Differential pressure detector with reduced reaction forces

A differential pressure detector having reduced reaction forces for providing to main fuel relief valve an output pressure modulated as a function of the pressure drop between the pressures measured upstream and downstream of a fuel metering device, said detector comprising first and second input chambers for connection respectively to said pressures upstream and downstream of said fuel metering device, a modulated pressure output chamber connected to said main fuel relief valve for supplying said modulated output pressure to said main fuel relief valve for actuating said main fuel relief valve, a sleeve which is linearly movable in response to changes in the difference between the pressures in said first and second input chambers, and a fixed slide valve which is partly received within said sleeve, said slide valve having a bore opening into said output chamber and at least one side port for communicating said first input chamber with said bore of said slide valve, and hence with said output chamber, the aperture of said side port being varied by said sleeve during linear movement of said sleeve to control the communication between said first input chamber and said output chamber.