731,698. Gas turbine plant. WIGG, R. E., and RUSTON & HORNSBY, Ltd. Nov. 18, 1953 [Oct. 7, 1952], No. 25118/52. Class 110 (3). [Also in Groups XXIX, XXXIV and XXXVII] A system for controlling the liquid or gaseous fuel supply to a gas turbine engine comprises means sensitive to the pressure of lubricating oil, whereby on failure of that pressure the fuel feed to the engine is discontinued. The system also includes a manually actuated controller for starting up and shutting down the engine, an overspeed trip valve and a fuel spill valve controlled by a governor driven by a free power turbine. The apparatus shown in Fig. 6 is suitable for liquid fuel and comprises a servopiston 58 subject on its right-hand face to lubricating oil pressure admitted through a port 64 and having a tubular portion coacting with outlet ports 68a in a slidable valve 67, whereby the piston is positioned in correspondence with the valve which is actuated by a crank 72 on a shaft 73 bearing a hand wheel 74. Instead of the hand wheel an electric motor may drive the shaft 73. An extension 59 of the piston forms an abutment for loading springs 65a, 65b of a fuel spill valve 56 and also constitutes a valve controlling ports 62, 63 leading to an igniter and main burners respectively. In operation, the hand wheel is moved from the "off " position to a first position in which a cam 75a closes an electric switch to start up electrically-driven fuel and lubricating oil pumps. As the spill valve 56 is loaded lightly only by the spring 65a fuel is by-passed freely from a supply conduit 37 to a return conduit 54, a connection (not shown) from the conduit 37 to the ports 62, 63 being interrupted by the valve 59. Further movement of the hand wheel is prevented by an abutment (not shown) carried by the servopiston and engaging a projection at the lower end of the shaft 73 until the lubricating oil pressure has built up sufliciently to move the servo-piston slightly against loading springs (not shown) to the position determined by the valve 67. Movement of the hand wheel to the second position causes the valve 59 to connect the port 62 to the supply whereby fuel is fed to the igniter under a pressure determined by an increased spring loading on the spill valve 56. This movement also closes and winds up a time switch (not shown) and closes a switch actuated by a cam 75c, the latter switch energizing a relay switch in series with the time switch and controlling a starter motor and a spark ignition device. In a third position of the hand wheel the piston 58 is advanced to uncover the main burner port 63. In moving the hand wheel to the fourth position the cam 75d causes a resistance to be removed from the motor circuit to increase the speed of the motor. The switch actuated by the cam 75c is opened when the fourth position is reached but a relay winding in series with the motor maintains the latter in circuit until its current consumption has fallen due to increasing speed to a value insufficient to hold the relay. The time switch ultimately cuts out the motor and spark device if the motor fails to reach the required speed. Movement of the hand wheel from the fourth to the fifth position causes the spring 65b to be compressed to provide a sharp rise in fuel pressure and the cam 75a to open the switch controlling the fuel and oil pumps, the engine driven pumps now being effective. A governor driven by the power turbine actuates a control valve for a servomotor which operates a spill valve in the fuel conduit between the port 63 and the burners. To shut down the engine the hand wheel is brought to a sixth position in which the valve 67 is withdrawn to the right resulting in the shutting off of the fuel supply and the closing of a switch S3 to start up the electrically-driven fuel and oil pumps so that engine is cooled by circulation of oil. The switch S<SP>3</SP> is actuated by an extension of the abutment (referred to above) carried by the servo-piston. The engine may also be shut down by valves (not shown) which release the oil pressure from the right-hand side of the piston 58, one such valve being manually operated and another tripped by an overspeed governor. When the pressure is so released passages 70 in the piston prevent the re-establishment of pressure until the valve 67 is moved back into phase with the piston. In a modification, for gaseous fuel, the piston 58 Fig. 13, has an extension 59a with a cam 137 for actuating, through a cranked lever 133, a poppet valve 127 controlling flow of fuel from a chamber 110 to an outlet 62a for the igniter, and other, angularly spaced, cams for actuating a pair of poppet valves (not shown) connecting, in parallel, the chamber 110 with the burner fuel supply. The cam 137 allows the valve 127 to close after the other two poppet valves are fully open. Fuel is fed from an inlet chamber 111 to the chamber 110 past a valve 120 which is operated by a servo-piston 116 moving in correspondence with a control valve 122 actuated by a bellows 125 which is subject to the pressure in the chamber 110. The valve 120 regulates the pressure in the chamber 110 in accordance with the loading imposed by the piston 58 on the bellows through an assembly of springs 65c, 65d, 65e so arranged as to provide an increasing rate when compressed. Specification 704,020 is referred to in the Provisional Specification.