DOC AIRBUS | AMM A320FLANDING GEAR - 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
** ON A/C NOT FOR ALL
1. Glossary
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| | ABBREVATION | SIGNIFICATION | |
| ------------------------------------------------------------------------------- |
| ! ACARS ! Arinc Communications Addressing and ! |
| ! ! Reporting System ! |
| ! ACSC ! Avionic Compartment System Cooling ! |
| ! ADIRU ! Air Data Inertial Reference Unit ! |
| ! ADF ! Automatic Direction Finding ! |
| ! AEVC ! Avionics Equipment Ventilation Controller ! |
| ! AIDS ! Aircraft Integrated Data System ! |
| ! APU ! Auxiliary Power Unit ! |
| ! ARINC ! Aeronautical Radio Incorporated ! |
| ! ATC ! Air Traffic Control ! |
| ! BITE ! Built-In Test Equipment ! |
| ! BRK ! Brake ! |
| ! BSCU ! Brakes and Steering Control Unit ! |
| ! C/B ! Circuit Breaker ! |
| ! CFDIU ! Centralized Fault Display Interface Unit ! |
| ! CFDS ! Centralized Fault Display System ! |
| ! CIDS ! Cabin Intercommunication Data System ! |
| ! CMPTR ! Computer ! |
| ! CONFIG ! Configuration ! |
| ! CRT ! Cathode Ray Tube ! |
| ! DFDR ! Digital Flight Data Recorder ! |
| ! DMC ! Data Management Computer ! |
| ! DME ! Distance Measuring Equipment ! |
| ! DU ! Display Unit ! |
| ! EFCS ! Electronic Flight Control System ! |
| ! EIS ! Electronic Instrumentation System ! |
| ! FAC ! Flight Augmentation Computer ! |
| ! FADEC ! Full Authority Digital Engine Control ! |
| ! FCDC ! Flight Control Data Concentrator ! |
| ! FGC ! Flight Guidance Computer ! |
| ! FIN ! Functional Item Number ! |
| ! FWC ! Flight Warning Computer ! |
| ! GPWS ! Ground Proximity Warning System ! |
| ! HF ! High Frequency ! |
| ! HP ! High Pressure ! |
| ! ILS ! Instrument Landing System ! |
| ! KT ! Knot(s) ! |
| ! LG ! Landing Gear ! |
| ! LGCIU ! Landing Gear Control and Interface Unit ! |
| ! LH ! Left Hand ! |
| ! LP ! Low Pressure ! |
| ! LRU ! Line Replaceable Unit ! |
| ! MLG ! Main Landing Gear ! |
| ! MRDS ! Maintenance and Recording Data System ! |
| ! NLG ! Nose Landing Gear ! |
| ! N/W ! Nose Wheel ! |
| ! PSI ! Pounds per Square Inch ! |
| ! RAM ! Random Access Memory ! |
| ! RH ! Right Hand ! |
| ! RMP ! Radio Management Panel ! |
| ! ROM ! Read Only Memory ! |
| ! SDAC ! System Data Acquisition Concentrator ! |
| ! SDI ! Source Data Identifier ! |
| ! STG ! Steering ! |
| ! TPIS ! Tire Pressure Indicating System ! |
| ! VHF ! Very High Frequency ! |
| ! VLE ! Maximum Landing Gear Extended Speed ! |
| ! VLO ! Maximum Landing Gear Operating Speed ! |
| ! VOR ! Very High Frequency Omnidirectional Range ! |
| ------------------------------------------------------------------------------- |
A. Description
The Landing Gear (L/G) system has:
The L/G support the aircraft on the ground and are oleo-pneumatic shock absorbers that absorb taxi and landing loads. During flight the L/G is retracted into the landing gear bays in the belly of the aircraft. When the L/G is extended or retracted the related doors close to make the aerodynamic contours of the aircraft.
The Landing Gear (L/G) system has:
- two Main Landing Gears (MLG) and their related doors (Ref. AMM D/O 32-10-00-00)
- a Nose Landing Gear (NLG) and its related doors (Ref. AMM D/O 32-20-00-00)
- two extension and retraction systems for the L/G and their related doors (Ref. AMM D/O 32-30-00-00)
- L/G wheels and their related braking systems (Ref. AMM D/O 32-40-00-00)
- a NLG steering system (Ref. AMM D/O 32-51-00-00)
- a L/G indication and warning system (Ref. AMM D/O 32-60-00-00).
