11.13 Landing Gear Flashcards
1
Q
What two types of landing gear are there
A
Nose wheel type (1 nose 2 main gear)
Tail wheel (2 nose 1 main gear)
2
Q
What type of landing gear do all jet aircraft have
A
Nose wheel type (Directional stability for take off and landing)
3
Q
Where is the centre of gravity on tail wheel aircraft
A
Aft of main wheels
Additional turning moment when landing on wet or icy runway
4
Q
How is the brake out moment influenced
A
Greater at higher speeds
Further the centre of gravity behind the wheels
Closer the main landing gears are together
5
Q
Where is the centre of gravity in nose wheel aircraft
A
Before main wheels
Returning moment around the centre of gravity on landing prevents ground loop of aircraft
6
Q
In relation to brakes, what is an advantage of nose wheel aircraft
A
More forceful application of brakes, landing at lighter speeds with out nosing over
7
Q
What does a greater angle of attack on nose wheel aircraft allow
A
Greater decrease of lift on touchdown
8
Q
What is the weight carried on the main wheels called
A
Main wheel loading
9
Q
What are 4 or 6 wheel landing gears called
A
Bogies
10
Q
How does the nose gear retract
A
Forward into the fuselage
11
Q
How far can the rudder pedals steer the aircraft
A
80’degrees left or right
12
Q
On what aircraft are hydraulic powered steering systems used
A
Heavy aircraft
Transmit signals from the rudder pedals to the steering control valve
13
Q
What does a shock strut do on landing gear
A
Absorb shock on landing
Uses compressed nitrogen and hydraulic fluid to absorb shock (dampening shock)
14
Q
What transmits the landing gear shock loads from the drag strut to the aircraft structure
A
Trunnion link
15
Q
What does the trunnion link rotate in
A
Spherical bearings
Transmit vertical and drag loads to airframe with out transferring torque to the structure
16
Q
What is the inner cylinder of the strut made of
A
Ultra high tensile steel
Keep weight low
17
Q
What are the torsion links used for
A
Allow inner cylinder to move up and down in the outer cylinder but not rotate
18
Q
What is a torsion link damper used for
A
Counteract wheel shimmy
19
Q
What is wheel shimmy and how does it occur
A
Rapid oscillation of the wheel to the left and right of direction of travel
Caused by uneven tire pressure, uneven runway surface, uneven tire wear
20
Q
Why is the torsion link damper filled with hydraulic fluid
A
To keep it pressurised
21
Q
What does the drag strut do
A
Stabilised the shock strut
22
Q
What does the side strut do
A
Gives lateral support to the shock strut
23
Q
What does the main gear actuator do
A
Converts hydraulic pressure into mechanical energy to extend and retract the gear
24
Q
What does the gear down lock mechanism do
A
Ensures 2 parts cannot fold together when main gear is extended
25
What does the fluid metering device measure in the gear actuator
Speed at which actuator cylinder operates
26
What is the lock strut also called
Jury strut (always centred)
27
What does the Dow lock sensor do
Sense when the gear is down and locked in position
28
On what part of the gear is a lock pin inserted to prevent reaction on the ground
Lock strut
29
What is the purpose of the up lock roller on the gear up lock
Push the up lock hook out of the release position in to spring held engaged position
30
What oil does the shock strut use for dampening
Red mineral oil
31
What is the purpose of the flow orifice in the shock strut
Allows laminar flow (non resistant) one direction and turbulent flow (high resistance) the other direction
32
How is progressive dampening achieved in a shock strut
A tapered metering pin (fitted to the inner cylinder)
33
What decelerates the vertical motion of aircraft on landing in the shock absorber
High gas pressure and greater restriction of fluid flow
34
What does the rebound valve do in the shock strut
Restricts return flow of oil
35
What do the upper and lower bearings do in the shock strut
Upper bearings - keeps inner cylinder aligned with the outer
Lower bearings - Keeps inner cylinder aligned inside the outer
36
What does the gland housing assembly do
Seals the housing against the environment and pressurises oil
37
What does the main gland seal do in the gland housing assembly in the shock strut
Keeps the nitrogen gas and hydraulic pressure in the strut
38
What seals are used in the inner and outer cylinder of the shock strut
Inner - Dynamic seal (linear or rotational movement)
Outer - Static seal (steady or pulsating pressure)
39
