General

The aircraft fuel system is designed to

provide the following functions :

- to control tank refueling and defueling.

- to deliver fuel to the engines for all

operating conditions of the aircraft,

� - to indicate to the crew normal function of

the fuel system and any malfunctions

which may occur during operation so that

appropriate safety measures may be taken.

FUEL SYSTEM COMPONENTS

TANKSGeneral

Fuel is stored in two integral wing tanksformed by the wing spar box betweenRIBS4 and 22 with the exception of thecenter section located above the fuselage.

Each tank has a capacity of 2866 liters(756.6 US gal.) i.e., 2250 kg (4950 lbs) for a density of 0.785 taking into account a 2% thermal expansion volume. RIB13 locatedat the wing break, constitutes an anti-surge baffle.

Engine Feed System

Under normal operating conditions, each engineis supplied from the associated tank by a systemcomprising :. An electric pump which delivers fuel to the

engine during engine starting. an engine feed jet pump which delivers fuel to

the engine after starting and during flight.The jet pump takes over from the electric pump

automatically when the engine is runningwithout any pilot action.. A jet pump maintains a constant fuel level in

the feeder tank where the electric pump and theengine feed jet pump are installed. The feedertank is located between RIB4 and RIB5.

Crossfeed System

A crossfeed system between the two tanks is used :

- to feed fuel to both engines from the same tank

- to feed fuel to one engine from the opposite tank.

LP Fuel Fire Shut Off Control

A fuel shut off system which serves to

isolate the engine from the feed line is

installed between the tank outlet and the

associated engine. System controls and

indicating are grouped together on the

FUEL section of panel 25VU on the

overhead panel in the flight compartment.

The fuel LP valves are closed by action on

the ENG FIRE handles described in

Chapter 26, Fire Protection.

Refuel/Defuel System

This system ensures refueling and distributionof fuel between the two tanks via tworefuel/defuel valves. The refuel/defuelcoupling is located on the leading edge of theright wing.

The system also serves for defueling of thetanks by suction. The controls and indicatorsassociated with this system are grouped on theREFUELING panel located in the rightlanding gear fairing. Two overwing refuelingcaps are also provided.

Fuel Quantity Indicating System

The fuel quantity indicating system

informs the crew of the quantity of fuel

available in each tank during flight. The

quantities are given in digital form on the

FUEL QTY indicator located on the upper

center instrument panel. The indicating

system also includes a high level safety

device in case of overfilling, by automatic

closure of the refuel/defuel valves before

spillage occurs.

Fuel Quantity Indicating System

A high level detection system doubles the safety offered by the indicator in case of overfilling, byclosing the refuel/defuel valves. This systemconsists of float type level sensors.Manual magnetic indicators are installed on thewing lower surface and may be used to indicatefuel quantities during refueling.A fuel quantity repeater, fuel quantitypreselector and two refuel/defuel valve position indicator lights are installed on theREFUELING panel.Two magnetic indicators, located onmaintenance panel 702VU, inform the crew of any failure to maintain full level in feeder tank.

Internal Access

The wing upper surface panel, comprised

of two sections for each half wing : from

RIB0 to RIB13 and from RIB13 to RIB23,

can be removed for inspection and internal

repair. Two access doors located on the

upper surface at either end of each tank

permit access to essential equipment

without removing the upper surface panel.

TANKS

Tank Draining

The wing lower surface panel is

designed so that any water collects in

the lowest parts of the tanks where

four self closing water drains per tank

are installed flush with the panel. They

serve to drain water from the tanks at

any aircraft attitude between ± 3°.

TANKS

Protection against Microbiological

ContaminationTo avoid deposits in

the tanks due to microbiological

corrosion, supports for strontium

chromate tablets are installed in each

tank and in the feeder tank.

TANKS

TANK VENTING SYSTEM

General

This system ensures tank venting

in all operating phases in flight and

on the ground.

Both tanks are vented in all flight configurations :

- via a vent line routed from RIB5 to RIB22

- via a float valve located in the outer wing section.

These two outlets are connected to a vent surge tank located outboard of the fuel tank.

The vent surge tank is vented to atmosphere througha NACA intake, installed on the wing lower surface. The vent surge tank serves to recover fuel enteringthe vent line and evacuated outwards in case of skidding.

The vent surge tank has a capacity of approximately100 liters (26.4 US gal.) and can contain 5 times line contents. The fuel is then recovered by siphoning.

TANK VENTING SYSTEM

A water drain, installed at the lowest point of the ventsurge tank, serves to avoid accumulation of water whichin icing conditions could freeze up to siphon level and prevent tank venting.

