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TEXTBOOK

Fuel system

020 00 00 00 AIRCRAFT GENERAL KNOWLEDGE

021 01 00 00 AIRFRAME AND SYSTEMS

021 08 00 00 Fuel system

LH

ENGINE

RH

ENGINE

ELPMP JETPMP JETPMP ELPMP

FUEL

S

O

V

S

O

V

X-FEED

A

U

T

O

A

U

T

O

Vent float valves Vent tank Flush inlet Overboard vent line


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Fuel System

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Fuel system

An aircraft fuel system need to be able to store enough fuel for the type of

mission the aircraft is designed for and supply this fuel to the respective engines

at various attitudes, altitudes and temperatures.

We will look at three different aircraft types to compare the fuel systems designs

used to do the same job.

The main constructural difference you will notice is the location where the fuel is

collected before it is supplied to the engine.

Lets look on an example.

The Dash 8 a high wing turbo prop with a dihedral of 2.5 and has the collector

bay at the innermost, or lowest, portion of the tank.

The Fairchild Dornier 328 Jet has a straight high wing and collects the fuel in the

feeder tanks at the outermost portion of the tank.

The Embraer 145 a low wing jet with a positive dihedral utilizes fuel collector

boxes in the center wing section.

Each of the three designes has the collector or feeder tank at the lowest portion

of the storage tank to use the effects of gravity in addition to feeder systems to

keep the fuel collection area full at all times regardles of total fuel quantity , flight

attitudes and manoeuvers.


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Fuel System

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Fuel tanks

"Dash 8 Fuel Tanks"

Fuel storage is provided by two separate integral wing tanks, one in each wing.

The capacity for each fuel tank is 1601 liters or 2882 lbs.

The tanks are interconnected through a refuel/defuel /transfer shutoff valve in

each tank by a single manifold.

REFUEL

DEFUEL

transfer

shutoff

valve


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Fuel System

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The manifold is used for pressure refueling, suction defueling and fuel transfer.

Please highlight the manifold on the sketch at the previous page

The fuel tank in each wing extends from station YW171.992 to YW387.00 and

from front to rear spar.

The inboard end of each tank is walled-in to form the collector bay.

An over-wing gravity filling point is provided in the wing upper skin.

When fueling by pressure, all fuel is pumped into the collector bay.

Sumps at the low points in each tank contain a drain valve.

Collector Bays

No. 1 Tank No. 2 Tank

Fuel Manifold


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Fuel System

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"Dornier 328 Fuel Tanks"

The fuel tanks of the DORNIER 328.

The LH and RH wing tank groups are located in the wing symmetrically about the

centerline of the aircraft.

Each wing tank group consists of an inner tank , an outer tank and a feeder tank.

The tanks are separated by the wing ribs as follows:

The inner tank extends from rib 0 to rib 11, the outer tank extends from rib 11 to

rib 19, and the feeder tank extends from rib 19 to rib 21.

The top and bottom surfaces of the tanks are formed by the upper and lower wing

skins.

The front and rear tanks walls are formed by the front and rear spars of the wing.

Primary sealing is achieved by mechanical attachment of the structural members.

Each tank is treated to prevent corrosion and is sealed with sealants that are

resistant to all approved fuels and additives.

Access to the tanks and to the internally-mounted fuel system components or fuel

lines is through access panels on the front and rear spars, and through panels on

the upper surface of the wing.

Fuel Tank Do328


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Fuel System

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Fuel feed

The fuel supply system of the Dornier 328.

The engine fuel feed systems installed in the LH and RH wing tank groups are

supplied with motive fuel flow from the related engine fuel pump.

The engine fuel pump is located on and driven by the engine accessory gearbox.


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Fuel System

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During the engine starting phase, the engine fuel pump receives low pressure

fuel from the feeder tank which is pressurised by the electrical booster pump.

When the engine is operating, the high pressure output from the fuel pump is

send back to the feeder tank to provide the two jet booster pumps with sufficient

motive fuel flow for normal operation.

In this phase, the engine fuel feed system is self supporting, and the electrical

booster pump is automatically switched off; it remains on standby if the pressure

of the two jet booster pumps decreases below an predetermined acceptable

level.

Identify the electrical booster pump and the jet booster pumps


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Fuel System

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"Dornier 328 Fuel crossfeed and transfer"

The aircraft has two fuel crossfeed sub-systems:

The engine crossfeed system and the wing tank group crossfeed system.

