Aircraft Main Landing Gear System

Study Notes

Each MLG consists of three legs that are not structurally independent or interchangeable, with different geometries
Attached to the fuselage at 11 points, with 3 retraction actuator points
Moving components are structurally independent
Controlled by the L/G lever, with a red arrow indicating when the L/G is not locked down in approach configuration
Location: main fitting at the lower hinge pin, lateral link at the lower hinge pin, and longitudinal link at the top main fitting
Forward leg is braced by 2 links: upper and lower links

Green arrows indicate the L/G is locked down
Pedestal has the L/G lever and 3 green arrows
Location: main fitting at the lower hinge pin, lateral link at the lower hinge pin, and longitudinal link at the top main fitting

Fwd doors open mechanically
Gear automatically centers upon full extension of the strut
Folding dragstay consists of a lower dragstay attached to the main fitting and a panel-type upper dragstay with a removable pintle pin
Locked in the down position by a lock link held by 2 tension springs
SOSV allows hydraulic pressure to the steering manifold when NLG is down or isolates aircraft hydraulic pressure when NLG is up

Emergency extension:
- Close cut-off valves to isolate hydraulic supply pressure
- Open 3 vent valves to dump all landing gear actuators in the return line
ECMU electrically operates EBMA
Down lock MLG: one per leg, equipped with a hook, trigger, and roller
Spring assist to lock gear down in emergency mode

Main wheel speed: tachometer
BTMU: temp sensors connected to IRDC
Anti-skid: compares wheel speed with aircraft speed (provided by GADIRS) to release brakes for that pair of wheels
- Touchdown protection inhibits braking before wheel spin-up
- Prevents loss of braking efficiency (disabled under 5m/s)
Autobrake function:
- Overrides auto brake system when pedals are used
- Requires ground spoiler p/b not to be pressed
- Set on HI/RTO for takeoff