Landing Gear

Question 1

Tricycle Landing Gear

Answer 1

Two sets of main wheels near CG
Smaller Nose wheel assembly

Question 2

Tail Wheel System

Answer 2

Provides propeller clearance
TO/LD can be difficult

Question 3

Retractable Vs Fixed Gear System

Answer 3

Fixed requires less moving parts less maintenance costs

Drag penalty’s

Gear systems use hydraulics and have an emergency lowering ability

Question 4

What is a Bogie

Answer 4

At least four wheels mounted to bogie beam

Internal space needed for stowage

Small turning radius give greatest load on torsion link

Think 787/747s

Question 5

Shock Absorbers Role

Answer 5

Absorb 90% of shock
Via Oleo Strut

Question 6

The Oleo Strut

Answer 6

Uses Gas (Nitrogen) pressure to absorb AC weight/spring to absorb load

Hydraulic oil to control compression/extension in leg assembly

Inner cylinder connected to wheel
Outer Cylinder connected to airframe
Sliding Restrictor prevents bouncing

Question 7

Signs of Oleo Strut (shock absorber) being too small and damaged

Answer 7

Low gas pressure
Bottom out on landing
Focalised portion being too small
Hydraulic fluid leaking

Question 8

Nose Wheel Assembly

Answer 8

Only direct compression loads
Max load is after main wheel have touched down

Features:
- Free castoring for steering
- Auto self venturing
- Shimmy Protection
- Steering

Components:

Retraction Actutator
Side brace
Torque Link
Oleo Strut
Steering Acutator
Taxi Lights

Question 9

Retraction/Extension of gear controlled by…

Answer 9

Selector valves

Sequence valves to sequence open/closing

Question 10

Landing Gear Speeds

Answer 10

VLE = max speed with gear down
VLO = max op speed for landing gear no faster

Question 11

What is Down Lock

Answer 11

Prevents accidental retraction
Over centre locks
No hydraulic power/mechanical to break lock

Question 12

What is uplock?

Answer 12

Hook lock controlled by hydraulic pressure

Question 13

What is a Ground Lock?

Answer 13

Prevent collapse of undercarriage on ground

Pins which prevent ops

Very obvious warning flags

Question 14

Indication of gear status

Answer 14

Green - Locked own
RED - Unlocked (travelling)
No Lights - gear up and locked
Amber - Door failure?

Question 15

Gear Selector Lever

Answer 15

Prevent inadvertent retraction on ground

Spring loaded plunger via solenoid retains down position

Flick off in cockpit when ready to TO

Question 16

3 x emergency gear extensions:

Answer 16

Manual systems via hand pump
Compressed Nitrogen to blow gear down
Gravity/free fall system

Question 17

X 2 Types of steering on light AC

Answer 17

Differential Braking - Applied to main wheels causing wheels to castor
NO DIRECT CONNECTION BETWEEN RUDDER PEDALS AND NOSE WHEEL

Rude Pedal Steering - direct mechanical link between pedals and nose gear

Question 18

What is castoring

Answer 18

Ability of nose wheel to turn to either side in response to differential braking of force from rudder

Question 19

Large AC Steering

Answer 19

Electric/hydraulic motor on nose wheel strut driving it left or right

Can steer 75 degree left or right

Small lever located in flight deck to control

Question 20

Nose wheel shimmy

Answer 20

Rapid sinusoidal oscillation of nose wheel and divergent in nature

Low/uneven tyre pressure
Wear in wheel bearing
Worn torque links

Prevention:
- hydraulic damper
- Heavy self centring springs
- Double nose wheels
- Twin contact tyres

Question 21

Role of torque links

Answer 21

Prevent inner cycle rotating within outer cylinder

Limits max extension when in flight

Bearings required to enable smooth movement

Question 22

Advantage of having steering capability on main landing gear

Answer 22

To relieve the sideway stress on main wheel assemblies