An overview on landing gear system and sub-systems of the Airbus A 380

1. 1

2. A380
• Role Wide-body, double-deck jet airliner
• National origin Multi-national
• Manufacturer Airbus
• First flight 27 April 2005
• Introduction 25 October 2007 (with Singapore Airlines)
• Status In service
• Produced 2005–present
• Number built 193 as of 31 July 2016
• Unit cost US $ 432.6 million (2016)
• Seating capacity typical: 644 (2-class) 868 (EASA Certification)
• Range at design load : 15,200 km (8,200 nmi; 9,400 mi)
2

3. L/G sys. Components
The Landing Gear (L/G) System includes:
A number of control devices in the cockpit
A number of computers in the avionics compartment
A number of Landing Gears and their related doors
An extension and retraction system for the gears and doors
A system of brakes and related systems
A tire pressure indicating system
An oleo pressure and tempreture monitoring system
A steering system (NLG and BLG).
3

4. Configuration
Two Wing Landing Gears (WLG) and related doors
Two Body Landing Gears (BLG) and related doors
A Nose Landing Gear (NLG) and related doors.
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5. 5

6. 6

7. 7

8. Flight crew inputs(or ground
personnel) :
The control devices in the cockpit let the flight crew make the
necessary inputs to some of the computers.These inputs tell
the computers how to control the L/G functions that follow:
• Extension and retraction
• Braking
• Steering
8

9. Wing Gear and Doors
9

10. Wing Gear components
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11. 11
Safety collars and pins for
protection in maintenance

12. The WLG includes :
• bogie trim actuator (BTA) and an oleo-pneumatic shock absorber. The BTA and the
shock absorber make sure that the four-wheel bogie beam is at the correct angle and
length at take off and landing.
• A two-piece side stay assembly holds the WLG in the extended position. A lock link
keeps the side stay assembly stable in the locked down position. Four doors close each
WLG bay. These are:
• A hydraulically-operated main door
• A mechanically-operated auxiliary door
• A mechanically-operated hinge door
• A leg door attached to the WLG leg.
• An electrically operated and controlled Ground Door Opening (GDO) system (for
maintenance personnel) lets the main doors be opened for access to the WLG bay,
when the aircraft is on the ground. 12

13. Body Gear and Doors
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14. 14

15. Safety collars and pins for
protection in maintenance
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16. 16

17. 17

18. Body landing gear
The landing gear retracts aft into a bay, in the fuselage. A two-piece dragstay
assembly mechanically locks the leg in the extended position. A bogie trim
actuator is used to position the bogie beam when weight is off the landing
gear during take-off, retraction and landing. The aft axle of the bogie beam
is not braked and has a steering mechanism .
Four doors close each BLG bay. These are:
• three hydraulically-operated doors
• a driven fairing door attached to the inner door
• An electrically operated ground door opening mechanism (for
maintenance personnel) lets the doors be opened for access to the BLG
bay when the aircraft is on the ground. 18

19. Nose Gear
and Doors
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20. 20

21. 21

22. Safety collars and pins for
protection in maintenance
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23. 23

24. Extension and Retraction
• The system is electrically controlled and hydraulically operated. Two independent electrical system
control the operation of the hydraulic components.
• proximity sensors give the L/G configuration to computers and avionic devices.
• Two Independent hydraulic circuits supply solenoid-operated selector valves. Each valve has a set task.
• These valves use the Green Hydraulic Power system for the WLG and NLG and the Yellow Hydraulic
system for the BLG to:
a· extend/retract the landing gear
b· open/close the L/G doors
• The LGERS (Landing Gear Extension and Retraction System)controls the valves to get the correct system
operation. If the normal Extension and Retraction System is not available, the Emergency (Free Fall)
Extension System extends the WLG, BLG and the NLG. The system includes electric actuators. The
actuators operate to open the gear and door uplocks and hydraulic valves. This lets gravity extend the
gears.
24

25. Schematic diagram
25

26. MLG extension/retraction
26

27. WLG extension/retraction
27

28. Free fall extension sys.
• The independency of free fall extension system makes sure that a failure in the normal
system cannot prevent the free fall system from operating.
• The system is activated from a dedicated free fall switch, installed on the instrument panel in
the cockpit.
• The emergency extension operating sequence is controlled by a Free Fall Control Module
(FFCM), which is a dual system.
• To get a free fall extension, the FFCM has to:
1. Isolate the hydraulic supply pressure from the L/G hydraulic circuits; this is achieved by cut
out valves. There is a cut out valve for each gear group (NLG, WLG and BLG):
2. To get free flow between the ports of gear and door actuators; this is achieved by vent
valves. There is a vent valve for each individual gear bay (NLG, L WLG, R WLG, L BLG and R
BLG):
3. To release gear and door uplocks, such as the gears and doors can fall under gravity.
28

