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Indoc > Landing Gear and Brakes > Flashcards

Landing Gear and Brakes Flashcards

1
Q

What are the purpose of the LGCIUs?

A

The landing gear is controlled by two Landing Gear Control Interface Units (LGCIUs). The LGCIUs also determine the aircraft’s air or ground status and supply landing gear information to the ECAM display. One LGCIU operates as the primary while the other operates as a backup. They alternate from primary to backup each time the landing gear is retracted.

The LGCIUs send landing gear position information to the ECAM and LGCIU 1 sends information to the landing gear indicator panel. If LGCIU 1 fails, refer to the WHEEL page for gear position information.

LGCIUs also monitor the landing gear lever position and electronically sequence gear extension or retraction.

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2
Q

How is nose wheel steering and braking controlled?

A

Nose wheel steering and braking is controlled by a Brake Steering Control Unit (BSCU). The BSCU interprets the commands and hydraulically positions the nose wheel.

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3
Q

How are the positions of the landing gears and doors monitored?

A

All 3 landing gears and doors are equipped with proximity detectors that monitor: landing gear uplock, downlock, and shock absorber positions as well as gear door positions and send information to the LGCIUs.

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4
Q

What prevents accidental gear retraction while on the ground?

A

The primary LGCIU process signals from the Landing Gear Selector Lever. If a main or nose gear shock absorber is sensed compressed by the proximity sensors an interlock is activated and the interlock inhibits the selector from being moved to the UP position.

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5
Q

A safety valve prevents landing gear movement when the airspeed is greater than _____ knots.

A

260 knots

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6
Q

When do the UNLK lights appear on the Landing Gear Selector Lever?

A

The UNLK light appears when the gear position differs from the position selected by the Landing Gear Selector Lever.

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7
Q

What does a red triangle on the WHEEL page indicate?

A

A red triangle on the WHEEL page indicates that the LGCIU senses the gear is not down and locked. One proximity detector may be faulty in this case and landing gear position can be confirmed with the other LGCIU.

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8
Q

What does a red triangle on the WHEEL page indicate?

A

A red triangle on the WHEEL page indicates that the LGCIU senses the gear is not down and locked. One proximity detector may be faulty in this case and landing gear position can be confirmed with the other LGCIU.

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9
Q

L/G GEAR NOT DOWN appears on the E/WD and the red arrow to the right of the L/G handle illuminates if:

A
  • The landing gear is not downlocked and the aircraft is below 750 RA with both engines operating below 75% N1; or if OEI the remaining engine is below 97% N1.
  • The landing gear is not downlocked and the aircraft is below 750 RA and both engines are not at takeoff power with flaps selected.
  • The landing gear is not downlocked and flaps are selected to 3 or FULL and both RAs have failed.
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10
Q

What does turning the GRAVITY GEAR EXTN handle accomplish?

A
  • The hydraulic cut off valve closes, which isolates Green hydraulic pressure from the system.
  • The gear door uplocks release, and the doors open.
  • The landing gear uplocks release and gravity causes the landing gear to extend.

After extending the gear, the crew can place the L/G lever DOWN which extinguishes the red UNLK lights on the Landing Gear Indicator panel and provides a correct down and locked indication. The gear doors will remain open since there is no hydraulic pressure to close them. The emergency extension system may be reset if a manual extension was performed for training.

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11
Q

How is nosewheel steering accomplished?

A

Nosewheel steering is electrically controlled through the dual channel Brake and Steering Control Unit (BSCU) and hydraulically powered by the Yellow hydraulic system. The BSCU process commands from the steering handwheels, rudder pedals, and the autopilot.

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12
Q

How does the nosewheel center after takeoff?

A

An internal centering cam within the nose gear strut returns the nose gear to a centered position after takeoff and can only take place after the strut has extended.

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13
Q

When would the N/W STEERING indication appear?

A
  • Nosewheel steering is lost
  • Both BSCU channels fail
  • Yellow hydraulic system pressure is low
  • A/SKID & N/W STRG switch is OFF
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14
Q

What are the steering limits of the nosewheel through the steering handwheels?

A

The steering handwheels are connected electrically to the nose gear through the BSCU. The handwheels can command a nose wheel turn angle up to 75 degrees at 20 knots or less. The amount of steering available varies based on groundspeed, the amount of steering authority decreases at a constant rate to 0 degrees at 80 knots.

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15
Q

What are the steering limits for the rudder pedals?

