Landing Gear and Brakes

Question 1

How is the landing gear extended and retracted?

Answer 1

Electrically commanded and hydraulically actuated

Question 2

When will the aural warning for the landing gear sound?

Answer 2

If the gear is not down and locked, and:

• < 700’ RA and low TLA, or:
• Any altitude with flaps set >= 5

Question 3

Can the landing gear aural warning be silenced by pushing the ‘LG WRN INHIB’ button?

Answer 3

Only if both radio altimeters have failed

Question 4

What are the three landing gear extension modes?

Answer 4

• Normal: LG lever down
• Electric override: Bypass PSEM to directly command selector valve
• alternate gear extension: manual unlock release opens free fall sequencing valve

Question 5

What is the purpose of the DN LOCK RLS button on the landing gear lever?

Answer 5

• Mechanically releases the landing gear lever lock

- Lock protects against inadvertent landing gear retraction when weight on wheels

Question 6

What keeps the gear locked in position?

Answer 6

• Extended: downlock springs

- Retracted: uplock hooks

Question 7

Describe the landing gear indications

Answer 7

• Green: down and locked
• White: up and locked
• Amber: in transit
• Red: gear position and lever disagree (20 sec grace period)

Question 8

How do the landing gear doors actuate?

Answer 8

Mechanically, during landing gear extension or retraction

Question 9

How are the brakes commanded?

Answer 9

• Brake by wire
• Electrically commanded and hydraulically actuated
• Pedal position transducers send brake requests to the BCM (brake control module)

Question 10

What hydraulic systems provide brake pressure?

Answer 10

• HYD 1: outboard brakes
• HYD 2: inboard brakes
• HYD 1 and 2: parking/emergency brake

Question 11

What protections are provided for braking?

Answer 11

• Touchdown: no braking until 3 secs or >50 kts wheel speed after touchdown
• Anti-skid: compares wheel speeds and releases pressure (inop <10 kts)
• Locked-wheel: allows up to 33% differential braking for steering purposes (inop <30 kts)

Question 12

How many applications will the parking/emergency brake provide?

Answer 12

6

Question 13

What stops the wheels from spinning during retraction?

Answer 13

• Mains: BCM applies brakes after weight off wheels

- Nose: snubbers in the nose bay stop the wheels

Question 14

What HYD system controls the nosewheel steering?

Answer 14

HYD 2

Question 15

What are the limits for the nosewheel steering?

Answer 15

• Angle varies with ground speed
• Up to 40kts: +-76 deg
• 41 to 100 kts: decreases linearly to 7 deg

Question 16

When are the auto brakes deactivated?

Answer 16

• Less the 60 kts
• Brake fault
• Toe brakes applied