What are the four gas turbine configurations?

• A. Turbojet, turbofan, turboprop, and turboshaft.
• B. Turbojet, turbofan, turbine, turbin.
• C. Turbojet, turbocharger, turboprop, turbine.
• D. Turbojet, turboprop, turbocharger, turbofan.

Answer: (A)

Gas turbine propulsion in aircraft comes in four common configurations, each defined by how the turbine’s power is used to create thrust or drive machinery. The turbojet produces thrust directly from high-speed exhaust with little to no additional propulsion from a front fan or propeller. The turbofan adds a large front fan and uses a bypass stream; most thrust comes from accelerating this bypass air, which makes it more efficient and quieter at a range of speeds. The turboprop relies on the turbine to drive a propeller through a reduction gearbox, so the propeller provides the majority of thrust, which is efficient at lower to mid speeds. The turboshaft uses the turbine to drive a shaft that powers a rotor or other machinery, common in helicopters and some auxiliary power setups, where the thrust comes from the rotor rather than jet exhaust.

Other terms listed don’t describe complete propulsion configurations for aircraft. Turbine by itself isn’t a standalone propulsion system in aviation, and turbochargers are devices used to force more air into piston engines rather than a primary aircraft propulsion type. Turbin isn’t a recognized propulsion category. So the four configurations above cover the standard ways a gas turbine can deliver propulsion or power in aviation.