A340-200/300

TECHNICAL TRAINING MANUAL

CMQ Inter Family : SA -> A340 CFM 56 - T1
LANDING GEAR
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 A340-200/300 TECHNICAL TRAINING MANUAL

LANDING GEAR
32 Landing Gear System Presentation (1) . . . . . . . . . . . . . . . . . . . . . . 2
Landing Gear System Line Maintenance Briefing (2) . . . . . . . . . . . . 56
LANDING GEAR AND DOORS
Landing Gear Special Features (3) . . . . . . . . . . . . . . . . . . . . . . . . . . 122
Normal Extension and Retraction D/O (3) . . . . . . . . . . . . . . . . . . . . 138
Free Fall Extension D/O (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
Door Ground Opening D/O (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
WHEELS AND BRAKES
Normal Braking D/O (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
Alternate Braking D/O (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194
Park/Ultimate Braking D/O (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
NOSE WHEEL STEERING
Nose Wheel Steering D/O (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
MAINTENANCE PRACTICE
Landing Gear MCDU Pages (2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
Landing Gear System Base Maintenance (3) . . . . . . . . . . . . . . . . . . 234
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32 LANDING GEAR SYSTEM PRESENTATION (1)

LANDING GEAR
The Landing Gear (L/G) system supports the aircraft on the ground and
transmits landing, TakeOff (TO) and taxi loads to the structure. It also
decreases the aircraft speed through the braking system and steers the
aircraft on ground. The L/G system is divided into:
- the gear and doors,
- the extension and retraction,
- the braking,
- the brake temperature and cooling,
- the Tire Pressure Indicating System (TPIS),
- the steering,
- the maintenance/test facilities.
When you work on A/C, you must obey all the safety procedures listed
in the AMM.
The L/G and doors are supplied by the green hydraulic system. The Nose
Landing Gear (NLG) system is composed of the nose gear and doors.
Some doors are electrically controlled and hydraulically operated; the
others are mechanically linked to the gear structure. The Main Landing
Gear (MLG) system is composed of the main gear and doors. Some doors
are electrically controlled and hydraulically operated, the others are
mechanically linked to the gear structure.. The Centerline Landing Gear
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(CLG) system is composed of the center gear and doors, which are
electrically controlled and hydraulically operated. When you work on
aircraft, you must obey all the safety procedures listed in the Aircraft
Maintenance Manual (AMM).

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LANDING GEAR

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LANDING GEAR

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32 LANDING GEAR SYSTEM PRESENTATION (1)

LANDING GEAR (continued)
MAIN LANDING GEAR (MLG)
Each MLG, which retracts inboard into its wheel bay in the fuselage
and the wing, includes these main parts:
- a side stay assembly,
- a MLG leg assembly,
- a bogie alignment pitch trimmer,
- a bogie beam assembly.
The MLG is hydraulically operated during the normal
extension/retraction sequence.
The MLG leg includes a shortening mechanism, a bogie pitch trimmer
and an oleo-pneumatic shock absorber. The shock absorber absorbs
the taxi, TO and landing loads. The shock absorber is a capsule type
that includes a sliding tube. It is an oleo-pneumatic unit that is installed
in the main fitting.
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LANDING GEAR - MAIN LANDING GEAR (MLG)

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32 LANDING GEAR SYSTEM PRESENTATION (1)

LANDING GEAR (continued)
MLG SIDE STAY ASSEMBLY
A two-piece side stay assembly holds the MLG in the extended
position. The lock stay is the mechanical down lock for the MLG. A
lock stay keeps the side stay assembly stable in the locked down
position. The lock stay is the mechanical down lock for the MLG. A
ground lock pin has to be installed through the links of the lock stay,
when they are in the over center position, to comply with the safety
precautions.
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LANDING GEAR - MLG SIDE STAY ASSEMBLY

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32 LANDING GEAR SYSTEM PRESENTATION (1)

LANDING GEAR (continued)
MLG BOGIE ALIGNMENT PITCH TRIMMER
The pitch trimmer is installed between the main fitting and the upper
links. A set of articulated links, two upper and one lower, connects
the main fitting to the front of the bogie beam. The green hydraulic
system continuously supplies pressure to the pitch trimmer, which
maintains the required geometry of the links during the retraction
sequence, TO, and landing phases.
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LANDING GEAR - MLG BOGIE ALIGNMENT PITCH TRIMMER

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32 LANDING GEAR SYSTEM PRESENTATION (1)

LANDING GEAR (continued)
MLG SHORTENING MECHANISM
During the retraction the shortening mechanism decreases the overall
length of the MLG to let the gears go into the available space in the
bays. The shortening mechanism includes a turnbuckle link connected
on one end to the airframe wing and a system of mechanical links that
is attached to the shock absorber. The MLG movement operates the
shortening mechanism during retraction or extension.
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LANDING GEAR - MLG SHORTENING MECHANISM

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LANDING GEAR (continued)
MLG DOORS
Three doors close each MLG bay. They follow the shape of the belly
fairing and protect the equipment in the bay from the airflow during
flight. The MLG doors are hydraulically operated. Each main door is
hinged at the keel beam and closes outboard. The fairing door is
attached to the MLG leg and operates with it. The hinged door is
connected to the MLG leg through an adjustable rod. When the main
gear operates, the rod operates to move the hinged door. A lock collar
can be installed on each door actuator when the aircraft is on the
ground to prevent closure.
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LANDING GEAR - MLG DOORS

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LANDING GEAR (continued)
CENTERLINE LANDING GEAR (CLG)
The CLG is designed to decrease the runway loading. It absorbs loads
that occur during taxiing and TO. The CLG is installed on the rear
bulkhead of the MLG bay and retracts forward into the CLG bay.
The CLG assembly is installed on the rear bulkhead of the MLG bay
and retracts forward into the CLG bay. The CLG leg includes a main
fitting and a shock absorber. It is the main part of the CLG.
The shock absorber decreases the TO and taxing loads transmitted to
the aircraft structure. The shock absorber is installed on the main
fitting. It is a 2 stage oleo-pneumatic units including a sliding tube.
The loads are transmitted to the hydraulic fluid and nitrogen gas in
the shock absorber when it compresses.
The down lock assembly mechanism is entirely contained on the drag
stay and functions by locking the drag stay central pivot by means of
over center lock links. A ground lock pin can be installed in the center
pivot point of the lock stay when the CLG is down locked.
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LANDING GEAR - CENTERLINE LANDING GEAR (CLG)

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LANDING GEAR (continued)
CLG DOORS
Four doors and one fairing door close the centerline gear bay. There
are:
- two hydraulically operated forward doors,
- two mechanically operated hinged doors,
- a fixed fairing door on the centerline gear leg.
A lock collar can be installed on each door actuator when the aircraft
is on the ground to prevent closure.
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LANDING GEAR - CLG DOORS

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LANDING GEAR (continued)
NOSE LANDING GEAR (NLG)
Each NLG, which retracts forward into the NLG bay, includes these
main parts:
- a lock stay assembly,
- a NLG leg assembly,
- steering actuators.
The nose wheels are steered by twin, double acting hydraulic actuators,
which pivot on attachments on the main fitting. The NLG is
hydraulically operated during the normal extension/retraction
sequence.
The L/G leg has a main fitting with a sliding tube assembly that
includes the axle and a shock absorber with a wheel steering assembly.
The nose wheels are steered by twin, double acting hydraulic actuators,
which pivot on attachments on the main fitting.
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LANDING GEAR - NOSE LANDING GEAR (NLG)

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LANDING GEAR (continued)
NLG LOCK STAY ASSEMBLY
The lock stay is installed between the main fitting and the center pivot
point of the drag stay. It has an upper link and a lower link. The lock
stay holds the drag stay in a straight configuration when the NLG is
extended. A ground lock pin can be installed in the center pivot point
of the lock stay when the NLG is down locked.
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LANDING GEAR - NLG LOCK STAY ASSEMBLY

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LANDING GEAR (continued)
NLG DOORS
A lock collar can be installed on each door actuator when the aircraft
is on the ground to prevent closure. Four doors and a fixed fairing
close the NLG bay. The two forward doors are hydraulically operated.
Each door has hinges at the side of the NLG bay and closes inward
at the front of the bay. The two aft doors and the fixed fairing are
mechanically operated. Each aft door has hinges at its outer edge.
Adjustable rods connect the rear doors to the NLG leg. The fixed
fairing is installed at the rear of the NLG leg.
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LANDING GEAR - NLG DOORS

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LANDING GEAR EXTENSION AND RETRACTION
The extension/retraction system has:
- the normal operation system,
- the free fall extension system,
- the door ground opening system.
L/G normal operation is controlled through a lever located on the landing
control panel. The L/G control lever has two positions only:
- the UP position for the retraction sequence,
- the DOWN position for the extension sequence.
Each Landing Gear Control and Interface Unit (LGCIU) controls one
complete cycle: one UP and DOWN selection.
An interlock mechanism controls a lever baulk solenoid to prevent unsafe
retraction when the L/G is not in flight conditions. The LGCIUs switch
over automatically at each L/G retraction cycle or in case of sequencing
system failure.
The L/G is powered by the green hydraulic system. At high air speed a
safety valve cuts hydraulic supply to the L/G system. In turn, each LGCIU
controls the selector valve manifold, which hydraulically operates all
gears and doors. The two LGCIUs process gear position, sequencing
information, gear lever selection and send landing status to other aircraft
systems. In case of normal extension failure, the L/G can be extended by
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gravity through an electro-mechanical system. The power supply is

duplicated and is controlled by toggle selectors on the main instrument
panel. There is no gravity extension system fitted on the CLG. On the
ground after a free fall extension, the CLG must be extended by the
maintenance crew. For maintenance functions, the system has a
hydraulically operating system for the opening and closing of the L/G
doors. The NLG ground opening system is located in the gear bay. The
MLG doors ground opening system is located under the fuselage forward
of the L/Gs.

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LANDING GEAR EXTENSION AND RETRACTION

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LANDING GEAR EXTENSION AND RETRACTION
(continued)
NLG NORMAL RETRACTION SEQUENCE
For the normal retraction sequence, the L/G lever must be on the UP
position to get gears and doors retraction. The cockpit crew knows
that the gears are retracted and the doors closed through the L/G
position on the LanDinG GEAR panel or on the ECAM WHEEL
page.
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LANDING GEAR EXTENSION AND RETRACTION - NLG NORMAL RETRACTION SEQUENCE

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LANDING GEAR EXTENSION AND RETRACTION
(continued)
MLG NORMAL RETRACTION SEQUENCE
For the normal retraction sequence, the L/G lever must be on the UP
position to get gears and doors retraction. The cockpit crew knows
that the gears are retracted and the doors closed through the L/G
position on the LDG GEAR panel or on the ECAM WHEEL page.
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LANDING GEAR EXTENSION AND RETRACTION - MLG NORMAL RETRACTION SEQUENCE

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brakes according to the pedals demand and the A/SKID protection.
NORMAL BRAKING Wheel rotation speed and braking pressure values are fed back to the
BSCU for braking and A/SKID computation. The BSCU sends data
Only the MLG wheels are installed with multi disks carbon brakes. Each
to the WHEEL page.
brake assembly is activated by two separated sets of pistons powered by
different hydraulic systems. There are three braking modes that can AUTO BRAKE
independently operate the brake units: Auto brake is available during a TO if an aborted TO is necessary or
- normal braking, at landing. Before TO, the auto brake is armed by pressing the
- alternate braking, MAximum P/B on the AUTO/BRaKe control panel. Then the
- parking/ultimate emergency braking. automatic braking will be activated by the ground spoilers extension
The normal braking system is used to decrease the speed of the aircraft command from the Flight Controls Primary Computers (FCPCs). The
when it moves on the ground and to stop the rotation of the MLG wheels MAX mode gives the maximum available braking without delay and
before L/G retraction. The normal braking system has an automatic or should be selected only for TO. Two automatic braking modes are
manual mode of braking operation, which automatically gives an available during a, LOw and MEDium landing. Pressing the related
Anti-Skid (A/SKID) protection for individual wheels. In manual mode, P/B on the AUTO/BRK makes the selection control panel. Activation
a differential braking is possible according to the left and right brake of the auto brake is started after deployment order of the ground
pedals position. The Braking and Steering Control Unit (BSCU) computes spoilers from the FCPC. When the auto brake is activated, the normal
the A/SKID protection and compares the speed of each individual MLG braking is working the same way as in manual control but the braking
wheel with the actual aircraft speed. Setting the Anti/SKID & Nose/Wheel inputs are generated according to the selected deceleration. The auto
SteeRinG switch to the ON position prepares the BSCU for normal brakes brake will be disarmed if at least one brake pedal is deflected over a
operation. The normal braking system is electrically controlled and defined threshold or by selecting change or loss of arming conditions.
hydraulically operated by the green hydraulic power.
IN FLIGHT BRAKING
MANUAL MODE
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Before the MLG start to move during retraction sequence, the braking
In manual mode, the aircraft on ground, with the braking pedals is automatically activated during few seconds to stop the rotation of
operating, the related braking inputs are sent to the BSCU, which the MLG wheels. The in flight braking is controlled by the BSCU
energizes the normal selector valve to connect the green hydraulic using the normal brake system. At the end of the gear retraction, the
power to the system. A pressure switch measures the hydraulic NLG wheels rotation is stopped by mechanical brake pads.
pressure in the system and supplies the data to the BSCU. The
automatic selector, operated by the hydraulic pressure, lets the green
system supply the normal brakes and cuts the blue hydraulic pressure.
When both hydraulic systems are available, by its internal design, the
automatic selector gives priority to the green system. The servo valve,
controlled by the BSCU, modulates the hydraulic pressure sent to the

