Landing Gear And Brakes

Question 1

When do LGCIU alternate as controlling computer?

Answer 1

Each time landing gear is retracted.

*if the controlling LGCIU fails, the backup automatically takes over.

Question 2

Can the landing gear selector be moved if a main gear or nose gear shock absorber is sensed compressed?

Answer 2

No- an interlock inhibits selector from being moved to the UP position.

Crew cannot override this.

Question 3

Which hydraulic system provides power for landing gear extension and retraction?

Answer 3

Green.

Question 4

At what speed does a safety valve prevent landing gear movement?

Answer 4

> 260kts.

Question 5

Which LGCIU provides information to the LDG GEAR indicating panel?

Answer 5

Only LGCIU 1.

If LGCIU 1 fails, must use WHEEL page for positive gear position information.

Question 6

What does it mean if one red and one green triangle is displayed for a gear on the WHEEL page?

Answer 6

One LGCUI senses the gear is not down and locked. Use the other LGCIU to confirm it is down and locked.

Question 7

What is the maximum altitude for gear extension?

Answer 7

FL250

Question 8

What are the gear speed limitations?

Answer 8

Extension: 250 kts
Extended operation: 280kts or .67 M
Retraction: 220 kts

Question 9

Gravity extension requires turning the crank clockwise 3 times. What does each turn accomplish?

Answer 9

1. Closes hydraulic cutoff valve which removes pressure from the system.
2. Releases gear door up locks and allows doors to fall open.
3. Releases gear uplocks, and the gear extends into place.

*the landing gear lever is then placed DOWN to extinguish red UNLK lights and provide correct down and locked indication.

*door will remain open and nose wheel steering will NOT be available.

Question 10

What is the maximum nose wheel turn angle that can be commanded on hand wheel?

Answer 10

75 deg- available up to 20kts GS.

Decreases at a constant rate to 0 deg at 80kts GS.

Question 11

The hand wheels move independently. What happens if both moved?

Answer 11

The combined input is summed and sent as a command to the BSCU. (Will not exceed highest angle available based on GS).

Question 12

What is the maximum nose wheel turn angle that can be commanded by the rudder pedals?

Answer 12

Full authority 6 deg up to 40kt GS.

Decreases at a constant rate to 0 deg at 130kts.

Question 13

What is the purpose of the pedal disconnect button on hand wheel?

Answer 13

Allows you to disconnect rudder pedal from nose wheel steering to check rudder travel during taxi.

Question 14

When does autopilot control nose wheel steering?

Answer 14

During an autoland rollout, autopilot commands nose wheel movement to track the localiser.

*autopilot can be disconnected by significant hand wheel or rudder pedal inputs.

Question 15

Where does hydraulic pressure for nose wheel steering come from?

Answer 15

Green system return line for the nose gear doors.

*if nose gear doors remain open (as they will if gear is gravity extended) nose wheel steering is NOT available.

Question 16

Which hydraulic systems are used for normal and alternate braking?

Answer 16

Two independent braking systems.

Normal- green

Alternate- yellow, backed up by a hydraulic brake accumulator.

Question 17

When is Anti-skid system operable? (2 items)

Answer 17

-Anti-skid Nose Wheel Steering switch ON.
-BSCU is functional.

Question 18

What inputs does BSCU receive to detect an impending skid?

Answer 18

-wheel tachometers to know rotational speed of each wheel.
-ADIRS to compute forward speed of aircraft.

Question 19

Is anti-skid available with alternate braking?

Answer 19

Yes- unless the cause of alternate braking is a failure of both BSCU channels.

*also if low yellow system pressure is detected when alternate braking in use, BSCU will deactivate anti-skid.

Question 20

What pilot action is required to activate alternate braking system if Green system is lost?
(1 item and 2 items)

Answer 20

None, will transfer automatically as long as:
-Yellow system pressure available.

-A/SKID & NW STRG selected ON.
-at least one channel of BSCU available.
(Without these will still switch automatically, WITHOUT anti-skid)

Question 21

If Green and Yellow systems lost, braking is still possible through a dedicated accumulator. How long will it last?
How is accumulator depletion prevented?

Answer 21

A maximum of 7 full brake applications before accumulator is depressurised.

*to prevent accumulators from being depleted, BSCU is deactivated and anti-skid is unavailable.

Question 22

What do the green arc and small green band indicate on accumulator pressure gage?

Answer 22

Green arcs indicate maximum alternate brake pressure that can be safely applied when anti-skid is inoperative.

Small green band indicates normal pressure of 3000psi that should be maintained in accumulator.

*gage is dedicated to Yellow system.

Question 23

Where is the park brake pressure supplied from?

Answer 23

Yellow system or from the dedicated Yellow system accumulator.

Question 24

How long will a fully charged accumulator maintain parking brake pressure for? Can this be extended?

Answer 24

Several hours.

*can be repressurised with YELLOW ELEC PUMP pb.

Question 25

What is the maximum thrust that can be applied on the park brakes?

Answer 25

75% N1.

Question 26

What is the maximum brake temperature for takeoff?

Answer 26

300 deg (fans off)
150 deg (fans on)

Question 27

What conditions are required for the auto brakes to activate? (4 items)

Answer 27

1. Normal bakes must be operational.
2. A/SKID & NW STRG switch ON.
3. At least 1 ADIRU must be functioning to provide speed and deceleration rates to BSCU.
4. Ground spoiler deployment signal must be sensed by BSCU.

Question 28

How can auto brakes be disarmed or disengaged (3 items) and how is it indicated?

Answer 28

-applying pressure to either brake.

-pressing MAX AUTO BRK pb.

-Retracting ground spoilers.

*AUTO BRK label on WHEEL page flashes for 10 seconds after disengagement.