The Engine Crossfeed System permits both engines to be supplied with fuel from

any one wing tank group, or any one engine to be supplied from both LH and RH

wing tank groups.

The engine crossfeed system components are the crossfeed valve 21QC and the

crossfeed pipeline between the LH and RH wing tank groups.

The crossfeed valve is controlled by the X-FEED switch 19QC in the FUEL

section on the overhead panel.

LH

ENGINE

RH

ENGINE

ELPMP JETPMP JETPMP ELPMP

FUEL

S

OV

S

OV

X-FEED

A

U

T

O

A

U

T

O


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Fuel System

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The crossfeed valve is installed in the inner tank of the LH wing tank group.

In flight, the crossfeed valve is usually closed and is controlled by the X-FEED

switch, which does not permit fuel to be pumped from one tank group to the

other.

On the ground during the aircraft refueling procedure, the crossfeed valve can be

opened, permitting fuel to be pumped from the LH to the RH wing tank group.

The crossfeed valve is controlled by the refueling/defueling panel on the RH

wing.

DEC

D

A

T

A

E

N

T

R

Y

LEFT RIGHTLEFT RIGHT

REFUELING VALVES

CLSD

OPEN

HI LEVEL

WARNING

FUEL QUANTITY REMANING

PRESELECTED QTY

REFUEL

AUTO

DEFUELINC

INTERTANK XFER

TO

LH

TO

RH

OFF

AUTOMATIC MANUAL

3416


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Fuel System

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The fuel supply of the Embraer 145.

The fuel distribution system permits engine fuel feeding, APU fuel feeding, tank

pressure refueling and tank defueling.

For engine and APU feeding three DC driven centrifugal fuel pumps are installed

in every collector box.

They are designated as 1A, 1B, and 1C for the left side and 2A, 2B,and 2C for

the right side.

A check valve in the outlet of each electric booster pump prevents fuel flow

through the pump when it is not operating.

If a failure of all electrical pumps occurs a suction valve is installed to increase

the engine fuel suction.

The ejector pump receives motive flow from the electric pumps to send a larger

fuel quantity back to the collector box than the engines and APU fuel

consumption.

Please identify the DC driven centrifugal fuel pumps, the electric booster pump, suction

valve and the ejector pump

APU

To FPMU /Engine 1 To FPMU /Engine 2


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Fuel System

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The APU fuel shutoff valve opens when the APU master switch is set to ON.

The APU fuel shut off valve can be closed by either selecting the APU master

switch to OFF, by pushing the APU shut off switch, or by pushing the APU fire

extinguisher switch.

In these cases the EICAS message APU FUEL SHUT OFF VALVE CLOSED will

displayed for 10 seconds.

On ground the valve will close automatically after 10 seconds when an APU fire

occurs or when the fire warning test button is pushed for longer than 10 seconds.

If any disagreement occurs between the actual and the commanded position, an

APU FUEL SHUT OFF VALVE INOPERATIVE message will be displayed on the

EICAS.

If no fuel pump is running and the fuel pressure is below 6.5 PSI, the APU fuel

pressure switch will send a signal to the data acquisition unit #2 and an APU

LOW PRESSURE message will be displayed.

APU CONTROL

ON

STARTOFF

FUEL SHUTOFFMASTER

STOP

FIRE

BAGG

EXTG

TEST

DET

APU

EXTG


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Fuel System

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DORNIER 328 JET REFUEL/DEFUEL SYSTEM

Pressure refueling is the normal method of refueling the aircraft.

This procedure is controlled by the refuel/defuel panel installed adjacent to the

2.5 inch refuel adapter on the right wing.

An additional fuel quantity pre-selector is installed in the flight compartment on

the center pedestal.

The automatic refuel control system monitors and controls the distribution of the

pre-set amount of fuel to the LH and RH wing fuel tanks .

To protect the wing tank group from overpressure, each outer tank has a

pressure relief valve installed in the rear wall.

DEC

D

A

T

A

E

N

T

R

Y

LEFT RIGHTLEFT RIGHT

REFUELING VALVES

CLSD

OPEN

HI LEVEL

WARNING

FUEL QUANTITY REMANING

PRESELECTED QTY

REFUEL

AUTO

DEFUELINC

INTERTANK XFER

TO

LH

TO

RH

OFF

AUTOMATIC MANUAL

2400

REFUEL ADAPTERREFUEL ADAPTER

Fuel quantity pre-selector

REFUEL/DEFUEL panel1 1200 200

EXCEED

TREND

IMT/FDR

REFUEL QTY

+

-

LI

M

IT

RUD

SPO

IL

GND


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Fuel System

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Fuel dumping system

Dornier 328 Fuel pressure dump, vent and drain systems

The fuel pressure dump, venting and draining systems of the Dornier 328.