The NACA intake enables a slight overpressure of approximately 20 mb (0.3 psi) to be maintained in thetank and also limits overpressure in the tank. Duringrefueling to maximum fuel level, the float valve closesdue to the increase in level to enable refueling up to thehigh lever sensors.

In the case of accidental overfilling, the excess fuel overflows through the vent line, routed from RIB5 toRIB22.

The float valve also closes when the aircraft is in turnconfiguration, preventing the fuel from flowing into thevent tank. For a normal refueling flow rate, overpressure is less than 120 mb (1.75 psi). A barriercomposed of a plate (1) attached at right angles to thewing lower surface between the NACA intake and theengine nacelle prevents overflow fuel running to theengine.

The NACA intake is located on the lower surface.

Function of the breather (self-draining) :

When the fuel level in the tank is below the breather(2), it acts as a drain and evacuates the fuel out of thetank vent line.

When the tank is full, the fuel cannot flow into the ventline.

WING CENTER BOX

VENTILATING SYSTEM

General

This system serves to evacuate any

vapor and fuel which may collect due

to leaks in the lines routed through the

wing center box.

Two lines cross through the wing center box, located above the fuselage.

- the engine fuel feed system crossfeed line

- the left tank filling line.

Neither of these lines has a double sheath and consequently may allow fuel to leak into thewing center box (leaks at unions).

To avoid high concentrations of fuel vaporsbuilding up in the wing center box, it isventilated and drained.

WING CENTER BOX

VENTILATING SYSTEM

Ventilation air is supplied from the left side

of the fuselage through a scoop located on

the fillet and is ducted into the wing center

box at front spar level.

The two air vent ports located at the lowest

points of the center box, also serve for

draining, and exhaust to outside aft of the

fillets on either side of the fuselage.

WING CENTER BOX

VENTILATING SYSTEM

DISTRIBUTION

General

The fuel distribution system is divided

into four sub-systems.

A. Engine feed system

B. Crossfeed system

C. LP fuel fire shut off control

D. Refuel/defuel system.

Engine Feed System

The engine feed system serves to

deliver fuel pressure and flow rate

necessary for correct operation of both

engines throughout the flight

envelope.

DISTRIBUTION

This system comprises per tank:

A. One electric pump

B. One engine feed jet pump permanentlymaintained filled by a jet pump.

C. A magnetic indicator informs the crew of failure to maintain full level in feeder tank.

The engine feed jet pump is supplied with fuel under high pressure taken from the engine and its operation is controlled by the motive flowvalve.

DISTRIBUTION

Crossfeed System

The left and right fuel feed systems are

interconnected by a crossfeed line

comprising a single motor solenoid valve.

LP Fuel Fire Shut Off Control

The engine feed system can be isolated by

means of a dual motor fuel LP valve.

DISTRIBUTION

Refuel/Defuel System

The refuel/defuel coupling for refueling underpressure is located on the right wing leadingedge. Two refuel/defuel valves provide systemopening and closing control.

The controls and indicators are grouped on the

REFUELING panel located in the right landinggear fairing. Gravity refueling facilities are provided by overwing refueling caps; one per half wing.

DISTRIBUTION

ENGINE FEED SYSTEM

General

Fuel is fed to each engine from thecorresponding tank by means of a feedsystem installed in a feeder tank betweenRIBS 4 and 5. The feeder tank has a capacity of approximately 200 liters (53 US gal). System controls and indicators are grouped on the FUEL section of panel 25VU located on the overhead panel in theflight compartment.

Electric Pump

A 28VDC electric pump installed in each feeder tanksupplies fuel to the engine during starting. It also servesto supply the engine throughout the flight envelope, in the event of feed jet pump failure or a restart in emergency. The flow rate delivered at engine starting is450 l/hr (119 US gal.) at a pressure of 0.9 bar (13 psi) under 16VDC supply.

The electric pump outlet is equipped with a check valveand connected to a collector tank. The line between theelectric pump and the engine is inclined towards theengine.

Electric Pump

A vapor relief valve, located at the high pointdirectly above the electric pump allows anyair in the line to be expelled; this valve isairtight when the line is pressurized. A thermal relief valve, installed on this line,

allows fuel to escape directly into the tank in the event of overpressure. The electric pumpis installed in a canister equipped with a selfsealing system in the wing lower surface. Thepump may be removed without emptying thefuel tank.

Engine Feed Jet Pump

The engine feed jet pump delivers

fuel to the engine after starting.

Driving flow is supplied through a

return line from the

hydromechanical unit (HMU).

