Landing Gear

Question 1

How is the Landing Gear normally extended and retracted?

Answer 1

• Electrically commanded and hydraulically actuated.

Question 2

Can the “Landing Gear” aural warning be silenced by pushing the LG WRN
INHIB button?

Answer 2

• Yes, if both Radio Altimeters have failed

i. If flaps are selected 5 or FULL it cannot be silenced

Question 3

What are three ways that the Landing Gear may be extended?

Answer 3

• Normal - LG lever DOWN
• Electric override - Bypasses PSEM to control Selector Valve
• Alternate gear extension - Manual uplock release opens Free-Fall
  Sequencing Valve

Question 4

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

Answer 4

• Mechanically releases the landing gear lever lock

Question 5

What keeps the gear locked in position?

Answer 5

• Extended - Downlock springs

- Retracted - Uplock hooks

Question 6

How do the landing gear doors actuate?

Answer 6

• Mechanically, during landing gear extension or retraction.

Question 7

How are the brakes commanded?

Answer 7

• Brake by Wire
  i. Electrically commanded and hydraulically actuated
  ii. Pedal position transducers send brake requests to the BCM (Brake
  Control Module)

Question 8

What hydraulic system(s) provide brake pressure?

Answer 8

• HYD 1 = Outboard brakes
• HYD 2 = Inboard brakes
• HYD 1 & 2 = Emergency/Parking brake

Question 9

What protections are provided for braking?

Answer 9

• Touchdown:
  i. No braking until 3 seconds or >50 kts wheel speed after
  touchdown.
  ii. Prevents airplane from touching down with the main landing gear
  brakes applied.
• Anti-skid
  i. Compares wheel speeds and releases pressure (inop when speed
  less than 10 kts)
• Locked-wheel
  i. active on ground and wheel speeds > 30 knots if wheel speed is
  33% or below is associated pair, the BCM commands zero
  pressure to the slower wheel
  ii. Allows up to 33% differential braking for steering purposes

Question 10

What stops the wheels from spinning during retraction?

Answer 10

• Main gear: BCM applies brakes after weight-off-wheels

- Nose gear: Snubbers in the nose bay stop the wheels

Question 11

Which hydraulic system(s) control the Nosewheel steering?

Answer 11

• HYD 2

Question 12

How many brake applications does the emergency brake provide?

Answer 12

• The accumulators have sufficient pressure to provide six full-brake
  applications.

Question 13

What is the purpose of the Brake Control Module (BCM)?

Answer 13

• Main functions are:
  i. locked wheel protection
  ii. antiskid protection
  iii. touchdown protection

Question 14

Can you use the emergency brakes at high speeds?

Answer 14

• Yes.

i. Pull carefully and slowly. There is no antiskid protection.

Question 15

When do you get a gear “disagreement” message?

Answer 15

• 20 seconds after the discrepancy is detected

Question 16

What are the brake temperature indications?

Answer 16

• Green: normal
• Amber: caution
• Amber dashed: invalid

Question 17

Is takeoff permitted if the brake temperature is in the Amber range?

Answer 17

• No

i. Brake temps must be in the green before take off

Question 18

How do you manually extend the landing gear in event of a failure of the gear
handle?

Answer 18

• Landing gear override switch

- Alternate landing gear handle to free fall the gear

Question 19

What is the steering angle for Nosewheel steering?

Answer 19

• Variable (based on speed):
  i. +/- 76° up to 10 knots
  ii. +/-7° at 100 knots

Question 20

When is the free wheel steering mode automatically activated?

Answer 20

• Air/Ground system failure
• Steering failure > 76 degrees
• Steering system failure

Question 21

What ways can you disconnect Nosewheel steering?

Answer 21

• Disconnect switch on either yoke

- Disconnect switch on GPU access panel.