CHAPTER 11

FUEL S Y S T E M

Page

TABLE OF CONTENTS 11-00-01/02

DESCRIPTION

General 11-10-01

Description 11-10-01

Controls and Indicators 11-10-02

COMPONENTS (NOT USED)

CONTROLS AND INDICATORS 11-30-01

FUNCTIONAL SCHEMATICS

Fuel System 11-40-01/02

JLFeb 1/75 11-00-01/02

FUEL SYSTEM

GENERAL

The fuel supply consists of threemain integral fuel tanks plus acompartmented center auxiliary tank,tank boost pumps, tank transferpumps, APU start pump, quantityindicating system, and associatedcontrols and indicators, The systemhas the capability for tank-to-tankfuel transfer, any tank to any enginefuel feed, fuel dumping, and refuel-ing. The system is designed forpressure refueling by one opera-tor, utilizing only airplane batterypower and an inverter to provide therequired ac power.

DESCRIPTION

DISTRIBUTION

The fuel supply is stored in threemain tanks and in a compartmentedcenter auxiliary tank. Main tanks 1and 3 are each comprised of aninboard and outboard compartment.Fuel is reserved in the outboardcompartment until the inboard com-partment decreases to a predeterminedlevel, then the outboard fuel passesinto the inboard compartment automat-ically. This arrangement is forstructural considerations.

Normally, fuel is delivered from eachmain tank directly to its associatedengine by fuel tank pumps. Eachindividual fuel tank pump in eachtank is powered by a separate elec-trical source. Engine 2 must havefuel tank pump pressure to operate.A fuel manifold, crossfeed valves,fill valves, transfer pumps, andassociated controls permit totalcrossfeed and transfer capability(any engine from any tank, allengines from any tank, any tank toany main tank[s]). Fuel from thecenter ccmpartmented auxiliary tankis normally transferred to the threemain tanks through the fuel supply

manifold and the respective main tankfill valves.

Scavenge jet pumps in all tanks drawfuel and water mixture from tank lowpoints to be pumped into the enginesupply system.

The APU normally receives fuel frommain tank 2. This tank is equippedwith a battery powered pump for APUstarting.

The APU may also be supplied by anyof the normal ac powered tank pumps.

VENT SYSTEM

Main tanks 1 and 3 are vented througha piping system to a vent box in theopposite wing tip. Main tank 2 isvented to the tank 1 vent manifold.In the event of tank 2 overflow itwill vent to both vent boxes. Theauxiliary tank is vented to tank 3vent manifold. An overflow stand-pipe is located in each vent box.This arrangement prevents loss offuel overboard due to adverseattitude, taxi sloshing, or centri-fuging during high speed taxi turns.Any fuel collected in the ventsystem drains back to the fuel tanksautomatically at predetermined fuellevels. The TANK OVERFILLED cautionlight indicates that the fuelaccumulating in either wingvent box has reached an imminentoverflow condition.

QUANTITY INDICATING SYSTEM

The fuel quantity indicating systemhas an individual, digital readoutindicator for each of the three maintanks and the compartmented centerauxiliary tank plus two fueltotalizer/gross weight indicators.On airplanes with AOL 10-1547 or pro-duction equivalent the fuel quantityindicators are identified for aspecific tank as: 2 SER ALL, 1 -& 3SER 30/40 and AUX/CTR SER 30/40.

JLFeb 1/85 ll-lO-01

The fuel totalizer/gross weight indicatorsdisplay aircraft total gross weight oncethe correct zero fuel weight has been setinto the instruments. A fuel quantity testbutton is provided to test the system.The temperature of the fuel in the out-board compartment of tank 3 or at anyof the three engines is selected for dis-play on a fuel temperature gage on theFlight Engineers Lower Panel.

FUELING AND DEFUELING SYSTEM

There are two fueling adapters undereach wing. Fueling is controlled by asingle-point fueling control panel under-neath the right wing leading edge. Theaircraft can be fueled from this stationusing only the aircraft's battery andinverter power, without a crewmemberin the cockpit. Fuel quantity repeater/fuel load selectors and appropriate con-trol switches allow the tanks to be filledto any preselected quantity and for fuelingto be terminated automatically. The maintanks may be defueled either by use ofthe tanks pumps or suction defueling.The center auxiliary tank is defueled bythe tank pumps.

DUMPING SYSTEM

The fuel dumping system utilizes thetransfer and tank pumps to pump fueloverboard through two exits, one at the

trailing edge of each wing. Dumping iscontrolled by two shutoff valves (one ineach wing), and dump level float switchesin the main tanks. The fuel dump rate isapproximately 5800 pounds per minuteand will vary with fuel loading and atti-tude. Fuel dumping is initiated byturning on all pumps, opening the cross-feed valves and moving the FUEL DUMPcontrol switch to OPEN. With the FUELDUMP control switch at OPEN, thedump level float switches close allcrossfeed valves when the fuel level inany main tank reaches the design mini-mum (undumpable) fuel level. The dumplevel float switches also turn off theirrespective transfer pump when the fuellevel in each tank reaches the designminimum fuel level for dumping. Allusable fuel in the auxiliary tanks can bedumped. Dumping may be terminated atany time by moving the FUEL DUMPcontrol switch to CLOSE.

