SECTION IV. FUEL SYSTEM

TM 1-1520-240-10 2-4-1 SECTION IV. FUEL SYSTEM 2-4-1. 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 are installed. Provisions are available within the cargo compartment for connecting Extended Range Fuel Sys- tem (ERFS) and ERFS II to the two fuel systems. Each fuel system consists of three fuel tanks contained in a pod on each side of the fuselage. The tanks are identified as forward auxiliary, main, and aft auxiliary tanks. During normal operation, with all boost pumps operating, fuel is pumped from the auxiliary tanks into the main tanks, then from the main tanks to the engine. A simplified fuel flow diagram is engraved on the FUEL CONTR (control) panel on the overhead switch panel (fig. 2-4-1). When the fuel is consumed in an auxiliary tank, the fuel pump is automatically shut off and a check valve closes to prevent fuel from being pumped back into that tank. Should a fuel pump fail in an auxiliary tank, the fuel in that tank is not usable. However, should both boost pumps fail in a main tank, fuel will be drawn from the main tank as long as the helicopter is below 6,000 feet Pressure Altitude (PA). Fuel is delivered to the APU from the left main tank and to the heater from the right main tank. Fuel system switches and the auxiliary tank low pressure indicating lights 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 nozzle adapter are on the right side above the forward landing gear. Refer to Section XV for fuel tank capacities, fuel grades, and fuel system servicing procedures. 2-4-2. Fuel Tanks. The fuel tanks are crashworthy self-sealing tanks with breakaway fittings. The main fuel lines are constructed of self-sealing material. Penetration of the tank wall or a fuel line by a projectile exposes the sealant to the fuel, activates the sealant, and close the hole. Breakaway self-sealing fittings are installed where the main fuel lines connect to the fuel tank and adjacent structure. Under high impact loads, the fittings shear or break at predetermined locations, seal themselves, re- tain the fuel, keeping fuel loss and post-crash fire hazard to a minimum. Electrical cables having lanyard-release type connectors are installed where the cables attach to adjacent structure. The connectors automatically re- lease if the fuel tank breaks away from the pod. Each main tank contains two fuel boost pumps, three fuel quantity probes, a jet pump for evacuating the pressure refueling 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 automatic shutoff feature, a quantity probe, a dual pressure refuel- ing shutoff valve, and a fuel level control valve. Figure 2-4-1. Fuel Control Panel A rollover vent system is installed in each tank. This system prevents fuel spillage from the vents should the helicopter roll over following a crash landing. The vent system within the tanks have a condensate drain at the aft end, however, aircraft maneuvering should never force fuel into the vents. Sump drains are also installed on the bottom forward end of each tank. 2-4-3. Controls and Indicators. The fuel controls are the FUEL PUMP switches, XFEED fuel valve switch, the engine fuel valve, and the manual defueling valve. Indicators include the crossfeed fuel and engine fuel valve warning lights, the FUEL QUANTITY indicator and caution capsules, FUEL flow indicator, AUX PRESS 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 eight two-position fuel boost pump switches, two PRESS-TO- TEST AUX PRESS indicating lights, a two-position XFEED switch, and a two-position REFUEL STA switch. a. FUEL PUMP Switches. Each switch controls a single-speed electrically driven fuel boost pump. La- beled next to each switch is the name of the pump which it 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 relay connecting power from the No. 1 or No. 2 AC bus to