TM 1-1520-240-102-4-1SECTION IV. FUEL SYSTEM2-4-1. Fuel Supply System.The fuel supply system furnishes fuel to the two engines,the heater, and the APU. Two separate systems, con-nected by crossfeed and a pressure refueling lines areinstalled. Provisions are available within the cargocompartment for connecting Extended Range Fuel Sys-tem (ERFS) and ERFS II to the two fuel systems.Each fuel system consists of three fuel tanks containedin a pod on each side of the fuselage. The tanks areidentified as forward auxiliary, main, and aft auxiliarytanks. During normal operation, with all boost pumpsoperating, fuel is pumped from the auxiliary tanks into themain tanks, then from the main tanks to the engine. Asimplified fuel flow diagram is engraved on the FUELCONTR (control) panel on the overhead switch panel(fig. 2-4-1).When the fuel is consumed in an auxiliary tank, the fuelpump is automatically shut off and a check valve closesto prevent fuel from being pumped back into that tank.Should a fuel pump fail in an auxiliary tank, the fuel in thattank is not usable. However, should both boost pumpsfail in a main tank, fuel will be drawn from the main tankas long as the helicopter is below 6,000 feet PressureAltitude (PA).Fuel is delivered to the APU from the left main tank andto the heater from the right main tank. Fuel systemswitches and the auxiliary tank low pressure indicatinglights are on the FUEL CONTR panel, the fuel line pres-sure caution capsules are on the master caution panel,and the fuel flow meter is on the center instrument panel.The single point pressure refueling panel and nozzleadapter are on the right side above the forward landinggear. Refer to Section XV for fuel tank capacities, fuelgrades, and fuel system servicing procedures.2-4-2. Fuel Tanks.The fuel tanks are crashworthy self-sealing tanks withbreakaway fittings. The main fuel lines are constructedof self-sealing material. Penetration of the tank wall or afuel line by a projectile exposes the sealant to the fuel,activates the sealant, and close the hole.Breakaway self-sealing fittings are installed where themain fuel lines connect to the fuel tank and adjacentstructure. Under high impact loads, the fittings shear orbreak at predetermined locations, seal themselves, re-tain the fuel, keeping fuel loss and post-crash fire hazardto a minimum. Electrical cables having lanyard-releasetype connectors are installed where the cables attach toadjacent structure. The connectors automatically re-lease if the fuel tank breaks away from the pod.Each main tank contains two fuel boost pumps, three fuelquantity probes, a jet pump for evacuating the pressurerefueling system, a dual pressure refueling shutoff valve,a dual fuel level control valve, and a gravity filler port.Each auxiliary tank contains a fuel pump with automaticshutoff feature, a quantity probe, a dual pressure refuel-ing shutoff valve, and a fuel level control valve.Figure 2-4-1. Fuel Control PanelA rollover vent system is installed in each tank. Thissystem prevents fuel spillage from the vents should thehelicopter roll over following a crash landing. The ventsystem within the tanks have a condensate drain at theaft end, however, aircraft maneuvering should neverforce fuel into the vents. Sump drains are also installedon the bottom forward end of each tank.2-4-3. Controls and Indicators.The fuel controls are the FUEL PUMP switches, XFEEDfuel valve switch, the engine fuel valve, and the manualdefueling valve. Indicators include the crossfeed fuel andengine fuel valve warning lights, the FUEL QUANTITYindicator and caution capsules, FUEL flow indicator, AUXPRESS indicating lights, and FUEL PRESS caution cap-sules. Refer to para. 2-4-10 for a description of the pres-sure refueling system controls and indicators.2-4-4. FUEL CONTR Panel.The FUEL CONTR panel (fig. 2-4-1) consists of eighttwo-position fuel boost pump switches, two PRESS-TO-TEST AUX PRESS indicating lights, a two-positionXFEED switch, and a two-position REFUEL STA switch.a.FUEL PUMP Switches. Each switch controls asingle-speed electrically driven fuel boost pump. La-beled next to each switch is the name of the pump whichit operates. Each switch has an ON and OFF position.When one of these switches is at ON, power from the No.1 or No. 2 DC bus closes the respective pump relayconnecting power from the No. 1 or No. 2 AC bus to
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