The L/G support the aircraft on the ground and are oleo-pneumatic shock absorbers that absorb taxi and landing loads. During flight the L/G is retracted into the landing gear bays in the belly of the aircraft. When the L/G is extended or retracted the related doors close to make the aerodynamic contours of the aircraft.
B. General Characteristics
Landing Gear Systems Functional-Interface ** ON A/C NOT FOR ALL
Landing Gear Systems Functional-Interface ** ON A/C NOT FOR ALL
| WHEEL BASE: Nose/Main : 12.64m (41ft 5in) |
| TRACK: MLG : 7.59m (24ft 11in) |
| MLG Wheels : 0.927m (3ft 0in) |
| NLG Wheels : 0.500m (1ft 7in) |
| SHOCK ABSORBER STROKE: MLG : 0.47m (1ft 6in) |
| NLG : 0.43m (1ft 5in) |
| Max Brake Pressure : 175 bar |
| Nose Wheel Steering Angle : +/- 75 deg |
| Max Steering Rate : 12 deg/s |
| Takeoff Rotation Angle : 13 deg 30 min |
| (MLG Shock Absorbers Extended) |
| L/G OPERATION ENVELOPE: |
| VLO (MLG Operating Speed) : Retraction : 220 kts |
| Extension : 250 kts |
| VLE (MLG Extended Speed) : 280 kts |
Landing Gear Systems Functional-Interface ** ON A/C NOT FOR ALL Landing Gear Systems Functional-Interface ** ON A/C NOT FOR ALL | WHEEL BASE: Nose/Main : 16.91m (55ft 6in) |
| TRACK: MLG : 7.59m (24ft 11in) |
| MLG Wheels : 0.927m (3ft 0in) |
| NLG Wheels : 0.500m (1ft 7in) |
| SHOCK ABSORBER STROKE: MLG : 0.47m (1ft 6in) |
| NLG : 0.43m (1ft 5in) |
| Max Brake Pressure : 175 bar |
| Nose Wheel Steering Angle : +/- 75 deg |
| Max Steering Rate : 15 deg/s |
| Takeoff Rotation Angle : 11 deg 38 min |
| (MLG Shock Absorbers Extended) |
| L/G OPERATION ENVELOPE: |
| VLO (MLG Operating Speed) : Retraction : 220 kts |
| Extension : 250 kts |
| VLE (MLG Extended Speed) : 280 kts |
| WHEEL BASE: Nose/Main : 11.04m (36ft 3in) |
| TRACK: MLG : 7.59m (24ft 11in) |
| MLG Wheels : 0.927m (3ft 0in) |
| NLG Wheels : 0.500m (1ft 7in) |
| SHOCK ABSORBER STROKE: MLG : 0.47m (1ft 6in) |
| NLG : 0.43m (1ft 5in) |
| Max Brake Pressure : 175 bar |
| Nose Wheel Steering Angle : +/- 75 deg |
| Max Steering Rate : 12 deg/s |
| Takeoff Rotation Angle : 15 deg 47 min |
| (MLG Shock Absorbers Extended) |
| L/G OPERATION ENVELOPE: |
| VLO (MLG Operating Speed) : Retraction : 220 kts |
| Extension : 250 kts |
| VLE (MLG Extended Speed) : 280 kts |
3. Component Location
Extension/Retraction Controls and Indications ** ON A/C NOT FOR ALL
Extension/Retraction Controls and Indications ** ON A/C NOT FOR ALL
Brake Controls and Indications - Location ** ON A/C NOT FOR ALL
Brake Controls and Indications - Location ** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL Extension/Retraction Controls and Indications ** ON A/C NOT FOR ALL Extension/Retraction Controls and Indications ** ON A/C NOT FOR ALL Brake Controls and Indications - Location ** ON A/C NOT FOR ALL Brake Controls and Indications - Location ** ON A/C NOT FOR ALL 4. System Description
A. Main Landing Gear and Doors (Ref. 32-10-00)
Each MLG has a MLG leg which includes an oleo-pneumatic shock absorber. The L/G retracts into the available space of its MLG bays.
A two-piece side stay assembly holds the MLG in the extended position. A lock stay keeps the side stay assembly stable in the lock down position.
Three doors close each MLG bay. These are:
A door opening mechanism lets the main door be opened on the ground for access to the MLG bay.