CONTROLS AND INDICATORS

The controls, indicators, and annunciatorlights are on the Flight Engineer's LowerPanel and Upper Panels No. 1 and 2,captain's instrument panel, Glareshield,and Overhead Panel. Illustrations ofthese major panels (except the wingrefueling panel) are in Chapter 1.Individual controls are illustrated anddescribed in another section of thischapter.

11-10-02JL

Aug 1/81

FUEL SYSTEM - Controls and Indicators

TANK PUMP Switch (TRANS,FWD, AFT) (2)Pumps are powered by separatesystems Each pump is capable ofsupplying fuel for two engines attakeoff thrust Activated aft pumpsprovide continuous scavenging oftanks Transfer pump provides amethod of transferring fuel from tank1 or 3 to any other mam tank withoutopening crossfeed valves or to anyengine by opening the receivingengine's crossfeed valve

UPR TANK PUMP PRESS LOLight (2)Comes on steady only when respec-tive pump switch is at ALL or UPRand indicates AUX TANKS uppermam fuel pump discharge pressure isbelow allowable minimum

FUEL QTY Indicator (3)Provides a continuous reading of fuelquantity in associated tank to nearest100 pounds

AUX PUMPS Switch (L or R)Pumps are powered by separatesystemsUPR position deactivates lowerpump, and powers respective pump inAUX TANKS upper mam compart-ment to transfer fuel to all mam tanksthrough fuel supply manifold andrespective mam tank fill valvesALL position powers respective pumpin AUX TANKS upper mam compart-ment, respective pump in AUXTANKS lower compartment, andpower to open upper fill valve totransfer fuel to upper mam compart-ment for subsequent transfer to mamtanks

OFF position deactivates magnetichold position of tank 1, 2, and 3 fillvalve switchesProlonged operation of pumps withPUMP PRESS LO light on steadyreduces service life of pumps

TANK PUMP PRESS LO Light (10)Comes on only when respective pumpswitch is on and tank pump dischargepressure is below allowable minimumLight will remain on until pump switchis moved to OFF

TANK PUMP Switch (TRANS,FWD, L AFT, R AFT)Pumps are powered by separatesystems Each pump is capable ofsupplying fuel for two engines attakeoff thrust Activated aft pumpsprovide continuous scavenging oftank Transfer pump provides amethod of transferring fuel from tank2 to any other tank without openingthe crossfeed valves or to any engineby opening the receiving engine'svalve Tank 2 left aft pump, which willnormally be on when APU isoperating, is powered by rightemergency ac bus This bus can bepowered by ADG

LWR TANK PUMP PRESS LOLight (2)Comes on steady only when respec-tive pump switch is at ALL and in-dicates AUX TANKS lower compart-ment fuel pump discharge pressure isbelow allowable minimum

C - S SWITCHA three position test switch placardedC and S with the center position notplacarded The switch is springloaded to the center position The Cposition (compensator) tests thecompensator circuits external of theindicator The S position (system)tests the indicator and its activepower supply channel

FUEL QTY Indicator (AUX)Provides a continuous reading of fuelquantity in auxiliary tank to nearest100 pounds

FUEL SCHED Light (1, 3 tank)Comes on to indicate an off-schedule(premature) transfer or failure totransfer fuel from outboard compart-ment depending on fuel quantity

FLIGHT ENGINEER'S LOWER PANEL

JLAug 1/86 11-30-01

FUEL SYSTEM - Controls and Indicators

FUEL QTY IND PWR SwitchNORM — Provides ac bus 1 power

for the indicating systemand a l l o w s g roundrefueling from batterypower

ALT — Provides an alternatepower (ac bus 2) source

FUEL QTY TEST ButtonWhen pushed to test, the threemam tank fuel quantity indicatorreadings will go to 99,900 poundsThe auxiliary tanks indicator read-ing will go to 199,900 pounds andthe totalizer will indicate the sumof the master indicators When thebutton is released, the indicatorsshould show original quantity

AUX TANK FILL VALVE OPEN LightComes on during fuel transfer intothe upper AUX TANK or refueling,indicating fill valve is open. Theupper compartment fill valve of theauxiliary tank will not automati-cally close when the FUEL DUMPswitch is at OPEN

FILL VALVE OPEN Light (3)Comes on during fuel transfer intothe mam tanks or refueling, indicatingfill valve is OPEN Mam tank fillvalves will automatically return toclose if FUEL DUMP switch is atOPEN

