In which type of engine is a separate turbine used to drive an accessory gearbox?

In turboprop and turboshaft engines, a separate turbine is used to drive an accessory gearbox, which is crucial for operating various engine components and accessories. This configuration allows these engines to efficiently convert gas turbine exhaust energy into mechanical power for propellers or rotors, while the accessory gearbox serves to transfer power to systems like electrical generators, fuel pumps, and hydraulic pumps.

Turboprop engines use the torque generated by a turbine to turn a propeller, while turboshaft engines are primarily designed for rotorcraft applications, providing the necessary power to turn helicopter rotors. The design of these engines optimally supports the operational needs of their respective vehicles, making the use of a separate turbine for driving the accessory gearbox an effective solution.

In contrast, turbojet engines lack this separate configuration as they focus on jet propulsion without mechanisms for additional accessories like those used in turboprop or turboshaft setups. High bypass turbofan engines and pure turbofan engines are also designed differently, emphasizing thrust generation through bypassed air rather than the mechanical outputs that require a separate accessory gearbox driven by a distinct turbine.