B767 ATA 28 Student Book

TRAINING MANUALFOR TRAINING PURPOSES ONLY

B767-3S2F ATA 28-00 Page - 1 4/26/13 EFF - ALL

FUEL SYSTEMSCH 28



ATA 28 FUEL SYSTEMS TABLE OF CONTENTS

Fuel 28-00

FUEL SYSTEM INTRODUCTION .......................................................... 4

FUEL SYSTEM GENERAL DESCRIPTION........................................... 6

LEFT REAR SPAR ................................................................................ 8

RIGHT REAR SPAR............................................................................ 10

FUEL 28-10

FUEL STORAGE GENERAL DESCRIPTION ..................................... 12

TANK ACCESS DOORS ..................................................................... 14

MAIN AND SURGE TANK SUMP DRAIN VALVES ............................ 16

CENTER TANK SUMP DRAIN VALVES............................................. 18

FUEL VENT SYSTEM ......................................................................... 20

FUEL 28-20

PRESSURE FUELING GENERAL INFO ............................................ 22

FUELING STATION............................................................................. 24

FUELING STATION (CONT) ............................................................... 26

OVERRWING FUELING........................................................................28

FUELING ADAPTERS......................................................................... 30

OVERFILL ........................................................................................... 32

FUELING SHUTOFF VALVE............................................................... 34

FUELING MANIFOLD DRAIN VALVES .............................................. 36

FUELING TROUBLESHOOTING........................................................ 38

ENGINE FUEL FEED GENERAL DESCRIPTION ............................. 40

MAIN TANK / OVERRIDE BOOST PUMPS ........................................ 42

BOOST AND OVERRIDE PUMP REMOVAL...................................... 44

MAIN TANK FUEL BOOST PUMP POWER ....................................... 46

CENTER TANK OVERRIDE PUMP POWER...................................... 48

MAIN TANK FUEL BOOST PUMP BYPASS VALVE .......................... 50

AUTOMATIC SUMPING JET PUMPS................................................. 52

FUEL SCAVENGE EJECTOR PUMP.................................................. 54

ENGINE FUEL SHUTOFF (SPAR) VALVE CIRCUIT.......................... 56

ENGINE FUEL CROSSFEED VALVE CIRCUIT ................................. 58

ENGINE FUEL FEED CONTROL AND INDICATION ......................... 60

APU FUEL FEED................................................................................. 62

DEFUELING ........................................................................................ 64

FUEL 28-30

FUEL JETTISON ................................................................................. 66

FUEL 28-40

FUEL INDICATING GENERAL INFO.................................................. 68

FUEL INDICATING GENERAL INFO (CONT)..................................... 70

FUEL INDICATING TANK / MEC COMPONENTS............................... 72

FUEL INDICATING TANK / MEC COMPONENTS (CONT) ................ 74

FUEL INDICATING TANK / MEC COMPONENTS (CONT) ................ 76

FUEL QUANTITY INDICATOR............................................................ 78

FUEL QUANTITY INDICATOR (CONT) .............................................. 80

FQIS INDICATION............................................................................... 82

FQIS INDICATION (CONT) ................................................................ 84

FQIS BITE............................................................................................. 86

FQIS BITE (CONT) ............................................................................... 88

FUEL TEMPERATURE INDICATING................................................... 90

FUEL QUANTITY MEASURING STICK ASSEMBLY............................92

HOT SHORT PROTECTOR ................................................................ 94



FUEL SYSTEM -- INTRODUCTION

General

The fuel system has these subsystems:

• Fuel storage • Pressure fueling • Engine fuel feed • APU fuel feed • Defueling • Fuel indicating

Fuel Storage

The fuel storage system has these fuel tanks:

• Left main tank • Right main tank • Center tank

Pressure Fueling

The pressure fueling system moves fuel from the fueling adapters to the main and center tanks. You operate the pressure fueling system with the fueling control panel.

Engine Fuel Feed

The engine fuel feed system supplies fuel to the engines from the main and center tanks. You operate the engine feed system from the fuel management panel on the P5 overhead panel.

APU Fuel Feed

The APU fuel feed system supplies fuel to the APU.

Defueling

The defueling system moves fuel from the airplane tanks to ground tanks or from one airplane tank into a different airplane tank. You operate the defueling system at the fuel control panel and the P5 overhead panel.

Fuel Indicating

The fuel indicating system measures fuel quantity in the tanks. The fuel quantity indicators in tight compartment and on the fueling control panel show fuel quantity. The fuel indicating system also measures fuel pressure and temperature.



FUEL SYSTEM -- INTRODUCTION



FUEL SYSTEM -- GENERAL DESCRIPTION

Purpose

The fuel system has these functions:

• Storage • Venting • Fueling • Engine and APU fuel feed • Fuel Jettison • Defueling • Fuel transfer • Fuel quantity indication

Fuel Tanks

These tanks hold fuel:

• Left main tank • Right main tank • Center tank

The left main, right main, and center tank are wet wing construction. A baffle rib in the main tanks controls outboard flow. A surge tank is outboard of the two main tanks to contain overflow and prevent fuel spills. The surge tanks are normally empty and drain into the main tanks through a check valve.

Vent System

The vent system keeps near ambient atmospheric pressure in the tanks. The system is a vent scoop with flame arrestors in the two surge tanks and vent channels and tubes in the tanks. Backup pressure relief valves attach on the inboard surge tank access door.

Refueling System

The refueling system is a manifold with six refueling valves in the tanks and a fueling station on the left wing leading edge. The fuel quantity indicating system(FQIS) controls the refueling valves to give versatility in fueling operations. A backup overfill sensor in each surge tank stops fueling operations if the tanks

have an overfill. An overwing fill port is on the upper wing surface for the two main tanks.

Feed System

The two engines and APU get fuel from the fuel feed system. There are two ac boost pumps for each main tank. There are two ac override pumps for the center tank. A bypass valve in each main tank supplies suction flow from the main tanks. A dc pump pressure supplies the APU when the ac pumps do not operate. Two crossfeed valves connect the isolated left and right feed manifolds together to let one or the other tank supply one or the other engine. Jet pumps operate by the ac pump fuel outflow to prevent water and contaminates at tank low points.

Defueling

The defuel valves connect the feed system and the fueling system together to give defueling and fuel transfer operations on the ground only.

Fuel Jettison

A fuel jettison system quickly decreases the gross weight of the airplane. Two jettison pumps operate with the center override pumps to move center auxiliary tank fuel overboard. Controls for the system are on the P5 overhead panel.

Fuel Quantity Indicating System (FQIS)

The FQIS is a microprocessor-controlled capacitance type fuel quantity measuring system. The FQIS uses 28v dc for operation. There is a digital display of fuel weight in the flight compartment and at the fueling station. Tank units give a volume measurement. Densitometers, one in each tank, give fuel density signals. The FQIS also controls the fueling valves to stop fueling at set quantity levels.

Measuring Sticks

Magnetic dripless-type measuring sticks are in the lower wing surface of each tank. These measuring sticks are a different device to measure fuel quantity.



FUEL SYSTEM -- GENERAL DESCRIPTION - LEFT REAR SPAR

These fuel system components are on the left rear spar:

• Fueling valves (2 main and 1 center) • Left defueling valve • Left engine fuel shutoff valve (spar valve) • FQIS wiring harness connections (left main and • left center) • Left main tank densitometer connector • APU dc pump • APU fuel shutoff valve • Fuel crossfeed valves (2) • Left aft boost pump pressure switch • Left center override pump pressure switch • Boost pump pressure switches • Left jettison transfer valve • Left jettison nozzle valve • Fuel temperature bulb



FUEL SYSTEM-- GENERAL DESCRIPTION - LEFT REAR SPAR



FUEL SYSTEM -- GENERAL DESCRIPTION-RIGHT REAR SPAR

General

These fuel system components are on the right rear spar:

• Fueling valves (2 main, 1 center) • Right defuel valve • Right engine fuel shutoff valve (spar valve) • FQIS wiring harness connections (right main and right center) • Right main tank and center tank densitometer connectors • Right Jettison transfer valve • Right jettison nozzle valve



FUEL SYSTEM -- GENERAL DESCRIPTION-RIGHT REAR SPAR



FUEL SYSTEM -- FUEL STORAGE - GENERAL DESCRIPTION

General

The fuel tanks have these functions:

• Contain the airplane fuel • Give component housing • Prevent fuel spills • Give fuel sampling access

Fuel Tanks

The three tanks are set by the front and rear spars, the top and bottom wing skins, and selected wing ribs.

The left and right main tanks are in the two wings. Dry bays are in the two wing leading edges at the engine hot sections. The dry bays make sure fuel leakage does not get to the engine. Baffle ribs in the main tanks keep the fuel level above the pump inlet ports. Each main tank holds 6000 US gallons.

The center tank is between the right and left main tanks. Fuel is in the inboard wing sections and the wing center section. The tank holds 12,000 US gallons.

The surge tanks are outboard of each main tank. These tanks are usually empty. The tanks contain the overflow to prevent fuel spillage. Tank venting is through the surge tanks.

Sump drain valves are in these locations:

• Low point of the two main tanks • Two surge tanks • Each side of the center tank

The dry bay for the engine hot section has a drain hole with a flame arrester.

Maintenance Practices

Access to the center, main tanks and surge tanks is through cutouts in the lower wing surface. In some sections, openings in the ribs give access to adjacent rib sections. The cutouts are different sizes. The smaller cutouts are outboard.

Measuring sticks are on set access doors, so you must make sure of correct placement and indexing. Dry bay access panels are in the tanks.



FUEL SYSTEM -- FUEL STORAGE - GENERAL DESCRIPTION



FUEL SYSTEM -- FUEL STORAGE - TANK ACCESS DOORS

Tank Access Doors

The tank access door fit inside the tank to seal the oval cutouts in the lower wing surface. A molded rubber seal fits between the inner skin and the door. No mounting holes are drilled in the wing surface to prevent cracks or leaks.

Locations

There are 25 doors in each main tank, five in the center tank and three in each surge tank. Many of the doors are the same size, but they are not interchangeable. The engine dry bays have a single access next to the pylon.

Construction and Installation

The oval aluminum access doors fit inside the tanks. The molded rubber seal is outboard of the bolt pattern to prevent leaks around the installation bolts. A clamp ring mates into recesses on the door and skin to secure the door. The assembly is flush to the lower wing skin when installed. A knitted aluminum gasket under the clamp ring gives proper interface and electrostatic bonding. Measuring sticks are in selected doors. A pressure relief valve is in the inboard door of both surge tanks.

Follow defueling procedures prior to removal of tank access doors.

Impact Resistant Tank Access Doors

Special impact resistant fuel tank access doors are fitted in the main tanks and center auxiliary tank in areas that are subject to possible impact damage.

Location

Five of these doors are on the left and right bottom wing surface of each strut.


The doors are made of bonded aluminum honeycomb. A nylon backing plate is bonded to the inner surface, and an aluminum sheet is bonded to the outer surface. The remainder of the door and door assembly is the same as the standard tank access doors. The gasket, clamp ring, and mounted bolt are

identical and interchangeable. It is possible to incorrectly install a standard door in these locations.

. To prevent this, a caution label is next to each impact resistant door access. This is the label.

CAUTION: INSTALL ONLY IMPACT RESISTANT DOOR AT THIS

LOCATION. THE LABEL IMPACT RESISTANT DOOR ISMOUNTED ON EACH IMPACT RESISTANT DOOR.



FUEL SYSTEM -- FUEL STORAGE - TANK ACCESS DOORS



FUEL SYSTEM -- FUEL STORAGE - MAIN AND SURGE TANK SUMP DRAIN VALVES

Purpose

The main and surge tank sump drain valves lets you do fuel sampling and defueling.

Location

The valves are at the low point of each main and surge tank.

Physical Description

The valves use a spring-loaded closed poppet for normal operations and a flapper to permit removal of the poppet with fuel in the tank. The valves installthrough a hole in the lower wing skin and are smooth to the lower wing surface.You rotate the poppet to unlock it. You push up on the poppet to drain the sump. You must rotate the poppet to lock it when you are finished draining the sump.


You turn the poppet to remove it for servicing. You use the internal hex fitting and hex key. The flapper seals the opening as the poppet comes out. Fuel can be in the tank.

Fuel Sump Draining

You must regularly drain the fuel tank sumps to remove collected water from the fuel tanks. Each fuel tank sump has a drain valve to drain water from the tank.You drain the sumps before and after refuel but not during refuel. There must be as much time as possible between refuel and sump draining to let the water go to the bottom.

Each fuel sample must have a check for water, ice, or contamination. Water in the fuel usually shows as a layer below the fuel or as small bubbles in the fuel.Ice crystals usually show as cloudiness in the fuel. Fuel with no water, ice, or contamination is clear and bright. One or two drops of water soluble food

coloring in the container before you take the sample helps you see the water in the fuel. The water becomes colored.



