Abstract: A gas turbine engine which comprises a rotary air compressor and a gas turbine, each with a rotor mounted on opposite ends of a rotor shaft, which is journalled in a housing positioned between the compressor and the turbine. The housing includes reduction gears. A combustion chamber is connected between the outlet air duct of the compressor and the hot gas inlet duct of the turbine. The power output is controlled by varying the air inlet to the compressor by means of an axially moving throttle control which limits the air passage into the compressor, either alone or in conjunction with variable angle compressor inlet pre-whirl vanes. It is also controlled by a shroud which surrounds the nozzle blades of the turbine. The shroud can be moved axially to limit the cross-section of flow of hot gas to the turbine blades.