What is the advantage of a spare seal actuating valve for shock struts
Seals do not have to be immediately replaced and can continue in service
40
Where are the spare seals for gland housing assembly kept
Spare seal cavities
41
What is the lock strut dimension 'H' a measure of
Extension of the inner cylinder
42
What is the result of too much gas or too much oil in a shock strut
Too much gas - soft strut
Too much oil - strut operates harshly
43
Why must the wheel gear tuck be able to be tilted
So it can be retracted in to the wheel well
44
Where do the body gears turn in relation to the nose gear
Opposite direction
45
What is the purpose of the body gear trunnion
Guides landing loads into the fuselage
46
What is the purpose of the side brace on the main gear
Directs forces from the body gear into the trunnion
47
What unit is the shock absorber on the centre gear
2 stage oleo pneumatic unit
48
What lever moves the connecting link in the shortening mechanism
Bell crank lever (turning the upper link)
49
What does the lock stay do for the nose gear
Gives secondary support for the down and locked position
| Controls alignment of the folding drag strut
50
What are the upper and lower links made of the lockstay
Upper - aluminium
Lower - Steel
51
How is an unlock position maintained
Up lock roller and uplock hook
52
What is the purpose of a fluid metering device on a downlock actuator
Slows down the alignment of the struts and speed of the nose gear operation
53
What gives the nose gear down lock indications
Two proximity sensors
54
What does the actuator do
Converts hydraulic pressure into mechanical energy to extend or retract a gear
55
What is the purpose of the cantering cams
Ensure the nose gear is in straight and forward position before retraction
56
When does the nose gear proximity sensor give a ground signal
When the shock absorber is compressed to a certain position or when within a certain distance of their overcentre position
(Otherwise give a flight signal)
57
What make up the shock absorber on nose gear with 4 tubes
Sliding tube and plunger tube
| Sliding tube has metering tube for oil transfer
58
Why do the centring cams return the wheels to the centre or neutral position
Prevent jamming when the gear is retracted
59
When are towing lugs designed to shear
If towing load is more than the limit
| Decreases risk of damage to the sliding tube
60
When do you know the re servicing of oil is good in the shock strut
The overflow is free of air bubbles
61
Is the shock absorber kept fully compressed during air servicing
Yes
62
What are hydraulically powered steering systems also called
Follow up systems
63
What are the 2 basic methods of actuation for nose wheels steering
2 jack method
Rack and pinion method
64
What do the cable drums do in a mechanical steering system
Transmit inputs from the tiller to the steering cables
65
Does the interconnect actuator have to be retracted or extended for the rudder pedals to be connected to the nose wheels steering system
Retracted
66
What does the bypas valve do in the steering control
Protects system against high pressure developed in the actuator during towing
67
What is a cable compensator for in a steering system
Prevent fails inputs to steering control valve
68
When is the null point on a mechanical steering system
Pulling actuator reaching the end of its stroke
69
For electrical system steering, what are the two main valves
Selector valve and servo valve
70
What is a BSCU
Braking and steering control unit
71
What are the 3 methods used to overcome tyre damage from scrubbing
Bogie beam
Rotating truck beam
Single axle for main gear wheels
72
What is main gear steering automatically activated
When the speed decreases below a certain value
| Automatically centred when speed increased above a certain value
73
What is the bypass valve for on the front doors
Opens the doors via gravity, up lock is unlocked
74
What gives signals when the doors are in the fully opened position
Proximity sensors
75
Where is the leg door connected to on the nose gear
Back of the nose gear leg
76
What fairings are used on the main doors
Hinged and fixed fairings
77
What do the ramps do inside the main doors
Make sure the doors do not interfere with the gear during fall extension
78
What are the 2 methods of locking the doors
Mechanical actuator with mechanical lock
Hook with door up p-lock and up lock roller
79
How are the hinged and fixed fairings attached to the aircraft
Hinged - via adjustable rod to wing skin
Fixed - attached to shock strut by studs and rods