The jet pump outlet is equipped

with a check valve.

Feeder Jet Pump

Operated by fuel from the

engine feed system the jet pump

maintains the feeder tank full of

fuel throughout the flight by

drawing fuel from beyond RIB5.

It is installed on semi-sealed

RIB5.

Engine Feed Jet PumpIn normal operation, the engine feed jet pump suppliesfuel to the corresponding engine throughout the flightenvelope certified for the aircraft. In the event of failureof the opposite engine feed system, the jet pumpsupplies both engines during all flight phases other thantake off. For different operating phases it supplies :

- flow necessary to supply both engines (up to 860 kg/h, 1896 lb/h).

- flow necessary to supply one engine at take off, between 430 kg/h (946 lb/h) and 550 kg/h (1210 lb/h).

- in both cases flow necessary for jet pump operation. Pressure at the engine feed jet pump outlet, for theabove flow rates should be greater than or equal to 840 mb (12 psi) to ensure correct engine fuel supply.

Feeder Jet Pump

The fuel flow supplied by the feeder jet pump is

sufficient to maintain the feeder tank full in all flight

configurations. In the event of jet pump failure, the

feeder is connected to the tank through a flap valve

installed at the bottom of RIB5 which allows the fuel to

flow from the tank to the feeder tank. A magnetic

indicator, associated with the feeder tank, indicates

failure to maintain full level in feeder tank. The time

delay of these magnetic indicators, installed on panel

702VU, is 10 mn.

Motive Flow Valve

The motive flow valve is

installed on the wing forward

spar near the LP valve on the

engine feed HP return line. It

controls supply to the engine

feed jet pump.

Motive Flow ValveThe electric pump is de-energized after enginestarting by pressure switch installed on theengine feed jet pump outlet, when pressuresupplied by this jet pump reaches 600 mb (8.7 psi).

In the event of engine feed jet pump failure P < 350 mb (5 psi), pressure switch 17QA (18QA) provides electric pump opening control whichensures fuel supply to the engine.

The electric pump delivers the necessary flow-rate for engine consumption and the flow to thejet pump nozzle.

Motive Flow Valve

The motive flow valve is open when the

valve solenoid is not energized. It opens in

the presence of pressure and closes in the

absence of pressure. So, whenever the

solenoid is energized fuel flow to the

engine feed jet pump is stopped. In closed

position, a thermal relief valve allows fuel

trapped between the motive flow valve and

the engine to run to the fuel tank.

It is controlled via the PUMP pushbutton switch located

on the FUEL section of panel 25VU, on the overhead

panel.

- aircraft network energized and PUMP pushbutton switch

released (out) : solenoid energized, motive flow valve

closed.

- system armed before engine start : PUMP pushbutton

switch pressed (in) : solenoid not energized, but absence of

return pressure, motive flow valve closed.

- after engine start and throughout flight, PUMP pushbutton

switch pressed (in) : solenoid not energized, presence of

return pressure, motive flow valve open.

Motive Flow Valve

Flight in Negative "G" Conditions

The system is capable of supplying fuel to

the engines for 10 seconds in negative 'g'

conditions via the feeder tank which has a

capacity of 200 liters. The feeder tank is

maintained full of fuel through the jet

pump which permanently draws fuel from

the fuel tank as long as the engine feed jet

pump or the electric pump is operating.

F. Indications and Warnings

Low pressure in the engine feed system is detected by

the fuel feed low pressure switch installed downstream

of the LP valve. The FEED LO PR caution light comes

on amber on the FUEL section of panel 25 VU on the

overhead panel, together with associated centralized

warnings (Ref. Chapter 31-50).

A magnetic indicator, installed on panel 702VU,

indicates failure to maintain full level in the feeder tank.

Fuel Panel 25VU

Maintenance Panel 702VU

CROSSFEED SYSTEM

The left and right fuel feed systems are interconnected by a crossfeed lineincorporating a single motor electric valve. The

crossfeed system allowseither one engine to be supplied from opposite

tank or both engines to besupplied from one tank. Crossfeed valve control

and indication is located onthe FUEL section of panel 25VU on the flight

compartment overhead panel.Action on the FUEL/XFEED pushbutton

switch sets the electric pumps .

The two fuel feed systems are connected by a line via the wing box center section.

The crossfeed valve is installed on the line inside the wing box center section. Access isgained through an access door on the wingcenter box upper surface.

Supplied with 28VDC, crossfeed valve control and indication is located on the FUEL sectionof panel 25VU on the flight compartmentoverhead panel.

