DOC AIRBUS | AMM A320FEXTENSION AND RETRACTION - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
Extension and Retraction - Schematic ** ON A/C NOT FOR ALL
Extension and Retraction - Schematic ** ON A/C NOT FOR ALL
The extension and retraction system extends and retracts the Landing Gear (L/G). The system is divided into two sub-systems:
Extension and Retraction - Schematic ** ON A/C NOT FOR ALL Extension and Retraction - Schematic ** ON A/C NOT FOR ALL - the Normal Extension and Retraction System (Ref. AMM D/O 32-31-00-00)
- the Free Fall Extension System (Ref. AMM D/O 32-33-00-00).
A. Normal Extension and Retraction
The L/G control lever (6GA) is on the First Officers side of the center instrument panel. It operates the extension and retraction of the landing gear.
The normal extension and retraction system is used to extend and retract the L/G. The system is electrically controlled and hydraulically operated. The hydraulic supply is from the Green hydraulic power system (Ref. AMM D/O 29-11-00-00). A Landing Gear Control and Interface Unit (LGCIU) controls the sequence of operations.
The two control and position-sensing systems each have a LGCIU, proximity sensors and targets.
The L/G control lever (6GA) is on the First Officers side of the center instrument panel. It operates the extension and retraction of the landing gear.
The normal extension and retraction system is used to extend and retract the L/G. The system is electrically controlled and hydraulically operated. The hydraulic supply is from the Green hydraulic power system (Ref. AMM D/O 29-11-00-00). A Landing Gear Control and Interface Unit (LGCIU) controls the sequence of operations.
The two control and position-sensing systems each have a LGCIU, proximity sensors and targets.
B. Free Fall Extension
The free-fall extension control-handle is on the rear of the center pedestal and operates the L/G mechanically.
If the normal extension and retraction system is not servicable, you can operate the free-fall extension system. It extends the nose landing gear (NLG) and the main landing gear (MLG) by gravity. The system is mechanically operated by cables, rods, and levers, used to make the necessary extend selections.
When you operate the free-fall extension control-handle, it releases the uplocks on:
A mechanically-operated valve isolates the hydraulic supply. To prevent cavitation and hydraulic locks, other mechanically-operated valves let fluid move in the hydraulic components of the normal extension and retraction system. When the uplocks release, gravity extends the L/G doors and the L/G. Springs pull the downlock-links of the L/G into the locked position and the L/G doors stay open.
When you put the free-fall extension control-handle to the NORMAL position and set the L/G control handle to DOWN:
The free-fall extension control-handle is on the rear of the center pedestal and operates the L/G mechanically.
If the normal extension and retraction system is not servicable, you can operate the free-fall extension system. It extends the nose landing gear (NLG) and the main landing gear (MLG) by gravity. The system is mechanically operated by cables, rods, and levers, used to make the necessary extend selections.
When you operate the free-fall extension control-handle, it releases the uplocks on:
- the MLG door
- the NLG door
- the MLG gear
- the NLG gear.
A mechanically-operated valve isolates the hydraulic supply. To prevent cavitation and hydraulic locks, other mechanically-operated valves let fluid move in the hydraulic components of the normal extension and retraction system. When the uplocks release, gravity extends the L/G doors and the L/G. Springs pull the downlock-links of the L/G into the locked position and the L/G doors stay open.
When you put the free-fall extension control-handle to the NORMAL position and set the L/G control handle to DOWN:
- the main doors close
- the system is set to the normal extension and retraction mode.
2. Component Location
Not applicable
** ON A/C NOT FOR ALL Not applicable
3. System Description
A. Normal Extension and Retraction
The normal extension and retraction system has two independently wired electrical circuits, SYSTEM 1 and SYSTEM 2. Each system contains a LGCIU, and proximity sensors to show the position of the L/G components. Only one LGCIU controls the System at one time. The LGCIU in control is the active unit and the other is the standby unit. Each circuit connects to the L/G control lever, a L/G and a L/G door selector valve. A safety valve connected to the ADIRS (Ref. AMM D/O 34-10-00-00) isolates the system from the Green hydraulic supply when the aircraft flies faster than 264 knots. This prevents the extension of the L/G. The L/G and the L/G door selector valves control the flow of the hydraulic fluid to and from the system hydraulic components.