Each MLG has a MLG leg which includes an oleo-pneumatic shock absorber. The L/G retracts into the available space of its MLG bays.
A two-piece side stay assembly holds the MLG in the extended position. A lock stay keeps the side stay assembly stable in the lock down position.
Three doors close each MLG bay. These are:
- a hydraulically-operated main door
- a mechanically-operated hinged door
- a fairing door on the MLG leg.
A door opening mechanism lets the main door be opened on the ground for access to the MLG bay.
B. Nose Landing Gear and Doors (Ref. 32-20-00)
The NLG includes on oleo-pneumatic shock absorber and retracts forward into a bay in the fuselage. A two-piece drag strut assembly with a lock stay locks the leg in the extended position. The leg includes a hydraulically-operated steering mechanism (Ref. AMM D/O 32-51-00-00).
Four doors and a fairing close the NLG bay. These are:
A door opening mechanism lets the forward doors be opened on the ground for access to the NLG bay.
The NLG includes on oleo-pneumatic shock absorber and retracts forward into a bay in the fuselage. A two-piece drag strut assembly with a lock stay locks the leg in the extended position. The leg includes a hydraulically-operated steering mechanism (Ref. AMM D/O 32-51-00-00).
Four doors and a fairing close the NLG bay. These are:
- two hydraulically-operated forward doors
- two mechanically-operated rear doors
- a fixed fairing on the NLG leg.
A door opening mechanism lets the forward doors be opened on the ground for access to the NLG bay.
C. Extension and Retraction (Ref. 32-30-00)
The normal extension and retraction system (Ref. AMM D/O 32-31-00-00) extends and retracts:
The system is electrically controlled and hydraulically operated.
Two independently wired electrical systems control the operation of the hydraulic components. Each system has:
The hydraulic circuit has actuators that extend and retract the gears and open and close the doors. The green hydraulic system (Ref. AMM D/O 29-11-00-00) supplies the hydraulic power to operate the actuators.
The system has two electro-hydraulic valves that control the operation of the actuators. One electro-hydraulic valve controls the actuators for the L/G. The other controls the actuators for the doors.
The LGCIU makes the selections of the valve assembly to retract or extend the L/G and move the doors in a given sequence.
The indicating and warning data for the L/G is given in (Ref. AMM D/O 32-61-00-00). The LGCIU also has Built-In Test Equipment (BITE) which is given in (Ref. AMM D/O 32-69-00-00).
The free fall extension system (Ref. AMM D/O 32-33-00-00) extends the MLG and NLG if the normal extension and retraction system is not available.
The system includes electrical rotary-type actuators. The actuators operate mechanical linkages to open the gear and door uplocks and hydraulic valves. This lets gravity extend the gears.
The normal extension and retraction system (Ref. AMM D/O 32-31-00-00) extends and retracts:
- the left and right MLG and doors (Ref. AMM D/O 32-11-00-00) and (Ref. AMM D/O 32-12-00-00)
- the NLG and doors (Ref. AMM D/O 32-21-00-00) and (Ref. AMM D/O 32-22-00-00).
The system is electrically controlled and hydraulically operated.
Two independently wired electrical systems control the operation of the hydraulic components. Each system has:
- a Landing Gear Control and Interface Unit (LGCIU)
- proximity sensors to show the position of the L/G components.
The hydraulic circuit has actuators that extend and retract the gears and open and close the doors. The green hydraulic system (Ref. AMM D/O 29-11-00-00) supplies the hydraulic power to operate the actuators.
The system has two electro-hydraulic valves that control the operation of the actuators. One electro-hydraulic valve controls the actuators for the L/G. The other controls the actuators for the doors.
The LGCIU makes the selections of the valve assembly to retract or extend the L/G and move the doors in a given sequence.
The indicating and warning data for the L/G is given in (Ref. AMM D/O 32-61-00-00). The LGCIU also has Built-In Test Equipment (BITE) which is given in (Ref. AMM D/O 32-69-00-00).
The free fall extension system (Ref. AMM D/O 32-33-00-00) extends the MLG and NLG if the normal extension and retraction system is not available.
The system includes electrical rotary-type actuators. The actuators operate mechanical linkages to open the gear and door uplocks and hydraulic valves. This lets gravity extend the gears.