There are five drain valves in each fuel tank group.

The drain valves are provided for draining condensed water and fuel samples.

The tanks can be completely drained through these valves.

The drain valves are installed on the underside of the LH and RH wing.

The drain valves for each wing are symmetrically located as follows:

LH/RH feeder tank, between ribs 20 and 21,

LH/RH outer tank (outboard valve), between ribs 18 and 19

LH/RH outer tank (inboard valve), between ribs 11 and 12

LH/RH inner tank, between ribs 11 and 12

LH/RH vent tank, between ribs 11 and 12.

LH - wing


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Fuel System

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The drain valves are manually operated by forcing the piston valve in an upward

direction.

Small quantities of water are drained using a special drain tool.

Larger quantities of fuel or water are drained using a gravity defuel adapter.

When the force is released from the piston valve, the spring pushes the piston

valve downward to close and seal the drain valve.

The poppet O-ring seals can be replaced without removal of the complete drain

valve and without defueling the tank.

The inner and outer tanks of each wing tank group are vented to the atmosphere

using the following components:

Main vent line, Vent Float valves, Vent tank, Flush inlet and an Overboard vent

line.

Vent float valves Vent tank Flush inlet Overboard vent line


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Fuel System

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The inner and outer tanks are vented by a main vent line which extends from rib

1 to rib 17, and is connected to the vent tank.

A check valve is fitted in the main vent line at rib 1. Outboard of the check valve

the main vent line is open ended, and terminates just below the upper surface of

the inner tank.

All other main vent line openings are controlled by float valves.

Four vent float valves are installed, one each at ribs 2, 3, 12 and 17.

They make sure that large quantities of fuel cannot flow through the main vent

line during extreme aircraft attitudes.

The vent tank is a cylindrical welded assembly with front and rear mounting

brackets.

The vent tank is mounted horizontally in the upper half of the outer tank and is

attached by screws to rib 11.

The fuel tank venting system supplies the inner and outer tanks with atmospheric

air pressure at all times regardless of whether the aircraft is on the ground or in

flight.

Bleed holes between the feeder, the outer and the inner tanks provide pressure

compensation within each wing tank group.


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Fuel System

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When the aircraft is on the ground with the tanks fueled to capacity, air pressure

enters the flush inlet.

The air pressure is then routed through the overboard vent line and the vent tank

to emerge from the partially open top float valves at ribs 12 and 17.

Should a pressure build-up occur in the tanks, the pressure can escape

overboard through the same route.

If the pressure in the tanks falls below atmospheric pressure, the spring loaded

check valve at rib 1 opens under the influence of the atmospheric pressure.

The check valve remains open until the tank pressure equals that of atmospheric

pressure, and is then closed by spring pressure.

Check valve


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Fuel System

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Fuel system monitor ing

"Dash 8 Fuel indication and warning"

The fuel quantity indicating system is capacitance type, operating from the

aircraft 28VDC power supply.

Here are the main functions of the system:

It measures the mass of fuel in each tank and displays the contents on two

separate fuel quantity master indicators on the fuel control panel in the flight

compartment.

VALVE VALVETRANSFER

OFF

TO

TANK ITO

TANK 2

FUEL CONTROL

5 10

150

FUELQTY

KGS X 100TANK I

AUX PUM P

OFF

TANK 2

AUX PUMP

OFF

QTY TEST

5 10

150

FUELQTY

KGS X 100TANK I

AUX PUM P

OFF

TANK 2

AUX PUMP

OFF

QTY TEST

CLOSEDCLOSED

OPENOPEN5 10

150

FUELQTY

KGS X 100

TANK 1 TANK 1


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Fuel System

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It also displays contents of tanks on two fuel quantity control and repeater

indicators at the refueling/defueling control panel.

The fuel quantity control and repeater indicators also provide fuel level selection

and shutoff control during pressure refueling and defueling.

Magnetic dipsticks installed in each tank provide an alternate fuel measuring

device.

