01/18/23 Landing Gear Flashcards
Under normal conditions, which system powers the landing gear?
Hydraulic System A
Hydraulic power for retraction, extension, and nose wheel steering is normally supplied by Hydraulic System A.
Describe how tires are protected from explosion during thermal expansion caused by hot brakes?
4 thermal fuse plugs in each inner wheel half
(main wheels only) 4 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 177°C (351°F).
When is the Landing Gear Lever locked? Can it be overridden?
On the ground, it can be overridden with the Lever Lock Override Trigger
On the ground, the Landing Gear Lever Lock mechanism prevents the LANDING GEAR lever from moving to the UP position.
The Lever Lock Override Trigger in the LANDING GEAR lever may be used to bypass the Landing Gear Lever Lock under certain conditions.
What do the red and green position lights on the forward landing gear panel indicate? (Source)
Green = Down and Locked
Red = Not down and locked, in transit or unsafe
The illumination of a red position light indicates the:
• landing gear is not down and locked (with either or both forward thrust levers retarded to idle, and below 800 ft AGL)
• related landing gear is in disagreement with LANDING GEAR lever position (in transit or unsafe)
NOTE: Pulling the LANDING GEAR lever out to select UP will cause the red position lights to illuminate.
When the red position light is extinguished, the:
• landing gear is up and locked with LANDING GEAR lever UP or OFF
• landing gear is down and locked with LANDING GEAR lever DN
NOTE: Failure of the LANDING GEAR lever to slide inward when selected to the DN position will result in the red position lights remaining illuminated.
The Position (green) Lights, when illuminated, indicate the related gear is down and locked. When a green position light is extinguished, the respective landing gear is not down and locked.
What is the purpose of the aft overhead panel Supplemental Landing Gear indicator lights?
A secondary means to indicate the gear is down and locked.
Supplemental Gear Position (green) Lights (aft overhead panel) use a dedicated proximity switch on each gear and associated wiring. The illumination of the Supplemental Gear Position Lights indicate the related gear is down and locked. When the green position light is extinguished, the respective landing gear is not down and locked.
What protects the aircraft from loose tread or foreign object debris in the main wheel well during landing gear retraction?
Main wheel well frangible fittings. If impacted by a loose tread it will relieve hydraulic pressure and the respective gear stops retracting and free falls to the down position.
There is a frangible fitting located on the outboard side of both wheel well rings in the main landing gear wheel well. The frangible fitting is a normally closed valve that opens when a force removes the lever from the fitting. When a spinning tire with loose tread impacts the frangible fitting in the wheel well ring opening, 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.
NOTE: The affected gear cannot be retracted until the fitting is replaced
If the No. 1 engine fails, how is the hydraulic capability of system A affected? How is the gear raised at a normal rate?
LANDING GEAR TRANSFER VALVE will open allowing HYD System B to supply the volume of hydraulic fluid needed,
The purpose of the Landing Gear Transfer Valve is to supply the volume of hydraulic fluid needed to raise the landing gear at the normal rate when Hydraulic System A engine-driven pump volume is lost due to the No. 1 N2 Speed dropping below 50% RPM. This improves second segment climb capability with the No. 1 engine below 50% N2 while attempting to retract the landing gear.
The Landing Gear Transfer Valve will automatically reposition, allowing the Hydraulic System B engine-driven pump to supply the volume of hydraulic fluid needed to retract the gear when all of the following conditions exist:
- airborne
- No. 1 engine N2 below 50%
- LANDING GEAR lever is positioned UP
- either main landing gear is not up and locked
When is Nose Wheel Steering active?
When the nose gear is in the down position and compressed by the weight of the aircraft.
Nose wheel steering is powered by Hydraulic System A when the LANDING GEAR lever is in the down position and the NOSE WHEEL STEERING switch, located on the Captain’s Forward Instrument Panel, is in the NORM (guarded) position.
Hyd B can power ALT:
- aircraft on ground
- B qty greater than 21%
If Normal and Alternate Brake pressure is lost, how is braking accomplished? Are there any limitations?
If both Normal and Alternate Brake System pressure is lost, trapped hydraulic pressure in the Brake Accumulator can still provide several (6) brake applications or parking brake application for eight hours.
Which hydraulic system(s) can pressurize the parking brake?
Either A or B, if both are not pressurized, parking brake pressure maintained by the Brake Accumulator
The parking brake can be set with either Hydraulic System A or B pressurized. If Hydraulic System A and B are not pressurized, parking brake pressure is maintained by the Brake Accumulator.
Which brake system(s) have Antiskid?
Antiskid protection is provided in the Normal and Alternate Brake Systems.
Is the Alternate Brake system capable of supplying Autobrakes?
No.
The Autobrake System uses Hydraulic System B pressure to provide maximum deceleration for rejected takeoff and automatic braking at preselected deceleration rates immediately after touchdown. The system operates only when the Normal Brake System and Antiskid System are functioning.
When can RTO braking be armed? When is RTO braking available?
The RTO mode can only be selected on the ground. If the takeoff is rejected after reaching a wheel speed of 90 kts, maximum braking is automatically applied when the forward thrust levers are retarded to IDLE.
To arm the RTO mode prior to takeoff the following conditions must exist:
- aircraft on the ground
- Antiskid and Autobrake Systems operational
- AUTO BRAKE select switch positioned to RTO
- wheel speed less than 60 kts
- Forward thrust levers positioned to IDLE
What does a Parking Brake Warning (red) light indicate?
Shutoff valve position is not full open
“Possibly trapping brake pressure.”
The Parking Brake Warning (red) Light illuminates when the Parking Brake Shutoff Valve internal switch detects that the shutoff valve position is not full open. The light extinguishes when the Parking Brake Shutoff Valve internal switch detects the valve has reached the full open position. The light operates using battery power.