D. Wheels and Brakes (Ref. 32-40-00)
The wheels are of aluminium alloy and can have a tubeless radial or bias ply tire.
The normal braking system (Ref. AMM D/O 32-42-00-00) is used to decrease the speed of the aircraft when it moves on the ground. The Brake and Steering Control Unit (BSCU) controls the operation of normal braking. Each brake has two hydraulically operated pistons. When braking is necessary, hydraulic pressure is supplied from the Green main hydraulic system (Ref. AMM D/O 29-11-00-00). The system has two modes of operation, manual and automatic, and gives automatic anti-skid protection in each mode.
The input signals from the brake pedals are proportional to the amount of pedal travel and supply braking independently to each MLG. For automatic braking three Pushbutton Switches (P/BSW) each set an automatic braking program (LO, MED or MAX) in the BSCU, which gives a different deceleration rate. Use of the pedals that supplies an input signal more than a specified value, cancels an automatic braking program.
The BSCU uses the input signals to make output signals which control the operation of the electro-hydraulic valves.
If the normal braking system is not available, control automatically changes to one of the alternate braking systems (Ref. AMM D/O 32-43-00-00) or (Ref. AMM D/O 32-44-00-00).
Alternate braking with anti-skid (Ref. AMM D/O 32-43-00-00) is a secondary electro-hydraulic braking system. It is automatically available if specified failures occur in the normal braking system. Braking inputs are made only at the brake pedals through a low-pressure hydraulic system. The BSCU controls four servo valves in the system to supply the anti-skid function. The hydraulic pressure that operates the brake pistons is supplied from the Yellow main hydraulic power system (Ref. AMM D/O 29-13-00-00).
Alternate braking without Anti-skid (Ref. AMM D/O 32-44-00-00) is the secondary mode of operation of the alternate braking system. Braking inputs are made only at the brake pedals. As electrical power is necessary to operate this system, it is usually used when the aircraft is towed. The hydraulic pressure is supplied from the Yellow main hydraulic power system (Ref. AMM D/O 29-13-00-00) or accumulators.
The parking brake system (Ref. AMM D/O 32-45-00-00) is an electro-hydraulic system. It is used to prevent movement of the aircraft when it is parked. It can also be used to stop the aircraft if all other braking systems are not available. The system operates from the accumulators in the alternate braking system.
The wheels are of aluminium alloy and can have a tubeless radial or bias ply tire.
The normal braking system (Ref. AMM D/O 32-42-00-00) is used to decrease the speed of the aircraft when it moves on the ground. The Brake and Steering Control Unit (BSCU) controls the operation of normal braking. Each brake has two hydraulically operated pistons. When braking is necessary, hydraulic pressure is supplied from the Green main hydraulic system (Ref. AMM D/O 29-11-00-00). The system has two modes of operation, manual and automatic, and gives automatic anti-skid protection in each mode.
The input signals from the brake pedals are proportional to the amount of pedal travel and supply braking independently to each MLG. For automatic braking three Pushbutton Switches (P/BSW) each set an automatic braking program (LO, MED or MAX) in the BSCU, which gives a different deceleration rate. Use of the pedals that supplies an input signal more than a specified value, cancels an automatic braking program.
The BSCU uses the input signals to make output signals which control the operation of the electro-hydraulic valves.
If the normal braking system is not available, control automatically changes to one of the alternate braking systems (Ref. AMM D/O 32-43-00-00) or (Ref. AMM D/O 32-44-00-00).
Alternate braking with anti-skid (Ref. AMM D/O 32-43-00-00) is a secondary electro-hydraulic braking system. It is automatically available if specified failures occur in the normal braking system. Braking inputs are made only at the brake pedals through a low-pressure hydraulic system. The BSCU controls four servo valves in the system to supply the anti-skid function. The hydraulic pressure that operates the brake pistons is supplied from the Yellow main hydraulic power system (Ref. AMM D/O 29-13-00-00).
Alternate braking without Anti-skid (Ref. AMM D/O 32-44-00-00) is the secondary mode of operation of the alternate braking system. Braking inputs are made only at the brake pedals. As electrical power is necessary to operate this system, it is usually used when the aircraft is towed. The hydraulic pressure is supplied from the Yellow main hydraulic power system (Ref. AMM D/O 29-13-00-00) or accumulators.