29. Schematic diagram
29

30. Ground door opening sys.
• The GDO system is operated on the ground from outside the A/C for access to the L/G
bays for maintenance.
• Five ground door-opening handles adjacent to the L/G bays operate the doors.
• To get door opening, first, the related hydraulic door actuator is isolated from the
LGERS hydraulic circuit.
• This is achieved by using a door bypass valve that connects extend and retract ports of
the door actuator together and blocks the door close pressure line.
• There is one door bypass valve per individual door(s) operation (NLG, L WLG, R WLG, L
BLG and R BLG).
• Following the door actuator isolation, the door uplock is unlocked and the door opens
under gravity.
• Closing the door is accomplished in reverse order by resetting the system; after that,
the control returns to the normal operating system.
• Resetting the GDO System is only possible if hydraulic pressure is available. 30

31. GDO system
31

32. GDO handle
32

33. Wheels, Braking and Related Systems
• The Braking Control System (BCS) supplies aircraft retardation during landing, taxi and in
case of a Rejected Take Off. The nose gear and the aft axles of the body gears do not have
brakes installed.
• The braking orders are generated by the auto brake system, the brake pedals and the
parking brake handle.
• The WLG and BLG braked wheels are interchangeable. Non braked wheels cannot be
installed on braked axles, however braked wheels can be installed to non braked axles.
• The Normal Braking System is a computer controlled electro-hydraulic system used to
decrease the speed of the aircraft when it moves on the ground. The system includes a
computer whose function is shared by a number of landing gear systems. Braking control
is provided by Remote Data Concentrators (RDC).The CPIOMs(Core Processing and Input
Output Modules) control the operation of the electro-hydraulic valves in the system.
33

34. Operation modes
• The BCS has five modes of operation :
1- Normal braking with anti-skid capability
2- Alternative braking with anti-skid capability
3- Emergency Braking (with Ultimate Braking)
4- Emergency braking without anti-skid protection is also available as an alternative
function of the alternate braking system.
5- A park brake system that is manually set is available for the BLG only. This system can
also be used to supply emergency braking.
• If the normal hydraulic system fails, the Local Electro-Hydraulic Generation System
(LEHGS) and/or accumulators supply power for the alternate and emergency modes. The
parking brake system operates only on the BLG wheels.
• Hydraulic pressure for the parking brake is from accumulators only.
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35. • There are three braking groups: WLG, left BLG and right BLG. Each group
can operate independently in normal, alternate or emergency modes.
• Hydraulic power for the alternate, emergency, ultimate and parking brake
is supplied by high pressure accumulators and/or Local electro-Hydraulic
Generator Systems (LEHGS) through the alternate circuit, one LEHGS for
the BLG and one LEHGS for the WLG.
Operation modes
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36. brake sys. general schematic
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37. Normal braking
• The control of the Braking Control System (BCS) is based on two redundant systems. Each
system has Core Processing Input/Output Modules (CPIOMs) and Interface Remote Data
Concentrators (IRDCs).
• The normal braking mode includes the following functions:
1- Pedal braking,
2- Auto brake,
3- Antiskid
4- Retraction braking.
• The normal braking circuit draws hydraulic power from the centralized aircraft hydraulic
system. Two valves in series are used to control the pressure in the circuit.
• The first valve is an isolation valve, named the Normal Brake Selector Valve (NBSELV), the
valve isolates the hydraulic power supply from the rest of the braking circuit. The NBSELV is
controlled by the CPIOMs.
• The second valve is the Normal Servo Valve (NSV) which function is to control pressure to the
demanded level and to supply regulation for the Anti-Skid function. Each NSV controls the
two brakes installed on the axle. The NSV is controlled by the CPIOMs via the Interface
Remote Data Concentrators (IRDC).
• The auto brake can be used during landing or during a Rejected Take Off (RTO).
• Brakes indications and warning are given by the CPIOMs through the ECAM.
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38. Normal mode schematic
38

