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Module 11 Richard > 11.13 Landing Gear > Flashcards

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)

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2
Q

What type of landing gear do all jet aircraft have

A

Nose wheel type (Directional stability for take off and landing)

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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

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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

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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

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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

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7
Q

What does a greater angle of attack on nose wheel aircraft allow

A

Greater decrease of lift on touchdown

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8
Q

What is the weight carried on the main wheels called

A

Main wheel loading

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9
Q

What are 4 or 6 wheel landing gears called

A

Bogies

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10
Q

How does the nose gear retract

A

Forward into the fuselage

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11
Q

How far can the rudder pedals steer the aircraft

A

80’degrees left or right

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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

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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)

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14
Q

What transmits the landing gear shock loads from the drag strut to the aircraft structure

A

Trunnion link

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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

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16
Q

What is the inner cylinder of the strut made of

A

Ultra high tensile steel

Keep weight low

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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

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18
Q

What is a torsion link damper used for

A

Counteract wheel shimmy

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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

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20
Q

Why is the torsion link damper filled with hydraulic fluid

A

To keep it pressurised

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21
Q

What does the drag strut do

A

Stabilised the shock strut

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22
Q

What does the side strut do

A

Gives lateral support to the shock strut

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23
Q

What does the main gear actuator do

A

Converts hydraulic pressure into mechanical energy to extend and retract the gear

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24
Q

What does the gear down lock mechanism do

A

Ensures 2 parts cannot fold together when main gear is extended

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25
Q

What does the fluid metering device measure in the gear actuator

A

Speed at which actuator cylinder operates

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26
Q

What is the lock strut also called

A

Jury strut (always centred)

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27
Q

What does the Dow lock sensor do

A

Sense when the gear is down and locked in position

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28
Q

On what part of the gear is a lock pin inserted to prevent reaction on the ground

A

Lock strut

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29
Q

What is the purpose of the up lock roller on the gear up lock

A

Push the up lock hook out of the release position in to spring held engaged position

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30
Q

What oil does the shock strut use for dampening

A

Red mineral oil

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31
Q

What is the purpose of the flow orifice in the shock strut

A

Allows laminar flow (non resistant) one direction and turbulent flow (high resistance) the other direction

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32
Q

How is progressive dampening achieved in a shock strut

A

A tapered metering pin (fitted to the inner cylinder)

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33
Q

What decelerates the vertical motion of aircraft on landing in the shock absorber

A

High gas pressure and greater restriction of fluid flow

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34
Q

What does the rebound valve do in the shock strut

A

Restricts return flow of oil

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35
Q

What do the upper and lower bearings do in the shock strut

A

Upper bearings - keeps inner cylinder aligned with the outer

Lower bearings - Keeps inner cylinder aligned inside the outer

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36
Q

What does the gland housing assembly do

A

Seals the housing against the environment and pressurises oil

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37
Q

What does the main gland seal do in the gland housing assembly in the shock strut

A

Keeps the nitrogen gas and hydraulic pressure in the strut

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38
Q

What seals are used in the inner and outer cylinder of the shock strut

A

Inner - Dynamic seal (linear or rotational movement)

Outer - Static seal (steady or pulsating pressure)

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39
Q

What is the advantage of a spare seal actuating valve for shock struts

A

Seals do not have to be immediately replaced and can continue in service

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40
Q

Where are the spare seals for gland housing assembly kept

A

Spare seal cavities

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41
Q

What is the lock strut dimension ‘H’ a measure of

A

Extension of the inner cylinder

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42
Q

What is the result of too much gas or too much oil in a shock strut

A

Too much gas - soft strut

Too much oil - strut operates harshly

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43
Q

Why must the wheel gear tuck be able to be tilted

A

So it can be retracted in to the wheel well

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44
Q

Where do the body gears turn in relation to the nose gear

A

Opposite direction

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45
Q

What is the purpose of the body gear trunnion

A

Guides landing loads into the fuselage

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46
Q

What is the purpose of the side brace on the main gear

A

Directs forces from the body gear into the trunnion

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47
Q

What unit is the shock absorber on the centre gear

A

2 stage oleo pneumatic unit

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48
Q

What lever moves the connecting link in the shortening mechanism

A

Bell crank lever (turning the upper link)