The L/G hydraulic system includes:
The L/G doors and the L/G have uplocks that lock the components in the retracted position. Geometric (overcenter) downlocks lock the L/G in the extended position.
An anti-retraction baulk in the L/G control lever prevents an UP selection when:
The normal extension and retraction system has two independently wired electrical circuits, SYSTEM 1 and SYSTEM 2. Each system contains a LGCIU, and proximity sensors to show the position of the L/G components. Only one LGCIU controls the System at one time. The LGCIU in control is the active unit and the other is the standby unit. Each circuit connects to the L/G control lever, a L/G and a L/G door selector valve. A safety valve connected to the ADIRS (Ref. AMM D/O 34-10-00-00) isolates the system from the Green hydraulic supply when the aircraft flies faster than 264 knots. This prevents the extension of the L/G. The L/G and the L/G door selector valves control the flow of the hydraulic fluid to and from the system hydraulic components.
The L/G hydraulic system includes:
- the actuators that move the mechanical L/G and L/G door components
- the mechanically operated valves that let the doors open on the ground.
The L/G doors and the L/G have uplocks that lock the components in the retracted position. Geometric (overcenter) downlocks lock the L/G in the extended position.
An anti-retraction baulk in the L/G control lever prevents an UP selection when:
- all three L/G shock absorbers are not fully extended (weight off the ground)
- the nose wheels are not in the center position.
B. Free Fall Extension System
The free-fall extension system includes a control handle. When rotated, it operates a mechanical control system, which releases the MLG and NLG door and gear uplocks. The mechanical system also causes the cut out valve (in the RH MLG bay) and a vent valve (in the LH MLG and NLG bays) to move in sequence.
The cut out valve isolates the L/G hydraulic system from the Green hydraulic power supply (Ref. AMM D/O 29-11-00-00). The vent valves let the hydraulic fluid move between some components to prevent cavitation and hydraulic locks. They also let the unwanted fluid go back to the Green hydraulic system return.
The free-fall extension system includes a control handle. When rotated, it operates a mechanical control system, which releases the MLG and NLG door and gear uplocks. The mechanical system also causes the cut out valve (in the RH MLG bay) and a vent valve (in the LH MLG and NLG bays) to move in sequence.
The cut out valve isolates the L/G hydraulic system from the Green hydraulic power supply (Ref. AMM D/O 29-11-00-00). The vent valves let the hydraulic fluid move between some components to prevent cavitation and hydraulic locks. They also let the unwanted fluid go back to the Green hydraulic system return.
4. Power Supply
A. Electrical Power Supplies
The normal extension and retraction system gets a 28V DC power supply from these busbars:
The free-fall extension system is mechanically operated and has no electrical power supplies.
The normal extension and retraction system gets a 28V DC power supply from these busbars:
- 401PP ESSENTIAL BUS
- 601PP SERVICE BUS.
The free-fall extension system is mechanically operated and has no electrical power supplies.
B. Hydraulic Power Supply
The Green hydraulic power system (Ref. AMM D/O 29-11-00-00) supplies the normal extension and retraction system.
The free-fall extension system is mechanically operated and has no hydraulic power supplies.
The Green hydraulic power system (Ref. AMM D/O 29-11-00-00) supplies the normal extension and retraction system.
The free-fall extension system is mechanically operated and has no hydraulic power supplies.
5. Interface
The extension and retraction system connects with the systems that follow:
** ON A/C NOT FOR ALL The extension and retraction system connects with the systems that follow:
- the normal extension and retraction system
- the free-fall extension system.
