FAA Powerplant Written Practice Test

Which type of engines utilize cold stream or cold and hot stream reversing?

1. Turboprop engines.

2. High bypass turbofan engines.

3. Turbojet engines.

4. Radial piston engines.

The correct answer is: High bypass turbofan engines.

High bypass turbofan engines utilize cold stream or cold and hot stream reversing systems. These engines have a significant portion of their thrust generated by the bypass air that is moved around the engine core, as opposed to through the core itself. In a cold stream reversing system, the bypass air can be redirected to produce reverse thrust, which is accomplished by deflecting the flow with thrust reversers. This feature is particularly important for larger aircraft, as it allows for shorter landing distances by effectively aiding in deceleration after touchdown. In contrast, other engine types such as turboprop engines and turbojet engines have different operational characteristics and mechanisms for thrust production and do not typically incorporate such features for reverse thrust. Radial piston engines, which operate on a completely different principle, also do not utilize cold stream reversing, as they do not have a bypass flow comparable to what is found in turbofan designs. Thus, the distinctive design and operational capabilities of high bypass turbofan engines make them the correct choice regarding the use of cold stream or cold and hot stream reversing.