FAA Powerplant Written Practice Test

What is the basic component of a pneumatic starter?

1. Electric motor

2. Axial flow turbine

3. Gearbox

4. Compressor fan

The correct answer is: Axial flow turbine

The basic component of a pneumatic starter is an axial flow turbine. Pneumatic starters operate on compressed air to rotate the engine until it can begin self-sustaining combustion. An axial flow turbine converts the energy from the compressed air into mechanical energy effectively. In this context, the axial flow design is specifically suited for pneumatic starters because it provides a high rotational speed with relatively low weight and size, making it ideal for starting aircraft engines where space and weight are critical considerations. The other choices do not serve as the primary component of a pneumatic starter. Electric motors are typically used in electric starters rather than pneumatic systems. A gearbox is more of a supplementary component that may be used for various applications but is not the fundamental element in pneumatic starting systems. A compressor fan typically refers to a part of a gas turbine engine designed to compress intake air; it is not a component found specifically in the operation of a pneumatic starter.