80
What is the gear lever shaped like
A gear wheel
81
How are control inputs from the landing gear lever transmitted
Via electrical signals or mechanical cables
82
What indicated gear up or gear down next to the gear lever
Green and red lights
83
What positions are there in a mechanical and electrical gear system
Electrical - Up, Down
Mechanical - Up, Down, Off
84
What is an LGCIU
Landing Gear Control Interface Unit
85
How many way valves are selector valves for the gears
3/4 way valves
(Up selected, piston moves to the left)
(Down selected, piston moves to the right)
Off - Centre position
86
What is the difference between electrical and mechanical selector valves
Electrical uses a solenoid to remove hydraulic pressure
87
How is the gear level Locked on the ground
De-Energised solenoid
88
When is the hydraulic pressure isolated from the landing gear in an electrical system where there is no OFF position
When speed is above 250KTS
| Safety valve closes
89
What shape Indicates the landing gear
2 triangles (Not visible when gear is up and locked)
If systems disagree green triangles always in front of red
90
What colour Indication are the doors when they are not up and locked
Amber
91
What does the door operating gear sequence valve do
Make sure the gear can begin to extend or retract only when the doors are fully open
92
How many sequence valves do the nose gear have
2
93
What allows the doors to be opened on the ground
Door bypass valve
94
What type of valves are hydraulic fuses
Safety valves
| Areas danger to hydraulic leaks due to foreign objects
95
How is the life span for tyres calculated
Number of landings and take offs (approx 150)
96
How quick can a tyre accelerate under load from zero to 220kts and what temp will it reach
60'seconds (110 Celsius in heat)
97
What temp can tyres drop to in flight
-20 Celsius
98
What load can each main gear tyre carry
23,000kg
99
What disk brakes do small or large aircraft use
Small - single disk
Large - multi disk
100
How many times the load may an aircraft have to carry a heavy landing
2 times
101
What are the wheels on large jet aircraft mainly made of
Aluminium alloy (light and strong)
102
How are the wheel halves held together
Tie bolts
103
What prevents heat from wheels damaging the wheels and tires during normal braking
Heat shield
104
What temperature can brake disks reach on heavy braking
1000 Celsius
105
What automatically releases tyre pressure when a temperature of a wheel increases to a certain level
Fusible plug (Thermal relief plugs)
(Filled with alloy of low melting point) (Inside wheel - 300 Celsius)
(Wheel flange - 180 Celsius)
106
When are fusible plugs melted after extreme high energy braking
10 mins after aircraft brings aircraft to stop
107
What bearings do all aircraft have
Tapered wheel baring
108
What are Type 3 tyres
Low pressure (less than 160mph)
Greater width section in relation to rim diameter
109
What are Type 7 tyres
High pressure (Jet aircraft up to 225mph)
110
What are Type 8 tyres
Very high pressure (military aircraft up to 280mph)
111
What are the 3 main measures of a tire size
Width, rim diameter and outside diameter
112
What is the tyre carcass made of
Layers of rubber coated nylon chord fabric
113
What are beads in the tyre
High strength tensile steel wires embedded in rubber (1,2 or 3)
(Anchor the carcass)
114
How many times can tyres be retreaded before being scrapped
10
115
How are the vent holes in tyres usually marked
Yellow or green
116
What is a balance mark on a tyre and what is it coloured
Lightest part of the tyre (red dot)
117
What do belt plies do in the tyre
Give tyres strength in tread
118
Where does the carcass give give strength to the tyre
Sidewall
119
What do chippers do in the tyre
Improve durability in bead area
120
What are advantages of radial tyre over conventional tyre
Lighter and better performance
121
What are the disadvantages of radial tyres compared to conventional tyres
Expensive and cannot be retreaded as much
122
What is hydroplaning
Tyre squeezing water from under tread (lifting the tyre)
123
What is viscous hydroplaning
Slippery action on thin film of water, acts like a lubricant
124
What is reverted rubber hydroplaning
Locked tyre skidded over runway, generating friction heat and steam, lifting tyre off runway
125
What does a properly inflated tyre have a deflection of
32% (good tread wear)
Over inflated - less than 32%
Under inflated - more than 32%
126
If the tyre is deflated more than 45% how much heat is generated
