LANDING GEAR Flashcards
Which hydraulic system(s) is used to raise and lower the landing gear normally?
Hydraulic power for retraction, extension, and nose wheel steering is normally supplied by hydraulic system A.
How are the wheels protected from thermal expansion?
The main wheels have four thermal-relief fuse plugs in each inner wheel half to prevent tire explosion due to thermal expansion from hot brakes.
What is the purpose of the supplemental landing gear indicator lights on the aft overhead panel?
The supplemental gear position lights located on the aft overhead panel use separate circuitry and lights to provide redundant gear-down indications.
What is the purpose of the lever lock override?
Pushing the LOCK OVRD switch bypasses the landing gear lever lock and allows the control lever to moved to the UP position if airborne.
What is the purpose of the frangible fitting on the main wheel wells?
To protect the wheel well from loose tread or foreign object debris. The frangible fitting valve opens and relieves hydraulic pressure from the retraction line. The respective gear stops retracting and free falls back to the down position.
What is the purpose of the landing gear transfer valve?
The transfer valve will allow hydraulic system B to supply the necessary fluid to the landing gear retract lines. The transfer valve will reposition when:
• airborne
• Engine No. 1 N 2 is below 50%
• landing gear control lever positioned UP
• either main landing gear is not up and locked
How is the landing gear lowered in the event of a loss of hydraulics?
In absence of hydraulic system A pressure, the landing gear may be lowered using the manual extension system.
Which system powers nose wheel steering?
Normal nose wheel steering is provided by hydraulic system A and alternate nose wheel steering is provided by hydraulic system B.
With the loss of hydraulic system A and B how is braking accomplished? Are there any limitations?
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.
Are autobrakes available on the alternate brake system?
Autobrakes are only available on the normal brake system (hydraulic system B).
What conditions must be met for RTO braking to activate?
To activate RTO braking, the thrust levers must be brought to IDLE with wheel speeds greater than 88 kts.
Which system(s) provide pressure to the parking brake?
The normal or alternate brake systems. If hydraulic systems A and B are not pressurized, parking brake pressure is maintained by the accumulator.
What is the purpose of the Proximity Switch Electronic Unit (PSEU)?
The PSEU processes signals from proximity switches located throughout the aircraft.
• 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
