landing gear and brakes

Question 1

how is the landing gear extended and retracted?

Answer 1

eletrically commanded and hydraulically actuated

Question 2

when will the aural warning for the landing gear sound?

Answer 2

if 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 over ride - 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 the landing gear lever?

Answer 5

mechanically released 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 - down lock 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 disagreement (20 second 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 systems 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 teh 3 modes of nose wheel steering?

what are the limits for the nosewheel steering?

Answer 14

hand wheel steering, rudder pedal steering and free wheel steering.

handwheel steering - must press down on the handwheel steering.

steering angle varies from ±76° up to 40 kt decreasing linearly to ±7° at 100 kt.

if you let go, defaults to rudder steering.

Over 100 kt the maximum deflection is ± 7°.

The maximum steering angle of the rudder pedal is ±7°.

The free wheel steering mode is mostly used for towing or when the normal steering sys- tem fails.

The free wheel mode is automatically selected when:
(a) Failure of the Air/Ground signal occurs.
(b) Nose wheel angle is greater than 76°.
(c) Nose wheel steering system failure is detected.

Question 15

what does it mean if the towing lights are green?

Answer 15

parking brakes not applied, main brakes not applied or steering disengaged thru the external steering disengage switch

Question 16

what does it mean if towing lights are red?

Answer 16

external disengage switch in the engaged position, parking brakes applied or main brakes applied