AMP - Aviation Maintenance Technician Powerplant Practice Exam

What distinguishes turbojet engines from turbofan engines?

1. Turbofans provide thrust solely from the engine exhaust

2. Turbofans use a fan to produce additional thrust

3. Turbojets have a longer operational lifespan

4. Turbojets can operate without an ignition system

The correct answer is: Turbofans use a fan to produce additional thrust

Turbofan engines are distinguished from turbojet engines primarily by their design and operational characteristics, particularly in the way they produce thrust. In turbofan engines, a large fan at the front of the engine compresses a significant volume of air. This fan generates additional thrust by accelerating a larger mass of air compared to the exhaust gases alone. The process involves bypassing a portion of the air around the engine core, which enhances efficiency, particularly at subsonic speeds. Turbojet engines, on the other hand, primarily rely on the high-speed exhaust of combustion gases for thrust. While they can be efficient at high speeds, they do not have the added thrust benefits of a fan, making them less suitable for modern commercial aviation where fuel efficiency and noise reduction are critical. Thus, the distinctive feature of turbofans utilizing a fan to produce additional thrust not only increases their efficiency but also helps to provide quieter operation compared to turbojets, which is crucial for compliance with noise regulations in commercial flights.