FAA Powerplant Written Practice Test

Which systems typically power turbojet and turbofan thrust reversers?

1. Electric systems

2. Hydraulics or pneumatics

3. Mechanical systems

4. Magneto systems

The correct answer is: Hydraulics or pneumatics

Turbojet and turbofan thrust reversers are primarily powered by hydraulics or pneumatics. These systems are used because thrust reversers require a significant amount of force to redirect engine thrust effectively during landing, which hydraulic or pneumatic systems can provide. They can generate the necessary power to operate the thrust reversers' moving parts, such as doors or cascades, allowing for a controlled and effective deceleration of the aircraft. The hydraulic systems are particularly advantageous in providing reliable and strong actuation due to the incompressibility of hydraulic fluid, which efficiently transmits force. Pneumatic systems can also be utilized, often leveraging compressed air to achieve similar operational effects. While electric systems can be present in various aircraft components, thrust reversers rely on the more robust hydraulic or pneumatic systems due to the substantial forces involved in reversing thrust during critical phases of flight. Additionally, mechanical and magneto systems are not typically used for this function, as they do not provide the same level of force or control needed for thrust reversal.