X-FEED DISAGREE Light (3)Comes on when the crossfeed valveposition disagrees with the cross-feed control knob position

TOTALIZER/GROSS WT Indicator

Provides continuous total fuel quanti-ty readout to the nearest 200 poundsand provides continuous gross weightreadout to the nearest 250 pounds(A repeater totalizer/gross weight in-dicator is also located on the Cap-tain's instrument panel)

FUEL Cue LightComes on when any mam tankpump pressure low light comes on

FILL VALVE Switch (3)OPEN - Fill valve switches for tank

1, 2, and 3 are solenoid-held in the OPEN position ifany auxiliary tank pump isturned on to transfer fuelFill valve switches for tank1 and 3 are also solenoid-held in the OPEN position iffuel quantity in tank 2 ex-ceeds 40,000 poundsWhen the fuel level is lessthan 40,000 pounds in tank2 , and AUX T A N K Sswitches are in the OFFposition, fill valve switchesfor tank 1 and 3 must bemanually held in the OPENposition if required

CLOSE - Switch is normally in theclosed position

X-FEED Control Knob (3)By positioning the appropriatecrossfeed valve(s) to the OPEN position, fuel feed can be from anytank to any or all engines and/ortransferred from any mam tank toany mam tank by utilizing the appropnate fill valve(s) and pumps

SET ZFW KnobCalculated zero fuel weight is setby pushing in and rotating knob inrequired direction Release knoband ZFW and fuel quantity will addup to gross weight As fuel is used,the fuel continuously subtracts topresent a current gross weight

(OVERHEAD PANEL)

(UPPER MAIN C/B PANEL)

FLIGHT ENGINEER'S LOWER PANEL

FUEL SYSTEM - Controls and Indicators

FUEL DUMP Switch

OPEN - Actuation of switch opensdump valves and arms dumplow level float switches inmam tanks. Two dumpvalves are on trailing edgeof each wing between out-board aileron and flap. Mamtank fill valves close ifv a l v e ( s ) we re open.Auxiliary tank upper com-partment fill valve will notautomatically close.All crossfeed valves closeautomatically when fuellevel in any mam tankreaches fuel dump levelf l o a t s w i t c h e s ( ap -proximately 11,500 poundsin tanks 1, 2, and 3).A s s o c i a t e d X - F E E DDISAGREE light will comeon and remain on untilassociated X-FEED knob isrotated to close or fueldump switch is moved toCLOSE. Individual transferpumps are shut off by ac-tuation of respective dumplevel float switch whendump switch is in OPENposition.

FUEL TEMP SwitchSelects indication at FUEL TEMPindicator of the fuel temperatureat either of the three engines or atnumber three fuel tank.

TANK OVERFILLED LightComes on to indicate that fuel ac-cumulating in either vent box hasreached an imminent overflow condi-tion, providing a warning to stop fueltransfer or refueling operation priorto fuel spillage overboard through thevent system.

FUEL DUMP VALVE OPENLight (L, R)Comes on when the respectivedump valve is open.

FUEL TEMP GageIndicates in degrees centigrade thefuel temperature at the locationselected by the FUEL TEMP switch.

MANIFOLD DRAIN & OUTBOARDFILL Switches (TANK 1, 3)DRAIN — Opens the respective tank/FILL 1 or tank 3 dram/fill valve

to provide refill of therespective outboard com-partment to maintainlateral balance when therespective 1 or 3 fill valveis failed closed Undersuch circumstances, fuelflows at a reduced rate.Opens the dram/fill valveto permit entry of air fromthe outboard mam com-partment to allow usablefuel in the manifold todram into tank 2 through afloat valve, when tank 2fuel level decreases to ap-proximately 2000 pounds

NORM — Is off (close) position

FLIGHT ENGINEER'S LOWER PANEL

JLFeb 1/86 11-30-03

FUEL SYSTEM - Controls and Indicators

FUEL USED indicator

FUEL USED RESET Button

For description of FUEL USED Indicatorand FUEL USED RESET Button, refer toPower Plant Chapter(FLIGHT ENGINEER'S LOWER PANEL)

FUEL QTY CHAN SELECT SwitchSelects either channel to power thefuel quantity indicator. Both chan-nels A and B receive ac bus 1 powerwith the FUEL QTY IND PWR switchat NORM or ac bus 2 power withFUEL QTY IND PWR switch at ALT.

FLIGHT ENGINEER'S EQUIPMENT PANEL

11-30-04JL

Feb 1/76

FUEL SYSTEM - Controls and Indicators

FUEL QTY Indicator

Typical for dial face or decal on air-planes with AOL 10-1547 or produc-tion equivalent

FLIGHT ENGINEER'S LOWER PANEL

JLAug 1/81 11-30-05/06

FUEL SYSTEM

JLFeb 1/86 11-40-01/02