FAA Powerplant Written Practice Test

What defines a turbo shaft engine?

1. A gas turbine engine that powers a propeller

2. A gas turbine engine that delivers power through a shaft

3. A turbo engine with variable geometry

4. A piston engine trained to function as a turbine

The correct answer is: A gas turbine engine that delivers power through a shaft

A turbo shaft engine is specifically designed to convert the energy generated by the combustion of fuel into mechanical energy delivered through a rotating shaft. This type of engine is typically used in applications such as helicopters and some industrial machinery where the primary objective is to provide power, rather than propulsion through a jet of exhaust. The key feature of a turbo shaft engine is its layout and design, which allows it to efficiently drive a rotor or other mechanical components through the shaft. This distinguishes it from other types of gas turbine engines, such as turbojets or turbofans, which are primarily designed to produce thrust for propulsion rather than mechanical power. The other options may refer to different types of engines or concepts but do not accurately capture the defining characteristics of a turbo shaft engine. For instance, the mention of a propeller pertains to a specific application of some gas turbine engines but does not encompass the essence of a turbo shaft engine, which is focused on shaft power delivery. Similarly, variable geometry pertains to specific design features that are not inherent to all turbo shaft engines, and referencing a piston engine trained to function as a turbine misrepresents the fundamental principles behind turbo shaft design and operation.