More than 3 times normal heat
127
Why is under inflation worse than over inflation
Excessive stress, ply separation and weakening of carcass
128
How much is the pressure reduced by when not under load
4%
129
How much does the tyre pressure change for every 3 Celsius
1%
130
When is the tyre worn on tyres with a centre groove
When middle groove is no longer visible over length of 10cm or more
131
How many times can an aircraft fly when a tyre has reaches its normal wear limit
15 times
132
When must a tyre be removed if a chevron cut is more than
8mm deeper than the bottom of the nearest groove
133
What are tyre bulges caused by
Overheating in tread area
134
Where can you find the wheel interface (transmission unit)
On the axle of the wheel
135
What do the pistons change in a brake piston housing
Hydraulic brake pressure into load
136
What is an advantage of a self sealing coupling in a break piston housing
Do not have to bleed the brakes after installation
137
What is the purpose of the adjuster in brakes
Responsible for brake clearance and compensate for brake wear
138
What does the torque tube do in the brake
Transmits the torque of the stator disks to the piston housing
(Done by splines)
139
What does the heat pack in the brake consist of
Rotors and staters
When brake pressure is applied friction between these give braking effect
140
What are the advantage of carbon packs over steel packs
Around a third lighter, less wear and can withstand much higher temperatures
141
What are the allowable temperature limits of carbon and steel heat packs after a rejected take off
Carbon: 2500-3000 Celsius
Steel: 1500-2000 Celsius
142
What are the disadvantages of carbon to steel heat packs
More expensive
However can be recycled (2 used can be made in to 1 new one)
143
What is the metal drive block for on carbon heat packs
Protects the carbon disk during installation on the axle and wheels are being installed on brake unit
144
What gives a visual indication of the overall wear of the heat pack
Wear indicator pin (Pack does not have to be removed)
Fully worn when pins align with bracket
145
How many landings does 1mm of pin length correspond to on brakes
20-30
146
What must be ensured when checking for brake wear
Parking brake is on
Brakes are cold
147
What do the brake pedals operate on large aircraft with power braking
A metering valve (more pressure to brakes)
148
What is differential braking
Independently operating left hand or right hand brakes
149
What are the brake pedals connected via
Connection rods
150
What hydraulic system normally powers the normal brake metering
4 (1 as backup)
151
What does in flight braking do
Stops rotation movement of the wheels during retraction
| Generates high Gyro movement
152
What is the BSCU
Braking Steering Control Unit
Controls normal braking, automatic braking, in flight braking, anti skid, nose wheel steering and temperature monitoring
153
What does the brake pressure transducer do
Limits the brake pressure in proportion to brake pedal travel
154
What gives the artificial feel at the brake pedals
Master cylinder
155
What powers the parking brake when the hydraulic power is switched off
Accumulator pressure
| If that decreases then restored with electrical pump
156
When does the anti skid automatically turn off
When the aircraft is below a certain speed ( e.g. 10 KTS)
| Avoids danger of releasing brakes when not wanted
157
What is the brake release signal for each wheel
2 sets of 4 green lines
158
Why would and automatic brake system be used
Reduce delay between touchdown and application of brakes (Less than 1 second)
Each second delay reduces stopping distance by 60m
159
How much increase of drag do speed brakes give
40-80%
160
When are the speed brakes applied (% of aircraft weight on wheels)
65%-90% weight on wheels
161
What does the servo valve do for the brakes
Sends pressure to the brakes
162
What does the deceleration rate depend on
Runway length
163
What rate of deceleration is selected when a blue light illuminates
Medium deceleration, auto braking system armed
164
What colours are 0-4 and 5-9 for brake temp
| 1-100 Celsius) (9-865 Celsius
0-4 white
5-9 amber above 300 Celsius
165
How is temperature of wheel brakes measured
Thermocouple
166
How are brakes cooled
Electrically driven cooling fan
| 3 phase motor
167
What are micro switches
Switch devices that can open and close an electrical circuit at very high speeds
168
What do 3 greens indicate
Landing gear is down and locked
Amber light - gear in transit and not locked