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NORMAL BRAKING - MANUAL MODE ... IN FLIGHT BRAKING

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blue pressure triple indicator. The pressure given by the brake
ALTERNATE BRAKING accumulators is sufficient to give a minimum of 7 full applications of
the brake pedals. When the alternate braking without A/SKID is used,
The alternate braking system is a hydro mechanical braking system. It is
the brake pressure has to be limited by the pilot to avoid wheel locking.
manually operated to decrease the speed of the aircraft when it moves
With the aircraft in flight (LGCIU signal) and a low blue hydraulic
on the ground. The alternate braking system automatically takes over if
system pressure the shut-off valve, isolates the supply between the
a failure occurs in the normal braking system or in case of green hydraulic
accumulators and the automatic selector to avoid depressurization of
system low pressure. It can operate with A/SKID or without A/SKID.
the brake accumulators due to internal leaks within the alternate
The alternate braking system is controlled by the auxiliary low-pressure
braking system.
distribution and hydraulically operated by the blue hydraulic power.
WITH ANTI-SKID
The BSCU controls only the A/SKID function in the alternate braking
system when the normal braking system is not available. The BSCU
de-energizes the normal selector valve. The AUTO brake is lost. The
automatic selector valve operates and lets blue system pressure go
into the alternate braking system. Control of the alternate braking
system is achieved by the pedals only, through the auxiliary low
pressure distribution control system. The blue pressure is regulated
via the dual valve. The BSCU sends A/SKID closing signals to the
alternate servo valve. The pressure delivered to the left hand and right
hand brakes as well as the blue accumulator pressure are indicated on
the blue pressure triple indicator.
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WITHOUT ANTI-SKID
Alternate braking without A/SKID becomes automatically active when
the A/SKID function is lost due to BSCU failure or if the blue
hydraulic power is not available and the system is powered by the
brake accumulators only. The pedals only achieve the control of the
alternate braking system through the auxiliary low-pressure distribution
control system. The blue pressure is regulated via the dual valve.
When the A/SKID function is lost, the alternate servo valves are left
fully open. The pressure delivered to the left hand and right hand
brakes as well as the blue accumulator pressure are indicated on the

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ALTERNATE BRAKING - WITH ANTI-SKID & WITHOUT ANTI-SKID

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PARKING/ULTIMATE EMERGENCY BRAKING
The parking/ultimate emergency braking system is an electro-hydraulic
system. Its function is to prevent movement of the aircraft when it is
parked. This system is electrically controlled and hydraulically operated
by the blue hydraulic power or by the blue pressure brake accumulators.
The parking/ultimate emergency braking system can also be used in an
emergency braking mode to stop the aircraft when no other braking mode
is available. When the PARKing BRK handle is set to ON, the parking
brake control valve is activated and connects the blue pressure to the
system. The dual shuttle valve, operated by the hydraulic pressure,
connects the blue pressure to the fully opened servo valves and closes
the supply downstream of the dual valve to isolate the brake pedals. The
park brake control valve sends a signal to the BSCU to isolate the other
braking systems. When the PARK BRK handle is set to OFF the parking
brake control valve cuts the blue pressure, the dual shuttle valve re-opens
the hydraulic supply from the dual valve. The triple pressure indicator
shows the available pressure from the brake accumulators. It also shows
the pressure applied on the MLG brakes. This pressure is limited by the
system to 2.580 psi. The accumulators have sufficient capacity to hold
the brakes on for a minimum time of twelve hours.
F4M09361 - F1LT1TU - FM32P8000000001

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PARKING/ULTIMATE EMERGENCY BRAKING

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32 LANDING GEAR SYSTEM PRESENTATION (1)

STEERING
The nose wheel steering system is used to change the direction of the
aircraft when it moves on the ground with engine power. It is electrically
controlled by the BSCU and hydraulically operated by the green hydraulic
power. The BSCU activates the nose wheel steering system by opening
the selector valve as soon as all the following specified conditions are
available:
- the aircraft speed is below 100 kts,
- one MASTER lever "ON", ojo
- the shock absorbers are compressed,
- the towing lever is in the normal position,
- the green hydraulic pressure is normal,
- the A/SKID & N/W STRG switch is set to ON.
The green hydraulic pressure supplies the system through the swivel
selector valve when the NLG is fully downlocked. The servo valve
controls the hydraulic pressure to the steering actuators depending on the
BSCU steering inputs. Two independent Rotary Variable Differential
Transducers (RVDTs) send the angular position of the nose wheels to
the BSCU. The BSCU transmits data to the ECAM, monitors the system
components and transmits the data to the Central Maintenance Computer
(CMC). A lever on the electrical de-activation box can be set in the towing
F4M09361 - F1LT1TU - FM32P8000000001

position. This cancels all the steering outputs from the BSCU to the
steering system and prevents damage during towing.

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STEERING

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32 LANDING GEAR SYSTEM PRESENTATION (1)

BRAKE TEMPERATURE AND COOLING (OPTION)
Each brake pack assembly has a temperature sensor connected to a Brake
Temperature Monitoring Unit (BTMU). The BTMU sends data to the
BSCU. Brakes temperature data and warnings are displayed on the ECAM
WHEEL page and on the BRK FAN P/BSW. An electrical fan assembly
installed on the wheel axle and manually controlled from the cockpit can
cool down the brake pack on demand.
F4M09361 - F1LT1TU - FM32P8000000001

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BRAKE TEMPERATURE AND COOLING (OPTION)

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32 LANDING GEAR SYSTEM PRESENTATION (1)

TIRE PRESSURE INDICATING SYSTEM (OPTION)
The TPIS includes an electronic pressure sensor on each wheel and a
Tire Pressure Indicating Computer (TPIC). The TPIC controls and
monitors the operation of the system and sends data to the ECAM.
F4M09361 - F1LT1TU - FM32P8000000001

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TIRE PRESSURE INDICATING SYSTEM (OPTION)

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32 LANDING GEAR SYSTEM PRESENTATION (1)

CONTROL AND INDICATING
This section will highlight the control panels and indications for the
landing gear system.
LANDING GEAR/BRAKES
The landing gear system has various control panels and indications
located in the cockpit:
- the L/G control lever,
- the LDG GEAR GRaViTY EXTeNsion panel and,
- the L/G panel.
The L/G panel includes:
- the LDG GEAR position indication panel,
- the AUTO/BRK mode selection,
- the BRK FAN P/B,
- the A/SKD & N/W STRG switch,
- the triple pressure indicator for brake accumulator pressure and
alternate/parking brake pressure.
The ECAM WHEEL page displays indications for the landing gear
system.
F4M09361 - F1LT1TU - FM32P8000000001

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CONTROL AND INDICATING - LANDING GEAR/BRAKES

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CONTROL AND INDICATING (continued)
INDICATOR, PARKING BRAKE HANDLE, RUDDER
PEDALS
The landing gear system also has in the cockpit:
- the parking brake handle,
- the rudder/brake pedals.
F4M09361 - F1LT1TU - FM32P8000000001

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CONTROL AND INDICATING - INDICATOR, PARKING BRAKE HANDLE, RUDDER PEDALS

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32 LANDING GEAR SYSTEM PRESENTATION (1)

CONTROL AND INDICATING (continued)
NOSE WHEEL STEERING
The nose wheel steering control is done through:
- rudder/steering pedals,
- nose wheel steering hand wheels.
F4M09361 - F1LT1TU - FM32P8000000001

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F4M09361 - F1LT1TU - FM32P8000000001

CONTROL AND INDICATING - NOSE WHEEL STEERING

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32 LANDING GEAR SYSTEM PRESENTATION (1)

COMPONENT LOCATION
The LGCIU, the BSCU and the TPIC are located in the avionics
compartment.
F4M09361 - F1LT1TU - FM32P8000000001

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COMPONENT LOCATION

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32 LANDING GEAR SYSTEM PRESENTATION (1)

MAINTENANCE/TEST FACILITIES
Each L/G computer has a BITE which tests, manages and records failures
to help the maintenance operations.
F4M09361 - F1LT1TU - FM32P8000000001

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MAINTENANCE/TEST FACILITIES

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32 LANDING GEAR SYSTEM PRESENTATION (1)

SAFETY PRECAUTIONS
When working on the L/G system, you must obey all the AMM safety
procedures. This will prevent injury to persons and/or damage to the
aircraft. The main safety precautions relative to the L/G system are:
- make sure that all circuits are isolated during any maintenance task.
Unwanted electrical or hydraulic power can be dangerous,
- make sure that the travel ranges of the L/G and doors are clear.
Movement of the L/G and doors can cause injury and/or damage,
- make sure that the wheel chocks are in position and the L/G ground
safety locks are installed. This prevents unwanted movement of the
aircraft or L/G,
- let the brakes and the wheels become cool before going near the L/G.
Do not apply a liquid or gas fire extinguisher directly on a hot wheel or
brake unit. This could cause an explosion,
- deflate the tire before removing the wheel. This prevents a possible
explosion,
- before removal or installation of a component, make sure that a man
can hold it because some components are heavy. If one falls, it can cause
injury to persons and damage to equipment,
- during L/G servicing, do not let high pressure gas get in contact with
the skin. Gas bubbles in the blood can kill a man,
F4M09361 - F1LT1TU - FM32P8000000001

- during work near the wheel brakes, use safety glasses and a mask.
Carbon brake dust can cause irritation to the eyes or lungs.

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SAFETY PRECAUTIONS

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LANDING GEAR SYSTEM LINE MAINTENANCE BRIEFING (2)

SYSTEM OVERVIEW
MAIN LANDING GEAR (MLG)
Each Main Landing Gear (MLG), which retracts inboard into its wheel
bay in the fuselage and the wing, includes these main parts:
- a side stay assembly,
- a MLG leg assembly,
- a bogie alignment pitch trimmer,
- a bogie beam assembly.
The MLG is hydraulically operated during the normal
extension/retraction sequence.
The MLG leg includes a shortening mechanism, a bogie pitch trimmer
and an oleo-pneumatic shock absorber. The shock absorber absorbs
the taxi, TO and landing loads. The shock absorber is a capsule type
that includes a sliding tube. It is an oleo-pneumatic unit that is installed
in the main fitting.
F4M09361 - F1LT1TU - FM32B1000000001

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SYSTEM OVERVIEW - MAIN LANDING GEAR (MLG)

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LANDING GEAR SYSTEM LINE MAINTENANCE BRIEFING (2)

SYSTEM OVERVIEW (continued)
MLG SIDE STAY ASSEMBLY
A two-piece side stay assembly holds the MLG in the extended
position. The lock stay is the mechanical down lock for the MLG. A
lock stay keeps the side stay assembly stable in the locked down
position. The lock stay is the mechanical down lock for the MLG. A
ground lock pin has to be installed through the links of the lock stay,
when they are in the over center position, to ensure safety precautions.
F4M09361 - F1LT1TU - FM32B1000000001

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SYSTEM OVERVIEW - MLG SIDE STAY ASSEMBLY

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LANDING GEAR SYSTEM LINE MAINTENANCE BRIEFING (2)

SYSTEM OVERVIEW (continued)
MLG BOGIE ALIGNMENT PITCH TRIMMER
The pitch trimmer is installed between the main fitting and the upper
links. A set of articulated links, two upper and one lower, connects
the main fitting to the front of the bogie beam. The green hydraulic
system continuously supplies pressure to the pitch trimmer, which
maintains the required geometry of the links during the retraction
sequence, TO, and landing phases.
F4M09361 - F1LT1TU - FM32B1000000001

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SYSTEM OVERVIEW - MLG BOGIE ALIGNMENT PITCH TRIMMER

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LANDING GEAR SYSTEM LINE MAINTENANCE BRIEFING (2)

SYSTEM OVERVIEW (continued)
MLG SHORTENING MECHANISM
During the retraction the shortening mechanism decreases the overall
length of the MLG to let the gears go into the available space in the
bays. The shortening mechanism includes a turnbuckle link connected
on one end to the airframe wing and a system of mechanical links that
is attached to the shock absorber. The MLG movement operates the
shortening mechanism during retraction or extension.
F4M09361 - F1LT1TU - FM32B1000000001

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SYSTEM OVERVIEW - MLG SHORTENING MECHANISM

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LANDING GEAR SYSTEM LINE MAINTENANCE BRIEFING (2)

SYSTEM OVERVIEW (continued)
MLG DOORS
Three doors close each MLG bay. They follow the shape of the belly
fairing and protect the equipment in the bay from the airflow during
flight. The MLG doors are hydraulically operated. Each main door is
hinged at the keel beam and closes outboard. The fairing door is
attached to the MLG leg and operates with it. The hinged door is
connected to the MLG leg through an adjustable rod. When the main
gear operates, the rod operates to move the hinged door. A lock collar
can be installed on each door actuator when the aircraft is on the
ground to prevent closure.
F4M09361 - F1LT1TU - FM32B1000000001

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SYSTEM OVERVIEW - MLG DOORS

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LANDING GEAR SYSTEM LINE MAINTENANCE BRIEFING (2)

SYSTEM OVERVIEW (continued)
CENTERLINE LANDING GEAR (CLG)
The CLG is designed to decrease the runway loading. It absorbs loads
that occur during taxiing and TO. The CLG is installed on the rear
bulkhead of the MLG bay and retracts forward into the CLG bay.
The CLG assembly is installed on the rear bulkhead of the MLG bay
and retracts forward into the CLG bay. The CLG leg includes a main
fitting and a shock absorber. It is the main part of the CLG.
The shock absorber decreases the TO and taxing loads transmitted to
the aircraft structure. The shock absorber is installed on the main
fitting. It is a 2 stage oleo-pneumatic units including a sliding tube.
The loads are transmitted to the hydraulic fluid and nitrogen gas in
the shock absorber when it compresses.
The down lock assembly mechanism is entirely contained on the drag
stay and functions by locking the drag stay central pivot by means of
over center lock links. A ground lock pin can be installed in the center
pivot point of the lock stay when the CLG is down locked.
F4M09361 - F1LT1TU - FM32B1000000001