FUEL SYSTEM -- FUEL STORAGE - MAIN AND SURGE TANK SUMP DRAIN VALVES



FUEL SYSTEM -- FUEL STORAGE - CENTER TANK SUMP DRAIN VALVES

Purpose

The center tank sump drain valves are for defueling and removal of a fuel sample.

Location

The valves are in the low points of the center tank.


The center tank sump drain valves are almost the same in construction and operation as the main and surge tank valves except for a flex hose connected to let the drainage go out of the wing-to-body fairing. To open the drain valve, you hold the hose near the drain valve body and push up.

Access

You release two snap open fasteners to open a hinged access door in the wing to body fairing above the environmental control system components door.



FUEL SYSTEM -- FUEL STORAGE - CENTER TANK SUMP DRAIN VALVES



FUEL SYSTEM -- FUEL STORAGE - FUEL VENT SYSTEM

General

Air and fuel vapors flow in and out of the fuel tanks through the fuel vent system. This prevents excess pressure and vacuum within the fuel tanks.

The fuel vent system keeps the fuel tank pressure near the ambient atmospheric pressure during all operating conditions . Overpressure in the tanks could cause structural damage. Under pressure could cause component malfunction and engine fuel starvation.

Construction and Components

The tanks vent to ambient pressure through vent channels. Three parallel vent channels extend into the main and center fuel tanks from the surge tanks. The surge tanks are normally dry. The surge tanks maintain near ambient pressures through a vent scoop. Backup vent to the surge tank is through a pressure relief valve.

Hat section stringers on the inside upper wing skin form the three vent channels in each wing. Open-en-ended vent tubes are on the bottom of the channels to give flow to the surge tank in nose-high attitudes. The center tank has cross-vents. The left side goes to the right surge tank, and the right side goes to the left surge tank. This cross-vent prevents fuel flow into the surge tanks during ground maneuvering and wing low attitudes.

Float valves are on some ports in the tanks to prevent fuel flow through the ports and into the surge tanks when the ports are immersed. Float drains let fuel trapped in the vent tubes drain into the tanks.

If fuel enters either surge tank, a drain line from the rear of each tank allows fuel to drain into the center tank via a drain check valve.

Vent Tube Drain Valve

There are eight vent tube drain valves on a flange mount on the aft ends of each of the six vent tubes and on the two surge tank standpipes. The drain valves let fuel in the vent system low points drain into the tanks. This increases the usable quantity of fuel. The drain valves also do not let fuel from the tanks go

into the vent system. The valves operate by fuel level. The valves close when they are below the fuel level and open when they are not below the fuel level.

Float Valves

There are four vent channel float valves on the vent ports and two float valves on rib 18 with a flange mounting. The free swinging valves are held normally open by gravity and close by the float when fuel immerses that tank section. There are no external indications of operation.

Vent Scoop

The vent scoop is on the lower wing surface aft of the rear spar and surge tank. It is recessed into the wing surface. It keeps the tank at or near ambient pressure during all operational conditions. A tube connects and ports the scoop to the surge tank. The tube port is near the top of the surge tank so that the surge tank must be almost full before fuel flows into the tube and overboard through the vent scoop.

Surge Tank Flame Arrester

The surge tank flame arrester is between the vent scoop and the tube aft of the rear spar. It is a passive device with a stainless steel honeycomb core. It is a heat sink to cool a flame to less than the ignition point. This prevents an external flame from going into the surge tank.

Pressure Relief Valve

The surge tank pressure relief valve opens a backup vent if the vent flame arrestor has a blockage. The relief valve attaches to the inboard access door in the surge tank. The valve is smooth with the outer wing skin when the door is closed. You can see the poppet is closed during walk-around inspection and if not their is a reset handle to reset the poppet.



FUEL SYSTEM -- FUEL STORAGE - FUEL VENT SYSTEM



FUEL -- PRESSURE FUELING - GENERAL INFO

General

You do normal fueling from the fueling station. The station is in the lower leading edge of the left & right wing outboard of the engine strut. The fuel quantity indicating system (FQIS) operates with the fueling system to stop fueling at set quantities or when the tanks are full by volume. Pressure Fueling Valves

The tanks fill through six fueling valves. There are two valves for each main tank and two valves for the center tank. The fueling valve switches and the FQIS processor control the valves. An overfill system closes all valves if fuel goes in the surge tanks. A knob on each valve gives manual operation.

Fueling Manifold Draining

The two manifold drain valves let fuel go into the manifold to drain into the center tank after refuel. A vent valve connects the fueling manifold to a ventchannel, so air can go in the manifold as fuel drains.

Defuel Valve

The Defuel Valve is identical to the Engine Fuel Shutoff Valve and Crossfeed Valve. A manual override lever is available to open and close the valve, and also provides a valve position indication.



FUEL -- PRESSURE FUELING - GENERAL INFO



FUEL -- PRESSURE FUELING - FUELING STATION

Access

Two quick-release latches let you open and latch closed the forward-hinged station door.

Power

You latch the door open to supply power to the fueling station. If the ground handling bus has power, the station gets power when the magnetic reed switch near the hold open catch aligns with its target. If there is no power on the ground handling bus, you can lift the guard on the BAT switch and move the power switch to ON to supply power from the hot battery bus. When thestation has power, the panel lights come on, and the load select indicators show the fuel weight for each tank.


The fueling station includes these components: • P28 fueling control panel • Fueling adapters (2) • Ground jacks (2) • Interphone jack • Panel light • Fueling adapter caps (2)

The fueling control panel has these controls: • Fueling valve control switches (3) • Blue press-to-test valve OPEN lights (6) • Battery power select switch • Load select indicators (3) • Load select control • Push-button switches (5) - three for set and one each for test and reset of

the systems

Fuel Load Requirements and Limitations

The main tanks normally have the same quantity of fuel. For flight, if you fill the main tanks to capacity, you can put fuel in the center tank. If the airplane stays

on the ground, the center tank can have fuel if the main tanks do not have a full capacity load. You can refuel all the tanks at the same time or individually in diff erent sequences.

Refuel

When you open and latch the fueling station door, and the ground handling bus has power, the bus supplies 28v dc to the fueling station, the overfill sensing system, and the fuel quantity processor unit. The panel lights show that the system has power. The fuel quantity also shows in the load select fuel quantity indicators. If there is no indication of system power, you put the fueling power select switch to the BAT position to supply power to the system from the hot battery bus.

Automatic Mode

The automatic mode stops refuel at set loads. To use the automatic mode, you select the necessary fuel quantity on the load select control. Then you push theSET switch below the applicable indicator. The set load shows on the lower indicator. You can do this for the tanks individually or for all tanks.

Manual Mode

To refuel in the manual mode, the lower part of the load select indicator must be blank. If the lower display is not blank, you must push the set switch tomake the display blank. To do a reset of all load select indicators to the manual mode, you close the fueling station door but not fully, and then you latchthe door back open again. You use the fueling valve toggle switches to stop refuel when you use the manual mode.



FUEL -- PRESSURE FUELING - FUELING STATION



FUEL -- PRESSURE FUELING - FUELING STATION (CONT)

Mechanical Mode (Refuel Without Electrical Power)

You must get access to the applicable fueling shutoff valve actuators. For the center tank, make sure you install the landing gear downlocks. You must make sure there is no pressure in the fueling manifold. The fueling manifold depressurizes through manifold drain check valves when you remove the fueling source pressure, and the center tank volume is less than 22,000 lb (9980 kg). As much as twenty minutes can be necessary for the pressure in the manifold to release. You turn the manual override knob 10 to 13 complete turns in the counterclockwise direction to open the applicable fuel shut valve.

CAUTION: REMOVE THE PRESSURE FROM THE FUELING MANIFOLD BEFORE YOU MANUALLY OPEN THE FUELING SHUTOFF VALVE. IF YOU DO NOT REMOVE THE PRESSURE, DAMAGE TO THE FUELING SHUTOFF VALVE OR FUELING MANIFOLD CAN OCCUR.

After refuel operations are complete, you do not close the fueling shutoff valve until there is no pressure in the fueling manifold. After you close the valve, youmust install a lockwire to the manual override knob.

CAUTION: THERE IS NO AUTOMATIC SHUTDOWN OR OVERFILL PROTECTION WITHOUT ELECTRICAL POWER.

Test Valve Shutoff

The SYSTEM TEST push-button makes sure the FQIS can stop refuel. To do the test, the blue fueling valve lights must be on while fuel goes into all relatedtanks. During the test, the FQIS closes all fueling valves. This shows when the blue lights go off. The valves close in sequence to prevent a pressure shock tothe system. After 10 seconds, the blue lights come on again and refuel continues. Automatic mode and manual mode shutdown must be in full operation for a successful test without relation to the mode used for the test.

Note: Do not do a system test at high (near cutoff) fuel levels.

Overfill Test

You push the OVERFILL TEST switch on the fueling control panel to do a test of the overfill system. You must make sure the fueling valve lights go off . Youpush the OVERFILL RESET switch to open the valves again.

Note: The overfill test closes all fueling valves at the same time. To prevent damage to the system, decrease the refuel pressure or do a test of only one valve at a time.

CAUTION: DO NOT USE MORE THAN 35 PSI FUEL PRESSURE AT THE FUELING NOZZLE FOR THE OVERFILL SYSTEM TEST. IF YOU USE MORE THAN 35 PSI FUEL PRESSURE, YOU CAN CAUSE DAMAGE TO THE REFUELING SYSTEM COMPONENTS.

After Refuel Stops

The fueling valves close to stop refuel for these conditions:

• Automatic mode - when the fuel weight gets to the selected weight (upper display the same as the lower display) on a load select indicator (FQIS processor)

• Manual mode - when the related tank is full by volume (FQIS processor) • Manual control - you put the toggle switches to OFF when necessary • Overfill trip - the overfill system senses fuel in the surge tank

When refuel is complete, you do these steps:

• Put all switches back to CLOSE, NORM, or OFF as necessary • Disconnect the nozzles and grounding plugs • Push to do a test of the blue lights to make sure the valves are closed • Close the fueling station door

There is no flight compartment indication of an open door.



FUEL -- PRESSURE FUELING - FUELING STATION (CONT)



FUEL -- PRESSURE FUELING - OVERWING FUELING

Purpose

The Overwing Fueling Ports provide a method of fueling main tanks without utilizing the Pressure Fueling Station. The ports may also be used to inspect a portion of the tank visually.

Location

Two ports, one on each wing, at Wing Station 785.2 (between Rib 23 and Rib 24) are available. Access is from the Wing Leading Edge. A grounding point for the nozzle is located close to the port.

Filler Cap

The Filler Cap seals the fueling port. Venting is not provided. A lanyard prevents the cap from being lost when removed. Lift and rotate the handle to remove the cap.

Fueling Port

The Fueling Port is installed using O-ring seals, a seal ring and a retaining nut. The tanks will contain 5925 gallons when fueled to the port level. The tanks will hold 6070 gallons when fueled with the pressure fueling system. The caps should not be removed when the main tanks are full to prevent spillage.



FUEL -- PRESSURE FUELING - OVERWING FUELING



FUEL -- PRESSURE FUELING - FUELING ADAPTERS

General

Two identical fueling adapters are in the fueling station, one on each side of the control panel. The adapters prevent backflow through an unused adapter bythe use of a sliding piston and poppet valve. Four combinations, or modes are possible.

Closed

Both the sliding piston and the poppet are closed when the nozzles are not connected.

Fueling Mode

The poppet opens mechanically when the nozzle is connected. The sliding piston opens by fuel pressure from the truck. This lets fuel flow into the manifold.

Reverse Flow Check Mode

The poppet is opened by the nozzle. The sliding piston is closed because of a lack of fueling pressure. This prevents a backflow of fuel into the fueling nozzle.

Defuel Mode

Turn the slot to DEFUEL to set the two pins outward to interface with the sliding piston. This connects the poppet and sliding piston together. When the nozzle isconnected, both valves are open. This permits a backflow for defueling purposes.



FUEL -- PRESSURE FUELING - FUELING ADAPTERS



FUEL-- PRESSURE FUELING - OVERFILL

Description

The Overfill System is designed to provide redundancy and backup to the FQIS for terminating fueling. It is independent of the FQIS in operation.

The system consists of sensors located in each Surge Tank and a Fuel Level Sensor Control Card located in the P50 card file in the MEC. The system removes power from all Fueling Valves simultaneously should fuel enter either Surge Tank.

Overfill Sensors

The sensors are concentric tube capacitors. They are in a bathtub type enclosure at the top of the Surge Tank under the vent channel ports.

