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_A319/A320/A321 TECHNICAL TRAINING MANUAL
MECHANICS / ELECTRICS & AVIONICS COURSE 32 LANDING GEAR
UF94200
EFFECTIVITY Page 260
ALL
32 - LANDING GEAR
32-51-00 NOSE WHEEL STEERING SYSTEM
DESCRIPTION/OPERATION
CONTENTS:
Rotating Joint
Selector Valve
Check Valve/Filter
Servovalve
Adjustable Diaphragm
Check Valves
Bypass Valve
Anti-Shimmy Valves
Steering Actuator
Accumulator
Bleed Screw
Operation
Self Examination
TMULDGS04 LEVEL 3
EFFECTIVITY 32-51-00 Page 1
Aug 31/00
_A319/A320/A321 TECHNICAL TRAINING MANUAL
MECHANICS / ELECTRICS & AVIONICS COURSE 32 LANDING GEAR
UF94200
EFFECTIVITY Page 261
ALL
NOSE WHEEL STEERING SYSTEM DESCRIPTION/OPERATION
ROTATING JOINT
The rotating joint is installed co-axially with respect
to the landing gear retraction axis and provides
hydraulic power supply when the gear is extended.
When the gear starts to retract, the rotating joint
cuts the hydraulic power supply.
SELECTOR VALVE
When the selector valve is energized the pressure is
applied to the servovalve via the slaved valve.
CHECK VALVE/FILTER
A 40 micron filter and a check valve are installed in
the hydraulic power supply line.
SERVOVALVE
The servovalve is of the deflection-jet type. It is
equipped with a Linear Variable Differential
Transducer (LVDT) sensor which detects the position
of the slide valve.
The LVDT provides position feedback for the steering
control.
ADJUSTABLE DIAPHRAGM
The ajustable diaphragms are used to adjust the flow
to each actuating cylinder chamber and consequently
the wheel steering speed.
CHECK VALVES
Two check valves ensure the distribution of fluid from
the accumulator to the chamber of the steering actuator.
BYPASS VALVE
The bypass valve interconnects the two chambers of the steering
actuator in the event of hydraulic system depressurization.
The bypass valve opens if the pressure exceeds 273 bars
(4000 psi).
ANTI-SHIMMY VALVES
There is one anti-shimmy valve per steering actuator chamber.
STEERING ACTUATOR
The steering actuator drives the rotating tube, which
is part of the nose landing gear structure, via a
rack-and-pinion assembly.
ACCUMULATOR
The anti-shimmy accumulator supplies pressurized fluid
in case of cavitation in one of the two chambers of
the steering actuator.
The accumulator can supply fluid pressurized up to 15
bars (220 psi).
BLEED SCREW
A bleed screw allows bleeding and depressurization of
the hydraulic block.
TMULDGS04-T01 LEVEL 3
EFFECTIVITY 32-51-00 Page 2
Aug 31/00
_A319/A320/A321 TECHNICAL TRAINING MANUAL
MECHANICS / ELECTRICS & AVIONICS COURSE 32 LANDING GEAR
UF94200
EFFECTIVITY Page 262
ALL
NOSE WHEEL STEERING SYSTEM DESCRIPTION/OPERATION - DESCRIPTION
TMULDGS04-P01 LEVEL 3
EFFECTIVITY 32-51-00 Page 3
Aug 31/00
_A319/A320/A321 TECHNICAL TRAINING MANUAL
MECHANICS / ELECTRICS & AVIONICS COURSE 32 LANDING GEAR
UF94200
EFFECTIVITY Page 263
ALL
NOSE WHEEL STEERING SYSTEM DESCRIPTION/OPERATION
OPERATION
When the nose gear is extended and the nose gear doors
are closed, the hydraulic block is pressurized.
When the MLG is compressed, both chambers of the
steering actuator are supplied and the nose wheels
servoed to an angle of 0º.
Depending on the BSCU reference speed and the nose
wheel steering orders, the nose wheels are steered.
TMULDGS04-T02 LEVEL 3
EFFECTIVITY 32-51-00 Page 4
Aug 31/00
_A319/A320/A321 TECHNICAL TRAINING MANUAL
MECHANICS / ELECTRICS & AVIONICS COURSE 32 LANDING GEAR
UF94200
EFFECTIVITY Page 264
ALL
TMULDGS04-P02 LEVEL 3
NOSE WHEEL STEERING SYSTEM DESCRIPTION/OPERATION - OPERATION
EFFECTIVITY 32-51-00 Page 5
Aug 31/00
_A319/A320/A321 TECHNICAL TRAINING MANUAL
MECHANICS / ELECTRICS & AVIONICS COURSE 32 LANDING GEAR
UF94200
EFFECTIVITY Page 265
ALL
SELF EXAMINATION
What is the purpose of the accumulator?
A - To compensate a complete pressure loss.
B - To dampen rapid movements.
C - To supply hydraulic pressure in case of
cavitation.
What is the purpose of the bypass valve?
A - To interconnect the two chambers of the
steering actuator.
B - To apply hydraulic pressure to the
servovalve.
C - To bypass the servovalve in case of BSCU
failure.
What are the adjustable diaphragms used for?
A - To ensure self centering of the nose
gear.
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