CHAPTER 11. Page TABLE OF CONTENTS /02 DESCRIPTION. General Description Controls and Indicators

Transcription

1 CHAPTER 11 FUEL SYSTEM Page TABLE OF CONTENTS /02 DESCRIPTION General Description Controls and Indicators COMPONENTS (NOT USED) CONTROLS AND INDICATORS FUNCTIONAL SCHEMATICS Fuel System /02 Feb 1/ /02

2 FUEL SYSTEM GENERAL The fuel supply consists of three main integral fuel tanks plus a compartmented center auxiliary tank, tank boost pumps, tank transfer pumps, APU start pump, quantity indicating system, and associated controls and indicators, The system has the capability for tank-to-tank fuel transfer, any tank to any engine fuel feed, fuel dumping, and refueling. The system is designed for pressure refueling by one operator, utilizing only airplane battery power and an inverter to provide the required ac power. DESCRIPTION DISTRIBUTION The fuel supply is stored in three main tanks and in a compartmented center auxiliary tank. Main tanks 1 and 3 are each comprised of an inboard and outboard compartment. Fuel is reserved in the outboard compartment until the inboard compartment decreases to a predetermined level, then the outboard fuel passes into the inboard compartment automatically. This arrangement is for structural considerations. Normally, fuel is delivered from each main tank directly to its associated engine by fuel tank pumps. Each individual fuel tank pump in each tank is powered by a separate electrical source. Engine 2 must have fuel tank pump pressure to operate. A fuel manifold, crossfeed valves, fill valves, transfer pumps, and associated controls permit total crossfeed and transfer capability (any engine from any tank, all engines from any tank, any tank to any main tank[s]). Fuel from the center ccmpartmented auxiliary tank is normally transferred to the three main tanks through the fuel supply manifold and the respective main fill valves. tank Scavenge jet pumps in all tanks draw fuel and water mixture from tank low points to be pumped into the engine supply system. The APU normally receives fuel from main tank 2. This tank is equipped with a battery powered pump for APU starting. The APU may also be supplied by any of the normal ac powered tank pumps. VENT SYSTEM Main tanks 1 and 3 are vented through a piping system to a vent box in the opposite wing tip. Main tank 2 is vented to the tank 1 vent manifold. In the event of tank 2 overflow it will vent to both vent boxes. The auxiliary tank is vented to tank 3 vent manifold. An overflow standpipe is located in each vent box. This arrangement prevents loss of fuel overboard due to adverse attitude, taxi sloshing, or centrifuging during high speed taxi turns. Any fuel collected in the vent system drains back to the fuel tanks automatically at predetermined fuel levels. The TANK OVERFILLED caution light indicates that the fuel accumulating in either wing vent box has reached an imminent overflow condition. QUANTITY INDICATING SYSTEM The fuel quantity indicating system has an individual, digital readout indicator for each of the three main tanks and the compartmented center auxiliary tank plus two fuel totalizer/gross weight indicators. On airplanes with AOL or production equivalent the fuel quantity indicators are identified for a specific tank as: 2 SER ALL, 1 -& 3 SER 30/40 and AUX/CTR SER 30/40. Feb 1/85 ll-lo-01

3 The fuel totalizer/gross weight indicators display aircraft total gross weight once the correct zero fuel weight has been set into the instruments. A fuel quantity test button is provided to test the system. The temperature of the fuel in the outboard compartment of tank 3 or at any of the three engines is selected for display on a fuel temperature gage on the Flight Engineers Lower Panel. FUELING AND DEFUELING SYSTEM There are two fueling adapters under each wing. Fueling is controlled by a single-point fueling control panel underneath the right wing leading edge. The aircraft can be fueled from this station using only the aircraft's battery and inverter power, without a crewmember in the cockpit. Fuel quantity repeater/ fuel load selectors and appropriate control switches allow the tanks to be filled to any preselected quantity and for fueling to be terminated automatically. The main tanks may be defueled either by use of the tanks pumps or suction defueling. The center auxiliary tank is defueled by the tank pumps. DUMPING SYSTEM The fuel dumping system utilizes the transfer and tank pumps to pump fuel overboard through two exits, one at the trailing edge of each wing. Dumping is controlled by two shutoff valves (one in each wing), and dump level float switches in the main tanks. The fuel dump rate is approximately 5800 pounds per minute and will vary with fuel loading and attitude. Fuel dumping is initiated by turning on all pumps, opening the crossfeed valves and moving the FUEL DUMP control switch to OPEN. With the FUEL DUMP control switch at OPEN, the dump level float switches close all crossfeed valves when the fuel level in any main tank reaches the design minimum (undumpable) fuel level. The dump level float switches also turn off their respective transfer pump when the fuel level in each tank reaches the design minimum fuel level for dumping. All usable fuel in the auxiliary tanks can be dumped. Dumping may be terminated at any time by moving the FUEL DUMP control switch to CLOSE. CONTROLS AND INDICATORS The controls, indicators, and annunciator lights are on the Flight Engineer's Lower Panel and Upper Panels No. 1 and 2, captain's instrument panel, Glareshield, and Overhead Panel. Illustrations of these major panels (except the wing refueling panel) are in Chapter 1. Individual controls are illustrated and described in another section of this chapter Aug 1/81