The parking brake system (Ref. AMM D/O 32-45-00-00) is an electro-hydraulic system. It is used to prevent movement of the aircraft when it is parked. It can also be used to stop the aircraft if all other braking systems are not available. The system operates from the accumulators in the alternate braking system.
(1) Brakes and Steering Built-in Test Equipment (BITE) (Ref. AMM D/O 32-46-00-00)
The BITE has hardware and software for these functions:
The BITE has hardware and software for these functions:
- to automatically do a self test at power-up
- to continuously monitor the related systems for failures
- to continuously monitor the interface with other specified systems in the aircraft
- to keep a record of each failure and defect and send this data to other systems in the aircraft
- to automatically do a functional test of some related systems before a landing
- to do specified system tests during ground maintenance.
(2) Brake Temperature System (Ref. AMM D/O 32-47-00-00)
The brake temperature system includes a temperature sensor at each brake which measures the temperature and sends the data to a brake temperature monitoring unit. The brake temperatures are shown automatically on the wheel page of the ECAM System Display (SD)
The brake temperature system includes a temperature sensor at each brake which measures the temperature and sends the data to a brake temperature monitoring unit. The brake temperatures are shown automatically on the wheel page of the ECAM System Display (SD)
(3) Brake Cooling System (Ref. AMM D/O 32-48-00-00)
The brake cooling system is a manually controlled system that decreases the temperature of the brakes when they are too hot. The system is usually used on the ground but can also be used in flight if a landing is necessary immediately. The system includes a P/BSW and an electrically operated fan in each MLG wheel. The P/BSW has:
The brake cooling system is a manually controlled system that decreases the temperature of the brakes when they are too hot. The system is usually used on the ground but can also be used in flight if a landing is necessary immediately. The system includes a P/BSW and an electrically operated fan in each MLG wheel. The P/BSW has:
- a HOT light that shows if the temperature of a brake is more than a specified value.
- an ON light that shows when the switch is pushed in (selected ON).
E. Steering (Ref. 32-51-00)
The steering system is controlled by the BSCU (Ref. AMM D/O 32-46-00-00). The steering system changes the direction of the aircraft when it moves on the ground. The system uses the Green main hydraulic-power system (Ref. AMM D/O 29-11-00-00) to operate a steering mechanism which changes the direction of the NLG wheels. Two handwheel transmitters in the cockpit supply the primary steering inputs to the BSCU. The rudder pedals and the autopilot supply secondary input to the BSCU through the flight control primary computers. The system operation can be cancelled to let the nose wheels move freely during aircraft ground movement.
The steering system is controlled by the BSCU (Ref. AMM D/O 32-46-00-00). The steering system changes the direction of the aircraft when it moves on the ground. The system uses the Yellow main hydraulic-power system (Ref. AMM D/O 29-13-00-00) to operate a steering mechanism which changes the direction of the NLG wheels. Two handwheel transmitters in the cockpit supply the primary steering inputs to the BSCU. The rudder pedals and the autopilot supply secondary input to the BSCU through the flight control primary computers. The system operation can be cancelled to let the nose wheels move freely during aircraft ground movement.
The steering system is controlled by the BSCU (Ref. AMM D/O 32-46-00-00). The steering system changes the direction of the aircraft when it moves on the ground. The system uses the Green main hydraulic-power system (Ref. AMM D/O 29-11-00-00) to operate a steering mechanism which changes the direction of the NLG wheels. Two handwheel transmitters in the cockpit supply the primary steering inputs to the BSCU. The rudder pedals and the autopilot supply secondary input to the BSCU through the flight control primary computers. The system operation can be cancelled to let the nose wheels move freely during aircraft ground movement.
The steering system is controlled by the BSCU (Ref. AMM D/O 32-46-00-00). The steering system changes the direction of the aircraft when it moves on the ground. The system uses the Yellow main hydraulic-power system (Ref. AMM D/O 29-13-00-00) to operate a steering mechanism which changes the direction of the NLG wheels. Two handwheel transmitters in the cockpit supply the primary steering inputs to the BSCU. The rudder pedals and the autopilot supply secondary input to the BSCU through the flight control primary computers. The system operation can be cancelled to let the nose wheels move freely during aircraft ground movement.
F. Position and Warning (Ref. 32-60-00)
The position and warning system has two parts which are:
The position and warning system has two parts which are:
- indicating and warning (Ref. AMM D/O 32-61-00-00)
- L/G BITE (Ref. AMM D/O 32-69-00-00).
