Download - Ata 28 Fuel System
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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.
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FUEL SYSTEM COMPONENTS
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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
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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
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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
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TANK VENTING SYSTEM
General
This system ensures tank venting
in all operating phases in flight and
on the ground.
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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
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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.
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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.
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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.
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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
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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
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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.
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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
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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
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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
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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
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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
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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.
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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.
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Fuel Panel 25VU
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Maintenance Panel 702VU
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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 .
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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
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CROSS FEED
OPERATION:
ONE TANK
TO BOTH
ENGINES
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CROSS FEED
OPERATION:
BOTH TANKS
TO ONE
ENGINES
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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.
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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
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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
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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
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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).
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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
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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).
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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.
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REFUELING Panel
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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.
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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.
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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.
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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.
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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.
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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.
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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
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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
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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.
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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
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ATA 28
RESUME
ATA 28
RESTART
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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