Landing Gear and Brakes

Question 1

On the nose landing gear tires, the tire chines are mounted outboard or inboard?

Answer 1

Outboard.

Question 2

What protections are available during normal braking?

Answer 2

Anti-skid protection, Locked Wheel protection and Touch-down protection.

Question 3

What is anti-skid protection?

Answer 3

• If one wheel is rotating slower than the average of the other 3 wheels, a skid is detected
• The BCU relieves pressure on the slow wheel to allow it to spin up to the speed of the others

Question 4

What is locked wheel protection?

Answer 4

• If a wheel is 30% slower than the same wheel on the opposite side, the BCU relieves pressure on the slow wheel(s):
– Allows maximum braking while maintaining directional control
– Available above 30 knots

Question 5

What is touch-down protection?

Answer 5

• Brake actuation is only allowed:
– After 3 seconds from the last touchdown; OR
– After the wheels have spun up to 50 knots
• In bouncing landings, the countdown is reset after each runway contact.

Question 6

When using the emergency brakes, do you have the anti-skid, locked wheel and touchdown protections?

Answer 6

No.

Question 7

In essential power mode, is nose wheel steering available?

Answer 7

No.

Question 8

When operating the emergency brakes, hydraulic pressure is applied to which brakes?

Answer 8

All main gear brakes.

Question 9

The Hydraulic System 2 accumulator has enough stored hydraulic pressure to supply a total of ____ emergency actuations or ____ hours of continuous parking brake actuation? How can hydraulic pressure to the parking brake be verified?

Answer 9

6 emergency actuations or 24 hours of continuous parking brake actuation. A BRAKE ON indicating light illuminates to indicate that pressure is being applied to the wheel brakes.

Question 10

What does the Free-Fall actuator do?

Answer 10

It requires no electrical or hydraulic power to extend the landing gear. It extends the gear by mechanically actuating the Free-Fall Selector Valve, thus removing hydraulic pressure and unlocking the three landing gear uplocks via cable linkage. All three gear then gravity fall to their downlock positions.

Question 11

With a total loss of hydraulic system #1, will the landing gear deploy/operate normally?

Answer 11

No. In this case, the landing gear free fall actuator would be used to lower the gear.

Question 12

When in essential power mode would you have normal braking?

Answer 12

Yes.

Question 13

Nose wheel tire rotation is stopped by ________.

Answer 13

4 mechanical snubbers upon retraction.

Question 14

In essential power, how is the landing gear extended?

Answer 14

Normally.

Question 15

What is the purpose of the Landing Gear Electrical Override switch?

Answer 15

The electrical override system is used to extend the landing gear should there be a normal landing gear extension failure. The system bypasses the LGEU (Landing Gear Electronic Unit) and directly actuates the landing gear electrovalve and the nose gear doors solenoid valve.

Question 16

How many degrees of nose wheel steering displacement do we have?

Answer 16

Ruder Pedals: ± 5°
Tiller: ± 71°
Combined ± 76°

Question 17

How is nose wheel steering powered?

Answer 17

• Electrically-controlled (steer-by-wire) using a tiller and/or rudder pedals
– DC powered
• Hydraulically-actuated – Hydraulic System 1
• This means after a hydraulic system 1 failure or loss of DC power, you won’t be able to use nose wheel steering!

Question 18

How do you actuate nose wheel steering? How do you disengage nose wheel steering?

Answer 18

• Pushing the tiller down actuates steering

* Nose wheel steering disengagement trigger behind the yoke disengages steering.

Question 19

What does the EICAS caution message BRAKE OVERHEAT mean?

Answer 19

The brake temperatures have exceeded 420ºC

Question 20

During gear retraction, how do the tires stop spinning?

Answer 20

• As soon as the aircraft is airborne and the gear is commanded up, the BCU applies pressure to the mains
• The nose wheel is stopped by 4 snubbers inside the wheel well

Question 21

How are the nose gear doors kept close?

Answer 21

• The nose gear doors are kept closed with system 1 hydraulic pressure and a DC Bus 2 solenoid valve maintaining pressure in the nose gear door actuators
• However, the main gear doors are mechanically attached to the gear leg and are mechanically held up in-flight

Question 22

Describe what happens during Normal Gear Extension?

Answer 22

• When the gear handle is moved to the down position, it signals the Landing Gear Electronic Unit (L.G.E.U.) to command the landing gear electro valve and the nose gear doors solenoid valve
• The nose gear doors open before the nose gear is extended
• Hydraulic system 1 powers the nose gear doors to open, and uses pressure to release the up lock hooks on all three gear legs

Question 23

Describe what happens during Normal Gear Retraction?

Answer 23

• The gear is Electrically commanded, Hydraulically operated and Mechanically locked.
• When the gear handle is moved to the up position, it signals the Landing Gear Electronic Unit (L.G.E.U.) to command the nose gear doors solenoid valve and landing gear electro valve
– The nose gear doors close after the nose gear is up and locked