KGS X 100

10

15

5

0

SET

FUELQTY

KGS X 100

10

15

5

0

SET

FUELQTY

PRE CHECK

TANK TANK

MASTER

VALVE

CLOSED

GROUND

CREW

JACK

REFUEL

TEST

OFF

DEFUELREFUEL

SHUT OFF

DUMPVALVE

OPEN

REFUEL

SHU T OFF

DUMPVALVE

OPEN

REFUEL

TANK 1 TANK 2

21

POWER ON


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Fuel System

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The fuel quantity indicating system for each fuel tank is identical.

Each consists of six probes, the master indicator and the fuel quantity control and

repeater indicator.

The two master indicators and the QTY TEST switch are located on the FUEL

CONTROL panel in the flight compartment.

The two fuel quantity control and repeater indicators, and the

REFUEL/OFF/DEFUEL switch are located on the refuel/defuel control panel.

The fuel quantity master indicators are single function, pointer-type display units.

Contained within each indicator is a closed loop oscillator which produces the

excitation voltage to the associated fuel probes.

Each master indicator also has a built-in self-test circuit which, when actuated by

the remote test switch, produces a test signal equivalent to indicator full scale

reading.

The indicators are calibrated from 0 to 1500 kg (0 to 3000 lb) in increments of

100 kg (200 lb). The indicators require 28VDC for operation.

The system also has a common

indicator self-test pressbutton switch

labeled QTY TEST and a

REFUEL/OFF/DEFUEL rotary switch

common to both fuel tanks.

The probes are mounted inside eachfuel tank, and one is housed in the

collector bay. The probes in each

fueltank are electricly connected in

parallel to feed the respective fuel

quantity master indicator.


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Fuel System

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The fuel quantity control and repeater indicators display system is similar to that

of the fuel quantity master indicators.

Unlike the master indicators, the repeaters do not have an oscillator or a built-in

test circuit but do have a refuel/defuel control circuit, controlled by a SET knob to

position an index pointer in the dial to a desired fuel level.

Dash 8 Fuel Control Panel

Should the main fuel quantity indicating system fail, two magnetic dipsticks in

each tank provide an alternate method of measuring fuel quantity.

Each dipstick is positioned vertically in the tank, and consists of a fiberglass rod

which slides in an outer tube.

When the rod is released from the wing lower skin, it falls slowly until trapped in

the tube by a floating magnet.

The tank contents can be read from markings on the calibrated rod.

The dipsticks are calibrated in U.S. gallons and in liters.

If the quantity of fuel in the tank is such that the inner dipstick will not drop (i.e.

the floating magnet is on top of the tank), contents can be read from the outer

dipstick.

VALVE VALVETRANSFER

OF F

TO

TANK ITO

TANK 2

FUEL CONTROL

5 10

150

FUELQTY

KGS X 100TANK I

AU X PU MP

OF F

TANK 2

AU X PU MP

OF F

QTY TEST

5 10

150

FUELQTY

KGS X 100TANK I

AU X PU MP

OF F

TANK 2

AU X PU MP

OF F

QTY TEST

CLOSEDCLOSED

OPENOPEN5 10

150

FUELQTY

KGS X 100


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Fuel System

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Fuel low level warning for each tank consists of a simple float switch which

operates a TANK FUEL LOW caution light on the caution lights panel in the flight

compartment.

The switch is mounted in the collector bay section of the fuel tank.

Power for low level warning is derived from the right essential 28VDC bus and is

protected by a 7-1/2-ampere CAUT LTS circuit breaker.

The normally open fuel low level warning switch is float-operated to close when

fuel in a tank falls below the pre-set level, and causes the appropriate TANK

FUEL LOW caution light to illuminate.

NOTE: Operation of the fuel low level warning system is completely independent

of the fuel quantity indicating system.

#1 TANKFUEL LOW

#2 TANKFUEL LOW


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Fuel System

The fuel tank temperature indication system consists of a temperature sensing

bulb and a fuel tank temperature indicator.

The system is operational whenever power is applied to the aircraft.

The temperature sensing bulb, located on the front spar of the left wing, is an

electrical resistance type in which resistance varies in direct proportion to sensed

fuel temperature.

The fuel tank temperature indicator is located on the engine instrument panel.

The indicator has an outer graduated scale which ranges from -60 degrees C to

+60 degrees C.

CLOSED CLOSED

ENGINE INTAKE BYPASS DOOR

1 2

+

-60

-30

0

30

60

FUEL

TANK TEMP

C

021_08_00_00_Fuel_system_Amend0

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