Landing Gear and Brake System

Question 1

(B) How is the landing gear extended and retracted?

Answer 1

Electrically commanded and hydraulically actuated

Question 2

(B) When will the aural warning for the landing gear sound?

Answer 2

If the gear is not down and locked:

• Less than 700’ RA and TLA below 45°
• SLAT/FLAP 5 or full regardless of altitude
• TLA below 59° for one-engine inop

Question 3

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

Answer 3

Yes, only if both radio altimeters fail

Question 4

(B) What are three landing gear extension modes?

Answer 4

• Normal: The landing gear level DOWN
• Electric Override: Bypasses PSEM to directly command selector valve
• Alternate Gear Extension: Manual uplock release opens free-fall sequencing valve

Question 5

(B) What is the purpose of the DN LOCK RLS button on the landing gear?

Answer 5

• Mechanically releases the landing gear lever lock
• Lock protects against inadvertent landing gear retraction when weight-on-wheels
  (This is a locking solenoid)

Question 6

(B) What keeps the gear locked in position?

Answer 6

• Extended Downlock Springs

- Retracted Uplock hooks

Question 7

(B) Describe the landing gear indications?

Answer 7

• GREEN: Down and Locked
• White: UP and Locked
• Amber: In Transit
• Red: Gear position and lever disagreement (20 sec grace period)

Question 8

(B) How do the landing gear doors actuate?

Answer 8

Mechanically, during landing gear extension or retraction

Question 9

(B) What is PSEM?

Answer 9

Proximity Sensor Electronic Module

Question 10

(I) What does PSEM do for the landing gear?

Answer 10

It monitors the WOW sensors to determine if the airplane is on the ground or in-flight
It controls the extension and retraction of the landing gear
(also indicates position of landing gear, spoiler and aircraft doors)

Question 11

(I) What is WOW?

Answer 11

Weight-on-Wheels

Question 12

(T) How many WOW sensors and where are they located?

Answer 12

Total of six

2 installed on each landing gear

Question 13

(T) What controls the Nose Steering lights?

Answer 13

NWSCM - Nose Wheel Control Module

Question 14

(O) How is the the nose-wheel powered in order to move?

Answer 14

Hydraulic Steering Motor

Question 15

(T) What keeps the Nose Wheel Down?

Answer 15

Folding Drag Brace and this is supported by a locking stay/pair of down-lock springs

Question 16

(T) How many doors in the nose-wheel section?

Answer 16

2 pair of doors - Front Doors must remain closed on ground

Question 17

(T) How many actuators per landing gear?

Answer 17

2 - Hydraulic Retraction Actuator and Hydraulic Actuator for the locking stay

Question 18

(B) How are the brakes commanded?

Answer 18

1. Brake by Wire (B-FBW)
2. Electronically commanded and hydraulically actuated
3. Pedal position transducers send brake requests to the BCM (Brake Control Module)

Question 19

(B) What hydraulic systems provide brake pressure?

Answer 19

HYD SYS 1 - Outboard Brakes
HYD SYS 2 - Inboard Brakes
HYD SYS 1 and 2 - Emergency Brakes/Parking Brake

Question 20

(B) What protections are provided for braking?

Answer 20

1. Touch-down: No Braking until 3 seconds or > 50 knots wheels speed after touchdown
2. Anti-Skid: Compares wheel speeds and releases pressure (inoperative below 10 knots)
3. Locked-Wheel: Allows up to 33% differential braking for steering purposes (inoperative below 30 knots)

Question 21

(B) How many applications will the parking/emergency brake provide?

Answer 21

Six fuell brake applications

Question 22

(B) What stops the wheels from spinning during retraction?

Answer 22

Main Gear - BCM applies brakes after WoffW

Nose Gear - Snubbers in the nose bay stop the wheels

Question 23

(B) Which hydraulic system controls the nose-wheel steering?

Answer 23

HYD SYS 2

Question 24

(B) What are the limits for the nose-wheel steering?

Answer 24

Angle varies with groundspeed
0 to 40 knots: + 76°s
41 to 100 knots: Decreases linearly from 76°s to 7°s

Question 25

(T) How many uplock/downlock sensors?

Answer 25

2 - Uplock Sensors
2 - Downlock Sensors
In each landing gear

Question 26

(T) Is there anti-skid protection with emergency brakes?

Answer 26

NO

Question 27

(I) When is Free Wheel Mode automatically selected?

Answer 27

1. Failure of the air/ground signal occurs
2. Nose wheel angle is greater than 76°s
3. Nose Wheel Steering system failure is detected

Question 28

(I) How do you know the condition of the brakes? and what kind of brakes do we use?

Answer 28

Brake Wear Pins - Must be at least flush to plate, if not it needs replacement
Carbon Brakes (Operates better in hot conditions, avoid braking multiple times in colder conditions as brakes wear out faster)