39. Alternate braking
• If the normal braking fails, the alternate braking takes over. The alternate
braking mode includes the following functions:
1- Pedal braking 2- Auto braking 3- Anti-skid
• The Alternate circuit maintains a similar hydraulic valve layout to the
Normal circuit, with an Alternate Brake selector Valve (ABSELV) placed in
series with an Alternate Servo Valve (ASV). The ABSELV is commanded by
the CPIOMs and the ASV is commanded by the CPIOMs through IRDCs.
• The hydraulic power is supplied by a Local Electro-Hydraulic Generation
System (LEHGS), which works in unison with an accumulator to meet the
pressure and flow requirements of the Alternate circuit. A Bogie Shuttle
Valve(BSV) selects the highest pressure from the Normal and
• Alternate circuits. The CPIOMs give brakes indications and warnings
through the ECAM. The triple gage indicator shows information related to
the BLG brake pressures in alternate, emergency, ultimate and parking
modes. It shows in the higher needle the lowest BLG accumulator pressure
and in the lower needles the left and right BLG alternate pressure. 39

40. Alternate braking schematic
40

41. Triple gage indicator
in the higher needle the lowest BLG accumulator pressure and in the lower
needles the left and right BLG alternate pressure.
41

42. Emergency braking
• If BCS function is lost, the Emergency Brake Control Unit (EBCU) is engaged
to control the emergency braking with pedals orders only and limited
braking pressure. It operates only in manual pedal braking mode and Anti-
Skid protection is not available. Braking inputs are made at the brake
pedals through their related transmitter.
• The EBCU uses the alternate hydraulic circuit and controls the ABSELV and
ASV.
42

43. Emergency braking schematic
43

44. Ultimate braking
• Ultimate braking supplies braking for the aircraft in the event that pedal
braking is unavailable or when control of Normal, Alternate and
Emergency Braking systems is not available. The LEHGS and/or the
accumulator supply power the ultimate braking. Braking is initiated by
parking brake switch action. The EBCU commands through the alternate
hydraulic circuit, a limited pressure on WLG brakes, when the flight
Control System (FCS) gives ground spoiler deployment signal.
• The Parking brake switch will simultaneously activate the Parking brake
circuit and apply Parking brake pressure on the BLG brakes.
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45. Ultimate braking schematic
45

46. Parking brake
• The parking brake function is available only for the BLG wheels.
• The Parking Brake Selector Valve (PBSELV) commanded by the park brake
switch is installed in parallel with the ABSELV, and the two sub-circuits are
joined via a Shuttle Valve(SV). The shuttle valve moves over to let the
highest pressure supply the service lines.
• Normal and Alternate braking circuits remain active during and after
application of Parking Brake. An accumulator re-inflate switch adjacent to
the park brake switch operates the BLG LEHGS and the WLG LEGHS, to
pressurize the BLG and WLG accumulators.
46

47. Parking brake schematic
47

48. Alternate Circuit Refilling
• The Alternate Refilling Valves (ARVs) are used to replenish the WLG and
BLG accumulators and reservoirs, from the aircraft hydraulic circuit. There
are two ARVs for the BLG, one for the Left BLG and one for the R BLG, and
one for the WLG (Left WLG and Right WLG).
• They are commanded open once per flight cycle only, after engine start.
• Each ARV is controlled independently by the CPIOMs and is commanded
open if the accumulator pressure is below a defined pressure, or the
LEHGS reservoir is not in the full condition.
• In the PARK BRK panel an ACCUS REINFLATE push button is connected to
the WLG LEHGS ECU and to the BLG LEHGS ECU allowing the BLG and the
WLG accumulators re-inflation.
48

49. Alternate Circuit Refilling
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50. Auto braking
• For automatic braking a rotary selector switch (LDG) in the cockpit sets the auto
braking program to be used during a landing.
• The switch sets one of four deceleration rates, LO, 2, 3 and HI. An adjacent P/BSW
sets (ARM) the automatic braking system for operation during a Rejected Take-off
(RTO).
• Auto braking is available in normal and alternate modes.
50