(1) Indicating and Warning (Ref. AMM D/O 32-61-00-00)
The indicating and warning system has proximity sensors on the L/G and L/G doors to give position data to the LGCIU. Indication is given to the flight crew on ECAM and:
The indicating and warning system has proximity sensors on the L/G and L/G doors to give position data to the LGCIU. Indication is given to the flight crew on ECAM and:
- L/G control lever
- LDG gear annunciators on panel 402VU, if specified failures occur
- a warning is given on the Engine Display Unit (EDU) (Ref. AMM D/O 31-66-00-00)
- the fuel page on the SD
- the flight warning computer (Ref. AMM D/O 31-52-00-00) gives an audible and visual warning to the flight crew.
(2) Landing Gear BITE (Ref. AMM D/O 32-69-00-00)
Each LGCIU contains BITE which continuously monitors the system for failures. The BITE supplies data to the Centralized Fault Display System (CFDS) (Ref. AMM D/O 31-30-00-00). The functions of the BITE are:
Each LGCIU contains BITE which continuously monitors the system for failures. The BITE supplies data to the Centralized Fault Display System (CFDS) (Ref. AMM D/O 31-30-00-00). The functions of the BITE are:
- To continuously monitor the system for failures
- To do a test of related systems during power-up
- To keep a record of failures and send this data to the CFDS and the data recording system (Ref. AMM D/O 31-30-00-00)
- To do a system test during ground maintenance
- To simulate the different configurations of landing gear during maintenance.
5. Power Supply
A. Electrical
Landing Gear - Electrical Power Supplies ** ON A/C NOT FOR ALL
Landing Gear - Electrical Power Supplies ** ON A/C NOT FOR ALL
Landing Gear - Electrical Power Supplies ** ON A/C NOT FOR ALL Landing Gear - Electrical Power Supplies ** ON A/C NOT FOR ALL B. Hydraulic
** ON A/C NOT FOR ALL
7. Operation/Control and Indicating
Operation of the Landing Gear System ** ON A/C NOT FOR ALL
Operation of the Landing Gear System ** ON A/C NOT FOR ALL
Operation of the Landing Gear System ** ON A/C NOT FOR ALL
Operation of the Landing Gear System ** ON A/C NOT FOR ALL
Operation of the Landing Gear System ** ON A/C NOT FOR ALL Operation of the Landing Gear System ** ON A/C NOT FOR ALL Operation of the Landing Gear System ** ON A/C NOT FOR ALL Operation of the Landing Gear System ** ON A/C NOT FOR ALL A. Main Gear and Doors
(1) Takeoff
On takeoff the loads on the MLG decrease. As the aircraft becomes airborne, the shock absorber extends which gives the effect of an increase in the length of the leg. This lets the aircraft move through a large angle during takeoff.
When L/G UP is selected the hydraulically operated door opens. Hydraulic pressure at the down lock actuator releases the overcenter lock of the lock stay. The MLG actuator retracts the MLG into the bay. During retraction the BSCU automatically puts the brakes on for a short time. This stops the rotation of the wheels before they go into the bays. The hydraulically operated door closes after the MLG is locked into the bay.
When L/G DOWN is selected the hydraulically operated door opens. The retraction actuator extends to extend the leg. The side stay and the lock stay move to the over center position to lock the gear in the extended position. The door closes after the gear is extended. With the gear extended the shock absorber absorbs the landing loads.
On takeoff the loads on the MLG decrease. As the aircraft becomes airborne, the shock absorber extends which gives the effect of an increase in the length of the leg. This lets the aircraft move through a large angle during takeoff.
When L/G UP is selected the hydraulically operated door opens. Hydraulic pressure at the down lock actuator releases the overcenter lock of the lock stay. The MLG actuator retracts the MLG into the bay. During retraction the BSCU automatically puts the brakes on for a short time. This stops the rotation of the wheels before they go into the bays. The hydraulically operated door closes after the MLG is locked into the bay.
When L/G DOWN is selected the hydraulically operated door opens. The retraction actuator extends to extend the leg. The side stay and the lock stay move to the over center position to lock the gear in the extended position. The door closes after the gear is extended. With the gear extended the shock absorber absorbs the landing loads.
(2) Nose Landing Gear and Doors
As the NLG wheels leave the ground on takeoff, the shock absorber extends. The cams in the leg make sure that the wheels are in the center. When the shock absorber is fully extended the BSCU prevents steering outputs to the steering mechanism.