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49
Q

What does the lock stay do for the nose gear

A

Gives secondary support for the down and locked position

Controls alignment of the folding drag strut

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50
Q

What are the upper and lower links made of the lockstay

A

Upper - aluminium

Lower - Steel

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51
Q

How is an unlock position maintained

A

Up lock roller and uplock hook

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52
Q

What is the purpose of a fluid metering device on a downlock actuator

A

Slows down the alignment of the struts and speed of the nose gear operation

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53
Q

What gives the nose gear down lock indications

A

Two proximity sensors

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54
Q

What does the actuator do

A

Converts hydraulic pressure into mechanical energy to extend or retract a gear

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55
Q

What is the purpose of the cantering cams

A

Ensure the nose gear is in straight and forward position before retraction

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56
Q

When does the nose gear proximity sensor give a ground signal

A

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)

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57
Q

What make up the shock absorber on nose gear with 4 tubes

A

Sliding tube and plunger tube

Sliding tube has metering tube for oil transfer

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58
Q

Why do the centring cams return the wheels to the centre or neutral position

A

Prevent jamming when the gear is retracted

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59
Q

When are towing lugs designed to shear

A

If towing load is more than the limit

Decreases risk of damage to the sliding tube

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60
Q

When do you know the re servicing of oil is good in the shock strut

A

The overflow is free of air bubbles

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61
Q

Is the shock absorber kept fully compressed during air servicing

A

Yes

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62
Q

What are hydraulically powered steering systems also called

A

Follow up systems

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63
Q

What are the 2 basic methods of actuation for nose wheels steering

A

2 jack method

Rack and pinion method

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64
Q

What do the cable drums do in a mechanical steering system

A

Transmit inputs from the tiller to the steering cables

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65
Q

Does the interconnect actuator have to be retracted or extended for the rudder pedals to be connected to the nose wheels steering system

A

Retracted

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66
Q

What does the bypas valve do in the steering control

A

Protects system against high pressure developed in the actuator during towing

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67
Q

What is a cable compensator for in a steering system

A

Prevent fails inputs to steering control valve

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68
Q

When is the null point on a mechanical steering system

A

Pulling actuator reaching the end of its stroke

69
Q

For electrical system steering, what are the two main valves

A

Selector valve and servo valve

70
Q

What is a BSCU

A

Braking and steering control unit

71
Q

What are the 3 methods used to overcome tyre damage from scrubbing

A

Bogie beam
Rotating truck beam
Single axle for main gear wheels

72
Q

What is main gear steering automatically activated

A

When the speed decreases below a certain value

Automatically centred when speed increased above a certain value

73
Q

What is the bypass valve for on the front doors

A

Opens the doors via gravity, up lock is unlocked

74
Q

What gives signals when the doors are in the fully opened position

A

Proximity sensors

75
Q

Where is the leg door connected to on the nose gear

A

Back of the nose gear leg

76
Q

What fairings are used on the main doors

A

Hinged and fixed fairings

77
Q

What do the ramps do inside the main doors

A

Make sure the doors do not interfere with the gear during fall extension

78
Q

What are the 2 methods of locking the doors

A

Mechanical actuator with mechanical lock

Hook with door up p-lock and up lock roller

79
Q

How are the hinged and fixed fairings attached to the aircraft

A

Hinged - via adjustable rod to wing skin

Fixed - attached to shock strut by studs and rods

80
Q

What is the gear lever shaped like

A

A gear wheel

81
Q

How are control inputs from the landing gear lever transmitted

A

Via electrical signals or mechanical cables

82
Q

What indicated gear up or gear down next to the gear lever

A

Green and red lights

83
Q

What positions are there in a mechanical and electrical gear system

A

Electrical - Up, Down

Mechanical - Up, Down, Off

84
Q

What is an LGCIU

A

Landing Gear Control Interface Unit

85
Q

How many way valves are selector valves for the gears

A

3/4 way valves

(Up selected, piston moves to the left)

