Turboprop

A turboprop is a gas-turbine engine that drives an aircraft propeller. Air enters an intake, is compressed, burned with fuel in a combustor, and expands through turbine stages; unlike a turbojet or turbofan, almost all of the energy is taken by the turbine to turn the propeller through a reduction gearbox, so the exhaust gives only about a tenth of the thrust. The propeller is normally a constant-speed, variable-pitch type that can also be feathered or set to reverse thrust for braking on landing. Some designs use a free power turbine on its own shaft, as in the Pratt and Whitney Canada PT6, while others use a fixed shaft, as in the Honeywell TPE331. Turboprops suit low-speed transport and commuter aircraft and are not usually used above about Mach 0.6 to 0.7, although the Tupolev Tu-95 is a well-known exception. The idea was published by the Hungarian engineer György Jendrassik in 1928 and patented in 1929; his Cs-1 engine was the first turboprop to run, and the first British turboprop flight followed in 1945.