An internal combustion engine in which energy is released from the fuel in a constant-pressure cycle. Air is taken into the engine and compressed by either an axial-flow or a centrifugal compressor. The compressed air then passes into the combustion chambers where fuel is sprayed into a continuously burning fire. The burning fuel heats and expands the air which then flows through a turbine, where some of the energy is extracted to turn the compressor. The energy remaining in the gases leaving the engine causes the exhaust velocity to be greater than that of the air entering the engine, and this acceleration produces thrust.

Some gas turbine engines use additional stages of turbines to extract energy from the hot gases to drive such devices as fans, propellers, rotors, generators, or pumps. Gas turbine engines are far superior to reciprocating engines, with regard to their weight-to-horsepower ratio.