51. Rudder Pedal operation
The output signals from the brake pedals are in relation to the amount of
pedal travel. Each pedal supplies braking independently to its related WLG
and BLG. The left pedal gives the quantity of braking on the left WLG
wheels and the left BLG wheels. The right pedal gives the quantity of
braking on the right WLG wheels and the wheels of the right BLG. If the
pedals give an input signal which is more than a specified value, this
cancels the automatic braking program.
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52. Brake Temp. Monitoring Sys. (BTMS)
• The brake temperature sensors monitor the temperature of the sixteen
brake packs and send the information to the CPIOMs through LGRDC.
• The CPIOMs compute and supply an alert to the flight and maintenance
crew when one or several brake temperatures are outside defined limits.
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53. BTMS
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54. Steering
• The Steering System is a computer controlled electro-hydraulic system used
to change the direction of the aircraft when it moves on the ground with
engine power. The system uses nose wheel steering (NWS) and body wheel
steering (BWS).
• Power for the hydraulic components in the system is supplied:
· by the Green Hydraulic Power system for the NWS
· by the Yellow Hydraulic System for the BWS.
• The N/WS system is also powered by a Local Electro-Hydraulic Generation
System (LEHGS) working in unison with an HP accumulator, for the alternate
mode of operation
54

55. • The hydraulic components operate a steering mechanism which
changes the aircraft direction. These mechanisms turn the NLG
wheels and the BLG aft axle wheels.
• The CPIOMs control and monitor the operation of the system. Two
hand-wheel transmitters in the cockpit supply the primary steering
inputs to the CPIOMs. The rudder pedals and the autopilot supply
secondary steering inputs to the CPIOMs through the flight control
computers .
• The system operation can be:
· cancelled to let the nose wheels castor during aircraft movement
on the ground
· isolated from the rudder pedal inputs during the pre-flight check.
• N/WS and BWS commands are reduced as A/C speed increases.
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Steering

56. 56

57. Nose Wheel Steering (N/WS)-Normal System
• The WSCS function receives the steering orders either from the rudder
pedals, the autopilot, or hand-wheels. The WSCS controls the Normal
Selector Valve (NSELV) and the Electro Hydraulic Servo Valve (EHSV) to get
the nose wheel steering position.
• The NSELV isolates the N/WS circuit from the green hydraulic supply when
it works in alternate mode.
• The EHSV controls the hydraulic flow to both steering actuators.
• Steering indications and warning are given by the WSCS through the
ECAM.
57

58. N/WS normal mode
58

59. Nose Wheel Steering (N/WS)-Alternate System
• If the normal system fails, the alternate system uses hydraulic power from the
LEHGS and the accumulator. The WSCS controls the Alternate Selector Valve
(ASELV). The ASELV isolates or supplies the N/WS circuit.
• There is a Shuttle valve (SV) located down stream of both the NSELV and ASELV,
which controls the supply of hydraulic fluid. The selected position of the shuttle
valve is achieved automatically by differential pressure.
• The Electro Hydraulic Servo Valve (EHSV) controls the hydraulic flow to and from
both steering actuators. Indications and warning are given by the WSCS through
the ECAM.
• The Alternate Refill valve (ARV) is opened, if necessary, at the beginning of each
flight to refill the accumulator.
59

60. N/WS alternate mode
60

61. N/WS Alternate circuit refilling
61

62. Steering disconnenction
A steering disconnection box installed on the nose landing gear to allow
steering deactivation for towing purpose as picture below :
62

63. Body Wheel Steering (BWS)
• The main function of the BWS is to increase low ground speed
maneuverability. The BWS is controlled and monitored by CPIOMs, hosting
the WSCS application. BWS command is a function of the N/WS angle.
The BWS Bay Mounted SELector Valve (BMSELV), controls yellow hydraulic
pressure to both the left and right hand BWS. The left and right Steering
SELector Valves (SSELV) are connected downstream of the BMSELV .The
left and right Electro Hydraulic Servo Valves (EHSV), meter the hydraulic
pressure to the actuators.
• The left and right Lock SELector Valves (LSELV) are connected to the
hydraulic supply line and isolate the lock actuator from the system
pressure.
• Indications and warning are given by the WSCS through the ECAM. 63

64. BWS sys schematic
64

65. Oleo Pressure Monitoring System (OPMS)
• This system measures and gives the oleo pressure of the gears to the flight
and maintenance crew.
• It monitors the pressure and temperature of the gears and transmits the
information to the Integrated Modular Avionics (IMA) through the Landing
Gear Remote Data Concentrator (L/G RDC).
• The Oleo Pressure and Temperature Sensors (OPTS) acquire pressure and
temperature for each L/G.
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66. 66

67. Tire Pressure Indicating System (TPIS)
• Tire pressure is indicated to the flight and maintenance crew through a
Tire Pressure Indicating System (TPIS) hosted in the CPIOMs.
• Tire pressure is measured by pressure sensor, one for each wheel and sent
to the CPIOMs through L/G RDC.
• Note: The TPIS is installed as an option.
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68. 68

69. ECAM L/G page
69

70. The End
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