Fuel Level Sensor Control Card

The control card is a solid-state device utilizing 28 volt DC airplane power. It sends and receives 250khz signals to the sensors, and receives TEST signals and RESET signals from push button switches on the Fueling Control Panel.

Operations

The Overfill Sensor System is powered whenever the Fueling Station is powered. The Control Card reads both sensors. If the capacitance measurement indicates that the sensors are not immersed in fuel, the Control Card allows the Fueling Valves to remain open.

If either sensor becomes immersed, the Control Card removes power from all Six Fueling Valves. An inoperative Fuel Level Sensor Control Card or a loss of a signal from either sensor trips and deenergizes the Fueling Valves.

The system operation is tested by activating the Overfill Test Button at the Fueling Station when fuel is flowing. A successful test is indicated by closure of the Fuel Valves. The Overfill Reset Button is pressed to reset the system.

Note: When performing this test only one tank at a time should be tested.

System Reset and Bypass

Push the momentary OVERFILL Reset Switch to supply a ground to the Overfill Control Relay. This resets the system if the sensors are not immersed. The system is also reset every time power is initially applied. Hold this switch closed to bypass a failed control card or sensor.

CAUTION: BY HOLDING THE RESET SWITCH THERE IS NO VOLUME METRIC TOP-OFF PROTECTION.

System Test

Push the OVERFILL System Test Switch to test the system. If both sensors and the card logic are okay, the card removes the ground to the overfill control relay just as though fuel were sensed.

Sensor and Card Operation

The system operates on a capacitance principle. The card excites the sensors with a 250 kHz Lo Z signal and measures the return signal. If the capacitance of either sensor is out of limits, or if the return signal cannot be measured due to wiring faults, the card removes the ground to the overfill control relay.



FUEL-- PRESSURE FUELING - OVERFILL



FUEL -- PRESSURE FUELING - FUELING SHUTOFF VALVE

General]

The fueling valve is fuel-pressure actuated and solenoid controlled. The fueling valve switches on the fueling control panel and the FQIS processor unitprovide 28v dc power and ground for the solenoid.

An independent overfill system can remove solenoid power to the valves automatically to prevent fuel spills when fuel enters the surge tank.

Location

The six fueling valves are on the rear spar.


The fueling valve has two major components, the fueling valve inside the tank, and the fueling valve actuator outside the tank.

The fueling valve is stud-mounted to the rear spar with three hex nuts. The actuator mounts to the valve studs with three actuator mount bolts. Two control ports with removal check valves let fuel into the actuator. A manual override knob is on the actuator to open the valve when the solenoid can not be energized. The actuator is an LRU and may be replaced without defueling.

Normal Operation

Fuel flows through the removal check valves to the two sides of the diaphragm in the actuator. When the solenoid de-energizes, the control port closes. Thismakes sure fuel does not flow from the spar side of the diaphragm through the control port into the tank. The fuel pressure is the same on the two sides of thediaphragm, and the spring holds the poppet closed. When the solenoid energizes, the control port opens and fuel flows from the spar side of the diaphragm into the tank. This fuel differential pressure across thediaphragm opens the poppet against the spring. This lets fuel flow through the outlet and into the tank.

At least 4 psi of fuel pressure is necessary at the fueling valve inlet to open the valve.

Valve Position Switch

The switch connects a ground to put on a blue light on the fueling control panel to show that the valve is not closed. The microswitch position is set by the movement of the diaphragm.

Manual Override

You turn a manual override knob on the actuator counterclockwise to push against a backplate and move the diaphragm plunger to open the poppet. This lets you open the valve when there is no solenoid operation. A safety wire keeps the knob in the valve closed position for normal use. To prevent damage to the fueling shutoff valve diaphragm, you must turn the manual override knob to the open position before you supply fuel pressure.



FUEL -- PRESSURE FUELING - FUELING SHUTOFF VALVE



FUEL -- PRESSURE FUELING - FUELING MANIFOLD DRAIN CHECK VALVES

Purpose

There are drain valves on the fueling manifold to increase the quantity of usable fuel in the fuel system. The fueling manifold drain check valves drain the trapped fuel into the fuel tank as fuel volume decreases in the tank.

Three drain valves let the fuel drain into the center fuel tank. The three valves are almost the same in construction. The valves have spring values.

Fueling Manifold Drain Valve

There is a manifold drain check valve adjacent to the side-of-body rib in the two sides of the center tank. This check valve lets fuel drain from the fuelingmanifold into the center tank after refuel is complete. The fuel head in the manifold opens the flapper valve but does not have sufficient pressure to move the plug valve down and closed. This lets fuel flow into the tank. During refuel, the high pressure moves the plug valve closed against the spring to prevent refuel of the center tank through the drain valves. The flapper valve prevents a backflow into the manifold from the tank. The plug valve closes at 8.5 psid. The permitted maximum leakage rate is 25 cc/min.

Fueling Manifold Vacuum Valve

The manifold vacuum valve connects the surge tank drain line and the fueling manifold outboard of rib 17 in the main tank. This valve lets air from the surge tank go in the fueling manifold to replace the fuel that drains into the center tank. The flapper valve and the plug valve are open. During refuel, the flapper valve closes to make sure fuel does not go in the surge tank drain line. During defuel, the plug valve closes by the suction from the defueling vehicle to make sure airdoes not go in the manifold. The plug closes at 2.5 psid



FUEL -- PRESSURE FUELING - FUELING MANIFOLD DRAIN CHECK VALVES



FUEL -- PRESSURE FUELING - FUELING TROUBLESHOOT-ING

General

Most problems found during pressure fueling operations have an easy work around. An operational pressure fueling system is not necessary for dispatch if an alternate means of verifying the fuel quantity is used. See fuel measuring sticks.

Door Switch (Magnetic Reed Switch)

If the switch fails, no power is available for the fueling station. Replace the switch to get fueling station power.

Overfill System Failure

For an overfill system failure, hold the RESET pushbutton to bypass the sensors and card.

Automatic (Pre-select) Mode Failure

If the load select input to the processor fails, the processor is not able to find the desired fuel shutoff weight. FAIL shows in the load select portion of theload select indicator and you must push the set switch to continue fueling in the manual mode.

FQIS Processor Fails

If the FQIS fails, the fueling valve relays cannot be energized. Use the mechanical mode (manual override knobs) and use the measuring sticks to the fuel quantity.

Note: If the fueling station has power, but all indicators are blank, you can use the indicator test switch to if the processor is connected and has failed or if the processor does not have power. An indicator test would show the fault code Ab where fuel weight normally shows if the processor has power but has failed outputs. An indicator test would not be active if the processor was not installed or did not have power.

Fueling With FQIS Accuracy Faults

If faults occur which degrade system accuracy, the processor permits fueling operations to continue if fuel weight and volume are known with enough accuracy to prevent overfill. When the processor can not safely prevent overfill, the fueling valves close and PUSH SET shows on the load select indicator(s). If you push the set switch, the fueling valves open but there is no processor overfill protection. Also after you push the set switch, the fuel weight in the load select indicator will either be blank or will flash.

If there is a blank indicator after you push the set switch, there is a fuel mass (weight) problem. If faults occur which exceed the design limits of five per cent for fuel weight indication (unknown accuracy), the processor is unable to find the fueling shutoff point for either the automatic or the manual modes. The fueling valves close immediately and PUSH SET shows on the load select indicator(s). If you push the set switch, one fueling valve per tank opens. Manual control is used to continue fueling and you must use the measuring sticks to find the fuel quantity.

If there is a flashing indicator after you push the set switch, there is a fuel volume problem. Volumetric topoff is done when the most outboard tank unit senses full volume. Compensator related problems can cause the volume as sensed by the last tank unit to be less accurate. The fueling valves close and PUSH SET shows when the tank is either 95 or 87 per cent full, depending on the failure (See FQIS compensator for details). If the most outboard tank unit has completely failed, the fueling valves close and PUSH SET shows when the last operational tank unit senses full volume. The processor also closes the fueling valves when the weight is 95 percent of the pre-selected weight in automatic mode and the system inaccuracy is between one and five percent.

Note: When the processor is in the degraded accuracy mode, a message in the processor BITE shows which volumetric top off (VTO) is used. (See FQIS for details)



FUEL -- PRESSURE FUELING - FUELING TROUBLESHOOTING



FUEL SYSTEM - ENGINE FUEL FEED - GENERAL DESCRIP-TION

Purpose

The engine fuel feed system supplies fuel flow to the engines.

General

Fuel can come from the main tanks or from the center tank for each engine. Two boost pumps in each main tank and two override pumps in the center tank pressurize fuel for the engines and APU. Main tank fuel boost pump bypass valves permit suction feed. The suction feed system increases the usable fuel.

These are the components in the engine fuel feed system:

• Engine fuel shut valve • Engine fuel crossfeed valve • Main tank fuel boost pump • Center tank override pump • Fuel boost pump discharge check valve • Fuel boost pump removal check valve • Main tank fuel boost pump bypass valve • Automatic sumping jet pump • Fuel scavenge ejector pump • Float operated shutoff valve

Automatic Sumping Jet Pumps

Automatic sumping jet pumps decrease contamination and water buildup. The pump inlets are at the tank low points where contamination and water collect. Fuel and contamination removed by the jet pumps go to the boost pump and override pump inlets.

Crossfeed

The crossfeed manifold connects all ac fuel pumps. The manifold also connects the two engine feed lines. Two crossfeed valves connect the left and right crossfeed manifolds. The valves are normally closed. You open the valves to correct a fuel imbalance.

Suction Feed

A flapper-type bypass check valve connects to the engine feed line in each main tank. This permits suction fuel w from the main tanks to the engines. Pump pressure in the engine feed line closes the bypass valves in normal operation.



FUEL SYSTEM -- ENGINE FUEL FEED - GENERAL DESCRIPTION



FUEL SYSTEM -- ENGINE FUEL FEED - MAIN TANK FUEL/OVERRIDE BOOST PUMPS

General

There are four 115v ac, three-phase, motor-driven fuel boost pumps. There are two for each main tank.

Location

Both forward and aft boost pumps are in a common dry bay housing over an oval cover panel in the lower wing surface. The assemblies are interchangeable between left and right tank and between forward and aft pumps.

Physical description/features

Each pump is a motor/impeller unit in a common housing unit. The nominal rated flow is 30,000 pph at 15 psi minimum when driven at 7650 RPM.

The pump is an impeller type. The pump unit is cooled and lubricated by fuel. A liquid ring pump is in a cavity in the bottom of the unit to supply cooling circulation around the motor and is to prime the impeller after dry operation. The motor cavity is charged during fueling through the wetting ports. Thecooling fuel returns to the tank through a vapor vent valve in the pump housing.

The pump output to the feed manifold is through two discharge check valves. If there is override pump output pressure, the discharge check valves are closed.This turns on the boost pump output to the engine feed line. The motive flow discharges through a motive flow screen module and then through a check valve into a common cavity to the motive flow port. Motive and cooling flows are supplied regardless of discharge check valve position. Two small pressure lines connect to the pump housing to supply an input to fuel boost pump pressure switches on the rear spar.

The common pump housing unit is on top of the lower wing skin. It connects to the suction line with a sliding sleeve type removal shutoff valve and to thecrossfeed manifold with two poppet type discharge check valves. The housing unit also has these components:

• Jet pump motive flow discharge

• Two pump wetting line ports • Primer discharge through two vapor vent valves • Pump pressure switch line connection

Center Tank Override Pumps

Four motor-driven override/jettison pumps are in the center tank. These pumps operate from three-phase 115v ac. The left override and left jettison pump are in the same housing. The right system has an installation almost the same. Access is from below the wing. All four pumps are interchangeable.

Physical description/features

The override pumps are a motor/impeller unit and a housing unit almost the same as the main tank boost pumps. The override pumps supply fuel to the engine at a higher pressure than the main boost pumps. This higher pressure holds the main tank boost pump check valves closed. This makes sure that the fuel supplied to the engines is from the center tank. The nominal rated flow is 25,000 pph at 30 psi minimum when the pump operates at 11,400 rpm.

Operation

To decrease electrical loads, the override pumps are off unless the fueling station door is open, or the related engine is in operation. The jettison pumps only operate when you arm and select the jettison system to on.



FUEL SYSTEM -- ENGINE FUEL FEED - MAIN TANK FUEL/OVERRIDE BOOST PUMPS



FUEL SYSTEM -- ENGINE FUEL FEED - BOOST AND OVER-RIDE PUMP REMOVAL

Main Tank Fuel Boost Pumps

There are three phillips-head screws that you must remove to remove the pump unit. Two allen-head shoulder screws and one allen-head index pin help to lock the shutoff sleeve during pump removal. This prevents a fuel spill. There is a drain plug on the bottom of the pump unit that you use to make sure the shutoff sleeve is closed.