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SYSTEM OVERVIEW - CENTERLINE LANDING GEAR (CLG)

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LANDING GEAR SYSTEM LINE MAINTENANCE BRIEFING (2)

SYSTEM OVERVIEW (continued)
CLG DOORS
Four doors and one fairing door close the centerline gear bay. There
are:
- two hydraulically operated forward doors,
- two mechanically operated hinged doors,
- a fixed fairing door on the centerline gear leg.
A lock collar can be installed on each door actuator when the aircraft
is on the ground to prevent closure.
F4M09361 - F1LT1TU - FM32B1000000001

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SYSTEM OVERVIEW - CLG DOORS

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LANDING GEAR SYSTEM LINE MAINTENANCE BRIEFING (2)

SYSTEM OVERVIEW (continued)
NLG
Each NLG, which retracts forward into the NLG bay, includes these
main parts:
- a lock stay assembly,
- a NLG leg assembly,
- steering actuators.
The MLG is hydraulically operated during the normal
extension/retraction sequence.
The L/G leg has a main fitting with a sliding tube assembly that
includes the axle and a shock absorber with a wheel steering assembly.
The nose wheels are steered by twin, double acting hydraulic actuators,
which pivot on attachments on the main fitting.
F4M09361 - F1LT1TU - FM32B1000000001

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SYSTEM OVERVIEW - NLG

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LANDING GEAR SYSTEM LINE MAINTENANCE BRIEFING (2)

SYSTEM OVERVIEW (continued)
NLG LOCK STAY ASSEMBLY
The lock stay is installed between the main fitting and the center pivot
point of the drag stay. It has an upper link and a lower link. The lock
stay holds the drag stay in a straight configuration when the NLG is
extended. A ground lock pin can be installed in the center pivot point
of the lock stay when the NLG is down locked.
F4M09361 - F1LT1TU - FM32B1000000001

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SYSTEM OVERVIEW - NLG LOCK STAY ASSEMBLY

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LANDING GEAR SYSTEM LINE MAINTENANCE BRIEFING (2)

SYSTEM OVERVIEW (continued)
NLG DOORS
A lock collar can be installed on each door actuator when the aircraft
is on the ground to prevent closure. Four doors and a fixed fairing
close the NLG bay. The two forward doors are hydraulically operated.
Each door has hinges at the side of the NLG bay and closes inward
at the front of the bay. The two aft doors and the fixed fairing are
mechanically operated. Each aft door has hinges at its outer edge.
Adjustable rods connect the rear doors to the NLG leg. The fixed
fairing is installed at the rear of the NLG leg.
F4M09361 - F1LT1TU - FM32B1000000001

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SYSTEM OVERVIEW - NLG DOORS

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LANDING GEAR SYSTEM LINE MAINTENANCE BRIEFING (2)

SYSTEM OVERVIEW (continued)
NORMAL BRAKING MANUAL MODE
In manual mode, the aircraft on ground, with the braking pedals
operating, the related braking inputs are sent to the BSCU, which
energizes the normal selector valve to connect the green hydraulic
power to the system. A pressure switch measures the hydraulic
pressure in the system and supplies the data to the BSCU. The
automatic selector, operated by the hydraulic pressure, lets the green
system supply the normal brakes and cuts the blue hydraulic pressure.
When both hydraulic systems are available, by its internal design, the
automatic selector gives priority to the green system. The servo valve,
controlled by the BSCU, modulates the hydraulic pressure sent to the
brakes according to the pedals demand and the A/SKID protection.
Wheel rotation speed and braking pressure values are fed back to the
BSCU for braking and A/SKID computation. The BSCU sends data
to the WHEEL page.
F4M09361 - F1LT1TU - FM32B1000000001

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F4M09361 - F1LT1TU - FM32B1000000001

SYSTEM OVERVIEW - NORMAL BRAKING MANUAL MODE

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LANDING GEAR SYSTEM LINE MAINTENANCE BRIEFING (2)

SYSTEM OVERVIEW (continued)
ALTERNATE BRAKING
The alternate braking system is a hydro mechanical braking system.
It is manually operated to decrease the speed of the aircraft when it
moves on the ground. The alternate braking system automatically
takes over if a failure occurs in the normal braking system or in case
of green hydraulic system low pressure. It can operate with A/SKID
or without A/SKID. The alternate braking system is controlled by the
auxiliary low-pressure distribution and hydraulically operated by the
blue hydraulic power.
F4M09361 - F1LT1TU - FM32B1000000001

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F4M09361 - F1LT1TU - FM32B1000000001

SYSTEM OVERVIEW - ALTERNATE BRAKING

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LANDING GEAR SYSTEM LINE MAINTENANCE BRIEFING (2)

SYSTEM OVERVIEW (continued)
PARKING/ULTIMATE EMERGENCY BRAKING
The parking/ultimate emergency braking system is an electro-hydraulic
system. Its function is to prevent movement of the aircraft when it is
parked. This system is electrically controlled and hydraulically
operated by the blue hydraulic power or by the blue pressure brake
accumulators. The parking/ultimate emergency braking system can
also be used in an emergency braking mode to stop the aircraft when
no other braking mode is available. When the PARK BRK handle is
set to ON, the parking brake control valve is activated and connects
the blue pressure to the system. The dual shuttle valve, operated by
the hydraulic pressure, connects the blue pressure to the fully opened
servo valves and closes the supply downstream of the dual valve to
isolate the brake pedals. The park brake control valve sends a signal
to the BSCU to isolate the other braking systems. When the PARK
BRK handle is set to OFF the parking brake control valve cuts the
blue pressure, the dual shuttle valve re-opens the hydraulic supply
from the dual valve. The triple pressure indicator shows the available
pressure from the brake accumulators. It also shows the pressure
applied on the MLG brakes. This pressure is limited by the system to
2.580 psi. The accumulators have sufficient capacity to hold the brakes
F4M09361 - F1LT1TU - FM32B1000000001

on for a minimum time of twelve hours.

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SYSTEM OVERVIEW - PARKING/ULTIMATE EMERGENCY BRAKING

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LANDING GEAR SYSTEM LINE MAINTENANCE BRIEFING (2)

SYSTEM OVERVIEW (continued)
SAFETY PRECAUTIONS
When working on the L/G system, you must obey all the AMM safety
procedures. This will prevent injury to persons and/or damage to the
aircraft. The main safety precautions relative to the L/G system are:
- make sure that all circuits are isolated during any maintenance task.
Unwanted electrical or hydraulic power can be dangerous,
- make sure that the travel ranges of the L/G and doors are clear.
Movement of the L/G and doors can cause injury and/or damage,
- make sure that the wheel chocks are in position and the L/G ground
safety locks are installed. This prevents unwanted movement of the
aircraft or L/G,
- let the brakes and the wheels become cool before going near the
L/G. Do not apply a liquid or gas fire extinguisher directly on a hot
wheel or brake unit. This could cause an explosion,
- deflate the tire before removing the wheel. This prevents a possible
explosion,
- before removal or installation of a component, make sure that a man
can hold it because some components are heavy. If one falls, it can
cause injury to persons and damage to equipment,
- during L/G servicing, do not let high pressure gas get in contact with
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the skin. Gas bubbles in the blood can kill a man,

- during work near the wheel brakes, use safety glasses and a mask.
Carbon brake dust can cause irritation to the eyes or lungs.

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SYSTEM OVERVIEW - SAFETY PRECAUTIONS

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MAINTENANCE
INSTALLATION OF THE SAFETY DEVICES ON THE
L/G

WARNING: INSTALL ALL SAFETY DEVICES AND WARNING

NOTICES BEFORE STARTING ANY
MAINTENANCE TASK ON OR NEAR THE L/G, THE
L/G DOORS, OR THE FLIGHT CONTROLS. USE
SOLVENTS AND CLEANING AGENTS IN
WELL-VENTILATED AREAS. MAKE SURE THAT
THE WHEEL CHOCKS ARE IN POSITION,
MOVEMENTS OF THE A/C COULD BE
DANGEROUS.
Install the ground safety lock pins in order to secure the down lock
mechanisms. If no other hydraulic servicing tasks have to be
completed, the area can be closed. All tools, test and support used
during this procedure have to be removed.
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MAINTENANCE - INSTALLATION OF THE SAFETY DEVICES ON THE L/G

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LANDING GEAR SYSTEM LINE MAINTENANCE BRIEFING (2)

MAINTENANCE (continued)
INSTALLATION OF THE SAFETY DEVICES ON THE
L/G DOORS
After door ground opening and before starting maintenance tasks
inside the L/G bay, the doors must be secured by fitting safety sleeves
on the door actuators. Different safety precautions have to be carried
out.
The doors are secured by installing the safety collar on each hydraulic
actuator. If no other hydraulic servicing tasks have to be completed,
the area can be closed. All tools, test and support used during this
procedure have to be removed.
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MAINTENANCE - INSTALLATION OF THE SAFETY DEVICES ON THE L/G DOORS

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MAINTENANCE (continued)
L/G DOORS GROUND OPENING
Make sure that the L/G lever agrees with the position of the L/G and
the free-fall extension switch is in the OFF position. Make sure that
the area is clear and the doors can be opened without any obstruction.
For the MLG and CLG, open the access panel located FWD of the
MLG. Pull the ground door-opening handle downwards to open the
door uplocks. Secure the handle with the safety pin and install the
safety devices on the MLG door actuators.
The NLG ground door-opening handle is installed on the aft bulkhead
of the NLG bay. Pull the ground door-opening handle downwards to
open the NLG door uplocks. Secure the handle with the safety pin
and install the safety devices on the NLG door actuators.
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MAINTENANCE - L/G DOORS GROUND OPENING

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MAINTENANCE - L/G DOORS GROUND OPENING

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MAINTENANCE - L/G DOORS GROUND OPENING

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MAINTENANCE (continued)
L/G DOORS GROUND CLOSING
Pressurize the green hydraulic system. Remove the safety devices
from the door actuators.
Push the ground door-opening handle upward to close the doors,
making sure that the uplocks engage. Secure the handle with the safety
pin and close the access panel. De-pressurize the green hydraulic
system. Remove the ground support equipment, special tooling, access
platforms and all warning notices. Make sure that the MLG
maintenance doors are closed before dispatch.
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MAINTENANCE - L/G DOORS GROUND CLOSING

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MAINTENANCE - L/G DOORS GROUND CLOSING

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LANDING GEAR SYSTEM LINE MAINTENANCE BRIEFING (2)

MAINTENANCE (continued)
TYRE PRESSURE CHECK
Make sure that each tire is cold before you measure its inflation
pressure.

NOTE: A tire is cold after approximately 3 hours since its previous

operation.
These pressures apply for loaded tires. You must obey the instructions
given by the AMM table 32-41-00 when you measure the tire
pressures: If there is a large temperature decrease (25 deg C) between
the departure and the destination airports, the tire given pressures must
be adjusted (Ref. TASK 12-14-32-614-801).
When the tires are still hot if you think that a tire has a low pressure,
do a pressure check of the tires on the same landing gear and make a
record of the tire pressures:
- identify the highest pressure that you recorded,
- if the pressure of a tire is less than 90% of the highest tire pressure
that you recorded, inflate that tire to the highest recorded pressure,
- make a record in the aircraft technical log.

CAUTION: YOU MUST NOT DECREASE THE PRESSURE OF

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A HOT TIRE. THIS PREVENTS AN INCORRECT

LOW PRESSURE WHEN THE TIRE IS COLD.

NOTE: It is possible that the tire pressure can be higher than the
maximum nominal value.