4 TANK PUMP Switch (TRANS, FWD, AFT) (2) Pumps are powered by separate systems Each pump is capable of supplying fuel for two engines at takeoff thrust Activated aft pumps provide continuous scavenging of tanks Transfer pump provides a method of transferring fuel from tank 1 or 3 to any other mam tank without opening crossfeed valves or to any engine by opening the receiving engine's crossfeed valve UPR TANK PUMP PRESS LO Light (2) Comes on steady only when respective pump switch is at ALL or UPR and indicates AUX TANKS upper mam fuel pump discharge pressure is below allowable minimum FUEL QTY Indicator (3) Provides a continuous reading of fuel quantity in associated tank to nearest 100 pounds TANK PUMP PRESS LO Light (10) Comes on only when respective pump switch is on and tank pump discharge pressure is below allowable minimum Light will remain on until pump switch is moved to OFF TANK PUMP Switch (TRANS, FWD, L AFT, R AFT) Pumps are powered by separate systems Each pump is capable of supplying fuel for two engines at takeoff thrust Activated aft pumps provide continuous scavenging of tank Transfer pump provides a method of transferring fuel from tank 2 to any other tank without opening the crossfeed valves or to any engine by opening the receiving engine's valve Tank 2 left aft pump, which will normally be on when APU is operating, is powered by right emergency ac bus This bus can be powered by ADG LWR TANK PUMP PRESS LO Light (2) Comes on steady only when respective pump switch is at ALL and indicates AUX TANKS lower compartment fuel pump discharge pressure is below allowable minimum AUX PUMPS Switch (L or R) Pumps are powered by separate systems UPR position deactivates lower pump, and powers respective pump in AUX TANKS upper mam compartment to transfer fuel to all mam tanks through fuel supply manifold and respective mam tank fill valves ALL position powers respective pump in AUX TANKS upper mam compartment, respective pump in AUX TANKS lower compartment, and power to open upper fill valve to transfer fuel to upper mam compartment for subsequent transfer to mam tanks OFF position deactivates magnetic hold position of tank 1, 2, and 3 fill valve switches Prolonged operation of pumps with PUMP PRESS LO light on steady reduces service life of pumps FLIGHT ENGINEER'S LOWER PANEL C - S SWITCH A three position test switch placarded C and S with the center position not placarded The switch is spring loaded to the center position The C position (compensator) tests the compensator circuits external of the indicator The S position (system) tests the indicator and its active power supply channel FUEL QTY Indicator (AUX) Provides a continuous reading of fuel quantity in auxiliary tank to nearest 100 pounds FUEL SCHED Light (1, 3 tank) Comes on to indicate an off-schedule (premature) transfer or failure to transfer fuel from outboard compartment depending on fuel quantity Aug 1/

