Landing gear system of the Airbus A 380

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

1. An outlook on Landing gear of the Airbus A380 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. 4

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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 10

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 13

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15. Safety collars and pins for protection in maintenance 15

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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 19

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22. Safety collars and pins for protection in maintenance 22

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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. 34

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 35

36. brake sys. general schematic 36

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 . 37

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. 44

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 49

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. 51

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. 52

53. BTMS 53

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. 55 Steering

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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. 65

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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. 67

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69. ECAM L/G page 69

70. The End 70