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MAINTENANCE - TYRE PRESSURE CHECK

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LANDING GEAR SYSTEM LINE MAINTENANCE BRIEFING (2)

MAINTENANCE (continued)
CHECK BRAKE PACK WEAR INDICATORS

WARNING: OBEY THE L/G GENERAL WARNINGS AND

SAFETY PROCEDURES.
LET THE BRAKES AND WHEELS COOL DOWN
BEFORE WORKING ON THEM.
DO NOT USE LIQUID OR GAS FIRE
EXTINGUISHERS DIRECTLY ON A HOT WHEEL
OR BRAKE.
Make sure that the wheel chocks are in position. Set the PARK BRK
to ON and check the accumulator pressure on the blue system triple
gauge indicator. If there is at least one brake wear indicator installed
and if the indicator is within limits, the brake is serviceable. If there
is no wear indicator installed, the brake must be de-activated until it
can be replaced.
Check each MLG brake wear indicator pin with the parking brake
applied. If the brake wear indicator pin is flush with the brake-housing
bracket, the brake must be replaced. If no other hydraulic servicing
tasks have to be completed, the area can be closed. All tools, test and
support used during this procedure have to be removed.
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MAINTENANCE - CHECK BRAKE PACK WEAR INDICATORS

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MAINTENANCE - CHECK BRAKE PACK WEAR INDICATORS

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- fully push in the related brake pedals and hold them in this position,
MAINTENANCE (continued) - make sure that there are no leaks on the green disconnected
hydraulic-pressure line,
MLG WHEEL BRAKE DEACTIVATION PROCEDURE
- release the brake pedals,
- depressurize the green hydraulic system,
WARNING: MAKE SURE THAT THE SAFETY DEVICES AND
- fully push in the related brake pedals and hold them in this position,
THE WARNING NOTICES ARE IN POSITION
- make sure that there are no leaks on the blue disconnected
BEFORE YOU START A TASK ON OR NEAR:
hydraulic-pressure line,
- THE FLIGHT CONTROLS,
- release the brake pedals,
- THE FLIGHT CONTROL SURFACES,
On the EWD, make sure that the caution BRAKES RELEASED
- THE LANDING GEAR AND THE RELATED
BRAKE * RELEASED does not show. (* = wheel No.). Do the EIS
DOORS,
stop procedure and de-energize the aircraft electrical circuits.
- COMPONENTS THAT MOVE.
MOVEMENT OF COMPONENTS CAN KILL OR
INJURE PERSONS.
MAKE SURE THAT THE GROUND SAFETY-LOCKS
ARE CORRECTLY INSTALLED ON THE LANDING
GEAR. THIS PREVENTS UNWANTED MOVEMENT
OF THE LANDING GEAR.
Make sure that the green and blue hydraulic systems are depressurized.
Set the PARK BRK to the OFF position.
Disconnect the half coupling, and use a clean miscellaneous and
cleaning agents to clean it.
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Safety the half coupling to the brake hose fairlead with the lockwire.
Tighten the lockwire and twist to lock it. Put the blanking cap on the
fixed half coupling. Remove the blanking screw and the washer from
the applicable bleed valve. Use a miscellaneous at the applicable bleed
valve to catch the hydraulic fluid. Loosen the bleed valve to release
the residual hydraulic pressure from the isolated brake. Tighten the
bleed valve and install the washer and the blanking screw. Tighten
the blanking screw.
Energize the aircraft electrical circuits. Start the EIS. Pressurize the
green hydraulic system. On the right center instrument panel, set the
A/SKID switch to ON. Then do the following test:
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MAINTENANCE - MLG WHEEL BRAKE DEACTIVATION PROCEDURE

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MAINTENANCE (continued)
ACTIVATING THE MLG SEAL CHANGEOVER VALVE
Obey the L/G general warnings and safety precautions. Make sure
that the green hydraulic system is depressurized and the wheel well
doors are closed. Open and safety tag the related C/Bs. Make sure
that the MLG safety devices are installed and that the wheel chocks
are in place. Place a warning notice in the cockpit to prevent L/G
operation. Also place a warning notice not to open the MLG door (if
the door is opened while the leg is deflated, the door will touch the
ground). Check the access plate to make sure that the spare seal
changeover valve has not been activated. If the message "Spare Seal
Energized" is visible, the seal has been activated and the shock
absorber seals must be replaced.
Remove the access plate, then fully depressurize the shock absorber
to get access to the spare seal changeover valve.
Turn the spare seal changeover valve fully clockwise and safety this
position.
Pressurize the shock absorber, then clean the chromed part of the strut
with a clean lint-free cloth and approved cleaning agents.
Check/replenish the fluid contents at the next opportunity. Install the
access plate again to display the message "Spare Seal Energized".
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Remove the ground support equipment, special tooling, and access

platforms. Remove all warning notices and close C/Bs.

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LANDING GEAR SYSTEM LINE MAINTENANCE BRIEFING (2)

MAINTENANCE (continued)
ACTIVATING THE NLG SEAL CHANGEOVER VALVE
Place a warning notice in the cockpit to prevent L/G operation and
make sure that the wheel chocks are in place. Make sure that the green
hydraulic system is depressurized. Open the NLG doors and fit the
NLG safety devices on the door actuator. Open and safety tag the
related C/Bs.
Check that the colored band of the spare seal changeover valve is in
view. This confirms that the valve has not been already activated. If
it has been activated, the NLG shock absorber seals have to be
replaced. Remove the cap screw. Turn the seal changeover valve
counter clockwise until it is closed. The colored band will be out of
view. Install the cap screw and safety the cap screw with a lock wire.
Clean the chromed part of the NLG shock strut with a clean lint-free
cloth and approved cleaning agents. Check/replenish the fluid contents
of the NLG shock strut at the next opportunity. Remove the ground
support equipment, special tooling, and access platforms. Remove all
warning notices. Close C/Bs.
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LANDING GEAR SYSTEM LINE MAINTENANCE BRIEFING (2)

MAINTENANCE (continued)
ACTIVATING THE CLG SEAL CHANGEOVER VALVE
Place a warning notice in the cockpit to prevent L/G operation. Make
sure that the green hydraulic system is depressurized. Open the CLG
doors and fit the CLG safety devices on the door actuator. Open and
safety tag the related C/Bs.
Check that the colored band of the spare seal changeover valve is in
view. This confirms that the valve has not been already activated. If
it has been activated, the CLG shock absorber has to be replaced.
Remove the cap screw. Turn the seal changeover valve clockwise
until it is closed. The colored band will be out of view. Install the cap
screw and safety the cap screw with a lock wire. Clean the chromed
part of the CLG shock strut with a clean lint-free cloth and approved
cleaning agents. Check/replenish the fluid contents of the CLG shock
strut at the next opportunity. Remove the ground support equipment,
special tooling, and access platforms. Remove all warning notices.
Close C/Bs.
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LANDING GEAR SPECIAL FEATURES (3)

MLG SHOCK ABSORBER
The shock absorber absorbs the taxi, take-off and landing loads. The
shock absorber is a capsule type that includes a sliding tube. It is an
oleo-pneumatic unit that is installed in the main fitting. When it is
compressed the load is transmitted to the hydraulic fluid and gas that fill
the shock absorber. The recoil stroke is slow, which makes sure that the
aircraft does not become airborne again after it touches down on landing.
The cylinder is the part of the shock absorber that moves when the
landing, take off or taxi loads increase or decrease. Its external face has
a wear-resistant surface at the bearing interfaces. The cylinder operates
around the piston, where the compression of the gas occurs.
During the compression stroke, the cylinder moves up around the piston.
Thus the volume in the cylinder decreases. This increases the pressure
in the piston chamber. As the hydraulic fluid flows into the piston
chamber, the gas compresses to absorb the compression load.
The pressure in the piston chamber forces the hydraulic fluid to return
to the cylinder chamber. At the same time, the volume of recoil chamber
is decreased. As the cylinder (sliding tube) extends, seals against the
piston seal closed ports in the piston to decrease the flow from the recoil
chamber. Thus the recoil slows at the end of the shock absorber extension
stroke.
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MLG SHOCK ABSORBER

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LANDING GEAR SPECIAL FEATURES (3)

NLG/CLG SHOCK ABSORBER
The shock absorber is a two-chamber, oleo-pneumatic telescopic strut,
made from the main fitting and the sliding tube. The main fitting has a
first stage chamber with nitrogen gas and hydraulic fluid, with no
separation between the gas and the fluid. The sliding tube has a second
stage high-pressure gas chamber. A floating piston in the sliding tube
separates the first stage chamber from the second stage chamber.
Damping rings and fixed orifices in the upper and lower diaphragm
control the movement of the fluid between the first and second stages to
decrease the speed at which the shock absorber extends. There is also a
damping ring between the first stage chamber and the recoil chamber.
F4M09361 - F1LT1TU - FM32D1000000002

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F4M09361 - F1LT1TU - FM32D1000000002

NLG/CLG SHOCK ABSORBER

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LANDING GEAR SPECIAL FEATURES (3)

SHORTENING MECHANISM
During retraction the shortening mechanism operates to decrease the
length of the L/G. Forces are transmitted through the adjustable link to
the bellcrank lever, which pushes the connecting link to turn the upper
link. As the upper link starts to turn it breaks the overcenter lock and
draws the lower link up. This pulls the shock absorber up into the main
fitting so that the MLG can go into the bay. When the landing gear control
lever is set to DOWN position, the movement of the MLG also causes
the shortening mechanism to extend the shock absorber. When the shock
absorber is fully extended the shortening links are overcenter and transmit
shock absorber loads to the structure of the aircraft.
F4M09361 - F1LT1TU - FM32D1000000002

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F4M09361 - F1LT1TU - FM32D1000000002

SHORTENING MECHANISM

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LANDING GEAR SPECIAL FEATURES (3)

MLG PITCH TRIMMER
The retracted and extended position.
The Pitch trimmer is a hydraulically operated cylinder installed between
the main fitting and articulating links. It has a cylinder, a piston rod. The
cylinder has a bleed screw and a vent plug. The bleed screw lets you
bleed air from the pitch trimmer. Hydraulic pressure is continuously
supplied to the pitch trimmer when the Green hydraulic system is
pressurized. When there is no mechanical force on the pitch trimmer,
hydraulic pressure causes the piston rod to stay in the retracted position.
When the piston extends, free flow hydraulic fluid goes through the two
way bi-directional restrictor and the pressure relief valve to the return
line. When the external force is released from the pitch trimmer the green
hydraulic system pressure causes the piston rod to retract.
When the aircraft starts to leave the ground during a take-off, the load
on the MLG decreases. This lets the shock absorber extend and the pitch
trimmer retract. As the pitch trimmer retracts, it operates the articulating
links, which subsequently turn the bogie (front wheels up). When the
piston of the pitch trimmer gets to its external stop, the shock absorber
continues to extend, which further turns the bogie to its trim angle.
The movement of the bogie beam and the extension of the shock absorber
increase the overall length of the MLG. This lets the aircraft move through
F4M09361 - F1LT1TU - FM32D1000000002

a large angle during a take-off. During retraction of the MLG, the

shortening mechanism causes the articulating links to move the bogie
beam back to its lateral position (for entry into the MLG bay).

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 A340-200/300 TECHNICAL TRAINING MANUAL
F4M09361 - F1LT1TU - FM32D1000000002

MLG PITCH TRIMMER

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F4M09361 - F1LT1TU - FM32D1000000002

MLG PITCH TRIMMER

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F4M09361 - F1LT1TU - FM32D1000000002

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LANDING GEAR SPECIAL FEATURES (3)

SEAL CHANGEOVER VALVE
The seal changeover valve is installed in the main fitting in a manifold.
The manifold is attached to a lug on the gland housing that holds the
shock absorber gland seals. The upper bearing of the shock absorber is
installed on the external surface of the gland housing and the sliding
member. The gland housing holds the primary and secondary seals. In
normal operation of the shock absorber the primary seals are used and
the secondary seals are balanced through oil pressure on the two sides of
the seal. If the primary seal leaks, the changeover valve stops the oil
pressure to one side of the seal to operate the secondary seals.
MLG
NLG
CLG
F4M09361 - F1LT1TU - FM32D1000000002

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F4M09361 - F1LT1TU - FM32D1000000002

SEAL CHANGEOVER VALVE

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F4M09361 - F1LT1TU - FM32D1000000002

SEAL CHANGEOVER VALVE

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 A340-200/300 TECHNICAL TRAINING MANUAL
F4M09361 - F1LT1TU - FM32D1000000002

SEAL CHANGEOVER VALVE

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F4M09361 - F1LT1TU - FM32D1000000002

SEAL CHANGEOVER VALVE

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F4M09361 - F1LT1TU - FM32D1000000002

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NORMAL EXTENSION AND RETRACTION D/O (3)

ELECTRICAL SYSTEM
An hydro-electrical system controls the operation of the L/G extension
and retraction sequences. The system has two independently connected
sub-systems, identified as SYSTEM 1 and SYSTEM 2 and these are
electrically isolated from each other.
Each sub-system contains a Landing Gear Control and Interface Unit
(LGCIU) and a number of proximity sensors. The proximity sensors are
electronic position indicators and are installed on the mechanical
components of each L/Gs and doors.
Both LGCIUs are continuously electrically supplied but only one LGCIU
is active and controls the operation of the extension/retraction sequence.
An LGCIU change-over occurs when gear UP is selected or if the active
LGCIU fails. The LGCIU calculates the necessary door and gear
configuration signals. It compares them with the configuration requested
from the L/G control lever. It then sends the necessary signals to operate
the selector valves which provide fluid to all gears and doors.
The LanDinG GEAR indicator displays green triangle when the
corresponding gear is downlocked. The information is given by an
independent circuitry for each gear. The signals go through LGCIU 1
position. The UNLK is in red when the corresponding gear is not locked
(UP or DOWN).
F4M09361 - F1LT1TU - FM32D2000000004

The The LGCIU controls the operation of the baulk solenoid in the L/G
control lever. After take-off, gear and bogie signals are sent to the
LGCIUs. Each LGCIU sends a signal to release the baulk. The baulk
solenoid stops the movement of the lever to the UP position:
- when the A/C is on the ground,
- when the L/G is not in the correct configuration for retraction.
The L/G system is equipped with an isolation safety valve. The isolation
safety valve is de-energized closed when the A/C airspeed is more than
280 Kts. As a consequence, the L/G is isolated from the green hydraulic
system and cannot be extended.

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F4M09361 - F1LT1TU - FM32D2000000004

ELECTRICAL SYSTEM

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NORMAL EXTENSION AND RETRACTION D/O (3)

L/G EXTENSION AND RETRACTION SEQUENCES
The normal L/G extension and retraction sequences will be described.
GENERAL
The L/G operational sequence is controlled by the LGCIUs in response
to information received from the proximity sensors. These signals are
used to establish the current configuration of the L/G, either locked
down or locked up, and the configuration of the door, either closed
or fully open.
The configuration of the shock absorbers and bogie beams are also
monitored. It enables the release of the L/G selector baulk during gear
retraction or extension.
L/G LOCKED DOWN, DOORS CLOSED
For clarity purpose, the schematic sequence only displays the R/H
gear and door operation (the principle is similar for the other gears
and doors). The LGCIUs take into account the L/G lever position and
the gears and doors position provided by the proximity sensors.
Here, the sequence starts with the LGCIU 2 active before a lever UP
selection. Note: The Nose Wheel Steering (NWS) is hydraulically
supplied by the door close circuit and 2 hydraulic fuses (which close
in case of leak) are on the door open and close circuits.
F4M09361 - F1LT1TU - FM32D2000000004

When the L/G lever is in the DOWN position, the following conditions
are maintained. The door selector valve DOOR CLOSED solenoid is
energized and the DOOR CLOSED hydraulic lines are pressurized.
All other solenoids are de-energized, and their corresponding hydraulic
lines are depressurized.
Pressure in the DOOR CLOSED lines will maintain the doors in the
closed position. The gear downlock remains in the overcentred locked
down condition.

