Aircraft Main Landing Gear System

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Questions and Answers

What is the function of the IRDC?

Manages the steering system

Manages the anti-skid, brake pressure control, and data acquisition systems (correct)

Operates the parking brake

Regulates the shuttle valve

What happens when the normal braking mode is lost?

Parking brake is engaged

Ultimate braking is activated

Alternate braking is disabled

Alternate braking takes over with a yellow indication (correct)

What is the purpose of the U-turn mode?

Required for braking on wet runways

Used for commercial aircraft only

Used for steering on the ground

Used for military aircraft only (correct)

What is the location of the EBCU?

Avio bay Signup and view all the answers

What is the function of the CPIOM-G?

Provides 1000VU of power Signup and view all the answers

What is the purpose of the steering system's RVDT?

Provides feedback to the control spool Signup and view all the answers

When is the automatic reset function initiated?

After landing gear extension Signup and view all the answers

What happens during the pre-land test?

Internal test after landing gear lock down Signup and view all the answers

What is the purpose of the lock valve in maintenance?

Replaces a wheel or brake Signup and view all the answers

What is the function of the parking brake light?

Reads 315 Signup and view all the answers

How many points is the main landing gear attached to the fuselage?

11 points Signup and view all the answers

What is the purpose of the SOSV in the nose landing gear?

To allow hydraulic pressure to the steering manifold when NLG is down Signup and view all the answers

What is the function of the lock link in the folding dragstay?

To lock the dragstay in the down position Signup and view all the answers

What is the purpose of the 3 vent valves in emergency extension?

To ensure all landing gear actuators are dumped in the return-line Signup and view all the answers

How many retractation actuator attachment points are there?

3 Signup and view all the answers

What is the purpose of the down lock MLG?

To lock the gear down in emergency mode Signup and view all the answers

What is the function of the nose door by-pass valve?

To allow both front doors to be opened for maintenance purposes Signup and view all the answers

How long does it take for sequence retraction?

12s Signup and view all the answers

What is the purpose of the anti-skid system?

To compare wheel speed with aircraft speed Signup and view all the answers

What is the purpose of the BTMU?

To monitor brake temperature Signup and view all the answers

Study Notes

Main Landing Gear (MLG) and Door

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

Control and Indications

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

Nose Landing Gear and Door

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

Extension and Retraction

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

Wheel and Brakes

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