Landing Gear & Brakes Questions

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 three landing gear extension modes?

Answer 4

• Normal - LG lever DOWN
• Electric override - Bypasses PSEM to directly command selector valve
• Alternate gear extension - Manual uplock 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 & locked
• White Up & locked
• Amber In transit
• Red Gear position & lever disagreement
  (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? What hydraulic system(s) provide brake pressure?

Answer 9

• Brake by Wire
• Electrically commanded and hydraulically actuated
• Pedal position transducers send brake requests to the BCM (Brake Control Module)
• HYD 1 Outboard brakes
• HYD 2 Inboard brakes
• HYD 1 & 2 Parking/emergency brake

Question 10

What protections are provided for braking?

Answer 10

• Touchdown - No braking until 3 seconds 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 11

How many applications will the parking/emergency brake provide?

Answer 11

• 6 applications

Question 12

What stops the wheels from spinning during retraction?

Answer 12

• Main gear - BCM applies brakes after weight-off-wheels
• Nose gear - Snubbers in the nose bay stop the wheels

Question 13

Which hydraulic system controls the nosewheel steering?

Answer 13

• HYD 2

Question 14

What are the limits for the nosewheel steering?

Answer 14

• Angle varies with ground speed
• Up to 40 kts = +76°
• 41 to 100 kts = Decreases linearly from 76° to 7°