Abstract: A fluid flow system suitable for controlling the flow of fuel to an engine comprises a fuel metering valve (2) to produce a metered output flow of fuel, and a pressure difference regulator (3) that is responsive to the pressure difference across said fuel metering valve (2) and operates in conjunction therewith to control said output flow of fuel, characterized in that the system includes a system control valve assembly (4) which in the event of a malfunction or failure of the system acts to regulate the output flow of fuel in order to alleviate the effects of the malfunction or failure. First valve means (7) of the valve assembly (4) controls an output line from the pressure difference regulator (3) to a fuel return line (18,19). An augmenting valve (5) is connected between the input (12) and output (14) of the fuel metering valve (2).

Abstract: A fluid flow control valve includes a first spool member (1) the position of which controls an output fluid flow from the valve, and a control (23, MP) which controls the position of the first spool member (1), a second spool member (6), independent of the first spool member (2), is mounted in a common chamber (1) with the first spool member (6) so as to cooperate with an outlet port (15) through which the output fluid flow passes and to be movable in response to the pressure drop across the outlet port (15) so that its position is related to the output fluid flow. A feedback (22', 24) is responsive to the position of the second spool member (16) and provides an input to the control (23, MP) so that the control operates as a servo control system. The first spool member (2) includes two landed sections (3, 4) which are spaced apart with the second spool member (6) therebetween.

Abstract: A servo valve comprises an electrical winding, an armature, flapper means fixed to the armature and a feedback arrangement including a radially extending plug fixed to an end of one of the arms of the flapper arrangement. The plug is located within the fluid flow of a supply bore and is deflected according to the flow. This deflection is passed back to the flapper to vary its position relative to the jet pipe nozzles thus offering feedback control.

Abstract: A hydraulic actuator system, for use in an aircraft, and in which the servo fluid supply to the system is used to provide for the operation and cooling of the system. The system comprises a hydraulically operated piston mechanism including at least one hydraulically operated piston, a servo vluid input to the system, which is connected in a ring main to a first side of the hydraulically operated piston, a servo fluid output from the system, which is connected in a ring main to a second side of the hydraulically operated piston, a variable restrictor arrangement which provides an interface between the servo fluid input ring main and the servo fluid output ring main, and a restrictor arrangement positioned in the servo fluid output side of the system. The position of the piston of the hydraulic piston and the adjustment thereof, are controlled by the restriction applied on the system by the variable restrictor arrangement.