When the L/G UP is selected the hydraulically operated doors open. Hydraulic pressure at the NLG downlock actuator releases the overcenter lock of the lock stay. The drag strut assembly folds as the NLG retracts. As the leg retracts a rotating joint on the leg cuts off the hydraulic pressure supply to the steering system. The hydraulically operated doors close after the gear is locked into the bay.
As the NLG wheels leave the ground on takeoff, the shock absorber extends. The cams in the leg make sure that the wheels are in the center. When the shock absorber is fully extended the BSCU prevents steering outputs to the steering mechanism.
When the L/G UP is selected the hydraulically operated doors open. Hydraulic pressure at the NLG downlock actuator releases the overcenter lock of the lock stay. The drag strut assembly folds as the NLG retracts. As the leg retracts a rotating joint on the leg cuts off the hydraulic pressure supply to the steering system. The hydraulically operated doors close after the gear is locked into the bay.
(3) Extension and retraction
(a) Normal Extension and Retraction
When the L/G control lever is moved the LGCIU sends a control signal to the electro-hydraulic safety valve. The LGCIU controls the sequence of operations to extend and retract the gears and open and close the doors. The LGCIU uses the position data from the proximity sensors (Ref. AMM D/O 32-61-00-00) to control the sequence of operations.
Only one LGCIU controls the sequence of operations. Control changes from one LGCIU to the other after each retraction/extension cycle.
When the L/G control lever is moved the LGCIU sends a control signal to the electro-hydraulic safety valve. The LGCIU controls the sequence of operations to extend and retract the gears and open and close the doors. The LGCIU uses the position data from the proximity sensors (Ref. AMM D/O 32-61-00-00) to control the sequence of operations.
Only one LGCIU controls the sequence of operations. Control changes from one LGCIU to the other after each retraction/extension cycle.
(b) Free Fall Extension
The free fall extension system is controlled by the free fall extension handle in the cockpit. The free fall extension handle is connected to the L/G and door uplocks. When the handle is turned the door uplocks are mechanically opened by the cables. When the doors are open the landing uplocks are also mechanically opened. Gravity then extends the L/G. Springs pull the NLG lock stay and the MLG side stay into the locked position and the L/G doors stay open.
A mechanically operated valve isolates the hydraulic supply. Other mechanically operated valves let fluid move into the hydraulic components of the normal extension and retraction system. This prevents cavitation and hydraulic locks.
The free fall extension system is reset when:
The free fall extension system is controlled by the free fall extension handle in the cockpit. The free fall extension handle is connected to the L/G and door uplocks. When the handle is turned the door uplocks are mechanically opened by the cables. When the doors are open the landing uplocks are also mechanically opened. Gravity then extends the L/G. Springs pull the NLG lock stay and the MLG side stay into the locked position and the L/G doors stay open.
A mechanically operated valve isolates the hydraulic supply. Other mechanically operated valves let fluid move into the hydraulic components of the normal extension and retraction system. This prevents cavitation and hydraulic locks.
The free fall extension system is reset when:
- the free fall extension handle is back in its original configuration
- the L/G control lever (6GA) is put in the down position.
(4) Braking and Related Systems
(a) Normal Braking
In the automatic mode the selection of a AUTO/BRK P/BSW (LO MED or MAX) sets a program to give a set deceleration rate. The BSCU automatically starts the program when the aircraft configuration is correct and then controls the pressure sent to the brakes.
In the manual mode the movement of the brake pedals operates the brake-pedal transmitter unit. The transmitter unit sends a signal to the BSCU which in turn sends the required input signal to the servovalves. The servovalves let a pressure, in proportion to the pedal travel go to the brakes.
The BSCU also controls the anti-skid function. It compares the MLG wheel speeds with the aircraft speed and releases a brake if there are indications of a skid.
In the automatic mode the selection of a AUTO/BRK P/BSW (LO MED or MAX) sets a program to give a set deceleration rate. The BSCU automatically starts the program when the aircraft configuration is correct and then controls the pressure sent to the brakes.
In the manual mode the movement of the brake pedals operates the brake-pedal transmitter unit. The transmitter unit sends a signal to the BSCU which in turn sends the required input signal to the servovalves. The servovalves let a pressure, in proportion to the pedal travel go to the brakes.