5 FUEL QTY IND PWR Switch NORM Provides ac bus 1 power for the indicating system and allows ground refueling from battery power ALT Provides an alternate power (ac bus 2) source FUEL QTY TEST Button When pushed to test, the three mam tank fuel quantity indicator readings will go to 99,900 pounds The auxiliary tanks indicator reading will go to 199,900 pounds and the totalizer will indicate the sum of the master indicators When the button is released, the indicators should show original quantity AUX TANK FILL VALVE OPEN Light Comes on during fuel transfer into the upper AUX TANK or refueling, indicating fill valve is open. The upper compartment fill valve of the auxiliary tank will not automatically close when the FUEL DUMP switch is at OPEN FILL VALVE OPEN Light (3) Comes on during fuel transfer into the mam tanks or refueling, indicating fill valve is OPEN Mam tank fill valves will automatically return to close if FUEL DUMP switch is at OPEN X-FEED DISAGREE Light (3) Comes on when the crossfeed valve position disagrees with the crossfeed control knob position TOTALIZER/GROSS WT Indicator Provides continuous total fuel quantity readout to the nearest 200 pounds and provides continuous gross weight readout to the nearest 250 pounds (A repeater totalizer/gross weight indicator is also located on the Captain's instrument panel) (UPPER MAIN C/B PANEL) (OVERHEAD PANEL) FUEL Cue Light Comes on when any mam tank pump pressure low light comes on FILL VALVE Switch (3) OPEN - Fill valve switches for tank 1, 2, and 3 are solenoidheld in the OPEN position if any auxiliary tank pump is turned on to transfer fuel Fill valve switches for tank 1 and 3 are also solenoidheld in the OPEN position if fuel quantity in tank 2 exceeds 40,000 pounds When the fuel level is less than 40,000 pounds in tank 2, and AUX TANKS switches are in the OFF position, fill valve switches for tank 1 and 3 must be manually held in the OPEN position if required CLOSE - Switch is normally in the closed position X-FEED Control Knob (3) By positioning the appropriate crossfeed valve(s) to the OPEN po sition, fuel feed can be from any tank to any or all engines and/or transferred from any mam tank to any mam tank by utilizing the ap propnate fill valve(s) and pumps SET ZFW Knob Calculated zero fuel weight is set by pushing in and rotating knob in required direction Release knob and ZFW and fuel quantity will add up to gross weight As fuel is used, the fuel continuously subtracts to present a current gross weight FLIGHT ENGINEER'S LOWER PANEL

6 FUEL DUMP Switch OPEN - Actuation of switch opens dump valves and arms dump low level float switches in mam tanks. Two dump valves are on trailing edge of each wing between outboard aileron and flap. Mam tank fill valves close if valve(s) were open. Auxiliary tank upper compartment fill valve will not automatically close. All crossfeed valves close automatically when fuel level in any mam tank reaches fuel dump level float switches (approximately 11,500 pounds in tanks 1, 2, and 3). Associated X-FEED DISAGREE light will come on and remain on until associated X-FEED knob is rotated to close or fuel dump switch is moved to CLOSE. Individual transfer pumps are shut off by actuation of respective dump level float switch when dump switch is in OPEN position. TANK OVERFILLED Light Comes on to indicate that fuel accumulating in either vent box has reached an imminent overflow condition, providing a warning to stop fuel transfer or refueling operation prior to fuel spillage overboard through the vent system. FUEL DUMP VALVE OPEN Light (L, R) Comes on when the respective dump valve is open. FUEL TEMP Gage Indicates in degrees centigrade the fuel temperature at the location selected by the FUEL TEMP switch. FUEL TEMP Switch Selects indication at FUEL TEMP indicator of the fuel temperature at either of the three engines or at number three fuel tank. FLIGHT ENGINEER'S LOWER PANEL MANIFOLD DRAIN & OUTBOARD FILL Switches (TANK 1, 3) DRAIN Opens the respective tank /FILL 1 or tank 3 dram/fill valve to provide refill of the respective outboard compartment to maintain lateral balance when the respective 1 or 3 fill valve is failed closed Under such circumstances, fuel flows at a reduced rate. Opens the dram/fill valve to permit entry of air from the outboard mam compartment to allow usable fuel in the manifold to dram into tank 2 through a float valve, when tank 2 fuel level decreases to approximately 2000 pounds NORM Is off (close) position Feb 1/

7 FUEL USED indicator FUEL USED RESET Button For description of FUEL USED Indicator and FUEL USED RESET Button, refer to Power Plant Chapter (FLIGHT ENGINEER'S LOWER PANEL) FUEL QTY CHAN SELECT Switch Selects either channel to power the fuel quantity indicator. Both channels A and B receive ac bus 1 power with the FUEL QTY IND PWR switch at NORM or ac bus 2 power with FUEL QTY IND PWR switch at ALT. FLIGHT ENGINEER'S EQUIPMENT PANEL Feb 1/76

8 FUEL QTY Indicator Typical for dial face or decal on airplanes with AOL or production equivalent FLIGHT ENGINEER'S LOWER PANEL Aug 1/ /06

9 FUEL SYSTEM Feb 1/ /02