170 Landing Gear and Brakes

Electrically commanded and hydraulically actuated

If the gear is not down and locked, and

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

Only if both radio altimeters have failed

• Normal:      LG lever DOWN

• Electric override:            Bypasses PSEM to directly command selector valve

• • Alternate gear extension:
• Manual uplock release opens free-fall sequencing valve

• Mechanically releases the landing gear lever lock

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

• Extended:      Downlock springs

• Retracted:      Uplock hooks

• • Green Down & locked
• • White Up & locked
• • Amber In transit
• • Red gear position & lever disagreement (20 sec grace period)

Mechanically, during landing gear extension or retraction

• 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

• 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:     Compares left and right inboard brakes and outboard brakes. Allows up to 33% differential braking for steering purposes (inop <30 kts)

6 applications

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

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

HYD 2

• Angle varies with ground speed

• Up to 40 kts +76°

• 41 to 100 kts Decreases linearly from 76° to 7°

If two WOW sensors on the same landing gear leg fail. Or if any landing gear does not extend completely.

- 76° allowed up to 10kt

- over 20 kts. Max is 20°

- overr 100kts. Max is 7°

- upon releasing the handle, steering goes to pedal steering.

Proximity sensor electronic module

6. 2 on each leg.