The BSCU also controls the anti-skid function. It compares the MLG wheel speeds with the aircraft speed and releases a brake if there are indications of a skid.
(b) Alternate Braking
When the brake pedals are operated the low-pressure hydraulic system operates a dual valve. This lets hydraulic pressure from the yellow hydraulic system go to the second set of pistons in the brakes. The BSCU controls the anti-skid function. If the BSCU cannot supply this control, braking is in proportion to the amount of pedal travel.
When the brake pedals are operated the low-pressure hydraulic system operates a dual valve. This lets hydraulic pressure from the yellow hydraulic system go to the second set of pistons in the brakes. The BSCU controls the anti-skid function. If the BSCU cannot supply this control, braking is in proportion to the amount of pedal travel.
(c) Parking Brakes (Ref. AMM D/O 32-45-00-00)
When the park brake selector switch is set to ON, pressure from the yellow hydraulic system or the related accumulators is sent to the second set of pistons in the brakes. When this system is in use all other braking systems are hydraulically isolated.
When the park brake selector switch is set to ON, pressure from the yellow hydraulic system or the related accumulators is sent to the second set of pistons in the brakes. When this system is in use all other braking systems are hydraulically isolated.
(d) Brake Temperature System (Ref. AMM D/O 32-47-00-00)
The brake temperature system continuously measures the temperature at each brake. The sensor at each brake sends a signal to a Brake Temperature Monitor Unit (BTMU). Each BTMU receives the signals from a pair of brake sensors and sends the data to the BSCU. The BSCU sends the data to other interface systems.
The brake temperature system continuously measures the temperature at each brake. The sensor at each brake sends a signal to a Brake Temperature Monitor Unit (BTMU). Each BTMU receives the signals from a pair of brake sensors and sends the data to the BSCU. The BSCU sends the data to other interface systems.
(e) Brake Cooling (if installed) (Ref. AMM D/O 32-48-00-00)
When the P/BSW is set to ON, the fans in the wheel shrouds turn and pull air through the brakes. This decreases the temperature of the brakes more quickly.
When the P/BSW is set to ON, the fans in the wheel shrouds turn and pull air through the brakes. This decreases the temperature of the brakes more quickly.
(f) Tyre Pressure Indicator System (if installed) (Ref. AMM D/O 32-49-00-00)
The TPIS automatically monitors the tire pressures and shows these values on the WHEEL page of the system display (Ref. AMM D/O 31-60-00-00). The tire pressure indicating computer also supplies other data and warnings when the pressures are unsatisfactory.
The TPIS automatically monitors the tire pressures and shows these values on the WHEEL page of the system display (Ref. AMM D/O 31-60-00-00). The tire pressure indicating computer also supplies other data and warnings when the pressures are unsatisfactory.
(g) Steering (Ref. AMM D/O 32-51-00-00)
The BSCU uses the steering input signals from the hand wheel transmitters in the cockpit to calculate:
The BSCU uses the steering input signals from the hand wheel transmitters in the cockpit to calculate:
- the necessary steering angle
- the necessary rate of movement
- the direction of the turn.
B. Indicating
Data from the L/G systems is shown on the WHEEL page of the systems display (Ref. AMM D/O 31-60-00-00).
System warnings are given on:
Refer to (Ref. AMM D/O 32-61-00-00) for the L/G configuration and fault warnings. For other warnings refer to the specified chapter.
Data from the L/G systems is shown on the WHEEL page of the systems display (Ref. AMM D/O 31-60-00-00).
System warnings are given on:
- the L/G control lever (6GA)
- the cockpit loudspeakers
- the master warning and caution lights
- the EWD
- LDG Gear UNLK annunciators.
Refer to (Ref. AMM D/O 32-61-00-00) for the L/G configuration and fault warnings. For other warnings refer to the specified chapter.
8. BITE Test
The BITE has these functions, it:
The BITE in the computers is described in these chapters:
The BITE has these functions, it:
- continuously monitors its system for failures
- sends failure data to other interface systems (maintenance and warnings)
- keeps a record of failures
- automatically does specified test of the systems, or part of the system, at specified times
- lets specified tests be done during ground maintenance.
The BITE in the computers is described in these chapters:
- the BSCU in (Ref. AMM D/O 32-46-00-00)
- the LGCIU in (Ref. AMM D/O 32-62-00-00).