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 A340-200/300 TECHNICAL TRAINING MANUAL
F4M09361 - F1LT1TU - FM32D2000000004

L/G EXTENSION AND RETRACTION SEQUENCES - GENERAL & L/G LOCKED DOWN, DOORS CLOSED

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NORMAL EXTENSION AND RETRACTION D/O (3)

L/G EXTENSION AND RETRACTION SEQUENCES
(continued)
L/G LOCKED DOWN, DOORS OPENING
UP selection is made. Notice that LGCIU 1 is now active. The first
step is to open the L/G doors. The door selector valve DOOR OPEN
solenoid is energized and the DOOR OPEN hydraulic lines are
pressurized.All other solenoids are de-energized, and their
corresponding hydraulic lines are depressurized.
The pressure in the DOOR OPEN hydraulic lines will release the door
uplocks, and cause the doors to open.
F4M09361 - F1LT1TU - FM32D2000000004

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F4M09361 - F1LT1TU - FM32D2000000004

L/G EXTENSION AND RETRACTION SEQUENCES - L/G LOCKED DOWN, DOORS OPENING

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NORMAL EXTENSION AND RETRACTION D/O (3)

L/G EXTENSION AND RETRACTION SEQUENCES
(continued)
L/G RETRACTING, DOORS OPEN
The gear selector valve GEAR UP solenoid is energized, and the
GEAR UP lines are pressurized .The landing gears are starting to
retract. At this step, the delay valve retards the gear actuator from
being supplied. This is to permit the gear downlock actuator to retract
and thus to fold the side stay easily.
The door selector valve DOOR OPEN solenoid remains energized
and the DOOR OPEN hydraulic lines are still pressurized.
All other solenoids are de-energized, and their corresponding hydraulic
lines are depressurized.
The pressure in the DOOR OPEN hydraulic lines will keep the doors
in the open position.. The pressure in the GEAR UP hydraulic lines
will ensure the L/G downlocks are released. The L/G up-locks are
maintained in the unlocked open position.
F4M09361 - F1LT1TU - FM32D2000000004

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F4M09361 - F1LT1TU - FM32D2000000004

L/G EXTENSION AND RETRACTION SEQUENCES - L/G RETRACTING, DOORS OPEN

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NORMAL EXTENSION AND RETRACTION D/O (3)

L/G EXTENSION AND RETRACTION SEQUENCES
(continued)
DOORS OPEN, AND L/G RETRACTS
The gear selector valve GEAR UP solenoid remains energized, and
the GEAR UP lines are still pressurized. The door selector valve
DOOR OPEN solenoid remains energized and the DOOR OPEN
hydraulic lines are still pressurized. Each L/G has an uplock bearing
which contacts the operating lever of the uplock assembly. This will
cause mechanical engagement of the uplock hook.
All other solenoids are de-energized, and their corresponding hydraulic
lines are depressurized.
The pressure in the DOOR OPEN hydraulic lines will keep the doors
in the open position.
F4M09361 - F1LT1TU - FM32D2000000004

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F4M09361 - F1LT1TU - FM32D2000000004

L/G EXTENSION AND RETRACTION SEQUENCES - DOORS OPEN, AND L/G RETRACTS

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NORMAL EXTENSION AND RETRACTION D/O (3)

L/G EXTENSION AND RETRACTION SEQUENCES
(continued)
L/G LOCKED UP, DOORS CLOSING
The door selector valve DOOR CLOSE solenoid is energized, the
DOOR CLOSE hydraulic lines are pressurized and the doors move
towards the closed position. The door uplock bearing makes contact
with the operating lever of the uplock assembly. It causes a mechanical
engagement of the door uplock hook.
The gear selector valve GEAR UP solenoid remains energized, and
the GEAR UP lines remain pressurized.
All other solenoids are de-energized, and their corresponding hydraulic
lines are depressurized.
The pressure in the GEAR UP hydraulic lines will ensure the L/G
remains in the UP condition.
F4M09361 - F1LT1TU - FM32D2000000004

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 A340-200/300 TECHNICAL TRAINING MANUAL
F4M09361 - F1LT1TU - FM32D2000000004

L/G EXTENSION AND RETRACTION SEQUENCES - L/G LOCKED UP, DOORS CLOSING

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NORMAL EXTENSION AND RETRACTION D/O (3)

L/G EXTENSION AND RETRACTION SEQUENCES
(continued)
L/G LOCKED UP, DOORS CLOSED
The door selector valve DOOR CLOSE solenoid remains energized
and the DOOR CLOSE hydraulic lines remain pressurized.
All other solenoids are de-energized, and their corresponding hydraulic
lines are depressurized.
F4M09361 - F1LT1TU - FM32D2000000004

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 A340-200/300 TECHNICAL TRAINING MANUAL
F4M09361 - F1LT1TU - FM32D2000000004

L/G EXTENSION AND RETRACTION SEQUENCES - L/G LOCKED UP, DOORS CLOSED

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NORMAL EXTENSION AND RETRACTION D/O (3)

L/G EXTENSION AND RETRACTION SEQUENCES
(continued)
ABOVE 280KTS
The pressure in the DOOR CLOSE hydraulic lines keeps the doors
in the closed position. If the A/C speed exceeds 280 Kts, the green
supply is isolated by the safety valve, and only the door uplocks ensure
the doors remain in the closed position.

NOTE: The safety valve operation is possible thanks to the ADIRUs

speed signal. On the ground, if the ADIRus are not aligned,
the safety valve solenoid valve is energized OPEN by the
LGCIUs or the Electrical Ground Power availability. In
flight, above 280 knots, the safety valve solenoid is
de-energized CLOSED.
F4M09361 - F1LT1TU - FM32D2000000004

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F4M09361 - F1LT1TU - FM32D2000000004

L/G EXTENSION AND RETRACTION SEQUENCES - ABOVE 280KTS

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NORMAL EXTENSION AND RETRACTION D/O (3)

L/G EXTENSION AND RETRACTION SEQUENCES
(continued)
L/G LOCKED UP, DOORS OPENING
Below 280 knots, when a DOWN selection is made, the safety valve
solenoid is re-energized OPEN. The door selector valve DOOR OPEN
solenoid is energized and the DOOR OPEN hydraulic lines are
pressurized. All other solenoids de-energized.
All other solenoids are de-energized, and their corresponding hydraulic
lines are depressurized.
The pressure in the DOOR OPEN hydraulic lines will unlock the door
uplocks and open the doors.
F4M09361 - F1LT1TU - FM32D2000000004

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 A340-200/300 TECHNICAL TRAINING MANUAL
F4M09361 - F1LT1TU - FM32D2000000004

L/G EXTENSION AND RETRACTION SEQUENCES - L/G LOCKED UP, DOORS OPENING

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NORMAL EXTENSION AND RETRACTION D/O (3)

L/G EXTENSION AND RETRACTION SEQUENCES
(continued)
DOORS OPEN, L/G EXTENDS
Once all doors are sensed fully opened, the LGCIU carries on to extend
the gear. The gear selector valve GEAR DOWN solenoid is energized,
and the GEAR DOWN lines are pressurized.
The door selector valve DOOR OPEN solenoid remains energized
and the DOOR OPEN hydraulic line is kept pressurized.
All other solenoids are de-energized, and their corresponding hydraulic
lines are depressurized.
The pressure in the DOOR OPEN hydraulic lines keeps the doors
open.
The pressure in the GEAR DOWN lines will release the L/G uplocks
and cause the L/G actuators to extend.
F4M09361 - F1LT1TU - FM32D2000000004

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 A340-200/300 TECHNICAL TRAINING MANUAL
F4M09361 - F1LT1TU - FM32D2000000004

L/G EXTENSION AND RETRACTION SEQUENCES - DOORS OPEN, L/G EXTENDS

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NORMAL EXTENSION AND RETRACTION D/O (3)

L/G EXTENSION AND RETRACTION SEQUENCES
(continued)
L/G LOCKED DOWN, DOORS CLOSING
The door selector valve DOOR CLOSE solenoid is energized and the
DOOR CLOSE hydraulic lines are pressurized. The door uplock
bearing makes contact with the operating lever of the uplock assembly.
It causes a mechanical engagement of the door uplock hook. The gear
selector valve GEAR DOWN solenoid remains energized, and the
GEAR DOWN lines remain pressurized until the doors are fully
closed. All other solenoids de-energized.
F4M09361 - F1LT1TU - FM32D2000000004

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F4M09361 - F1LT1TU - FM32D2000000004

L/G EXTENSION AND RETRACTION SEQUENCES - L/G LOCKED DOWN, DOORS CLOSING

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NORMAL EXTENSION AND RETRACTION D/O (3)

L/G EXTENSION AND RETRACTION SEQUENCES
(continued)
L/G LOCKED DOWN
Pressure in the DOOR CLOSED lines will maintain the doors in the
closed position. The gear downlock remains in the overcentred locked
down condition. All other solenoids are de-energized, and their
corresponding hydraulic lines are depressurized.
F4M09361 - F1LT1TU - FM32D2000000004

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 A340-200/300 TECHNICAL TRAINING MANUAL
F4M09361 - F1LT1TU - FM32D2000000004

L/G EXTENSION AND RETRACTION SEQUENCES - L/G LOCKED DOWN

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 A340-200/300 TECHNICAL TRAINING MANUAL

FREE FALL EXTENSION D/O (3)

ELECTRICAL SYSTEM
The electrical actuators operate the free fall extension system. They
release the MLG and the NLG door and gear uplocks through the
mechanical system.
The A/C batteries supply 28 VDC through two hot bus bars. There are
two independent circuits between the bus bars and the free-fall actuators.
Usually the circuits are energized at the same time, but each circuit will
operate the free-fall electrical actuators (at half speed) if the other circuit
is not available.
Each circuit has a lock-toggle type switch, each switch operates a motor
in the L/G free-fall electrical actuator. A ganging bar connects the two
switches together.
It is possible to move the ganging bar away from the switches (during
maintenance) and operate the switches independently.

MLG MECHANICAL SYSTEM

In the right MLG bay a linkage connects the free-fall actuator to the
cut-out valve.
The linkage also connects, through the cut-out valve to the vent valve,
the MLG uplock and the MLG door uplock. When the output shaft of
the free-fall actuator turns, it moves the linkage, which operates the valves
F4M09361 - F1LT1TU - FM32D3000000003

and opens the door and gear uplocks.

The left MLG configuration is almost the same as the right MLG, but
does not include a cut-out valve.

NLG MECHANICAL SYSTEM

In the NLG bay, a linkage connects the free-fall actuator to the vent valve
and the NLG uplock. A flexible cable connects the free-fall actuator to
the NLG door uplock. When the output shaft of the free-fall actuator
turns, it moves the linkages and flexible cable, which operates the vent
valve and opens the door and gear uplocks.
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 A340-200/300 TECHNICAL TRAINING MANUAL
F4M09361 - F1LT1TU - FM32D3000000003

ELECTRICAL SYSTEM ... NLG MECHANICAL SYSTEM

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FREE FALL EXTENSION D/O (3)

OPERATION
-In this scenario, we assume a dual LGCIU failure.
Landing gear lever is set to down. This is to avoid nuisance messages.

CAUTION: The free fall extension system can be operated with the A/C
not electrically powered (the hot buses supply the electrical
actuators). Normally both motors are energized together and
the actuators reach full travel in approximately ten seconds.
F4M09361 - F1LT1TU - FM32D3000000003

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 A340-200/300 TECHNICAL TRAINING MANUAL
F4M09361 - F1LT1TU - FM32D3000000003

OPERATION

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FREE FALL EXTENSION D/O (3)

OPERATION (continued)
RELEASE
When the LDG GEAR free-fall switches are set to DOWN, the
electrical actuators are energized. The actuators turn the output shaft
and move the mechanical linkage to operate the hydraulic and
mechanical components in sequence as follows:
- (1) the cut-out valve operates. This isolates the whole L/G system
from the green hydraulic supply,
- (2) the vent valves operate, connecting all gear and door actuators
to the green hydraulic system return,
- (3) the door uplock boxes operate, releasing the hook,
- (4) the gear uplock boxes operate and the gear falls down by gravity.
During this sequence, the electrical actuators operate the output shaft
from the 0 degree position to the 90 degrees position.

WARNING: After a free fall landing, the first maintenance action is

to install gear safety pins and set all the ground opening
handles down.
RESET
When RESET is selected, the actuators turn back to their initial
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positions and automatically set the system back to the normal extension
and retraction mode. The actuator output shaft moves by 90 degrees
in reverse direction.
Upon completion of the reset, the hydraulic pressure is restored. Doors
are pressurized open while the L/G is retracted and then the doors
close. The switches are set to OFF after the system goes back to the
normal extension and retraction mode.

