64.28 Turbine Engine Performance

64.28.2 Define the following terms and describe the relationship between them, and their application to engine operation:

(a) power

Power is the rate at which work is done.

In a turbine engine, power represents the rate at which energy is converted into useful output.

Depending on the type of engine, this useful output may be:

• thrust, in a turbojet or turbofan engine; or

• shaft power, in a turboprop engine.

Power is therefore a measure of how rapidly the engine can perform useful work.

(b) thrust

Thrust is the propulsive force produced by accelerating a mass of air or gas rearwards, producing an equal and opposite force on the engine.

In turbojet and turbofan engines, thrust provides the main force which propels the aircraft forward.

In a turboprop engine, most of the available gas energy is extracted by the turbine and delivered as shaft power to the propeller, although some additional thrust is produced by the exhaust gases.