CROSSFEED SYSTEM

CROSS FEED

OPERATION:

ONE TANK

TO BOTH

ENGINES

CROSS FEED

OPERATION:

BOTH TANKS

TO ONE

ENGINES

LP FUEL FIRE SHUT OFF

The LP fuel fire shut off control system comprises a dual motor

spherical-plug type valve, locatedbetween the tank outlet and thecorresponding engine. Valve operationis controlled via the ENG1 and 2 FIRE handles located on the overheadpanel in the flight compartment. Valveposition is indicated on the FUEL section of panel 25VU.

Fuel LP Valve

The LP valve is mounted on the wing front

spar between RIBS 11 and 12, at engine level.

Each LP valve includes a thermal relief valve

which allows fuel trapped between the engine

and the LP valve to flow back when the LP

valve is closed. The valve is closed by a

28VDC dual motor actuator installed on the

valve.

LP FUEL FIRE SHUT OFF

Each valve is supplied separately either

by the battery or by "GEN1(2)". If

one motor fails, the other operates the

valve. Valve position is indicated by a

mechanical index. The line between

the LP valve and the fire wall is double

sheathed and drained so fuel from a

leak cannot reach hot parts of the

engine.

LP FUEL FIRE SHUT OFF

Action on the ENG FIRE handle enables

simultaneous energization of the two

motors of the actuator causing valve

closure and engine shut down. The

resulting pressure drop causes the motive

flow valve on the engine feed return line to

close. The two systems are isolated.

Operation of the associated annunciator

on the FUEL section of panel 25VU

LP FUEL FIRE SHUT OFF

REFUEL/DEFUEL SYSTEM

The refuel/defuel system serves to refuel thetanks under pressure; it also serves to defuel thetanks by suction. A refuel/defuel coupling islocated on the leading edge of the right wing. The controls and indicators associated with thissystem are grouped on the REFUELING panel, located in the right landing gear fairing. Oneoverwing refueling cap for gravity refueling isinstalled on the outer surface of each wing(zones 522 and 622).

Pressurized RefuelingAn assembly comprised of a refuel/defuel coupling with a cap and two refuel/defuel valves is installed directly on thewing spar box front spar on the right wing leading edgebetween.

This assembly is installed in a dry bay which is drained so that any fuel leakage cannot run to the engine inside theleading edge. Access is gained to this dry bay through anaccess door in the wing leading edge. Each refuel/defuelvalve is directly connected to two lines inside the tanks. Theright tank refuel branch line is in the right tank, the left tankrefuel line is routed through the wing center box. Fuel through the lines is admitted into the tanks at the tank lowpoints and the end of each branch line is equipped with a diffuser to limit formation of foam and fuel vapor.

REFUEL/DEFUEL SYSTEM

Each tank includes two float-type high level sensors (1 sensor comprised into each gauge Number 5 151QT/152QT and 1 sensor 11QU/12QU), which serve to close the refuel/defuel valves when 98% of the maximum fuel level is reached. They also illuminate the two HIGH LEVEL indicator lights on the REFUELING panel. These refuel/defuel valves could close by means of preselector who's selected the fuel quantity load. Total refueling rate for both tanks is 24 m3/h. (847 Ft /h) for an inlet pressure of 3.5 bars (50 psi). The tanks are completely filled 5732 litres (1513 US gal) in 17 minutes. Two restrictors installed at the refuel/defuel valve outlets provide the correct fueling rate and balance flow in the two lines so that tanks are filled simultaneously. Each 28VDC refuel/defuel valve is equipped with a manual control to operate the valve in the event of electrical control failure. Two indicator lights identified VALVE/LH/OPEN and VALVE/RH/OPEN located on the REFUELING panel come on to indicate opening of the refuel/defuel valves. Defueling is performed using the refueling system and fuel is drawn towards the tanker by suction. Maximum negative pressure at the refuel/defuel coupling is -0.77 bars (-11 psi).

Refueling Assembly

The assembly comprises the refuel/defuelcoupling for connection of the tankeradapter and the two refuel/defuel valves. Three closing features are provided toprevent any inadvertent fuel spillage duringflight :

A- the refuel/defuel valve

B- the self-sealing mechanism (closed whetanker adapter is not connected)

C- the cap.

REFUELING Panel

Gravity Refueling

Two overwing refueling caps are installed

on the wing upper surface between RIBS21

and 22 (to limit lightning strike risks). Each

cap includes a support attached to the

structure and a filter. The cap is equipped

with a locking mechanism flush with the

wing upper surface. A grounding

connection, installed near the cap, provides

electrical connection between the refueling

cap and the aircraft structure.

