cannot replace in-flight power generation.