For pump removal, it is necessary to disconnect the electrical connector, the three phillips screws, and the bonding strap. You pull the pump handle down and slowly pull the pump unit down from the housing 1 1/2 inches.

WARNING: WARNING: DO NOT ROTATE THE PUMP UNIT YET. IT IS POSSIBLE THAT A FUEL SPILL CAN OCCUR.

When you remove the drain plug, all of the fuel in the pump drains out. One liter of fuel drains out. If the shutoff sleeve closes, you can then continue to removethe pump unit with fuel in the tank.

If a stream of fuel continues to come out, the removal check valve did not close correctly. You can install the pump again and try to remove it again. If you are not successful, you must do a defuel of the tank.

Turn the pump unit 12 degrees counterclockwise (looking up) and make sure that the dog latch engages in the locking slot of the shutoff sleeve. You can then pull the pump unit down and out of the housing.

Note: A 12-degree turn makes sure that the dog latch engages into the shut sleeve slot and also lets the shoulder screws be clear of the keyhole slots of the pump unit for removal.

Center Tank Override Pumps

You remove the override/jettison pumps the same as you do the main boost pumps.



FUEL SYSTEM -- ENGINE FUEL FEED - BOOST AND OVERRIDE PUMP REMOVAL



FUEL SYSTEM-- ENGINE FUEL FEED - MAIN TANK FUEL BOOST PUMP POWER

Power Sources

The pumps get power from the left, right, and ground service (right power channel) buses. Loss of power to any one bus does not cause all the pumps on one side to lose power.

Features

A non-resettable thermal fuse in each of the three phases prevents overheat of the motor. The thermal fuses open at a temperature of 400F (204C).

Operation

AC relays energize to send power to the boost pumps. The relays energize when the boost pump switch is on and the appropriate bus has power. Each relay has Ground Fault Interruption (GFI) protective control logic built into it. This will de-energize the relay if the pump circuit has a short.

The left forward pump also operates when all of these conditions are true:

• AC power is available • The boost pump control switch is on • You start the APU • The APU fuel pump transfer relay K505 is energized.The APU switch is on • The APU fire switch is in • The battery switch is ON

See the APU control circuit for more information.

The pump PRESS light turns off when pump pressure is more than four psi. For more information on the pressure switch, see the Fuel Pressure Indicatingsection.

If the pump output pressure is less than four psi, the PRESS light comes on and after 10 seconds, and an EICAS message, L (R) FWD (AFT) FUEL PUMP shows.



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ON

FUEL SYSTEM - ENGINE FUEL FEED - MA IN TANK FUEL BOOST PUMP - FUNCTIONAL DESCRIPTIONSEE APU FUEL FEED SYS OPERATION

EICAS

10 SEC

K188 L FWDFUEL BOOST

K505 APU FUELPUMP XFR RLY

(P37)

L FWD FUEL

115V AC

BUS

P6 MAIN PWR DIST

P

L FWD FUEL

L FWD FUEL PUMP (C)

TO APU FUEL FEED

BOOST PUMP

OFF

MD&T

L FWD FUEL BOOSTPUMP CONT SW (P5)

UPPER EICAS DISPLAY

PRESS

GND SVCE

L FWD FUELBOOST PUMPPRESS SW

(L FWD ONLY)

W

A

1

PUMP CONTRLY (P33)

BOOST PUMP

1

MD&T

BITE RESET

PRESS

ON

PRESS

ON

AFT

FWD

LPUMPS

LEFT

ON

GFI RLYCONTROLLOGIC

- 369 -

FUEL SYSTEM-- ENGINE FUEL FEED - MAIN TANK FUEL BOOST PUMP POWER



FUEL SYSTEM - ENGINE FUEL FEED - CENTER TANK OVER-RIDE PUMP POWER

General

The override pumps operate the same as the boost pumps, except that circuit logic turns the override pumps off when they are not necessary. This decreases the load on the electrical system.

Power Sources

The pumps receive power from the left and right power channels. Loss of power to one bus does not cause loss of power to the two pumps. A non-resettable thermal fuse in each of the three phases prevents an overheat of the motor.

Each pump control relay has Ground Fault Interruption (GFI) protective control logic built into it. This will de-energize the relay if the pump circuit has a short.

Operation

The engine must be in operation (left pump, left engine; right pump; right engine) or the fueling station must have power to energize the pump relay. The pumps operate when the fueling station has power to allow a pump test. They also operate to allow defueling of the center tank.

Indication

The override pump PRESS light indications are different than the main tank boost pumps. The override pump PRESS light goes off when the pump switch is off. This is because the center tank can be empty during normal operation. Empty main tanks do not occur during normal operation.

For normal operation, it is necessary to use center tank fuel before main tank fuel. The FQIS processor finds that the two override pump switches are off(series circuit) by auxiliary contacts on the switches. If there is more than 1000 pounds of fuel in the center tank, and the two switches are off, the FUEL CONFIG light comes on and the EICAS advisory message FUEL CONFIG shows.



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FUEL SYSTEM - ENGINE FUEL FEED - CENTE R TANK OVERRIDE PUMP - FUNCTIONAL DESCRIPTION

UPPER EICAS DISPLAY

EICAS

FUEL CONFIG (C)

CTR L FUEL PUMP (C)10 SEC

FUELCONFIG

P5FQIS PROCESSOR (E2-4)

PUMP PRESS

FUEL INCENTER

PPUMP CONT RLY (P36)

S423 L AUXFUEL OVRD

S6 L OVRD PUMP CONT SW

OFF

S3 R OVERRIDE

OFF

SIGNAL

PUMP CONT SW

MD&T

A

A

28V DCL BUS

L CTRFUEL PUMP

K2089

IND RELAY

ENERGIZEDFUELINGSTATION

TO R OVRDPUMP CONT

>50%

L N2 ENG SPEEDCARD (P50)

K633 OVRD PUMPSGRND ENABLE

P11 CIRCUITBREAKER

SW

TANK

L JETTISON

ONON

PRESS VALVE PRESS

C PUMPSPRESS

PRESS

RL

FUELCONFIG

BITE RESET

GFI RLYCONTROLLOGIC

L AUX TANKOVRD PUMP(LOWER WINGSURFACE)

K329 L FUEL OVRD

L OVRD FUEL

115V AC

P6 MAIN PWR DIST

BUS L

PUMP

- 371 -

FUEL SYSTEM - ENGINE FUEL FEED - CENTER TANK OVERRIDE PUMP POWER



FUEL SYSTEM -- ENGINE FUEL FEED - MAIN TANK FUEL BOOST PUMP BYPASS VALVE

Purpose

The main tank fuel boost pump bypass valves permit engine suction feed or main tank suction defueling. The valves bypass fuel around non-operating boost pumps. A check valve prevents reverse fuel into the main tanks when the engine feed line is pressurized.

Location

There is one boost pump bypass valve in each main tank. The valve is between rib 3 and rib 4. Tank entry is made through the access door between rib 5 and rib 6 for access to the bypass valve.

Operation

With the pump pressure on the feed manifold, the flapper valve is held closed. During suction flow, the valve is opened by fuel, that permits the fuel to enterthe feed manifold without passing through the boost pumps. Operation is automatic. External indication of operation are not given.



FUEL SYSTEM -- ENGINE FUEL FEED - MAIN TANK FUEL BOOST PUMP BYPASS VALVE



FUEL SYSTEM -- ENGINE FUEL FEED - AUTOMATIC SUMP-ING JET PUMPS

Purpose

The automatic sumping jet pumps scavenge water from the low point of the tanks. The jet pumps discharge the fuel and water near the fuel pump intakes. Because of this, contaminates are drawn into the pumps before anaccumulation can occur.

Main Tanks

The boost pump housing supplies outflow to operate two jet pumps. The jet pumps are mounted to rib 3.

Center Tank

Each center tank override pump housing supplies outflow to operate a center auxiliary tank jet pump. The jet pump is mounted to rib 2.

Operation

The operating pump pressurizes the motive port of the jet pump. Flow through the jet nozzle draws fuel and scavenged water through the inlet screen to the induced port and out through the discharge port.



FUEL SYSTEM -- ENGINE FUEL FEED - AUTOMATIC SUMPING JET PUMPS



FUEL SYSTEM -- ENGINE FUEL FEED - FUEL SCAVENGE EJECTOR PUMP

Purpose

The fuel scavenge ejector pumps decrease the unusable fuel in the center tank. The center tank is at and wide, so a considerable amount of fuel remains in itwhen the override pumps lose pressure and are off. The fuel scavenge ejector pumps transfer the remaining fuel to the on-side main tank when that main tank decreases to below half full. The pump is also called the transfer jet pump.


These are the components related to the scavenge pumpsystem:

• Manifolds for fuel ow • Scavenge pump (2) • Float valve • Scavenge pump inlet

The scavenge pump is on the inboard side of each sideof- body (SOB) rib. The pump inlets are in the center tank low points, inboard of the side-of-body ribs. The float valve is outboard of rib 3 in each main tank.

Operation

When the center tank is empty and the main tanks have room for additional fuel, the scavenge pumps operate to transfer the remaining center tank fuel to both main tanks. The pump is a jet pump type. Motive flow to create the pump suction is supplied by each aft boost pump. A float valve prevents fuel transfer until fuel is used out of the main tank. A ball check valve in the scavenge pump prevents boost pump output into the center tank when the scavenge pump is off.



FUEL SYSTEM -- ENGINE FUEL FEED - FUEL SCAVENGE EJECTOR PUMP



FUEL SYSTEM -- ENGINE FUEL FEED - ENGINE FUEL SHUT-OFF (SPAR) VALVE CIRCUIT

Power

The spar valve motor actuator and disagree circuit get power from the hot battery bus.

Operation

When the fuel control switch is in the RUN position, the spar valve opens. The circuit through the RUN contact energizes the open coil in the permanent motoractuator. This changes the polarity of the coil which causes 28v dc to drive the valve open. Limit switches turn the actuator o when the valve is in the correctposition. The amber SPAR VALVE light comes on during valve transit. The fuel control switch to CUTOFF energizes the close coil on the actuator until thevalve fully closes. Failure of the valve to move to the correct position causes the light to stay on and the EICAS message L/R FUEL SPAR VALVE to show after 6 seconds.

Indication

The amber VALVE light comes on during valve transit. An EICAS level C message L(R) FUEL SPAR VALVE shows if the valve does not move to the correct position within six seconds. The circuit is through a disagree relay on the fuel control panel.



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S4

S2

S1

S3P6

SPARFUEL VALVE

BUSHOT BAT28V DC

CLOSE

OPEN

ENGINE FUEL SHUTOFF

CUTOFF

MD&T

SPAR VALVE

VALVESPAR A

FIRE SWITCHRIGHT ENGINE

NORMAL

FIRE

ENGVALVE

ENGVALVE

FUEL CONTROL SWITCHRIGHT ENGINE

DISAGREE RELAYSPAR VALVE

6 SEC

EICAS

DISAGREE LIGHT

FUEL CONTROL PANEL

TYPICAL - RIGHT SPAR VALVE

R(L) FUEL SPAR VALVE (C)

VALVE (SPAR VALVE)

VALVESPAR

VALVESPAR

RUN

FUEL CONTROL PANEL (P10)

FUEL CONTROL RL

CUT OFF

RUN

FUEL SYSTEM - ENGINE FUEL FEED - ENGINE FUEL SHUTOFF (SPAR) VALVE CIRCUIT

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FUEL SYSTEM --ENGINE FUEL FEED - ENGINE FUEL SHUTOFF (SPAR) VALVE CIRCUIT



FUEL SYSTEM -- ENGINE FUEL FEED - ENGINE FUEL CROSSFEED VALVE CIRCUIT

Power

The crossfeed valve motor actuator and indication circuits get power from the battery bus.

Operation

The fuel crossfeed valves are normally closed (fuel crossfeed valve control switches not latched). When the fuel crossfeed valve control switch latches in, the related crossfeed valve opens. The flight crew can balance the fuel load by feeding both engines from a single tank.

Indication

A VALVE light in the control switch comes on during valve transit. An EICAS level C message, AFT (FWD) FUEL XFEED, shows if the valve does not move to the correct position in less than 6 seconds. The circuit is through disagree relays in the P33 panel. Limit switches in the actuator permit valve transit and open/close position indication.

When the two valves close, a signal goes to EICAS for the L(R) FUEL SYS PRESS message logic. The valves closed signal goes if the two switches are OFF or if one switch is ON, but the related valve is in disagreement with the switch position. Refer to the engine fuel low pressure circuit for fuel system pressure message logic information.