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OPERATION - RELEASE & RESET

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OPERATION - RELEASE & RESET

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OPERATION - RELEASE & RESET

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OPERATION - RELEASE & RESET

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DOOR GROUND OPENING D/O (3)

DESCRIPTION
MAIN LANDING GEAR
The MLG door ground opening control handle is accessible through
a panel located at the center fuselage, forward the MLG door. This
location gives the operator a safe position and a clear view of the door
travel. The control handle is connected, through a push-pull cable, to
a layshaft at the outboard side of MLG bay.
Each door has a door ground opening mechanism that enables door
opening for maintenance. The mechanism has these following primary
components:
- a control handle,
- a bi-stable mechanism,
- a bypass valve,
- a release mechanism in the door uplock.
The control handle has two lockable positions. When it is set to the
DOOR OPEN position, it causes the mechanical system to:
- operate the door bypass valve,
- release the door from its uplock.
The bi-stable mechanism is attached to the operating shaft of the
bypass valve. It makes sure that the bypass valve and the control
handle can only stay in the doors FULLY OPEN position or the doors
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FULLY CLOSED position.

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DESCRIPTION - MAIN LANDING GEAR

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DOOR GROUND OPENING D/O (3)

DESCRIPTION (continued)
NOSE LANDING GEAR
The NLG door ground opening handle is installed on a housing on
the aft bulkhead of the NLG bay. This location gives the operator a
safe position and a clear view of the door range of travel. The control
handle is connected, through a bell-crank and rod to the bypass valve.
It is also connected through a spindle and push-pull cable to the NLG
door uplock.
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DESCRIPTION - NOSE LANDING GEAR

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DOOR GROUND OPENING D/O (3)

DESCRIPTION (continued)
CENTERLINE LANDING GEAR
The Centerline Landing Gear (CLG) door ground opening handle is
accessible through a panel located at the forward of the CLG bay.
This location gives the operator a safe position and a clear view of
the door travel. The handle is connected through a push-pull cable,
to a bell-crank lever on the door uplock. This bell-crank lever operates
the hooks of the uplock and is connected, through a rod, to the bypass
valve located on the front of the CLG bay.
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DESCRIPTION - CENTERLINE LANDING GEAR

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DOOR GROUND OPENING D/O (3)

MAIN DOOR OPENING SCHEMATIC
As the principle is the same, the MLG door ground opening mechanism
has been chosen as an example. When the door ground opening
mechanism is used, the control handle is connected through a push-pull
cable and different components to a door uplock. During normal operation
of the extension and retraction system, the hydraulic fluid goes through
the bypass valve (between ports B and C) to the door actuator.
The initial movement of the handle causes the bypass valve to isolate the
door actuator from the door-close hydraulic line and interconnects the
two chambers of the door actuator. Further movement of the handle
operates the release mechanism in the door uplock, which lets the main
door open by gravity. The bypass valve includes a baulk device. This
device prevents movement of the door ground opening handle to the door
close position unless the green hydraulic system is pressurized.
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MAIN DOOR OPENING SCHEMATIC

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NORMAL BRAKING D/O (3)

SYSTEM ARCHITECTURE NORM BRK SELECTOR VALVE
The Normal Brake Selector Valve controls the supply of the normal
This graphic presents the entire braking system architecture. system. The valve is supplied by the green hydraulic system and
electrically controlled by the BSCU. It is set to OPEN when energized
GENERAL
and CLOSED when de-energized.
In the normal brake system, hydraulic power is supplied from the green PRESSURE SWITCH
system to actuate one set of pistons on each brake unit. The normal
braking system is electrically signaled by the Brake and Steering Control The pressure switch measures the green hydraulic pressure upstream
Unit (BSCU) and fulfills: from the normal brake selector valve and supplies data to the BSCU.
- manual braking mode via the brake pedal deflection, SERVO VALVES
- automatic braking mode (pre-set selection), The servo valves, one per braked wheel, release brake pressures as a
- in-flight braking mode (automatic braking of the main wheels during function of the pressure control orders and anti-skid orders generated
landing gear retraction), by the BSCU.
- anti-skid protection.
HYDRAULIC FUSES
DESCRIPTION The hydraulic fuses (1 per braked wheel) are located downstream
The normal braking system is composed of different components that from the normal servo valves to prevent excessive fluid loss in case
will be described. of brake line rupture. They require manual reset after activation.

BRAKE PEDAL ASSEMBLIES NORMAL BRAKE PRESSURE TRANDUCERS

The brake pedal assemblies, at each pilot position, are mechanically The normal brake pressure transducers, one per braked wheel, are
interconnected. They transmit the manual braking inputs through the located downstream from the hydraulic fuses to allow the BSCU to
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brake pedal transmitter unit to the BSCU. control and monitor the pressure delivered by the servo valves.

L/G PANEL RETURN ACCUMULATORS

The auto brake rotary selector switch provides 3 auto brake modes In addition, two return accumulators (1 per L/G) are installed on the
intended for use during landing (LO, MED and HI). return line of each normal brake manifold. They prevent pressure
surge in the return line during brake release.
BSCU
BRAKE UNIT SUPPLY
The dual channel BSCU controls and monitors the normal manual
and automatic braking system with the anti-skid protection. It converts In the normal brake system, the green hydraulic power supply actuates
data for display and warnings, does various tests and supplies one set of pistons on each brake unit.
information to the Central Maintenance System (CMS).
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SYSTEM ARCHITECTURE ... DESCRIPTION

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NORMAL BRAKING D/O (3)

MANUAL BRAKING MODE
Brake pedal deflections are converted into a voltage signal by the brake
pedal transmitter unit and transmitted to the BSCU. Following a positive
pedal deflection of more than 2 degrees, the BSCU will energize the
normal brake selector valve,
Which in turn port the fluid to the automatic selector valve. At this step,
the green system prevails over the blue one.
The BSCU regulates the pressure through the servo valves. The current
to the servo valve is proportional to the required pressure (ie.: 0A =
0press., 35mA = max. press.)
The BSCU will also provide ANTI-SKID signals to the servo valves. A
pressure transducer downstream of the normal brake fuse confirms green
pressure is available to the system. The normal brake pressure transducers
transmit signals (corresponding to the applied pressure on the brakes) to
the BSCU.
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MANUAL BRAKING MODE

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MANUAL BRAKING MODE

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MANUAL BRAKING MODE

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MANUAL BRAKING MODE

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NORMAL BRAKING D/O (3)

AUTO BRAKING MODE
When selected, the auto brake system automatically activates all the main
wheel brakes via the normal braking system. The BSCU controls the
servo valves to apply the level of braking required to decelerate the A/C.
The pilot can select one of three preset rates, via the auto push buttons
switch on the L/G instrument panel. During auto brake operation, the
anti-skid function is available. The auto brake function is armed when
the following conditions are met:
- green hydraulic pressure available,
- no BSCU failures, which prevent correct operation of auto brake,
- at least two Flight Control Primary Computers (FCPCs) available.
- at least one Air Data/Inertial Reference Unit (ADIRU) available.
Following the arming selection, the auto brake mode (Landing modes)
is activated when both the left and right L/G wheels have compressed,
and the BSCU receives two out of three ground spoiler deployed signals
from the FCPCs. The BSCU opens the normal brake selector valve, and
regulates the servo valves pressure anti-skid control. The commanded
deceleration is achieved using an auto brake program, which computes
an auto brake pressure order as a function of the required deceleration
and the actual A/C deceleration received from the ADIRUs.
The auto brake engagement is lost if auto brake is manually disarmed by
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selection at the auto brake panel, or by pressing one brake pedal above
80% or both pedals above 60%. When auto brake is engaged the green
DECEL illuminates at 80% of the required rate of deceleration. If a second
auto brake mode is selected, either before or during the operation of the
system, the second deceleration mode is selected.

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AUTO BRAKING MODE

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NORMAL BRAKING D/O (3)

IN-FLIGHT BRAKING MODE
Braking occurs automatically during the retraction of the L/G. This stops
the rotation of the MLG wheels before the L/G retracted goes into the
related bays. When the L/G selector lever is put in the UP position, the
normal brake selector valve is energized in order to connect the green
hydraulic pressure to the brake manifolds. The servo valves are energized
with a set control current to get the necessary pressure. After 3 sec. or
when the NLG moves away from the downlocked position, the normal
brake selector valve and servo valves are de-energized. This connects
the system to return to release the pressure at the brakes.
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IN-FLIGHT BRAKING MODE

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NORMAL BRAKING D/O (3)

ANTI-SKID PROTECTION
The anti-skid system implements a protection algorithm which inhibits
braking before wheel spin-up and prevents loss of braking efficiency due
to wheel skid during manual and auto braking modes. Anti-skid authority
is reduced progressively at A/C speeds below 5 m/s. Anti-skid protection
is implemented to achieve maximum braking efficiency under all runway
conditions and tire/brake conditions, and it is available in normal
(including auto brake) and alternate modes. The system uses wheel speed
(measured by tachometers installed in the axles of each of the MLG
wheels) and A/C reference speed together with other parameters to
compute brake release orders (anti-skid current orders).
These are summed with the braking orders (commanded currents) from
pedals or auto brake in order to maintain wheel slip at the optimum level
for maximum retardation over varying runway surfaces. In the normal
system, anti-skid protection is given on an individual wheel basis. The
anti-skid current orders are combined with the related corrected currents
to produce the normal brake servo-valve current orders. The pin
programming used to specify brake type lets the anti-skid protection
tuned to brakes from different manufacturers.
The braking efficiency for normal braking under all runway conditions
will be at least 92% when anti-skid is operative. Wheel locking will not
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occur on icy runways, in stable conditions, providing that A/C ground

speed is greater than 20 m/s. Anti-skid operation will not cause loss of
braking at any speed or during any A/C maneuver. When the anti-skid
system is releasing the brake pressure, 3 vertical green lines are displayed
beside the related wheel number on the ECAM wheel page.

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ANTI-SKID PROTECTION

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ALTERNATE BRAKING D/O (3)

SYSTEM ARCHITECTURE TRIPLE INDICATOR
The triple pressure indicator provides the pressure indication of the
This graphic presents the entire braking system architecture. alternate brake system plus accumulators pressure. An indicator band
from 0 to 1000 psi is provided on the left and right brake pressure
GENERAL
indicators for alternate braking without anti-skid.
System operation will switch from normal to alternate braking when BRAKE ACCUMULATOR
normal braking is unavailable due to:
- green hydraulic system failure, The accumulators are of the oleo-pneumatic bladder type. Parking
- normal braking component failure, brake accumulators are located forward of the main landing gear bay
- braking/Steering Control Unit (BSCU) specific failure in the belly fairing. They are serviced from the blue hydraulic ground
- anti-skid switch is OFF service panel, each having its own gage and inflating valve. They are
able to provide seven applications of the brakes with no system
DESCRIPTION pressure available. Two pressure gages are provided on the blue ground
service panel for the correct servicing of the accumulators.
The alternate braking system is composed of different components, which
will be described. DUAL VALVE
The dual valve is a hydro-mechanical valve that controls the quantity
BRAKE PEDAL ASSEMBLIES of the hydraulic system pressure that goes to the brakes. It operates
The brake pedal assemblies give signals to the BSCU for alternate in proportion to the pressure that comes from the brake pedals.
braking with anti-skid (A/SKID) function. A LP hydraulic system is
connected to the brake pedals. It gives artificial feel in proportion to DUAL SHUTTLE VALVE
the pedal travel and supplies a control pressure to the dual valve. The dual shuttle valve is located downstream from the dual valve. It
supplies the brakes with pressure from the alternate circuit.
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BSCU
The BSCU controls and monitors the alternate braking system with ALTERNATE BRAKE SERVOVALVE MANIFOLD
the A/SKID protection. It converts data for display and warnings, ASSEMBLY
performs various tests and supplies information to the Central The alternate brake servovalve manifold assembly is installed
Maintenance System (CMS). downstream of the dual shuttle valve. It permits installation of
hydraulic components in a limited space. It contains two servovalves,
PRESSURE TRANSDUCER
a return accumulator, one pressure relief valve, two fuses (safety
A pressure transducer measures the blue accumulator pressure for valves).
cockpit indication. It measures pressure in the left and right alternate
brake supply lines. The third one, measures the blue accumulators
pressure for alternate braking.
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SERVO VALVE assembly to allow the BSCU to control or monitor the pressure in the
The servo valves are electrically controlled. They are permanently alternate brake supply line.
energized with a minimum of current to get the pressure to the brake RETURN ACCUMULATORS
quickly. Current increases to a maximum value to release the pressure
The return accumulators are bladder type accumulators. They are
in the brake with A/SKID function. The alternate servo valves are
identical to the normal brake accumulators with a nitrogen charging
identical to the normal servo valves. The electrical control is different:
point. Their function is to make sure the brakes release smoothly.
- only one coil is connected to the electrical connector,
Each one is fitted with a pressure gage for correct quantity of charging.
- the coil is only energized to release the pressure in the brakes.
Those return accumulators, one per L/G, are installed on the return
PRESSURE RELIEF VALVE line on each alternate brake manifold. They prevent pressure surge in
The pressure relief valve lets the pressure in the return line go to the the return line during brake release and reduce brake release time.
supply line when necessary conditions occur. BRAKE UNIT SUPPLY
SAFETY VALVE The alternate system is powered by the blue hydraulic system to
Safety valves are located downstream of the servo valves. They are actuate the second independent set of pistons on each brake unit.
normally sprung loaded open valves with up and downstream chamber RESERVOIR
s controlling valve position. With a leak downstream, the downstream
The alternate brake reservoir is located in the avionics compartment.
chamber will lose pressure and the valve forced closed on its seat.
The reservoir provides sufficient quantity of pressurized hydraulic
SHUT-OFF VALVE fluid to keep the master cylinders full. A transparent indicator with a
To ensure that alternate braking remains effective following green red and green line indicates the low and correct fluid level in the
system failure during a long flight, the shut-off valve, installed in the reservoir.
alternate braking system, prevents depressurization of the parking They provide a related feel force during brake pedal operation. They
brake accumulators. The valve is energized to close if the blue system change the mechanical input into an hydraulic pressure to operate the
pressure falls. This stops the internal leakage through the dual valve, dual valve. Pedal pressure moves the spring and supplies pressure to
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thus maintaining accumulator pressure. This valve de-energizes to the dual valve. With no pressure on the pedals, the spring and hydraulic
open at landing gear selection. pressure return the sliding assembly to its original position.

