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Global Expresss > Landing Gear > Flashcards

Landing Gear Flashcards

1
Q

What type of landing gear is used

A

The Global series aircraft has a conventional tricycle landing gear with a dual wheel installation on each gear assembly. The landing gear system consists of a landing gear extension and retraction system, manual release system, nosewheel steering system and a brake system.

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2
Q

What type is main landing gear

A

The main landing gear assembly (mounted at each wing root) is an inboard retracting, lever suspension type, fitted with a mixed gas/oil shock strut. The nose gear assembly (mounted on the forward fuselage centerline) is forward retracting and has an internal gas/oil shock strut. Both the main and nose landing gear are fully enclosed by landing gear doors while retracted.

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3
Q

How is gear controlled

A

Normal landing gear extension and retraction is electrically controlled by the landing gear electronic control unit (LGECU), and carried out in response to the movement of the landing gear selector lever in the flight deck. Hydraulic pressure from systems no. 2 and 3 is used for gear extension and retraction, and for a normal brake operation.

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4
Q

What does LGECU do

A

The landing gear electronic control unit (LGECU) provides landing gear and door position information for status display, warnings, and gear control. It also provides weight-on-wheels (air ground/mode) information to other aircraft systems.

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5
Q

Is nose gear steer by wire

A

The nose gear is equipped with a steer by wire electronically controlled steering system, which provides precise control from the cockpit via the nosewheel steering hand wheel or the rudder pedals. The nosewheel steering system is controlled and monitored by the steering control unit (SCU).

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6
Q

Are the brakes by wire

A

The main wheels are equipped with carbon disk brakes controlled by a brake by wire antiskid system with an autobraking capability. The brake system is controlled and monitored by the brake control unit (BCU).

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7
Q

Is there a mute for horn

A

Yes

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8
Q

Is their BTMS o/h warn reset

A

Yes

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9
Q

How is gear held in up position

A

Uplock hook

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10
Q

Where are faults detected

A

The main gear sequencing and position sensing system are controlled and continuously monitored by the LGECU. Any fault or position deviation detected is displayed on EICAS.

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11
Q

Where does event marker store

A

NVM

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12
Q

Does it have auto brake

A

Yes, set in fms in flight

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13
Q

Where is event button

A

By gear select lever

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14
Q

Does EICAS disappear after t/o

A

Yes after 28 secs, except if there is a problem, then will re appear

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15
Q

What hyd system retracts gears

A

Each main gear retracts inward and up into the main landing gear bay and is mechanically held in the retracted position by an uplock mechanism. The gear is mechanically locked in the extended position by internal locking side brace actuators. During normal operation, the uplock and downlock mechanisms are hydraulically actuated to release the main gear. Hydraulic system no. 3 pressure is maintained to the side brace actuators while the gear is extended. This serves as a secondary downlock safety feature. Hydraulic system no. 3 is used to release all gear and door uplocks, downlocks, nose gear actuator (extension and retraction), and main gear side brace actuators during normal locking and unlocking. The main gear retract actuators (used to raise and lower the main gear) are powered by hydraulic system no. 2 and also assist during manual gear extension operation.

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16
Q

Where is shock strut serviced

A

The strut is serviced with oil (MIL-H-5606) through a check valve located at the bottom of the piston, and charged with nitrogen through the top of the cylinder.

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17
Q

How many prox sensors in wheel well

A

9 in each wheel well

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18
Q

Where is mlg charging valve

A

Top of leg

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19
Q

Where is Nlg charging point

A

Bottom of leg

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20
Q

What hyd syst to raise

A

Syst 2 to raise and lower the MLG

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21
Q

How many actuators

A

Retraction actuator and side brace actuator

22
Q

When does side brace assy actuate

A

Hydraulic pressure is introduced to the extend side of the side brace assembly only when the gear is around 5 degrees from the fully extended position. This ensures that the gear extends fully so the downlock can engage. In the retract mode, hydraulic pressure is introduced to release the downlock on the UP selection, but is removed as the main gear passes the first 5 degrees of retraction. The side brace assembly uses hydraulic system no. 3 pressure.

23
Q

What happens with no hyd power

A

During manual gear extension, a shutoff valve blocks system no. 3 pressure from going to the gear and door selector valves, and the side brace actuator. System no. 2 pressure is still used to activate the retract actuators to the extend position, and this will force the side brace to the down-andlocked position.

In the event of a loss of the system no. 2 pressure, the uplocks would release normally on an extend command, using system no. 3 pressure. Gravity would allow the main gear to extend, with system no. 3 pressure being applied to the side brace actuators, once they come within approximately 5 degrees of full extension. This

24
Q

What do the actuators do during retraction/extension

A

Retraction= the side brace retracts and the retraction actuator extends, controlled by prox switches ans LGECU to port fluid

25
Q

What is hydraulic uplock actuator

A

It sits above the uplock and is a plunger type , which pushes on lever only acting against a spring

26
Q

What does uplock do

A

The uplock is a locking device that automatically secures the main gear in the retracted position. The uplock is bolted to a bracket affixed to the main wheel well structure. The uplock is locked mechanically and unlocked hydraulically by the uplock hydraulic actuator during normal gear extension. The lock is mechanically released during emergency gear extension by a cable attached to the manual release lever. A proximity sensor provides for the uplock sensing.