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VALVE

ONON

PRESS

ON

PRESS

ON

VALVE

VALVE

AFT

FWD

FUELXFEED

LPUMPS

C PUMPSPRESS

PRESS

RL

FUEL SYSTEM - ENGINE FUEL FEED - ENGINE FUEL CROSSFEED VALVE CIRCUIT

BATBUS

CROSSFEEDVALVE

FWD FUEL

XFEED INDFUEL

P11 OVHD CB PNL

VALVECROSSFEEDAFT FUEL

MD&T

CLOSE

FWD FUELCROSSFEED

AFT FUELCROSSFEED

P5 PILOT FWD OVHD PANEL

OPENW LIGHTING

OPEN

CLOSE

S1

S3OPEN

S2

S4

EICAS

AFT FUEL CROSSFEED

FWD CROSSFEED VALVE SWITCHFWD FUEL CROSSFEED

AFT CROSSFEED

CONTROL PNL (P5)FUEL MANAGEMENT

DISAGREE RLYVALVE ACTUATOR

VALVE ACTUATOR

28V DC

A

VLV SW

A

W LIGHTING

DISAGREE RLY

CLOSE

S1

S3OPEN

S2

S4

6 SEC

6 SECL(R) FUEL

LOGICSYS PRESS

CLOSE

VALVE

AFT FUEL X-FEED (C)

FWD FUEL X-FEED (C)

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FUEL SYSTEM -- ENGINE FUEL FEED - ENGINE FUEL CROSSFEED VALVE CIRCUIT



FUEL SYSTEM -- ENGINE FUEL FEED - CONTROL AND INDI-CATION

Normal Operation

During normal operation, all boost and override pumps are on, the crossfeed valves are closed, and the spar valves are open. Because the override pumps have higher pressure than the boost pumps, the boost pump check valves are closed, and fuel comes from the center auxiliary tank first.

Fuel Management Panel

Control of engine crossfeed and engine fuel pumps is from the fuel management panel. A FUEL CONFIG light on the fuel management control panel shows this data:

• Low fuel • Fuel unbalance • Override pump switches off with fuel in the center tank

Boost Pumps

The four main tank boost pumps operate when ac is on and the switches are in (flowbar and ON show). The amber PRESS light on the bottom half of the switch comes on when the pump pressure is less than 4 psi. The PRESS light off shows when the pump pressure is more than 7 psi. An EICAS advisory message shows after 10 seconds. The left forward boost pump operatesregardless of switch position when the APU switch is ON, and the airplane is on the ground. Refer to the APU feed system.

Override Pumps

It is a normal condition for the center tank to be empty. The amber PRESS lights go off when the override pump switches are off to keep the amber lights off during normal operation.

The override pumps go off by the engine speed card when engine operation stops. This decreases electrical loads. The FQIS processor causes the FUEL CONFIG light and EICAS advisory message if the two override pump switches are OFF, and there is fuel in the center tank. This prevents incorrect use of main tank fuel before the center tank is empty.

Suction Flow

If all three pumps on one side show low pressure when the crossfeed is closed, the EICAS caution message L (R) FUEL SYS PRESS shows. This shows a suction flow condition. When the crossfeed is open, and all 6 pumps are in a low pressure condition, the messages L FUEL SYS PRESS and R FUEL SYS PRESS show.

Crossfeed Valve Control

The crossfeed valve switches are alternate-action pushbutton switchlights. When you push a switch in, a flow bar shows that the switch gives a command for the valve to go to the open position. An amber VALVE light in theswitch comes on when the valve has a disagreement with the command position or during transit. The EICAS advisory message FUEL CROSSFEED shows after 6 seconds when there is a disagreement for one or the other valve.

Engine Fuel Shutoff Valve Control

A fuel control switch on the P10 panel on the control stand normally controls each engine fuel shutoff valve (spar valve). The valve closes when the switch is in the CUTOFF position and opens when the switch is in the RUN position. The amber SPAR VALVE disagreement light above each fuel control switch comes on when the valve is not in the command position. The EICAS advisory message L (R) FUEL SPAR VAL shows after 6 seconds when there is a disagreement. The valve closes when you pull the fire handle.



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ONON

PRESS

ON

PRESS

ON

VALVE PRESS

ON

VALVE PRESS

AFT

FWD

FUELXFEED

LPUMPS

RPUMPS

AFT

FWD

C PUMPS

ON

PRESS

PRESS

RL

FUELCONFIG

ENGVALVE

VALVESPAR

FUEL CONTROL RL

CUT OFF

RUN

FUEL SYSTEM - ENGINE FUEL FEED - CONTROL AND INDICATION

UPPER EICAS DISPLAY (P2)

CTR L(R) FUEL PUMP (C) L(R) AFT FUEL PUMP (C) L(R) FWD FUEL PUMP (C)

FUEL CONFIG (C)

L(R) FUEL SYS PRESS (B)

L(R) FUEL SPAR VAL (C) FUEL CROSSFEED (C)

FUEL MANAGEMENT PANEL (P5)

FUEL CONTROL SWITCHES (P10)

ENGVALVE

VALVESPAR

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FUEL SYSTEM -- ENGINE FUEL FEED - CONTROL AND INDICATION



FUEL SYSTEM -- APU FUEL FEED

General

Either the AC fuel pumps or the DC fuel pump may supply APU fuel. The AC pumps have priority. Priority and control are automatic. The position of the APU switch and the APU fire switch control the APU fuel shutoff valve.

Normal Operation

Normal APU fuel feed is from the left crossfeed manifold. The same AC pumps that are feeding the left engine also feed the APU. The left override pumpprovides APU fuel if it operates and if fuel is in the center tank. The left boost pumps supply fuel if the override pump cannot. If the crossfeed valve is open,the right boost or override pumps may also supply APU fuel feed.

The left forward boost pump automatically supplies APU fuel feed even when the pump control switch is OFF. This occurs during these conditions:

• APU switch is ON • Airplane is on the ground • AC ground service bus has power

When AC power is not available, the DC pump automatically provides APU fuel feed. The DC pump operates during these conditions:

• APU switch is ON • Battery switch is ON • Pump system pressure switch on the left rear spar finds low fuel pressure

on the left crossfeed manifold

Backup Operation

If there is a total failure of the AC pumps or AC power while airborne with the APU switch ON, the DC pump operates to supply APU fuel feed. If the pump system pressure switch finds low left crossfeed manifold fuel pressure, it turns on the DC pump.

Indication

The APU FAULT light shows valve transit. The FAULT light and an EICAS APU FUEL VAL advisory message show valve disagreement. The EICAS maintenance message DC FUEL PUMP ON shows that the DC pump operates. This message is controlled by a pressure switch on the DC pump

APU DC Pump

The APU DC pump is on the left rear spar. The pump operates on 28v dc power from the battery bus when these conditions are true:

• The APU control switch is ON • There is no fuel pressure on the left feed manifold

A pressure switch on the pump sends data to the EICAS. The maintenance message DC FUEL PUMP ON shows when the pump produces pressure.

APU Fuel Shutoff Valve

The APU fuel shutoff valve operates by the same (interchangeable) permanent magnet motor actuator as the other shutoff valves in the fuel system. The valvebody is not interchangeable with other valves. There is no adapter shaft between the shutoff valve body and the actuator.

APU Fuel Supply Line

The fuel supply line is a rigid aluminum tube. It is routed through the left SOB rib and out of the top of the center tank to a special fitting. This fitting is a Kevlar braid plastic coated ex-line and a rigid aluminum shroud to contain flex-line leaks. A drain mast to the rear of the left hand main wheel well removes excess fuel if the kevlar hose should leak.



FUEL SYSTEM -- APU FUEL FEED



FUEL SYSTEM -- DEFUELING

General

The defueling system moves fuel from the airplane fuel tanks to fueling station. It also moves fuel from one airplane tank to a different airplane tank (tank-to tank transfer). You can only defuel and do tank-to-tank transfer on the ground. You use these pumps to get fuel out of the center and main tanks:

• Airplane fuel pumps (pressure-defuel) • Ground pumps (suction-defuel)

Two 28v dc motor-operated defuel valves connect the engine fuel feed manifold to the fueling manifold. Guarded switches at the fueling station control the defuel valves. You must open the defuel valve to move fuel to the fueling station. Fueling hoses move fuel to ground tanks or to a defuel truck.

You do these things to move fuel from the main or center tank for tank to tank transfer:

• Open the defuel valve • Open the applicable fueling valves • Operate the applicable fuel pumps

Pressure Defuel

Turn the adapter cams to the defuel position and connect the nozzles. Open the defueling valves. Operate the applicable boost or override pumps for therelated tanks.

Suction Defuel

Suction defuel of the main tanks is the same as pressure defuel of the tanks, but you do not use the fuel pumps. Suction supplied from the defuel vehiclelets fuel flow through the bypass valves and defuel valves into the vehicle.

Suction defuel of the center tank is not possible.

Tank-To-Tank Transfer

Tank-to-tank fuel transfer is the same procedure as pressure defuel. You must operate the applicable boost or override pumps to supply sufficient pressure tooperate the fueling valve diaphragms. You open the fueling valves for the tank to receive the fuel and put on the related tank boost or override pumps for thetank transferring the fuel. The quantity gages show fuel level. It is not necessary to connect fueling nozzles or turn the adapter cams to the defuel position.

Defuel Valve Position Indication

A blue press-to-test light for each defuel valve shows valve position. The light comes on when the valve fully opens and stays on until the valve fully closes.

Location

The two valves are in the center tank, one in each outboard section. The actuators are on the rear spar inboard of each main gear strut.


You must first remove fuel from the center wing tank to change a defueling valve. Seals in the adapter assembly prevent fuel spillage when you remove the actuator. The actuator attaches to an adapter plate. Refer to the motor-operated valves for more information.



FUEL SYSTEM -- DEFUELING



FUEL SYSTEM - FUEL JETTISON

Purpose

The fuel jettison system lets the gross weight of the airplane be decreased quickly so that design limits for wheels, tires, and brakes are not exceeded during an emergency landing. Only fuel from the center auxiliary tank is jettisoned.

General Description

The fuel jettison system has two jettison pumps, two jettison transfer valves, two jettison valves, two manifolds, and two nozzles. The jettison pumps are inthe same housing as the center tank override pumps. The jettison pumps and the override pumps are interchangeable. When the jettison system is operating,the override pumps and the jettison pumps send fuel to the jettison transfer valves. Jettison flow is 160,000 pounds per hour at 30 psi.

The jettison transfer valves are between the output of the override and jettison pump assembly and the fueling manifold. A manifold check valve prevents fuel from the main tank boost pumps from entering the fueling manifold when the transfer valve is open. One jettison manifold connects to each end of the fueling manifold.

The jettison valve at the end of each jettison manifold controls fuel flow to the nozzle. The jettison transfer valves and jettison valves are motor actuated valves. The actuator is identical and interchangeable with the actuators of the other motor actuated valves of the fueling system. The valve bodies are notinterchangeable with the other valve bodies due to the smaller diameter of the jettison manifold.

The fuel jettison outlet tube assembly consists of an aluminum tube with a shroud (bond assembly) made of titanium. The assemblies are immediately inboard of the outboard aileron on each wing.

Functional Description

Fuel jettison control is from the flight deck. The fuel jettison control panel is on the P5 overhead panel. The control panel has jettison selector switch and left and right jettison valve switches.

Operation

The rotary, two-position fuel jettison switch (S3) operates the two jettison transfer valves. The switch controls power to the jettison and override pumps. Itstarts an electrical system load shed logic (refer to chapter 24). When you put the switch to ON, the jettison manifold pressurizes.

When you put the nozzle valve switch to the latch position, dc power opens the valve. When you put the switch to the unlatch position, dc power closes the valve. The valves operate on the ground.

Indication

An amber jettison fault light comes on for one or two conditions. If one or the other jettison transfer valve has a disagreement with the commanded position for more than 10 seconds, the fault light comes on. This also causes the EICAS level C message L(R) JET XFR VALVE. The transfer valve indication relays are normally energized. If there is no control signal, C1, for more than 10 seconds, the relay de-energizes. This causes the light and message.

If the output pressure of one of the jettison pumps is less than 7 psi for more than 10 seconds with the control switch on, the fault light comes on. This alsocauses the EICAS level C message L(R) FUEL JET PUMP. The circuit for the left side is through the K2 jettison pump indication relay, the L jettisonindication relay, and the L fuel jettison pump pressure switch.

The VALVE light comes on during transit and disagreement through the L or R nozzle valve indication relays. The EICAS level C message FUEL JET NOZ shows if a nozzle valve has a disagreement for more than 6 seconds.

If you latch in a nozzle valve switch while the airplane is on the ground, the EICAS level C message FUEL JET NOZ shows.