Refueling

Opening of the REFUELING panel door energizes a microswitch allowing electrical supply of the refuel/defuelsystem and the quantity indicating system from theGND/HDLG XFR BUS busbar. This microswitch alsoensures simultaneous supply of the GND/HDLG XFR BUS busbar from the HOT BAT BUS busbar if no other powersource is available. When the two REFUEL VALVES switches are in NORM position, the refuel/defuel valves are opened by placing the REFUEL/OFF/DEFUEL switch in REFUEL position. Two indicator lights identifiedVALVE/LH/OPEN and VALVE/RH/OPEN located onthe REFUELING panel come on to indicate refuel/defuelvalve opening. Fuel load, preselected via the fuel quantitypreselector is read on the fuel quantity repeater indicatorlocated on the REFUELING panel.

Quantity indicating system

When the fuel quantity in the tanks reaches a maximum value (4500 kg) (9900 lbs.), the fuel quantity indicator sends an electrical signal toclose the refuel/defuel valves via relays 15QU and 16QU. This system can be tested by theFQI TEST pushbutton switch, which simulatesa fuel quantity greater than 4500 kg (9900 lbs.), on the fuel quantity indicator causing therefuel/defuel valves to close. The twoVALVE/LH/OPEN and VALVE/RH/OPEN indicator lights located on the REFUELING panel go off to indicate valve closure.

Float-type high level sensors

If the probes do not operate, the high levelsensors close the refuel/ defuel valves, and thecorresponding HI LEVEL indicator lights17QU and 18QU come on. This safety devicecannot be tested. In the case of partial refueling, the operation is stopped by placing theREFUEL/OFF/DEFUEL switch in OFF position. OPEN position enables refueling up tothe high level sensor operating threshold : theprobes cannot close the refuel/defuel valves.

Defueling

The refuel/defuel valves are opened

for defueling operations by placing the

REFUEL/OFF/DEFUEL switch in

DEFUEL position and the REFUEL

VALVES switches in OPEN position.

The two refueling safety devices are

inhibited.

QUANTITY INDICATING

This system provides the flight crew

with information concerning the mass

quantity of fuel available in each tank

throughout the flight. This

information is displayed in digital form

on a dual indicator located on the

upper center instrument panel 4VU.

ProbesFuel mass is measured by five capacitance probesinstalled in each tank. They are attached to the tankupper surface wall and can be removed from theoutside without emptying the tank. Five electricalharnesses installed inside the tank, connect theprobes to the bulkhead connectors. Any change in fuel quantity results in a change in probeimmersion and a consequent change in probecapacitance.The summing of the fuel quantity in a tank isperformed by connecting the five probes in parallel.

QUANTITY INDICATING

Dual Indicator

The fuel quantity indicator indicates the fuel mass in each tank. The two indications are givenin digital form in kg or in lbs according to theaircraft version. This indicator includes twoamplifiers which process electrical signals fromthe tanks. The two channels, supplied with28VDC, are completely isolated. The channelsinclude a low level detection system.

QUANTITY INDICATING

MANUAL (MAGNETIC)

INDICATORS

Manual magnetic indicators are

installed on the wing lower surface and

can be used during refueling

operations.

They indicate loaded fuel quantity in

the event of failure of the electrical

system.

Each tank is equipped with two manual magnetic indicators; onebetween RIBS5 and 6, the other between RIBS21 and 22 (zones522 and 622). Access to the indicators is gained from the winglower surface. Each indicator comprises :- a sealed tube installed vertically in the tank,- a rod, graduated in centimeters, which slides in the tube,- an annular float which slides up and down the outside of tube.When the indicator rod is unlocked it falls under its own weightand is magnetically linked to the float. The fuel level is read in centimeters on the section of the rod which protrudes from thewing lower surface.A chart is used to convert centimeters into liters and units of weight (kg. or lbs.) as a function of aircraft roll attitude and fuel density.Roll attitude can be checked on a clinometer located on the mainlanding gear bay.

MANUAL (MAGNETIC)

INDICATORS

ATA 28

RESUME

ATA 28

RESTART

ATR 42/72

TRAINING

ATA 21

ATA 27

ATA 26

ATA 25

ATA 24

ATA 23

ATA 22

ATA 28

ATA 30

ATA 29

ATA 00

ATA 70 PW121

ATA 61

ATA 52

ATA 36

ATA 35

ATA 34

ATA 33

ATA 32

ATR DIFERENCES

ATA 31

ATA 70 PW127