HYDRAULIC FUSES
The hydraulic fuses, one per braked wheel pair, are located
downstream from the shuttle valves to prevent excessive fluid loss in
case of brake line rupture or brake assembly leakage.
ALTERNATE BRAKE PRESSURE TRANSDUCERS
The alternate brake pressure transducers, one per braked wheel pair,
are located upstream from the alternate brake servovalve manifold
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SYSTEM ARCHITECTURE ... DESCRIPTION

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ALTERNATE BRAKING D/O (3)

ALTERNATE BRAKE WITH ANTI-SKID
When the brake pedals are operated, pressure from the LP system is sent
to the dual valve in proportion to the brake pedal travel. When the dual
valves are displaced, the brake fluid pressure is then sent to the brake
units via the shuttle valves and the alternate servovalves.

NOTE: There is no fluid mixture between the LP circuit and the blue
alternate braking system fluids.
The pressure delivered to the left hand and right hand brakes as well as
the blue accumulator pressure are indicated on the triple indicator.
If the wheel reaches a skid condition, the BSCU A/SKID protection will
reduce the current to the appropriate servovalves, so the pressure to both
wheels on the same axle is released which in turn port surplus fluid to
return circuit.
The vertical lines are displayed at the corresponding pair of wheels on
the ECAM wheel page
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ALTERNATE BRAKE WITH ANTI-SKID

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ALTERNATE BRAKE WITH ANTI-SKID

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ALTERNATE BRAKING D/O (3)

ALTERNATE BRAKE WITHOUT ANTI-SKID
The alternate brake without A/SKID is available when:
-the A/SKID switch is set to OFF,
-the BSCU is not available.
When the brake pedals are operated, pressure from the LP system is sent
to the dual valve in proportion to the brake pedal travel. If the blue
hydraulic supply is not available, accumulators give sufficient pressure
for at least seven full applications of the brakes. The alternate servo valve
remains fully open as it receives no anti-skid signals from the BSCU.
The brake pressure has to be limited by the pilot to avoid wheel locking.
The pressure delivered to the left hand and right hand brakes as well as
the blue accumulator pressure are indicated on the blue pressure triple
indicator.
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ALTERNATE BRAKE WITHOUT ANTI-SKID

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ALTERNATE BRAKE WITHOUT ANTI-SKID

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ALTERNATE BRAKING D/O (3)

ALTERNATE BRAKE PRESSURE INDICATION
The triple gage indicator provides left and right brake pressure indications
by monitoring the applied pressure to the brakes mounted on the FWD
axle on each MLG. The upper part of the gage displays the pressure
available from the accumulators. The transducers, for applied pressure
indication, are the same units, fitted to the alternate brake manifold, that
supply pressure information to the BSCU.
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ALTERNATE BRAKE PRESSURE INDICATION

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PARK/ULTIMATE BRAKING D/O (3)

GENERAL ACCUMULATOR PRESSURE TRANSDUCER
The accumulator pressure transducer measures the blue hydraulic
The park braking system is supplied by the blue system pressure or the pressure at the brake accumulator manifold and sends signals to the
brake accumulators. The park braking system is designed to prevent the triple gage indicator and BSCU.
A/C from rolling on a paved, level runway with take-off power on the
critical engine, and all other engines at ground idle. When active, it will BRAKE ACCUMULATORS
cause the Brake/Steering Control Unit (BSCU) to inhibit all other braking The park brake accumulators are of the oleo-pneumatic bladder type,
modes. and maintain a specific volume of pressurized hydraulic fluid in case
When the parking brake selector switch, in the cockpit, is set to ON, the of blue system failure. They are serviced at the blue hydraulic ground
motors in the parking brake control valves are energized. Pressure is service panel, which is equipped with two pressure gages. The system
supplied to the automatic selector valve which closes the return lines design will allow the park breaking to be supplied by the accumulators
from the alternate brake servovalves. Pressure is supplied to the parking for up to 12 hours after a blue system failure or shut off.
brake operated valve which isolates the dual valve from the parking brake
system. The dual shuttle valve connects the pressurized fluid to the brakes. PARK BRAKING SELECTOR SWITCH
Accumulator replenishment is automatic by means of the blue electric The PRK BRK selector switch is a four-pole, two-position (OFF/ON)
pump. The pressure in the brakes is required to be maintained for a switch that sends the power supplies to the park brake control valve.
duration of 12 hours at 175 bars (2540 psi). When the parking brake PARK BRAKE OPERATED VALVE
selector switch is set to OFF, the motors are energized to release the
applied pressure and to open the hydraulic line to the blue return manifold. Parking brake operated valve is located in the main landing gear bay.
It is a mechanical valve containing one spring loaded shuttle valve.
DESCRIPTION When the parking brake is selected "ON", the supply pressure from
the parking brake control valve moves the shuttle valve on to its seat
The park braking system is composed of different components. to isolate the supply from the automatic selector valve.
F4M09361 - F1LT1TU - FM32D7000000003

PRESSURE RELIEF VALVE AND CHECK VALVE PARK BRAKE CONTROL VALVE
The pressure relief valve and check valve are integral part of the brake The park brake control valve is operated by two motors, which are
accumulator manifold. A check valve prevents discharge of the supplied by the 28 VDC HOT BUS and by the 28 VDC SERVICE
accumulator when the blue hydraulic system is unavailable. The BUS. The limit switches in the valve motor will cancel the power
pressure relief valve enables the accumulator to be discharged supply when the selected position is reached. In the OFF position it
automatically following an overpressure at 3400 psi, or manually for connects the park braking supply from the manifolds to the blue system
servicing. return. This is done by the parking brake operated valve and the
automatic selector. When activated, the park brake control valve
delivers a predetermined pressure (2500 psi) to the MLG brakes via

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the 4 alternate servo valves. It also sends an electrical signal to the
BSCU in order to inhibit other braking modes. This signal is disabled
within the BSCU if blue system pressure, sent to the brake units and
monitored by the pressure transducers, falls below 1450 psi.
PARK BRAKE MANIFOLD
Parking brake manifold is located in the main landing gear bay. The
manifold receives the blue hydraulic system supply and the two brake
accumulators pressure. These are separated by the check valve. The
manifold contains the pressure transducer and the pressure relief valve.
The pressure relief valve operates to return at 265 bars(3843 psi). A
manual lever can be operated to open the pressure relief valve.
DUAL SHUTTLE VALVE
Dual shuttle valve is located in landing gear bay. It contains two spring
loaded shuttle valves. When the parking brake is selected "ON", the
dual shuttle valve closes the supply to the dual valve and opens the
supply to the alternate servo valves.
HYDRAULIC FUSES (F)
The hydraulic fuses (1 per braked wheel pair) are located downstream
of the servo valves. They prevent excessive fluid loss in case of brake
line cut or brake assembly leakage.
ALTERNATE BRAKE PRESSURE TRANSDUCERS
F4M09361 - F1LT1TU - FM32D7000000003

(ALTN BRK PRESS XDCR)

The alternate brake pressure transducers on each MLG confirm parking
pressure to the triple indicator.

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GENERAL & DESCRIPTION

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PARK/ULTIMATE BRAKING D/O (3)

OPERATION
When the PRK BRK selector switch is set to ON, the motors in the park
brake control valve are supplied and the valve opens. When the valve is
open, it connects the hydraulic pressure supply to the park braking system,
isolate the alternate servo valves return circuit and an electrical signal is
sent to the BSCU in order to isolate the other braking modes. The park
brake control valve is also a pressure-reducing valve that reduces the
supply pressure to 175 bars (2500 psi) and sends the hydraulic pressure
to the alternate brake manifolds of each MLG. The hydraulic pressure
operates the shuttle valves to pressurize the alternate brake pistons. The
triple gage pressure indicator shows the pressure that is available from
the brake accumulators.
If the monitored park braking pressure (done by the pressure transducers)
to the brake units falls below 1450 psi, the BSCU inhibition is no longer
active. Therefore the normal braking system can be used provided the
green hydraulic system is pressurized and pedals are depressed.
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F4M09361 - F1LT1TU - FM32D7000000003

OPERATION

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NOSE WHEEL STEERING D/O (3)

GENERAL
The nose wheel steering (N/WS) system controls the direction of the A/C
on the ground by acting on the position of the nose wheels (N/Ws) in
relation to the A/C centerline, as a function of the relevant steering
command. A dual system computer - the Braking/Steering Control Unit
(BSCU) - controls and monitors the steering system. The steering system
is supplied by the green hydraulic system.
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GENERAL

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NOSE WHEEL STEERING D/O (3)

CONTROLS
Steering command inputs come from 3 independent sources: the dedicated
steering handwheels, rudder pedals and the autopilot guidance orders.
The steering angle decreases in proportion to the increase in the A/C
speed. In case of simultaneous action, orders are added algebraically.
HANDWHEELS
The maximum steering angle using the handwheel is ±72° when the
ground speed is less than 40 kt.
PEDALS AND AUTOPILOT
Steering orders from the pedals and the autopilot are sent to the BSCU
via the 3 Flight Control Primary Computers (FCPCs). The maximum
steering angle using the pedals and the autopilot is ±6° when the
ground speed is less than 100 kt. When a pedal disc P/B is pressed in,
N/WS by the pedals is disconnected.
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CONTROLS - HANDWHEELS & PEDALS AND AUTOPILOT

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NOSE WHEEL STEERING D/O (3)

BSCU
The two systems of the BSCU are supplied independently. Each system
is divided into two channels, a monitoring channel and a command
channel. The command channel calculates and generates the command
signals while the monitoring channel checks if the command channel is
operating correctly. In order to maintain maximum steering system
availability, the BSCU and most of its electrical peripherals are duplicated
and segregated into system 1 and system 2. The two systems switch over
automatically at each L/G down selection, or in case of system 1 or 2
failure.
The BSCU uses the steering inputs to calculate the required steering
angle, the rate of movement and the direction to turn. It sends steering
outputs to the electro-hydraulic components: selector valve and
servovalve. The BSCU receives servovalve position feedback through
its Linear Variable Differential Transducer (LVDT) and sliding tube
position feedback through 2 Rotary Variable Differential Transducers
(RVDTs) in order to servo-loop the steering function.
PRE-LANDING SELF TEST
In flight, after the L/G has extended, the BSCU does a test sequence
to check the availability of the steering system. The test sequence
checks the capability of the BSCU to control and monitor the correct
F4M09361 - F1LT1TU - FM32D8000000003

operation of the selector valves and the servovalve and their inhibition
in case of failure.

NOTE: Note that during the test sequence, commanded steering

movements are checked and the nose wheels move slightly.

STEERING ACTIVATION LOGIC

The steering system is activated in steering mode when the conditions
displayed on the screen are satisfied.

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F4M09361 - F1LT1TU - FM32D8000000003

BSCU & STEERING ACTIVATION LOGIC

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NOSE WHEEL STEERING D/O (3)

MONITORING INTERFACES
Steering system data, such as fault indications and system status, is
displayed on the EWD and the SD on the wheel page. Fault indications
are stored in the BITE of the BSCU and are also reported to the Central
Maintenance System (CMS).

OPERATION
In flight, the N/Ws are automatically driven to the center position by two
cams on full extension of the shock absorber. When the shock absorber
is pressed, the upper cam moves upward to disengage from the lower
cam, and this lets the sliding member rotate. When the gear is extended,
the swivel selector valve lets the hydraulic pressure pressurize the
hydraulic control unit to the servovalve. When the Nose Landing Gear
(NLG) is retracted, the swivel selector valve isolates the system from
hydraulic pressure.
The selector valve is energized open when all the conditions are fulfilled.
At touchdown, the BSCU lets hydraulic pressure be ported. The
servovalve supplies the hydraulic pressure to the steering actuators in
proportion to an electrical signal from the BSCU. This valve has two
coils - each coil is connected to one system of the BSCU. The LVDT
sends the data to the monitoring channel of the BSCU to give the correct
F4M09361 - F1LT1TU - FM32D8000000003

position of the servovalve. The supply pressure is routed to the correct

chamber of each steering actuator through the rotating selector valves.
The RVDT monitors the correct angular position of the N/Ws and sends
data to the command and monitoring channels of the BSCU.