27
Q

How many prox sensors in side brace actuator

A

2

28
Q

What is nose gear configuration

A

The nose landing gear consists of a nose gear assembly with a built-in shock strut, a folding drag brace incorporating a mechanical downlock, a dual acting hydraulically operated retraction actuator, an uplock assembly and nose steering components. The nose gear retracts forward into the nose bay area and is held in the retracted position by an uplock mechanism. During normal operation, a downlock actuator within the drag brace ensures downlock when the gear is extended. The nose gear is actuated by hydraulic system no. 3 to operate the uplock, downlock and retraction actuator. Hydraulic system no. 3 pressure to the nose gear is

29
Q

How many prox sensors in nose gear

A

11

30
Q

Is there a blowout panel in nose gear

A

Yes avionics blowout panel

31
Q

Does nose have re centering

A

Yes its mechanical and electric with sensors

32
Q

How does nose gear uplock work

A

The uplock assembly secures the nose gear in the retracted position. The lock closes mechanically and is opened by a hydraulic actuator for normal extension. The actuator extends hydraulically to release the uplock and allow nose gear extension. On a retract command, the actuator plunger is hydraulically retracted to prevent interference with the lock mechanism. An uplock proximity sensor is installed on the uplock assembly for indication and control purposes. During an alternate gear extension the uplock is mechanically released by a cable input from the manual release handle.

33
Q

What side can nose leg pin be fitted

A

L/h side

34
Q

How are doors operated

A

The landing gear door system consists of hydraulically and mechanically actuated doors, a selector valve, actuators and door uplocks. The landing gears are completely faired while the gears are in the retracted position. Each main gear has one door, which moves with the gear and one hydraulically actuated door. The nose gear has one small door, which moves with the gear and two forward doors that are positioned by one hydraulic actuator. The same door selector valve actuates all hydraulically actuated landing gear doors.

35
Q

What happens on gear retraction

A

On a landing gear retraction selection, one door at each main gear and two doors at the nose gear open hydraulically to allow the gear to retract. After the gear is up and locked, the hydraulically activated doors return to the closed position. One door is fixed to each gear assembly and moves with its gear. On an extend selection, the doors open fully hydraulically, and once the gear is down and locked, the doors will again close.

36
Q

Where is door actuator attached

A

The actuator cylinder end is attached to the keel structure while the piston end is attached to the door. UP and DOWN ports are located on either end of the outer casing of the actuator. Flexible lines extend from the actuator fittings to the tee connectors on a bracket mounted on the forward bulkhead of the main wheel well. Ground safety collars are placed on the MLG door actuator inner cylinder to prevent closing during maintenance activities.

37
Q

Where is door uplock

A

The door uplock and release mechanism is mounted on the forward edge of the wheel well. The uplock housing, containing a latch that engages a roller on the door, is bolted to the airframe. A torsion spring, concentric with the latch pivot pin, ensures positive engagement of the latch. A spring-loaded lock lever, activated by a hydraulic release actuator, releases the latch from the roller on the door on an extend selection. Attached to the lock lever is a target for a proximity sensor that provides an indication signal to the landing gear electronic control unit (LGECU). The uplock can also be manually unlocked by the manual release system.

38
Q

What hyd press is used for nose gear door

A

A hydraulically activated nose door actuator positions the forward nose doors. The actuator is mounted to the uplock assembly and is also connected to the NLG door torque tube. Hydraulic system no. 3 pressure is used in the NLG door actuator. The actuator extends to open the nose doors.

39
Q

How to open gear doors

A

Pull up manual release in flight deck

40
Q

How to close doors

A

Hyd 3 and button on l/h side service panel

41
Q

What is LDGCIS

A

The landing gear and door control and indication system (LGDCIS) consists of 29 proximity sensors, the landing gear panel, landing gear door selector valves, and the landing gear electronic control unit (LGECU).

42
Q

How many prox sensors LGDCIS

A

29

The LGECU combines inputs from the landing gear panel, the 29 sensors (23 landing gear and door sensors, plus 6 WOW sensors), and processes this information. The LGECU then provides landing gear control (extension and retraction), weight-on-wheels (WOW) status (to landing gear and other aircraft systems) and landing gear and fuselage doors position status.

43
Q

What does LGECU do

A

The landing gear electronic control unit (LGECU) provides:
• Landing gear extend/retract control
• Landing gear doors opening and closing control
• Landing gear and landing gear door position and locked status
• Baggage door closed and latched status • Overwing emergency exit door status
• Aft equipment bay door closed status
• Large maintenance hatches and doors closed status In addition to landing gear control and indication functions, the LGECU provides aircraft weight-onwheels (WOW) status to the aircraft systems for operational and maintenance purposes.

