Abstract: A control system for a gas turbine, which control system comprises a fuel pressurizing pump and two fuel flow restrictors supplied with fuel at different pressures from the pump, said restrictors being in communication with a common fuel pipe line, and there being electrically actuated means, e.g. a rotenoid, for varying the fuel pressure in the common fuel pipe line whereby said varying fuel pressure can be used for controlling the output of the gas turbine.

Abstract: In order to automatically adapt the control of an ultrasonic fuel-injection system or other system in which fuel delivery from nozzles is normally controlled by varying the mark/space ratio of energising current supplied to the nozzles, to variation of ambient pressure, a pressure-regulating unit is provided in a line leading from a source of fuel under pressure to the nozzles through a manually adjustable throttle valve and is arranged to maintain the pressure difference between the inlet and outlet of this series arrangement constant for any given ambient pressure P1. An altitude compensator comprising a spring-expanded vacuum capsule and a mechanical transmission is provided for varying this pressure difference in proportion to the ambient absolute pressure P1.