A

The rudder pedals provide limited nose wheel steering. Full authority +/- 6 degrees is available up to 40 knots. The amount of steering authority decreases at a constant rate to 0 degrees at 130 knots.\

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16
Q

What are the four modes of brake operation?

A
  • Normal braking - Uses the Green system
  • Alternate braking with anti-skid - Uses the Yellow system, backed up by a hydraulic brake accumulator
  • Alternate braking without anti-skid
  • Parking brake

The main wheels are equipped with carbon multi-disc brakes which can be actuated by either of two independent systems. Each brake has two wear pin indicators. The braking system is not designed to hold the aircraft in a stationary position when a high thrust level is applied.

17
Q

When is alternate braking with anti-skid automatically activated?

A

Alternate braking with anti-skid is automatically activated when the Green hydraulic system is lost, and:
* Yellow pressure is available
* The A/SKID & NW STRG switch is ON
* The parking brake is not set

18
Q

What is the purpose of the ABCU?

A

When the brake pedals are pressed, a signal is sent to the Alternate Braking Control Unit (ABCU), which signals the alternate brake selector valve to open, allowing Yellow hydraulic pressure to supply the alternate brakes. The ABCU then modules the alternate servo valve which modulates the pressure applied to the individual brakes. Anti-skid continues to function normally and is controlled by the BSCU. The autobrakes are INOP when alternate braking is active. Pedal displacement in the alternate mode produces more braking action than in normal mode.

19
Q

When is alternate braking without anti-skid activated?

A

Alternate braking without anti-skid is activated if:
* A/SKID & NW STRG switch is selected OFF
* BSCU failure
* The Yellow and Green hydraulic systems have failed

20
Q

Is it possible for alternate braking to function if both Yellow and Green systems faill?

A

It is still possible for alternate braking to function if both Yellow and Green systems fail via the Yellow brake accumulator. When the brake pedals are pressed, a signal is sent to the ABCU, which signals the alternate brake selector valve to open, allowing Yellow brake accumulator pressure to supply the alternate brakes. Brake pressure applied to the brakes and the accumulator pressure are indicated on the ACCU-PRESS/BRAKES gauge. The Yellow brake accumulator is only capable of providing a maximum of 7 full brake applications before the accumulator is depressurized.

21
Q

How long should a fully charged accumulator maintain parking brake pressure?

A

A fully charged accumulator will maintain parking brake pressure for at least 12 hours.

22
Q

When does the HOT light illumincate on the BRK FAN pb?

A

Temperature sensors are installed in each main wheel brake. A green arc appears over the hottest wheel when the brake temperatures exceed 100°C. The BRAKES HOT caution is triggered above 300°C and the HOT light illuminates on the BRK FAN pb.

23
Q

When is anti-skid operable?

A

Anti-skid is operable when:
* The A/SKID and N/W STRG switch is ON
* The BSCU is functional

24
Q

How does the BSCU control anti-skid?

A

The BSCU receives input from wheel tachometers as well as the ADIRS to compute the forward speed of the aircraft. By comparing these two inputs, the BSCU can detect when a wheel skid is about to occur. When it senses this impending skid, the BSCU sends a release signal to the normal and alternate brake servo valves for that wheel. Anti-skid is always available with normal braking. Anti-skid is available with alternate braking unless the cause of alternate braking is a failure of both BSCU channels.

If low Yellow pressure is detected, the BSCU will deactivate anti-skid.

25
Q

How does the flight crew know if the anti-skid system is on or functioning?

A

On the WHEEL page, green bars represent the anti-skid system and appear when the gear is lowered to indicate that the wheel brakes are released and will remain released until touchdown. The bars also indicate that the anti-skid function is armed. The bars are removed when braking occurs but reappear when anti-skid is functioning.

26
Q

When is maximum auto braking automatically activated?

A

Maximum auto braking is immediately applied when the spoiler deployment signal is triggered. The ground spoiler signal requires at least 2 SECs to be operative, both main gears must be compressed, and main gear wheel speed must be greater than 72 knots.

27
Q

How are the autobrakes disarmed?

A
  • Applying pressure to either brake
  • Pressing the MAX AUTO/BRK pb
  • After the aircraft becomes airborne
  • One or more arming conditions is lost
  • Retracting the ground spoilers - deactivates but remains armed
28
Q

When does the changeover between the two BSCU channels take place?

A

A changeover between the two BSCU channels takes place at each DOWN landing gear lever selection, or in case one channel fails.

29
Q

What protection against tire burst do the main gear wheels have?

A

The main gear wheels are fitted with fusible plugs which protect against tire burst, in the event of overheat.

Indoc (80 decks)

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