Landing Gear

Question 1

Which hydraulic system is used to raise and lower the landing gear normally?

Answer 1

Hydraulic System A.

Question 2

How are wheels protected from thermal expansion?

Answer 2

There are four thermal fuse plugs in each inner wheel half to prevent tire explosion due to thermal expansion caused by hot brakes. The plugs melt to release tire pressure at approximately 199 degrees C.

Question 3

What is the purpose of the Supplemental Landing Gear indicator lights on the aft overhead panel?

Answer 3

Verification that the gear is down and locked through an independent set of proximity switches and wiring.

Question 4

What is the purpose of the lever lock override?

Answer 4

Pushing the lever LOCK OVRD switch bypasses the landing gear lever lock and allows the control lever to be moved to the UP position if airborne.

Question 5

What is the purpose of the frangible fitting on the main wheel wells?

Answer 5

Protects the wheel well from loose tread or foreign object debris.

Question 6

What is the purpose of the landing gear transfer valve?

Answer 6

The landing gear transfer unit is designed to assist hydraulic system A with gear retraction in the event of an Engine No. 1 failure.

Question 7

How is the landing gear lowered in the event of a loss of hydraulics?

Answer 7

• In the absence of hydraulic system A pressure, the landing gear may be lowered using the manual extension system. Manual gear extension is possible regardless of landing gear control lever position.
• The manual gear extension handles are located behind the manual extension access door. The handles are pulled to manually release the respective mechanical up-lock, allowing the gear to free fall to the down and locked position.

Question 8

Which system powers nose wheel steering?

Answer 8

Normal nose wheel steering is provided by hydraulic system A and alternate nose wheel steering is provided by hydraulic system B.

Question 9

With the loss of hydraulic system A and B, how is braking accomplished? Are there any limitations?

Answer 9

• If both hydraulic system A and B are not supplying pressure, the brake accumulator pressure moves the accumulator isolation valve, sending accumulated pressure from the brake accumulator to the normal brake system.
• The accumulator can provide six brake applications or eight hours of the parking brake.

Question 10

Are autobrakes available on the alternate brake system?

Answer 10

No

Question 11

What conditions must be met for RTO braking to activate?

Answer 11

To activate RTO braking, the thrust levers must be brought to idle with the wheels speed greater than 88 knots.

Question 12

Which system(s) provide pressure to the parking brake?

Answer 12

• The parking brake may be set with using either normal or alternate brake systems.
• If hydraulic systems A and B are not pressurized, parking brake pressure is maintained by the accumulator.

Question 13

What is the purpose of the Proximity Switch Electronic Unit (PSEU)?

Answer 13

• Air ground sensing for aircraft systems.
• Landing gear position indication and warning.
• Landing gear transfer valve control.
• SPEEDBRAKES EXTENDED light control.
• Takeoff warning horn and TAKEOFF CONFIG light control.
• Door Warning System.
• Flight Control indication (e.g., flap/slat position).
• Stall management yaw damper inputs.
• Tail Skid Control.