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MONITORING INTERFACES & OPERATION

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NOSE WHEEL STEERING D/O (3)

OPERATION (continued)
STEERING ACTUATOR MECHANISM
The mechanically-controlled rotating selector valves connect two
service lines to their related steering actuator. Each service line is
used either as a supply or return line, or is connected to the full bore
or annulus end of the actuator as necessary. The configuration of the
valve changes when the N/W moves past a certain angle. Thus, the
service lines are always connected to the correct end of the actuator.
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OPERATION - STEERING ACTUATOR MECHANISM

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NOSE WHEEL STEERING D/O (3)

OPERATION (continued)
CASTORING AND SHIMMY DAMPING
In the event of either dual BSCU power supply loss, dual BSCU
system failure or hydraulic system failure, N/WS can freely castor
into the direction of A/C travel. When the N/W is castoring, a residual
pressure of 15 bars (217 psi) is maintained in the system by the
pressure-maintaining valve and the accumulator. The accumulator
and the refilling valves prevent cavitation in the actuator chambers.
The hydraulic fluid in the actuators can move from one actuator to
the other through the anti-shimmy and by-pass valves. These valves
operate to power the steering mode and to reduce the pressure. The
anti-shimmy damping function is the same as in the powered steering
mode.
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OPERATION - CASTORING AND SHIMMY DAMPING

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NOSE WHEEL STEERING D/O (3)

TOWING
Towing of the A/C via the nose leg-towing bracket is done without any
mechanical disconnection of the steering mechanism. The maximum
authorized towing angle is ±65°. This avoids inducing excessive loads
on the MLG during towing. Markings painted on the gear-driven NLG
doors identify the maximum towing angle. A steering system deactivation
facility, in the form of a lever-operated switch mounted on an electrical
deactivation box on the NLG, is provided for ground crew use when the
A/C has to be towed. This deactivates the steering control system to let
the N/Ws castor and be freely rotated by the towing vehicle. In towing
configuration, the lever must be secured by a safety pin. The control box
also has an indicator light with a light check button, which is illuminated
when the park brake handle is set to on.

NOTE: Note that the steering actuator mechanical stop of ±95° must
not be reached.
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TOWING

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NOSE WHEEL STEERING D/O (3)

STEERING ANGLE PROTECTION
The NLG Steering Angle Protection System gives a visual warning of
excess angular travel of the NLG steering during towing and pushback
operations. In the warning condition, which operates at more than 93
degrees, it shows that possible damage can have occurred to the
components of the NLG steering system. Two warning lights, one on the
NLG and one on the flight deck, come on when this condition has
occurred.
The system uses two proximity sensors, one installed on each side of the
NLG, which operate with a single target. The target is attached below
the upper attachment points of the torque links (which move with the
direction of the nosewheel). When the target nears one of the sensors the
warning lights operate. If the circuit operates, it stays latched on until the
cockpit push-button is reset. The circuit can only be reset with the a/c
power supplies connected.
The system power is supplied from the aircraft or the towing tractor.
Discrete signals from the Landing Gear Control and Interface Units
(LGCIUs) control the a/c power supplies to the system.

NOTE: When a standard tow bar is used (that has shear pins) the NLG
Oversteer warning can be ignored only if the shear pins are not
F4M09361 - F1LT1TU - FM32D8000000003

damaged. If the shear pins are sheared or damaged, an

inspection of the NLG must be completed.

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STEERING ANGLE PROTECTION

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LANDING GEAR MCDU PAGES (2)

EXTN/RETRN
Selecting EXTN/RETRN enables direct access to the
EXTENSION/RETRACTION main menu.
All LGCIU main menus are identical.
As well as the standard CMS functions, the LGCIU menu includes a
specific page.
The LGCIU SIMULATION function is displayed on the second MCDU
screen, which is accessible through the scrolling keys.
Using the first left key enables access to the LANDING GEAR
SIMULATION.
Using the second left key enables the LANDING GEAR SIMULATION
to be confirmed.
The display shows the available alternative configuration. A selection of
the related MCDU key starts the simulation sequence.
During the L/G simulation, the selected LGCIU :
- disables its outputs to the L/G and door selector valves.
- Continues to output the correct data for the L/G not selected.
This function lets the LGCIU BITE circuits send specific output signals.
These output signals relate to the flight or ground configuration and to
the uplocked or downlocked configuration of each landing gear.
The line key symbol "<" shows the configuration that can be set. When
F4M09361 - F1LT1TU - FM32P7MCDUTST02

there is no symbol "<", this shows the configuration that is set.

The initial configuration always shows the ground configuration.

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EXTN/RETRN

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EXTN/RETRN

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EXTN/RETRN

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LANDING GEAR SYSTEM BASE MAINTENANCE (3)

INTRODUCTION
This module highlights the gas and fluid replenishment applicable to the
L/G shock absorbers.

WARNING: MAKE SURE THAT THE SAFETY DEVICES AND THE

WARNING NOTICES ARE IN POSITION BEFORE YOU
START A TASK ON OR NEAR:
- THE FLIGHT CONTROLS,
- THE FLIGHT CONTROL SURFACES,
- THE L/G AND THE RELATED DOORS,
- COMPONENTS IN MOTION.
MOTION OF COMPONENTS CAUSES DEATH OR
INJURY TO PERSONS.
MAKE SURE THAT THE GROUND SAFETY-LOCKS
ARE CORRECTLY INSTALLED ON THE L/G AND ON
THE L/G DOORS.
USE SOLVENTS AND CLEANING AGENTS IN
WELL-VENTILATED AREAS.
DO NOT GET IN CLOSE CONTACT WITH
COMPRESSED GAS. GAS CAN CAUSE INJURY AND
CONTAMINATE YOUR BLOOD AND CAUSE DEATH.
F4M09361 - F1LT1TU - FM32Y2BASEMCE04

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INTRODUCTION

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LANDING GEAR SYSTEM BASE MAINTENANCE (3)

GAS REPLENISHMENT OF THE MLG SHOCK ABSORBER
Put a warning notice in the cockpit to inform personnel not to operate
the L/G controls.
Make sure that the green hydraulic system is depressurized.
Make sure that the safety devices are installed on the MLG.
Open the MLG doors and fit the MLG door safety devices.

CAUTION: DO NOT INFLATE THE MLG SHOCK ABSORBER AT

THE LOWER VALVE. IF YOU USE THE LOWER
VALVE, HYDRAULIC FLUID WILL ESCAPE.
Measure and write down the shock absorber dimension H.
Measure and write down the surface temperature of the aluminum piston
adjacent to the bleed inflation valve.
Use the inflation chart to find out the correct pressure from the
temperature and dimension H measurements you have just recorded.
Connect the charging equipment to the upper bleed/inflation valve and
read the pressure on the pressure gauge.
If the measured pressure is lower than the inflation chart pressure, the
shock absorber must be inflated. If it is higher, the shock absorber must
be deflated.
If the dimension H changes during the adjustment, the procedure must
F4M09361 - F1LT1TU - FM32Y2BASEMCE04

be repeated from the beginning.

Remove the Ground Support Equipment (GSE), special tooling and access
platform. Remove all warning notices.

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GAS REPLENISHMENT OF THE MLG SHOCK ABSORBER

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GAS REPLENISHMENT OF THE MLG SHOCK ABSORBER

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GAS REPLENISHMENT OF THE MLG SHOCK ABSORBER

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GAS REPLENISHMENT OF THE MLG SHOCK ABSORBER

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LANDING GEAR SYSTEM BASE MAINTENANCE (3)

GAS REPLENISHMENT OF THE NLG SHOCK ABSORBER
Make sure the NLG wheels are central to the A/C axis.
Put warning notices in the cockpit to inform personnel not to operate the
L/G and the nosewheel steering controls.
Make sure that the green hydraulic system is depressurized.
Deactivate the nosewheel steering.
Open the NLG doors and fit the NLG door safety devices.
Make sure that the bottom chamber pressure is at least 6.9 bars (100 PSI)
higher than the top chamber pressure.
Measure and write down the shock absorber dimension H.
Measure the ambient temperature.
Adjust the nitrogen pressure until the dimension H agrees ±1 mm with
the top chamber pressure and the ambient temperature as shown in the
graph.
Make sure that the bottom chamber pressure is still at least 6.9 bars (100
PSI) higher than the top chamber pressure.
If the measured top chamber pressure is higher than the nominal top
chamber pressure shown on the graph, deflate at the top chamber bottom
port, and adjust the dimension H as before.
The pressures in the top and bottom chambers are now adjusted. Check
again that the bottom chamber pressure is at least 6.9 bars (100 PSI)
F4M09361 - F1LT1TU - FM32Y2BASEMCE04

higher than the top chamber pressure. If not, repeat the procedure.
Pressurize the green hydraulic system and make sure that the NLG wheels
are still in the central position. Reactivate the nosewheel steering.
De-pressurize the green hydraulic system, remove the placards, tooling
and equipment. Remove the safety devices from the NLG doors and close
the doors.

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The pressures in the top and bottom chambers are now adjusted. Check
GAS REPLENISHMENT OF THE CLG SHOCK ABSORBER again that the bottom chamber pressure is at least 10 bars (145 PSI) higher
than the top chamber pressure. If not, repeat the entire procedure.
Put warning notices in the cockpit to inform personnel not to operate the
Remove the safety devices from the CLG doors and close the doors.
L/G control.
Remove the placards, tooling and equipment.
Make sure that the green hydraulic system is depressurized.
Make sure that the safety devices are installed on the Centerline Landing
Gear (CLG). Open the CLG doors and install the safety devices.
Measure the ambient temperature adjacent to the CLG. Measure and
write down the dimension H of the shock absorber. Use the chart to
determine the correct dimension H from the temperature. Adjust pressure
if necessary at the top/bottom port.
Measure and write down the ambient temperature of the shock absorber
adjacent to the bottom charging valve.
Use the inflation chart to determine the correct bottom chamber pressure
from the temperature.
Connect the charging equipment to the bottom chamber charging valve
and read the pressure on the pressure gauge.
If the measured pressure is lower than the inflation chart pressure, the
shock absorber must be inflated. If it is higher, the shock absorber must
be deflated.
Measure and write down the shock absorber extension (dimension H).
Measure and write down the ambient temperature near the top chamber
F4M09361 - F1LT1TU - FM32Y2BASEMCE04

charging valve.
Use the inflation chart to find the correct pressure from the temperature
and dimension H measurements you have just recorded.
Connect the charging equipment with a pressure gauge to the top charging
valve and read the pressure.
Adjust the nitrogen pressure in the top chamber to the pressure determined
by the chart with steps of 5 bars.
If the dimension H changes during the adjustment, the top pressure
chamber must be adjusted again.

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LANDING GEAR SYSTEM BASE MAINTENANCE (3)

HYDRAULIC REPLENISHMENT OF THE MLG SHOCK
ABSORBER
Put a warning notice in the cockpit to prevent L/G operation and at the
access panel to prevent MLG ground door opening.
Make sure that the green hydraulic system is depressurized.
Fit the MLG safety devices. Make sure that the applicable MLG door is
closed.
Open the bleed screw. Fit a bleed tube to the 3-way valve connected to
the bleed/inflation valve. The free end of the tube should be at least 400
mm below the valve.
Check the pressure control valve is closed, and open the bleed/inflation
valve and measure DIM H = 43.5-52.5 mm. Wait for 2 hours, to ensure
complete nitrogen/fluid separation, and close the bleed screw.
Connect the hydraulic source to the filling valve via a shut-off valve.
Connect the secondary bleed valve to the container and open it. Pump
the fluid from the hydraulic source up to a pressure of 1.7 bars (25 PSI).
Let the fluid bleed through the secondary valve until 5 liters of air-free
fluid has come out. Close the secondary bleed valve.
When the fluid from the bleed/inflation valve is free from air, close the
filling valve and the shut-off valve. 10 minutes later, close the
bleed/inflation valve.
F4M09361 - F1LT1TU - FM32Y2BASEMCE04

Remove the bleed tubes, the container and the hydraulic supply line.
After fluid replenishment, the shock absorber must be serviced with
nitrogen.
Remove the warning notices and safety devices.

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HYDRAULIC REPLENISHMENT OF THE CLG SHOCK
ABSORBER
Put warning notices in the cockpit to inform personnel not to operate the
L/G control.
Make sure that the green hydraulic system is depressurized.
Make sure that the safety devices are installed on the CLG. Open the
CLG doors and install the safety devices.
Open the bottom chamber charging valve to depressurize the High
Pressure (HP) chamber. Open the top chamber charging valve to
depressurize the LP chamber.
Open the bottom chamber drain valve to let any fluid drain out, then close
the valve (if no fluid drains out, add a small amount, then let it drain out).
Using the axle jacks, compress the shock absorber until dimension H is
equal to 20 mm.
Connect a hydraulic supply to the oil-filling valve. Pressurize the shock
absorber with fluid to 10 bars (145 PSI) and maintain the pressure for
two minutes.
Depressurize the hydraulic supply and connect the top chamber charging
valve to a container. Pressurize the hydraulic supply again in order to
collect the fluid from the top chamber charging valve. Let the fluid flow
until there is no air in the hydraulic oil. Depressurize the hydraulic supply.
F4M09361 - F1LT1TU - FM32Y2BASEMCE04

To bleed the shock absorber, do the following steps:

- fully compress the shock absorber,
- bleed the oil through the top chamber charging valve,
- close the top chamber charging valve,
- pressurize with hydraulic fluid at 10 bars (145 PSI) through the oil-filling
valve,
- let the shock absorber extend by 20 mm,
- close the oil-filling valve and depressurize the shock absorber. Repeat
the previous six steps until there is no air remaining in the hydraulic oil.
Do the gas replenishment of the shock absorber.
Remove the warning notices and safety devices.
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HYDRAULIC REPLENISHMENT OF THE NLG SHOCK
ABSORBER (A/C ON JACKS)
The hydraulic replenishment of the NLG must be done in the same way
as the hydraulic replenishment of the CLG (as shown previously).
F4M09361 - F1LT1TU - FM32Y2BASEMCE04

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 AIRBUS S.A.S.
31707 BLAGNAC cedex, FRANCE
STM
REFERENCE F4M09361
SEPTEMBER 2009
PRINTED IN FRANCE
AIRBUS S.A.S. 2009
ALL RIGHTS RESERVED

AN EADS COMPANY