Gas turbine engine fuel system

Claim 1

A GAS TURBINE ENGINE FUEL SYSTEM COMPRISING A CONSTANT DISPLACEMENT PUMP, MEANS FOR SUPPLYING THE LOW PRESSURE SIDE OF THE PUMP WITH FUEL AT A LOWER PRESSURE, A HIGH PRESSURE CONDUIT COMMUNICATING WITH THE HIGH PRESSURE SIDE OF THE PUMP, RESTRICTOR MEANS FOR RESTRICTING FLOW THROUGH THE HIGH PRESSURE CONDUIT, A FUEL PASSAGE ADAPTED TO BE CONNECTED TO THE ENGINE BURNERS SO AS TO SUPPLY THE LATTER WITH FUEL, A SPILL PASSAGE LEADING TO THE LOW PRESSURE SIDE OF THE PUMP, METERING VALVE MEANS WHOSE POSITION CONTROLS THE RELATIVE QUANTITIES OF FUEL WHICH MAY FLOW FROM SAID HIGH PRESSURE CONDUIT TO THE FUEL PASSAGE AND SPILL PASSAGE RESPECTIVELY, SAID METERING VALVE MEANS HAVING A FIRST PRESSURE SURFACE, WHICH IS OPEN TO THE HIGH PRESSURE CONDUIT DOWNSTREAM OF THE RESTRICTOR MEANS, AND SECOND PRESSURE SURFACES WHICH ARE OPPOSITELY DISPOSED WITH RESPECT TO THE FIRST PRESSURE SURFACE AND WHICH ARE RESPECTIVELY OPEN TO THE HIGH PRESSURE CONDUIT UPSTREAM OF THE RESTRICTOR MEANS AND TO THE SPILL PASSAGE, A SPILL PRESSURE CONTROL VALVE WHOSE POSITION CONTROLS FUEL PRESSURE IN THE SPILL PASSAGE, OPPOSITELY FACING PRESSURE SURFACES ON SAID SPILL PASSAGE CONTROL VALVE BEING RESPECTIVELY OPEN TO THE PRESSURES PREVAILING IN SAID SPILL PASSAGE AND FUEL PASSAGE RESPECTIVELY IMMEDIATELY DOWNSTREAM OF THE SAID METERING VALVE MEANS, WHEREBY THE PRESSURE IN THE SPILL PASSAGE UPSTREAM OF THE SPILL PRESSURE CONTROL VALVE IS ALWAYS CLOSELY EQUAL TO THE PRESSURE IN THE FUEL PASSAGE, A SUPPLY DUCT COMMUNICATING WITH THE HIGH PRESSURE CONDUIT AND WITH THE SPILL PASSAGE UPSTREAM OF THE SPILL PRESSURE CONTROL VALVE, AND A FLOW ADJUSTMENT VALVE MEANS IN SAID SUPPLY DUCT TO CONTROL FLOW THERETHROUGH IN RESPONSE TO FLUID PRESSURE FUNCTIONALLY RELATED TO THE INLET PRESSURE OF THE ENGINE COMPRESSOR.