If the airplane is inflight, it is possible for fuel to hit the airplane during a jettison operation if the flaps are at a position more than 20 units. The FUEL JET NOZ message will show to remind to the flight crew to retract the flaps to prevent the fuel from hitting the airplane. The fuel pump control relays have Ground Fault Interruption (GFI) protective control logic built into them. This will de-energize the relay if the pump circuit has a short.



FUEL SYSTEM - FUEL JETTISON

FAULT

VALVEVALVE



FUEL SYSTEM -- FUEL INDICATING- GENERAL INFO

General

The FQIS measures the weight of fuel in the main and center tanks. The system has these components:

• Tank units • Compensators • Densitometers • Processor unit • Flight compartment indicators • Load select indicators • Load select control unit

Fuel weight indication shows in the flight compartment and at the fueling station. The FQIS uses fuel shutoff weights set for ground refuel. It stops refuel when the tanks are full. The FQIS has BITE for fault isolation.

Design Features

The FQIS is a microprocessor-controlled variable capacitance system. These are its features:

• It uses 28v dc • A densitometer measures fuel density • Tank units and compensators measure fuel volume • Fuel weight and volume show on LCD indicators • Tank unit characterization is by the FQIS software • The FQIS has electronics and wiring for each tank; this is so a failure of

one component does not effect the fuel quantity data for more than one tank

• Redundant data outputs make sure that one fault does not decrease system performance

• The FQIS has an energy limit in the fuel tanks for arc suppression

Processor Unit

The processor is in the main equipment center. It controls FQIS and refuel operations. The processor does these functions:

• Gives excitation for and monitors data from the tank units and compensators

• Gives excitation for and monitors data from the densitometers • Calculates and transmits fuel weight • Controls power to the fueling valves • Does BITE operations

The processor has two channels that operate independently.

Tank Units

There is a total of 37 tank units in the three tanks. They are the same, but the lengths are different. The processor gives excitation for and monitors data fromeach tank unit independently and changes the data to fuel volume.

Compensators

There are three compensators, one in each main tank and one in the center tank. The compensators send a reference signal to the processor to calculate fuel volume.

Densitometers

There are three densitometers, one in each main tank and one in the center tank. They send signals to the processor to calculate the fuel density.



767 TRAINING MANUAL

28-40-00

767_

28-4

0-00

-002

.600

.fm

BOEING PROPRIETARY

13-Dec-2011

RL C

TEMP o LATOTC

FUEL QTYKGS X 1000

LB KGLB KGLB KG

FUEL SYSTEM - FUEL INDICATING - GENERAL DESCRIPTION

LOAD SELECT

FUEL QTY

X 1000

LOAD SELECT

FUEL QTY

X 1000

LOAD SELECT

FUEL QTY

X 1000

OPEN OPEN

TEST

IND SYSTEM

RESETTEST

OVERFILLFUEL

OFF

INBD OUTBD

MAINLEFT

TESTES

SYSTEM

OFF

FUEL

FUELING

RIGHT LEFT

OFF

FUELVALVESFUELING

INBDOUTBD

SET

CENTERAUX

LOADTANK

MAINRIGHT

NORM

BATT

POWER

OPEN

OPEN

CLOSE

OPEN

OPEN

CLOSEVALVESDEFUEL

QTY X 1000

2 31

LOAD SELECT

LOW FUEL (B)FUEL CONFIG (C)

FUEL QTY CHANNEL (S)FUEL QTY IND (S)

FUEL QTY BITE (S,M)

LOWER EICAS DISPLAY

UPPER EICAS DISPLAY

FUEL QUANTITY INDICATOR (P5)

FQIS PROCESSOR UNIT

TANK UNIT37 TOTAL

COMPENSATOR(1 PER TANK)

DENSITOMETER(1 PER TANK)

HOT SHORTPROTECTOR

FUELING CONTROL PANEL

YES

MENU OFFON/

NO

- 423 -

FUEL SYSTEM -- FUEL INDICATING- GENERAL INFO

14 TANK UNITS PER EACH MAIN TANKND 9 UNITS IN THEENTER TANK



FUEL SYSTEM -- FUEL INDICATING- GENERAL INFO (CONT)

Wiring Harness

There are four tank unit/compensator wiring harnesses. One harness is in each main tank, and one harness is in each side of the center auxiliary tank. A different wiring bundle goes from the front spar to the FQIS processor for each harness. There are also two other wiring bundles that go from the rear spar to the processor. One is for the right and center tank densitometers, and the other is for the left tank densitometer. All wire bundles between the wing and processor are one piece. There are no bulkhead connectors. The harness has a shield and a permanent potting to hermetically sealed plugs. You can do crimp repairs on the wires between the tank and the processor.

Load Select Indicators

The load select indicators are in the fueling station on the left wing leading edge outboard of the engine. The upper displays show fuel quantity by weight. Thelower displays show the refuel shutoff weight. See the fueling section for more information on the load select indicators.

Load Select Control

The load select control is on the fueling control panel adjacent to the load select indicators. Three thumbwheel switches permit selection of the value that goes to a load select indicator. See the fueling section for more information on the load select control.

Fuel Quantity Indicator

The fuel quantity indicator in the flight compartment is one module with five LCD indicators. These are the indications:

• One indicator for fuel weight in each of the three tanks • Total fuel weight • Fuel temperature

FQIS BITE

The FQIS processor has BITE. Fault data from an FQIS LRU can go in the processor unit NVM. This does not include the load select indicators. There

are pushbuttons on the face of the processor to do different BITE operations. A 32-character alpha-numeric display shows system and fault data in English.

Indications

EICAS alert messages and a dedicated light show low fuel and fuel configuration faults.

EICAS status and maintenance messages show faults in the FQIS.

Measuring Sticks

Magnetic float-type measuring sticks are in main and center tanks. Access to the measuring sticks is from the lower wing surface. There are seven sticks in each main tank and two in each side of the center tank.



FUEL SYSTEM -- FUEL INDICATING- GENERAL INFO (CONT)

767 TRAINING MANUAL

28-40-00

767_

28-4

0-00

-002

.600

.fm

BOEING PROPRIETARY

13-Dec-2011

RL C

TEMP o LATOTC

FUEL QTYKGS X 1000

LB KGLB KGLB KG

FUEL SYSTEM - FUEL INDICATING - GENERAL DESCRIPTION

LOAD SELECT

FUEL QTY

X 1000

LOAD SELECT

FUEL QTY

X 1000

LOAD SELECT

FUEL QTY

X 1000

OPEN OPEN

TEST

IND SYSTEM

RESETTEST

OVERFILLFUEL

OFF

INBD OUTBD

MAINLEFT

TESTES

SYSTEM

OFF

FUEL

FUELING

RIGHT LEFT

OFF

FUELVALVESFUELING

INBDOUTBD

SET

CENTERAUX

LOADTANK

MAINRIGHT

NORM

BATT

POWER

OPEN

OPEN

CLOSE

OPEN

OPEN

CLOSEVALVESDEFUEL

QTY X 1000

2 31

LOAD SELECT

LOW FUEL (B)FUEL CONFIG (C)

FUEL QTY CHANNEL (S)FUEL QTY IND (S)

FUEL QTY BITE (S,M)

LOWER EICAS DISPLAY

UPPER EICAS DISPLAY

FUEL QUANTITY INDICATOR (P5)

FQIS PROCESSOR UNIT

TANK UNIT37 TOTAL

COMPENSATOR(1 PER TANK)

DENSITOMETER(1 PER TANK)

HOT SHORTPROTECTOR


YES

MENU OFFON/

NO

- 423 -

14 TANK UNITS PER EACH MAIN TANKAND 9 UNITS IN THECENTER TANK



FUEL SYSTEM -- FUEL INDICATING - TANK / MEC COMPO-NENTS

Compensators

The compensators supply a capacitance value proportional to the dielectric constant of the fuel. The processor uses this information to make the fuelvolume calculation more accurate.

Operation

The compensators are excited by the processor (low Z) and return an electrical capacitance value for the fuel (high Z). Tank compensators share a common high Z signal wire with tank units and are individually driven by low Z signals.

Unlike the tank units, the compensators are always completely immersed in fuel, so the high Z value does not vary because of fuel depth. Other factors such as temperature and fuel quality cause the capacitance value to vary. These other factors affect the dielectric constant. The processor compensates the tank unit capacitance value with this dielectric constant.

Substitute values for the dielectric constant affect system accuracy and indication and fueling.

Construction

The fuel system compensator is similar in construction and function to a short tank unit. Compensators have relatively wide gaps between the electrodes to prevent contamination. They are in the lowest part of the fuel tanks so they are always covered with fuel.

Calibration

Compensators are LRUs and may be replaced without recalibration. Access to the compensators is through the fuel tank access doors on the lower wing surface.

DENSITOMETER

There are three densitometers, one in each tank. The densitometers measure fuel density. The densitometers also give a cross-check of the compensator specific gravity data to improve the FQIS accuracy. The densitometers are line replaceable units which do not require system recalibration when changed.

Location

The densitometers, like the compensators, mount in the lowest part of the fuel tank so that they are always covered with fuel. They are connected to the in-tank wiring harness with terminal studs.

Operation

Each densitometer has a vibrating spool in a cylindrical alloy housing. Holes in the housing permit fuel to cover the spool.

The FQIS processor sends an AC signal through a coil to excite the spool, which in turn vibrates. The processor reads the frequency of the vibration, and changes the frequency of the excitation signal until the spool vibrates at its resonant frequency. This resonant frequency is a function of fuel density only. The processor calculates fuel density from the resonant frequency.

Tank Units

The tank units are also called fuel probes. There is a total of 37 tank units, 14 in each main tank and nine in the center tank. The tank units are concentric aluminum tube capacitors. They are identical except for length. The capacitance of the units varies with the immersion depth of the fuel in the tank (wetted sensing length). The fuel volume in the tank is calculated from the tankunit capacitance. There are no moving parts.



FUEL SYSTEM -- FUEL INDICATING - TANK / MEC COMPONENTS



FUEL SYSTEM -- FUEL INDICATING - TANK -MEC-COMPO-NENTS (CONT)

Tank Unit Characterization (Weighting)

The tank units are used for volume calculations. They supply a capacitance value to the processor. Some tank unit failures affect fueling operations and also fuel quantity indication. See fueling troubleshooting or flight deck indications for more details..An irregular fuel tank shape causes a non-linear relationship between fuel volume and tank unit capacitance. Each tank is divided into a series ofprofile points that specify known fuel volumes. These points are in characterization tables in the FQIS software. The capacitance changes for the wetted sensing length (WSL). The capacitance is then correctedbased on the characterization table. The result is a calculation of the volume in the tank. This is called characterization or weighting of the tank units. Also,the fuel tanks have different shapes as a function of fuel quantity and whether the aircraft is on the ground or in the air.

The computer program selects one of up to six different characterization tables based on the air/ground switch and the WSL of the tank unit. This permits accurate indications both in the air and on the ground and eliminates the need for contoured tank units.


The tank units have straight outer and inner tubes of polyurethane coated, anodized aluminum. End caps are on the tank unit ends. The brackets and the terminal block are glass-filled nylon. The terminal block uses different size studs to mount the in-tank wiring harness lugs. The terminal block shields the high impedance (Z) lead. The individual tank units are line replaceable and recalibration is not necessary when units are changed. Access to the tank units is through the access doors on the lower wing surface.

Access

The tank units are accessible from the access doors on the lower wing surface.

Processor Unit

The processor unit is the central component of the FQIS. It does these functions:

• Calculates fuel weight • Controls pressure fueling operations • BITE

The processor unit is an LRU in the E2-4 rack of the main equipment center. Internal cards and components are not LRUs.

Physical Description/Features

The processor has six circuit board cards with a BITE display and control push-buttons on the front face. Three of the six cards are identical and interchangeable (bench only) individual fuel quantity cards (IFQC). The IFQCs do these functions:

• Provides excitation for and monitors data from the tank components • Calculate the individual tank quantity • Transmit the tank quantity to the input/output cards (IOCs)

The two IOCs are identical and interchangeable (bench only). The IOCs do these system calculations:

• Total fuel • Lateral imbalance • Fuel shutoff weight • Format the data to ARINC 429

The IOCs also control fueling operations. The single BITE card stores system faults and contains the fueling valve drivers. Bench certification is not required after card replacement. There are connectors on the front face for ARINC channels A, B, and C.

BITE display and control switches are on the front face of the processor. Bench certification is necessary after internal repairs.



FUEL SYSTEM -- FUEL INDICATING - TANK -MEC-COMPONENTS (CONT)



FUEL SYSTEM -- FUEL INDICATING - TANK -MEC-COMPO-NENTS (CONT)

Operation

The IFQCs measure and calculate the fuel weight for each of the tank unit areas of their respective tank. Each IFQC card makes an excitation signal (low Z) which goes sequentially to each of the tank units and the compensator in the respective tank (left main, center auxiliary or right main). The return signal, or high Z capacitance, is characterized for the shape of each tank unit area. The fuel density is calculated from the densitometer. The fuel weight is the product of fuel volume and density.

