Landing Gear Flashcards
What is a proximity switch?
A switch that magnetically senses ‘contact’ between two surfaces when the two surfaces come into close proximity of each other (not physically touching).
Used in the landing gear system.
How many proximity switches re associated with the air/ground positioning system?
Five (weight on wheels).
Two on each main gear and one on the nose gear.
What is the nose gear proximity switch used for?
Nose wheel steering.
Reverse thrust.
How do the four main gear proximity switches function?
A ‘majority rules’ logic.
With 4 valid signals, 3 must agree.
With 1 invalid signal (i.e. 3 valid signals), 2 must agree.
With 2 invalid signals, the remaining 2 must agree.
What happens if the air/ground positioning logic can’t tell if the aircraft is in the air or on the ground?
It sends the most conservative signals to the dependant systems.
What EICAS warning may appear if a crosswind landing is executed?
LG AIR/GND FAIL.
The air/ground positioning system may momentarily display this message if one main wheel touches the ground first.
Which hydraulic system operates the landing gear?
Hydraulic system 1.
What are the three ways the pilot can deploy the landing gear?
Main landing gear handle (electric/hydraulic).
Landing gear override knob (electric/hydraulic).
Landing gear free-fall actuator (mechanical).
How does the landing remain retracted in flight?
J hooks on each gear.
How does the gear remain down after extension?
An over centre elbow and large springs.
Is anything held under hydraulic pressure when the gear is retracted?
Yes. The nose wheel doors.
What is the purpose of the bonding straps?
To bond two hinged surfaces together and protect against hinge damage in case of a lightening strike.
What is the proper orientation of the taxi lights on the nose gear?
Clear on top for forward distance and the corrugated on the bottom for a wider beam in turns.
How many gear pins are there and what do they do?
Four. One on each gear and one in the hydraulics bay. Disable the retracting mechanism. Only an engineer can install and remove these pins.
