Fuel Quantity Indicators

TM 1-1520-238-10 2-40 2.36.3 Fuel Quantity Indicators. The pilot vertical- scale fuel quantity indicator (fig 5-1) indicates the quantity (in pounds X 10) of fuel remaining in the forward and aft fuel cells. A digital display at the bottom of the indicator shows the combined total of remaining fuel (in pounds X 10). The CPG selectable digital display (SDD) indicates the pounds of fuel remaining in the forward and aft fuel cells. The SELECT knob is rotated until the FUEL QTY X 10 display is illuminated thus causing the pounds of fuel remaining in each cell to appear on the digital display. Combined total fuel is not indicated. The fuel quantity transmitters are capacitance-type transmitters. There are three fuel quantity transmitters: two are in the forward fuel cell because of the shape of the fuel cell, and one is in the aft fuel cell. The transmitters provide data to the fuel signal conditioner which, in turn, provides a readout to the fuel quantity indicators in the crew stations. 2.36.4 Fuel System Caution/Warning Lights. Fuel system caution/warning segments on the caution/warning panel are discussed in Section XIV, (tables 2-4 and 2-5). Their positions are shown on the caution/warning panel (fig 2-44). 2.36.5 Auxiliary Fuel Tank. For ferry missions, there are provisions for as many as four external fuel tanks to be carried on the wing pylon attachment points. The external tanks can be jettisoned in the same manner as any other externally mounted stores. 2.36.6 Refueling Provisions. All fuel service points are located on the right side of the helicopter. For all re- fueling operations, the REFUEL valve switch must be placed in the OPEN position and then CLOSED after completion of refueling. Section XV contains fuel specifi- cations and weights. Chapter 6 describes the effects of fuel loading on weight and balance. a. Gravity Filling. The forward and aft cells and the external auxiliary tanks are gravity-filled separately. Fuel cell filler ports are located forward and aft of the wing. Re- fueling time required for gravity refueling depends on the flow-rate capability of the servicing equipment. Section XV contains specific filling procedures. NOTE For gravity refueling, the closed vent system requires the refuel valve to be open to obtain maximum fill above the opening of the filler neck. When fuel has reached this level, the fuel flow rate will have to be decreased to accommodate the restricted vent flow rate. b. Pressure Refueling. The pressure service man- ifold, located forward of the right wing, has two adapters for accommodating either a single point adapter (SPA) or a closed-circuit adapter (CCA). Using either nozzle, for- ward and aft cells may be filled separately or simulta- neously dependent upon the refueling panel switch set- tings (fig 2-45). The shutoff valve at the bottom of each fuel cell responds to an adjoining float-type pilot valve at the top of the cell. This valve will automatically stop fuel flow when the cell is full. Shutoff is set to allow space for a 3% expansion in each cell. The IND switch to the left of the FUEL QTY indicator on the refueling panel energizes the quantity indicator and advisory lights. After refueling, the REFUEL VALVE switch must be returned to the CLOSED position, or fuel transfer from cell-to-cell cannot be accom- plished by either crewmember. The inside panel of the re- fueling panel access door contains servicing instructions. Section XV contains complete pressure refueling proce- dures. 2.36.7 APU Fuel Supply. The APU receives fuel from the aft fuel cell. Fuel is routed from the aft fuel cell through the APU fuel shutoff valve to the APU boost pump and on to the APU. a. APU Fuel Shutoff Valve. The APU fuel shutoff valve is controlled by the APU OFF,-RUN, and,-START switch When the switch is moved to the RUN position, the shutoff valve is electrically opened to allow fuel flow to the APU boost pump. If the FIRE APU PULL handle is pulled, the APU fuel shutoff valve will close. b. APU Boost Pump. The electrically-driven APU boost pump is energized when the APU START/RUN switch is at the START or RUN position. The pump will continue to run until the APU is shut down. The pump de- livers fuel to the APU integral fuel shutoff valve. Pulling the FIRE APU PULL handle will stop the pump.