Each of the three IFQCs send signals to both IOCs. The three tank weights are summed by each IOC to get a total fuel weight. Each of the IOCs has an ARINC bus. The bus is A for IOC one, and B for IOC two. Fuel quantity data goes over both the ARINC digital buses to the flight deck fuel quantity indicator and to the fueling station load select indicators. It also goes to the flight management computers and to either the aircraft condition monitoring system (ACMS) or the digital flight data acquisition Unit (DFDAU).

The IOCs also send signals to the BITE card. Analog signals for fuel configuration, low fuel, and fueling valve control go to drivers on the bite card. Fault information also goes to the BITE card over the ARINC buses. IOC 1 supplies the excitation for and monitors the load select module and also supplies the excitation for the discrete inputs for both the IFQCs and IOCs. The IOC 2 monitors the digital output of the IOC one and stores the load select value.

The BITE card monitors the digital output of the IOCs for fault information and stores FQIS faults. It has an interface with BITE controls on the face of theprocessor for fault display. The BITE card has ARINC bus C which sends fuel system information and fuel quantity data from the IOCs to EICAS for message logic.

System Discretes

The FQIS gets airplane discrete signals to permit the processor to determine the necessary airplane parameters.

The fueling valves test, load select indicator test, and SET switches are system discretes for fueling.

The FUEL QTY TEST discrete comes from a toggle switch on the P61 test panel. This discrete tells the processor to do an indicator test.

The center tank override pump switch position discrete lets the processor unit send a signal to the EICAS computers when the center tank contains fuel and both override pump switches are OFF.

Air-ground switch discretes are for different fuel tank shapes on the ground and in the air. Also air-ground inputs calculate flight legs in BITE fault history.

The fueling door switch is a discrete signal that starts fueling functions and indications, and causes switchover to fueling station power sources. A lbs/kgs dual discrete jumper selects output signals to the indicators in either pounds or kilograms.



FUEL SYSTEM -- FUEL INDICATING - TANK -MEC-COMPONENTS (CONT)



FUEL SYSTEM -- FUEL INDICATING-FUEL QUANTITY INDICA-TOR

General

The fuel quantity indicator shows this information:

• Left fuel quantity • Right fuel quantity • Center fuel quantity • Total fuel quantity • Main tank fuel temperature

Location

The indicator is on the P5 overhead panel in the flight compartment. The fuel quantity test toggle switch is on the P61 right sidewall.

Power

The indicator module gets all power, except lighting, from the FQIS processor.

Physical Description/Features

The indicator has four separate circuits, one for each tank display and one for the fuel temperature and the total fuel quantity display. The indicator electroniccircuits use architecture that makes sure a failure in one display circuit does not affect the operation of the other tank indicators. However, a failure in the total/temperature circuit may affect the total and the temperature displays. The microprocessor-controlled circuits contain a background and an operator-initiated built-in test (BITE) function. The BITE function identifies and shows these failures:

• System communication failures • Internal circuitry failures • Memory failures

The fuel quantity indicator is a line replaceable unit (LRU). The unit may be replaced without system adjustment or calibration.

Fuel quantity shows to a resolution of 100 lbs/kgs. These LCD legends show when the unit is active:

• L • C • R • FUEL TEMP • TOTAL Qty • FUEL QtyX 1000 • Lb or kg

Operation

The indicator receives fuel quantity information over one of two ARINC digital data buses, A or B. Bus A is normally used and is selected at start-up or after acircuit test is complete. If bus A information becomes unavailable, the indicator keeps bus A data and after four seconds, changes to bus B. If you do not receive data on bus B after four seconds, the receiver continues to cycle at a four-second rate until valid data is recognized. If both buses are inactive, the tank indicator(s) show the letters -AB to show a dual bus failure.

Flight Deck Indicator Test/Lamp Test

When you use the fuel quantity test switch, each indicator does an internal check of its circuitry and looks for data output from data buses (A and B). Theindicator does these functions:

• Do a check of its circuits • Do a check for valid data bus output • Show bus fault codes is four seconds for each event



OVERHEAD PANEL, P5

FUEL QUANTITY INDICATOR, M10054 (REF) SEE B

OVERHEAD CIRCUIT BREAKER PANEL, P11

LMISCELLANEOUS TEST PANEL, M10398 SEE C

RIGHT SIDE PANEL, P61

FUEL TEMP

C R

FUEL LBS x 1000

TOTAL QTY

FUEL QUANTITY INDICATOR - TEST NORMAL

B

FLIGHT COMPARTMENT

TEST AIR DATA

L COMPT

LL STALL

WING ANTI ICE

CONFIG R T/O GRND PROX

R LDG DUCT LEAK

INOP YAW DAMP L EQUIP COOL

FUEL L PUMP CROSSFEED R PUMP

NO NO TFA TFA

PRESS VALVE PRESS

NO NO DWF DWF

PRESS VALVE PRESS

C PUMPS

L C R

FUEL WINDOW/ FUEL QTY R

PROBE HEAT HYD GEN

LEFT ON

P P CONFIG. R RE E ON S S RIGHT S S

LBS x 1000

FUEL TEMP TOTAL QTY

FUEL QUANTITY TEST SWITCH, YEIS6

MISCELLANEOUS TEST PANEL, M10398 (REF)

C

FUEL MANAGEMENT PANEL (ON THE P5 PANEL)

FUEL QUANTITY INDICATOR - CHANNEL FAULT CODES

B

FUEL QUANTITY INDICATOR (SIMMONDS)

FUEL SYSTEM -- FUEL INDICATING-FUEL QUANTITY INDICATOR



FUEL SYSTEM -- FUEL INDICATING-FUEL QUANTITY INDICA-TOR (CONT)

Operation

The indicator receives fuel quantity information over one of two ARINC digital data buses, A or B. Bus A is normally used and is selected at start-up or after a circuit test is complete. If bus A information becomes unavailable, the indicator keeps bus A data and after four seconds, changes to bus B. f you do not receive data on bus B after four seconds, the receiver continues to cycle at a four-second rate until valid data is recognized. f both buses are inactive, the tank indicator(s) show the letters -AB to show a dual bus failure.

Flight Deck Indicator Test/Lamp Test

When you use the fuel quantity test switch, each indicator does an internal check of its circuitry and looks for data output from data buses (A and B). The indicator does these functions:

• Do a check of its circuits • Do a check for valid data bus output • Show bus fault codes is four seconds for each event

This is the indicator test sequence:

• Indicators go blank for four seconds while the indicators do an internal circuitry test and request test data from Bus A.

• Test data (88.8) from bus A shows for four seconds while bus B does a test. If bus A information is not valid, the indicators stay blank for this four-second interval. If bus B information is valid, test data from bus B shows for the next four seconds. If bus B data is not found, the appropriate fault codes show for this four-second interval.

• After the test of both data buses, the indicators return to normal display of fuel weight. If either bus A or bus B information was not received by an indicator, that indicator shows an A or B after the test display for four seconds before it returns to the normal display of fuel weight. If neither bus A nor bus B data is valid, the display stays blank through the test (the first eight seconds) and the fault code AB follows.

Note: One wire (pair) for bus A and one wire for bus B goes from the

processor to the indicator, then a separate wire for each bus goes

to each indicator (total fuel and temperature are together). If the channel fault codes are different or only in one or two of the indicators, the fault is internal to the indicator. If a channel fault code shows in all three indicators, the problem is between the indicator and the processor or internal to the processor. Use processor BITE to identify which fault exists. IOC 1(2) FAILED shows when an internal failure of the IOC board circuitry is detected. ARINC BUS A(B) shows when a bus is shorted or there is a failure of the ARINC bus transmitter circuitry on the associated IOC.

In addition to the indicator test, the FUEL CONFIG light comes on and these EICAS messages show:

• LOW FUEL (B) • FUEL QTY CHANNEL (S) • FUEL QTY IND (S) • FUEL QTY BITE (M)

Existing EICAS fuel status messages clear at test complete. If faults still exist, the EICAS messages may not return until up to one minute later.



OVERHEAD PANEL, P5

FUEL QUANTITY INDICATOR, M10054 (REF) SEE B

OVERHEAD CIRCUIT BREAKER PANEL, P11

LMISCELLANEOUS TEST PANEL, M10398 SEE C

RIGHT SIDE PANEL, P61

FUEL TEMP

C R

FUEL LBS x 1000

TOTAL QTY

FUEL QUANTITY INDICATOR - TEST NORMAL

B

FLIGHT COMPARTMENT

TEST AIR DATA

L COMPT

LL STALL

WING ANTI ICE

CONFIG R T/O GRND PROX

R LDG DUCT LEAK

INOP YAW DAMP L EQUIP COOL

FUEL L PUMP CROSSFEED R PUMP

NO NO TFA TFA

PRESS VALVE PRESS

NO NO DWF DWF

PRESS VALVE PRESS

C PUMPS

L C R

FUEL WINDOW/ FUEL QTY R

PROBE HEAT HYD GEN

LEFT ON

P P CONFIG. R RE E ON S S RIGHT S S

LBS x 1000

FUEL TEMP TOTAL QTY

FUEL QUANTITY TEST SWITCH, YEIS6

MISCELLANEOUS TEST PANEL, M10398 (REF)

C

FUEL MANAGEMENT PANEL (ON THE P5 PANEL)

FUEL QUANTITY INDICATOR - CHANNEL FAULT CODES

B

FUEL QUANTITY INDICATOR (SIMMONDS)

FUEL SYSTEM -- FUEL INDICATING-FUEL QUANTITY INDICATOR (CONT)



FUEL SYSTEM -- FUEL INDICATING - FQIS - INDICATION

General

Indications of the fuel weight and the operation status of the FQIS show in the flight compartment. These are the indications:

• Fuel quantity indicator • FUEL CONFIG light • EICAS messages

Fuel Quantity Indicator

The fuel quantity indicator shows left, center, and right fuel tank quantities and total fuel quantity. Fuel quantity shows as a weight in pounds or kilograms.Fuel temperature shows in degrees celsius. Only one of the two ARINC buses (A or B) is necessary for fuel quantity indication. Bus A normally supplies data to the flight compartment and fueling station indicators. If bus A has a failure, the last received value shows for 4 seconds, and then bus B data is used forindication.

When system errors are less than 5 percent, indications are normal. The failure of one tank unit or an out-of range input from one tank unit normally does not cause a tank quantity error of more than 5 percent. Multiple same-tank failures that cause fuel tank quantity errors of more than 5 percent (accuracy not known) cause the tank and total quantity indications to go blank. The same fuel quantity indication on the load select indicator at the fueling station goes blank. Refer to fueling troubleshooting.

If there is a 28v dc power source failure to an LRU, the system gets power from the remaining source. Except for the fueling valve that has a power source failure, the FQIS has full operation and indication is normal. There is no FQIS flight compartment indication for this type of failure. An FQIS processor internal power conditioning circuit failure does not have an effect on system operation.

EICAS Messages and Fuel Config Light

Fuel system operation problems show by the FUEL CONFIG light and EICAS messages. FQIS system faults show by EICAS messages.

Detection of operation problems and system faults is by the IOCs. The IOCs send three analog discrete signals and a digital signal (ARINC buses A and B) to the BITE card. The analog discrete signals go to drivers on the BITE card. The drivers give signals to EICAS and also put on the FUEL CONFIG light at the applicable time. The BITE card sends the data received from the digitalbuses to EICAS on ARINC bus C.

The FUEL CONFIG light comes on, and an EICAS message shows during these conditions:

• Low fuel • Fuel imbalance • Center tank fuel not used before the main tank fuel

For a fuel imbalance with fuel in the center tank, the EICAS status message FUEL CONFIG shows with the FUEL CONFIG light. For low fuel, the EICAS level B alert message LOW FUEL shows with the light.

Fuel imbalance is a difference of 1800 lb (800 kg) between the left and right main tank quantities. When the imbalance is correct to less than 1600 lb (750 kg), the message goes away, and the light goes off.

If the two override pump switches are OFF with more than 1000 lb (500 kg) of fuel in the center tank, an indication of main tank fuel use before center tankfuel shows. The message and light go off when fuel in the center tank goes to less than 900 lb (400 kg), or you put on an override pump. Refer to the override pump circuit for more information.

A low fuel indication shows when the left or the right main tank quantity is less than 2200 lb (1000 kg). The message goes away, and the light goes off when the two main tanks have more than 3000 lb (1364 kg) each.

