Turboprop engine. Diagram of a type of aircraft jet engine known as a turboprop engine. The bottom half of the main diagram has the external casing partly removed to show the engine. The top half shows how the engine works. Most of the thrust is provided by air accelerated by the large propeller that is powered by the jet engine behind it. Air enters this engine from left, passes through two compressors (orange and red), into the combustion chamber (yellow). Fuel is added and the mixture is ignited. The exhaust gases provide some thrust, but mostly drive turbines (centre right) to power the compressors and the propeller. This engine has low-speed fuel efficiency, used in cargo aircraft.