Landing Gear Flashcards
Which hydraulic system is used to raise and lower the landing gear normally?
Hydraulic System A.
How are wheels protected from thermal expansion?
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.
What is the purpose of the Supplemental Landing Gear indicator lights on the aft overhead panel?
Verification that the gear is down and locked through an independent set of proximity switches and wiring.
Extinguished lights indicate the gear is not down and locked
What is the purpose of the lever lock override?
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.
What is the purpose of the frangible fitting on the main wheel wells?
Protects the wheel well from loose tread or foreign object debris.
When struck with debris it opens a valve relieving the LG of hyd. pressure from retraction line. The gear the free falls to the down position
What is the purpose of the landing gear transfer valve?
The landing gear transfer unit is designed to assist hydraulic system A with gear retraction in the event of an Engine No. 1 failure.
* Airborn
* Eng. 1 N2 <50%
* Landing gear lever is
positioned up
*either main LG is not up
and locked
How is the landing gear lowered in the event of a loss of hydraulics?
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.
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?
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.
Are autobrakes available on the alternate brake system?
No
Only on normal brake system (Hyd B)
What conditions must be met for RTO braking to activate?
To activate RTO braking, the thrust levers must be brought to idle with the wheels speed greater than 88 knots.
To arm the RTO mode prior to T/O:
* AC on the ground
*Antiskid and autobrakes
systems are operational
*Wheel speed <60 kts
* Thrust levers at idle
Which system(s) provide pressure to the parking brake?
- 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.
What is the purpose of the Proximity Switch Electronic Unit (PSEU)?
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
Door Warning System.
Flight Control indication (e.g., flap/slat position).
Stall management yaw damper inputs.
Tail Skid Control.
The Proximity Switch Electronic Unit (PSEU) is a solid-state device with two halves: system
1 and system 2. The two systems, including their proximity switches and input signals, are
constantly being monitored for internal faults.
The PSEU processes signals from proximity switches located throughout the aircraft.
Proximity switches are used due to their resiliency, especially in areas subject to exposure to
ice, dirt, and other contaminants. A proximity switch operates through a change in inductance
based on a metal target attached to a pivoting arm and a sensor face. When the target moves
within proximity of the sensor face, the inductance value changes and is used to indicate that
a component has reached a predetermined position.
The PSEU provides the following functions:
*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 skidD control
*Extra Question
Which hydraulic systems allow antiskid protection to operate?
Antiskid protection is provided by both normal and alternate brake systems, as well as braking by the accumulator system.
Normal brakes are off of Hyd. Sys B and alternate brakes are off of Hyd. Sys A.
*Extra Question
Which systems support Auto Brakes?
Auto Brakes are only powered by hydraulic system B