6. Component Description
Not applicable
** ON A/C NOT FOR ALL Not applicable
7. Operation/Control and Indicating
Landing Gear - Control and Indication ** ON A/C NOT FOR ALL
Landing Gear - Control and Indication ** ON A/C NOT FOR ALL
Landing Gear - Control and Indication ** ON A/C NOT FOR ALL
The L/G control and Indication have two operation procedures:
Landing Gear - Control and Indication ** ON A/C NOT FOR ALL Landing Gear - Control and Indication ** ON A/C NOT FOR ALL Landing Gear - Control and Indication ** ON A/C NOT FOR ALL The L/G control and Indication have two operation procedures:
- normal
- free-fall.
A. Normal Extension and Retraction
When the L/G control lever is put in the UP position, it sends a signal to the active LGCIU. A baulk device in the control lever prevents this if the aircraft is not in the correct configuration. The LGCIU sends a signal to the L/G and the L/G door selector-valves to move the doors and gears in this sequence:
The proximity sensor signals supply the necessary position data to the LGCIU. If the aircraft is in the correct configuration, a DOWN selection of the L/G control lever starts this extend sequence:
The control of the operation of the retraction and extension sequence changes from one LGCIU to the other. This occurs after each retract/extend cycle (when the landing gear control lever is moved away from the DOWN position). If a failure occurs in the active LGCIU, the standby LGCIU becomes active. The LGCIU also sends L/G configuration data to other aircraft systems.
When the L/G control lever is put in the UP position, it sends a signal to the active LGCIU. A baulk device in the control lever prevents this if the aircraft is not in the correct configuration. The LGCIU sends a signal to the L/G and the L/G door selector-valves to move the doors and gears in this sequence:
- the door uplocks release and the doors open fully
- the L/G downlocks open
- the L/Gs retract and lock
- the doors close and lock.
The proximity sensor signals supply the necessary position data to the LGCIU. If the aircraft is in the correct configuration, a DOWN selection of the L/G control lever starts this extend sequence:
- the door uplocks release and the doors open fully
- the L/G uplocks open
- the L/Gs extend and lock
- the doors close and lock.
The control of the operation of the retraction and extension sequence changes from one LGCIU to the other. This occurs after each retract/extend cycle (when the landing gear control lever is moved away from the DOWN position). If a failure occurs in the active LGCIU, the standby LGCIU becomes active. The LGCIU also sends L/G configuration data to other aircraft systems.
B. Free Fall Extension
The operation of the landing-gear free-fall extension handle-assembly:
The landing gear doors stay open, when the landing gear is extended and locked down by the lock springs.
The normal extension and retraction control is available when the free-fall handle-assembly is put back to its initial position.
The operation of the landing-gear free-fall extension handle-assembly:
- operates the cut-out valve and vent valves
- releases the door uplocks
- releases the gear uplocks.
- extend the landing gears
- open the landing gear doors.
The landing gear doors stay open, when the landing gear is extended and locked down by the lock springs.
The normal extension and retraction control is available when the free-fall handle-assembly is put back to its initial position.
C. Indicating
(1) Normal extension and retraction
The L/G position indications are given on:
If a failure of the L/G operation occurs, a failure warning message shows on the Engine Warning Display Unit. When the specified failure-warning messages show, an aural and visual warning is also given (Ref. AMM D/O 32-61-00-00).
The L/G position indications are given on:
- the WHEEL page of the Systems Display Unit
- the L/G downlock indicator lights on panel 402VU.
If a failure of the L/G operation occurs, a failure warning message shows on the Engine Warning Display Unit. When the specified failure-warning messages show, an aural and visual warning is also given (Ref. AMM D/O 32-61-00-00).
(2) Free fall extension
There is no specified indicating system in this mode. The indications are the same as for the normal extension and retraction system.
There is no specified indicating system in this mode. The indications are the same as for the normal extension and retraction system.
8. BITE Test
A. Normal Extension and Retraction System
Each LGCIU has BITE (Ref. AMM D/O 32-69-00-00). The BITE (hardware and software) makes it possible for each LGCIU to:
Each LGCIU has BITE (Ref. AMM D/O 32-69-00-00). The BITE (hardware and software) makes it possible for each LGCIU to:
- continuously monitor itself and its related electrical system for failure
- keep a record of failure data and transmit this data to the CFDS
- do a BITE test (during maintenance)
- simulate different L/G configurations (during maintenance).