The EICAS status messages FUEL QTY CHANNEL and FUEL QTY IND identify dispatch critical FQIS faults. FUEL QTY BITE shows as an EICAS maintenance message when there are system faults and also as a status message when there is a loss of all fuel quantity indication, or the digital input to EICAS (bus C) has a failure. The IOCs transmit failed channel and accuracy not known faults on the ARINC bus output to the BITE card. The IOCs sendan analog discrete signal to a driver on the BITE card when there is a system fault or bus C has a failure.



R MAIN TANK DENSITOMETER 28V DC R MAIN BUS

28V DC BAT. BUS

P11 28V DC

GND HDLG BUS

P34

28V DC HOT BAT. BUS

P6

FUEL QTY NO. 2

FUEL QTY NO. 1

FUEL STATION DOOR OPEN FUEL QTY PWR

FUEL QTY TRANS RELAY REFUEL

GND PWR FUELING QTY BAT. PWR

FUELING PWR TRANS RELAY

R AUX TANK DENSITOMETER

L MAIN TANK DENSITOMETER FUELING PWR TRANS

FUEL LEVEL SENSOR CONT CARGO

FUEL STATION DOOR OPEN

FUELING PWR CONT RELAY

L MAIN TANK LOAD SELECT INDICATOR

AUX TANK LOAD SELECT INDICATOR

R MAIN TANK LOAD SELECT INDICATOR


FUEL IND TEST SW

L/R FUEL CONT PANEL

FUEL MANAGEMENT PANEL

TANK UNIT BUSSING L AUX TANK FQIS

PLUG WIRING HARNESS TANK UNIT

COMPENSATOR

BUSSING L MAIN TANK FQIS PLUG WIRING HARNESS

TANK UNIT COMPENSATOR

BUSSING R AUX TANK FQIS PLUG WIRING HARNESS

TANK UNIT

COMPENSATOR

BUSSING R MAIN TANK FQIS PLUG WIRING HARNESS

FUEL QUANTIY INDICATOR

L/R EICAS COMPUTERS

OFF FUEL QTY FUEL QTY TEST SW

P61 MISC TEST PANEL

L CTR FUEL OVRD R CTR FUEL OVRD PUMP CONT SW PUMP CONT SW

FUEL MANAGEMENT PANEL AIR

GND

SYS NO. 2 AIR/GND AIR

RELAY GND

SYS NO. 1 AIR/GND RELAY FQIS PROCESSOR

FQIS OPERATION

Low Fuel & Con g EICAS message appears when L/R tanks have less than 2200 lbs. Fuel Con g EICAS message appears for a fuel imbalance of 1800 lbs. or greater between L/R Tanks or if 1000 pounds or greater is in the Center Tank and the Override Pumps are not engaged.

FUEL SYSTEM -- FUEL INDICATING - FQIS - INDICATION



FUEL SYSTEM -- FUEL INDICATING - FQIS - INDICATION (CONT)

The status message FUEL QTY CHANNEL shows if one or the other IOC (ARINC A or B) has a failure. If the two channels have failures, there is a loss of all indication, and the status message FUEL QTY BITE shows as an alternative to the channel message.

The status message FUEL QTY IND shows for accuracy not known in one or two tanks. If the accuracy of all three tanks is not known, there is a loss of all indication, and the status message FUEL QTY BITE shows as an alternative to the indicator message.

The maintenance message FUEL QTY BITE shows when there is a fault in the system. If the fault goes away, the message goes away.

The status message FUEL QTY BITE shows when bus C has a failure because the dispatch critical channel and indicator faults go to EICAS on ARINC bus C. The same driver gives EICAS an indication that there is a fault, and bus C has a failure. Because of this, when EICAS receives the discrete input, EICAS finds if there is a valid bus C signal. If there is no bus C input, the status message FUEL QTY BITE shows. If bus C input is valid, the maintenance message FUEL QTY BITE shows. If the bus C output is normal from the processor, but there is a fault in the circuit between the processor and EICAS, there is no message until a fault or bus C failure causes EICAS to do a check of the bus C input. The status message shows when there is a fault, and EICAS receives no digital data.



FUEL SYSTEM -- FUEL INDICATING - FQIS - INDICATION (CONT)

R MAIN TANK DENSITOMETER 28V DC R MAIN BUS

28V DC BAT. BUS

P11 28V DC

GND HDLG BUS

P34

28V DC HOT BAT. BUS

P6

FUEL QTY NO. 2

FUEL QTY NO. 1

FUEL STATION DOOR OPEN FUEL QTY PWR

FUEL QTY TRANS RELAY REFUEL

GND PWR FUELING QTY BAT. PWR

FUELING PWR TRANS RELAY

R AUX TANK DENSITOMETER

L MAIN TANK DENSITOMETER FUELING PWR TRANS

FUEL LEVEL SENSOR CONT CARGO

FUEL STATION DOOR OPEN

FUELING PWR CONT RELAY

L MAIN TANK LOAD SELECT INDICATOR

AUX TANK LOAD SELECT INDICATOR

R MAIN TANK LOAD SELECT INDICATOR


FUEL IND TEST SW

L/R FUEL CONT PANEL

FUEL MANAGEMENT PANEL

TANK UNIT BUSSING L AUX TANK FQIS

PLUG WIRING HARNESS TANK UNIT

COMPENSATOR

BUSSING L MAIN TANK FQIS PLUG WIRING HARNESS

TANK UNIT COMPENSATOR

BUSSING R AUX TANK FQIS PLUG WIRING HARNESS

TANK UNIT

COMPENSATOR

BUSSING R MAIN TANK FQIS PLUG WIRING HARNESS

FUEL QUANTIY INDICATOR

L/R EICAS COMPUTERS

OFF FUEL QTY FUEL QTY TEST SW

P61 MISC TEST PANEL

L CTR FUEL OVRD R CTR FUEL OVRD PUMP CONT SW PUMP CONT SW

FUEL MANAGEMENT PANEL AIR

GND

SYS NO. 2 AIR/GND AIR

RELAY GND

SYS NO. 1 AIR/GND RELAY FQIS PROCESSOR

FQIS OPERATION

Low Fuel & Con g EICAS message appears when L/R tanks have less than 2200 lbs. Fuel Con g EICAS message appears for a fuel imbalance of 1800 lbs. or greater between L/R Tanks or if 1000 pounds or greater is in the Center Tank and the Override Pumps are not engaged.

Page 83



FUEL SYSTEM -- FUEL INDICATING - FQIS - BITE

Purpose

The FQIS BITE finds, stores, and shows FQIS faults.


The face of the processor unit has these parts:

• 32-character LED plain language display • BIT procedure placard • Menu switch • YES switch • NO switch • ON/OFF switch • Up and down arrow switches

FQIS Fault Detection and Storage

The processor does continuous self-tests and isolates and stores FQIS faults. Faults are in memory by flight leg from the current leg (0) to 99. The transition from one flight leg to a different flight leg is at the air ground transition on takeoff. Each time the flight leg changes from ground to air, all flight leg numbers increase by one. Faults that occur in the system go to the BITE circuit card nonvolatile memory (NVM) on the A or B ARINC 429 bus for display.

Fault Recovery and Erase

You read the stored faults with a menu-driven, 32- character LED plain language display and 6 control push-buttons on the processor front face. Faults show in two groups, present faults (real-time faults) and fault history (stored faults). There are real-time messages with some real-time faults. For example, the message VOLUME SHUTOFF OF LM (left main) at 95 percent shows with the faults that have a relation to degraded system accuracy. This has a relation to the volume calculation problems in fueling troubleshooting. An intermittent fault goes in memory and shows with the number of times the fault occurs on a leg up to a count of 99. The fault also shows if it occurred in the air or on the ground. When you do a recall of the faults from memory, only flight leg numbers .with recorded faults show.the last 10 flight legs.

When you erase fault history, you can erase all but the last 10 flight legs.

BITE Menu Operation

These are the functions and operation of the processor front panel BITE switches and BITE display:

• ON/OFF button puts the processor BITE display on and off • MENU button selects, or goes back to, the current menu; if you push the

MENU button a second time, the main menu shows • UP and DOWN arrow buttons move up and down in a menu list of

questions • YES and NO buttons let you give answers to menu questions

The messages xx IN PROGRESS (TEST or ERASE) inhibit normal push-button operation when the messages show. For some menu operations, some push-buttons are not in operation. If you push one of these push-buttons, the message BUTTON INACTIVE shows for 1 second. The message inhibits if IN PROGRESS shows. When a question shows, you give the answer with the YES or NO buttons.

Present Faults

The present faults menu shows active or hard faults in the current flight leg. An A or a G follows each fault to show whether the processor is in the air mode or in the ground mode.



FUEL SYSTEM -- FUEL INDICATING - FQIS - BITE



FUEL SYSTEM -- FUEL INDICATING - FQIS BITE (CONT)

Fault History

The fault history menu shows stored faults from each of up to 64 previous flights that had a fault occur. A flight leg is specified by transition of the air/groundsensor to air. A flight leg is the time in the air during the flight and all time on the ground that the system has power until the next takeoff. An A or a G and a number follows each fault to show whether the fault first occurred while in the air or while on the ground. The number shows intermittent faults by the number oftimes the fault occurred during that flight leg.

Operation/Erase Fault History

Any fault currently detected shows in the present faults menu. The memory for the current flight leg in the fault history menu is flight leg 0. Intermittentfaults on the current flight leg are stored in flight leg 0. When the next ground to air transition occurs, the faults from flight leg 00 and the present faults combine and are in flight leg one. The flight number increments by one on every takeoff to F64. When you look at the fault history, only flight legs with stored faults show. The erase fault history menu first asks if you want to erase fault history information and, if you answer YES, then asks if you want to erase flight legs from the NVM for flight legs 11-64. If you answer this second question YES, the menu asks Are You Sure? 11-64? If you answer the third question YES, Erase In Progress shows (flashing). When the erase is complete, End Hist Erase Complete shows. All flight legs can be erased when the processor is in the shop ID mode.



FUEL SYSTEM -- FUEL INDICATING - FQIS - BITE (CONT)



FUEL SYSTEM -- FUEL INDICATING - FUEL TEMPERATURE INDICATING

General

The temperature of the fuel is measured to find ice in the fuel. A fuel temperature sensor measures the fuel temperature in the left main tank. The sensor is a resistance bulb. The signal goes to the fuel quantitymodule in the flight compartment. The fuel temperature indication shows in degrees Celsius. The indicator operates when the left 28v dc bus has power.

Location and Installation

The fuel temperature sensor is on the left rear spar just below the engine fuel shutoff valve. Defueling is not necessary to replace the sensor.

Testing

The temperature indicating system does a test with the FUEL QTY switch on the test panel on P61. If the system operates properly, an indication -188 shows on the temperature indicator while the switch is down.



FUEL SYSTEM -- FUEL INDICATING - FUEL QUANTITY MEA-SURING STICK ASSEMBLY

Purpose

The measuring sticks give a mechanical indication of the fuel level in each tank.

Location

There are eight sticks in the bottom surface of each wing. Six sticks are through tank access panels in each main tank and one through the lower wing skin. Thecenter tank has one stick through the lower wing skin. The sticks are numbered are from inboard to outboard on each side.


The measuring stick assembly has a stick housing on the lower wing surface. A oat with a ring magnet goes around the housing in the tank. An upper float stopkeeps the float on the housing. A stick is in the dry part of the housing. The stick is flat and can bend. There are calibrations on the stick. There is latch assembly on one end of the stick and a magnetic armature on the other end.

Operation

You use a screwdriver to push up and turn the stick head counterclockwise for release. When the stick releases, and you lower it, the stick armature magnetically engages the ring magnet in the float and holds the stick at the tank fuel level. You then make a reading from the stick calibrations. You find the airplane attitude by a plumb bob and leveling scale on the keel beam in the left wheel well.

You use the stick and airplane attitude data with the Fuel Quantity Measurement Correction Data For Fuel Measuring Sticks document to change these readings into fuel weight.



FUEL SYSTEM -- FUEL INDICATING - FUEL QUANTITY MEASURING STICK ASSEMBLY



FUEL SYSTEM -- FUEL INDICATING - HOT SHORT PROTEC-TOR

General

The hot short protector is a device which will not let high voltage go into the center fuel tank densitometer harness. This keeps a spark from igniting explosive fumes in the center tank.

The hot short protector is on the rear spar outboard of the right main gear wheel well.

The hot short protector contains special diodes and fuses.

The diodes will send high voltage to ground when it is present. The fuses will open if the voltage continues. When the fuses open, the voltage cannot go into the tank.

When the fuses open, you must replace the hot short protector.

Indication

If the fuses in the hot short protector open, EICAS will show an FQIS BITE Status message.



FUEL SYSTEM -- FUEL INDICATING - HOT SHORT PROTECTOR

B767 ATA 28 Student Book

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