44
Q

How many power sources to LGECU

A

The LGECU is located in the right side of the underfloor avionics compartment for the Global Express/XRS and above floor avionic rack for the Global 5000. The LGECU is comprised of two independent subsystems (A and B), each have dual power sources. Subsystem A is powered by 28 VDC from DC bus 1 and the battery bus. Subsystem B is powered by 28 VDC from DC bus 2 and the battery bus.

45
Q

How many selector valves

A

3, 1 per gear

46
Q

When does gear horn sound

A

The “Gear” aural warning horn will sound if any gear is not downlocked and the aircraft begins its landing phase. In some instances (i.e. one engine shutoff) the horn can be muted. If the aircraft is in its final landing phase and the “Gear” aural warning sounds, the horn cannot be muted. A red GEAR warning message is also posted on the EICAS primary page. A white GEAR HORN MUTED status message is posted on the EICAS primary page whenever the horn is muted. The MUTED pushbutton is located on the landing gear panel. The red GEAR warning indication remains posted regardless of muting condition. The mute pushbutton is guarded against inadvertent operation by a spring-loaded cover.

To avoid nuisance warnings, the aural warning is inhibited for 2 minutes after takeoff, when barometric altitude is above 16,500 ft, airspeeds greater than 191 kt with flaps/slats retracted or at airspeeds greater than 165 kt with flaps commanded to less than 30 degrees.

The IAC 1 and 2 aural warning systems, including the “Gear” aural warning, can be muted by two pushbutton annunciators (PBAs) labeled IAC l MUTE and IAC 2 MUTE to be used to mute continuous unwanted warnings in the event of a fault in the IAC 1 or 2 alerting system. Operation of the IAC mute PBAs does not inhibit the red “GEAR” EICAS warning. The PBAs are located on the overhead panel. The mute PBAs are protected against inadvertent actuation by springloaded plastic guards.

47
Q

What is total LGECU failure

A

Total LGECU Failure The LGECU fail safe default is weight off wheels (WOFFW) to most systems except BCU, FMQGC which default to ground: On ground: • Loss of steering • Pressurization control for GRD sequences • Loss of TRs under 45 kt In flight: • Extend/retract control • Loss of gear indication

48
Q

Manual release

A

The landing gear manual release system provides an alternative means of lowering the landing gear in the event of a malfunction in the landing gear control system, or hydraulic system no. 3 not being available. The landing manual release system consists of the handle assembly, the main and nose gear and door quadrant assemblies and valves. The system is activated through a single handle located on the center pedestal in the flight compartment. Operating the release system causes the hydraulic system no. 3 pressure to be dumped from the normal landing gear hydraulic circuit, and mechanically releases all of the door and gear uplocks, allowing the three gear assemblies to freefall. The main gear retraction actuators will still be powered to extend by hydraulic system no. 2, if available.

49
Q

What is shutoff and dump valve

A

The shutoff and dump valves are two separate identical valves in one assembly. The valve is a four-way, two-position mechanically operated spool valve. The spool protrudes from the valve body and attaches directly to the cam follower link activated by the MLG quadrant cam. The shutoff valve is hydraulically located upstream of the landing gear and door selector valves. The valve normally allows hydraulic system no. 3 pressure to go directly to the inlet ports of the selector valves. When the shutoff valve is activated, pressure is blocked and the lines that normally supply pressure to those components are dumped to return. The dump valve is T-connected into the return lines from the MLG uplocks, the close side of the MLG door uplocks and the upside of the side brace actuators. The gear up and the door close lines are connected to the dump valve ports. Activation of the dump valve connects the close line of the MLG door actuators, the upside of the side brace actuators, and the uplocks to return via a separate line.

50
Q

What is alternate power valve

A

The alternate power valve is a six-way, twoposition valve, hydraulically located downstream of the hydraulic system no. 2 selector valve. Its purpose is to completely bypass the hydraulic system no. 2 gear selector valve when activated by the manual release system. When actuated, the valve ports hydraulic system no. 2 pressure directly to the gear downside of the MLG retraction actuator. It also connects the gear up port of the MLG retraction actuator to hydraulic system no. 2 return. When the alternate power valve is not activated through the manual gear release system, it connects the MLG retraction actuator to the hydraulic system no. 2 gear selector valve.

51
Q

What happens to doors after manual release

A

RESET After extending the landing gear using the release system, it is only necessary to return the handle to the stow position while pressing on the PUSH FULLY TO STOW button to return the system to its normal configuration. This resets the manually activated valves and removes pressure from the uplock release levers.

Pulling the handle mechanically releases the door uplocks, blocks hydraulic system no. 3 pressure from the landing gear and ensures the door system is hydraulically routed to return.

The following procedure is used to close the landing gear doors: • All door safety pins and locks are removed • Hydraulic system no. 3 is pressurized and the gear door close momentary switch, located inside the access panel on the left side of the aircraft nose, is pushed in and held • This signals the LGECU to energize the close coil on the door selector valve and allow hydraulic pressure to close the gear doors • Once the gear doors are fully closed the switch can be released

Global Expresss (28 decks)

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