(Down selected, piston moves to the right)

Off - Centre position

86
Q

What is the difference between electrical and mechanical selector valves

A

Electrical uses a solenoid to remove hydraulic pressure

87
Q

How is the gear level Locked on the ground

A

De-Energised solenoid

88
Q

When is the hydraulic pressure isolated from the landing gear in an electrical system where there is no OFF position

A

When speed is above 250KTS

Safety valve closes

89
Q

What shape Indicates the landing gear

A

2 triangles (Not visible when gear is up and locked)

If systems disagree green triangles always in front of red

90
Q

What colour Indication are the doors when they are not up and locked

A

Amber

91
Q

What does the door operating gear sequence valve do

A

Make sure the gear can begin to extend or retract only when the doors are fully open

92
Q

How many sequence valves do the nose gear have

A

2

93
Q

What allows the doors to be opened on the ground

A

Door bypass valve

94
Q

What type of valves are hydraulic fuses

A

Safety valves

Areas danger to hydraulic leaks due to foreign objects

95
Q

How is the life span for tyres calculated

A

Number of landings and take offs (approx 150)

96
Q

How quick can a tyre accelerate under load from zero to 220kts and what temp will it reach

A

60’seconds (110 Celsius in heat)

97
Q

What temp can tyres drop to in flight

A

-20 Celsius

98
Q

What load can each main gear tyre carry

A

23,000kg

99
Q

What disk brakes do small or large aircraft use

A

Small - single disk

Large - multi disk

100
Q

How many times the load may an aircraft have to carry a heavy landing

A

2 times

101
Q

What are the wheels on large jet aircraft mainly made of

A

Aluminium alloy (light and strong)

102
Q

How are the wheel halves held together

A

Tie bolts

103
Q

What prevents heat from wheels damaging the wheels and tires during normal braking

A

Heat shield

104
Q

What temperature can brake disks reach on heavy braking

A

1000 Celsius

105
Q

What automatically releases tyre pressure when a temperature of a wheel increases to a certain level

A

Fusible plug (Thermal relief plugs)

(Filled with alloy of low melting point) (Inside wheel - 300 Celsius)

(Wheel flange - 180 Celsius)

106
Q

When are fusible plugs melted after extreme high energy braking

A

10 mins after aircraft brings aircraft to stop

107
Q

What bearings do all aircraft have

A

Tapered wheel baring

108
Q

What are Type 3 tyres

A

Low pressure (less than 160mph)

Greater width section in relation to rim diameter

109
Q

What are Type 7 tyres

A

High pressure (Jet aircraft up to 225mph)

110
Q

What are Type 8 tyres

A

Very high pressure (military aircraft up to 280mph)

111
Q

What are the 3 main measures of a tire size

A

Width, rim diameter and outside diameter

112
Q

What is the tyre carcass made of

A

Layers of rubber coated nylon chord fabric

113
Q

What are beads in the tyre

A

High strength tensile steel wires embedded in rubber (1,2 or 3)

(Anchor the carcass)

114
Q

How many times can tyres be retreaded before being scrapped

A

10

115
Q

How are the vent holes in tyres usually marked

A

Yellow or green

116
Q

What is a balance mark on a tyre and what is it coloured

A

Lightest part of the tyre (red dot)

117
Q

What do belt plies do in the tyre

A

Give tyres strength in tread

118
Q

Where does the carcass give give strength to the tyre

A

Sidewall

119
Q

What do chippers do in the tyre

A

Improve durability in bead area

120
Q

What are advantages of radial tyre over conventional tyre

A

Lighter and better performance

121
Q

What are the disadvantages of radial tyres compared to conventional tyres

A

Expensive and cannot be retreaded as much

122
Q

What is hydroplaning

A

Tyre squeezing water from under tread (lifting the tyre)

123
Q

What is viscous hydroplaning

A

Slippery action on thin film of water, acts like a lubricant

124
Q

What is reverted rubber hydroplaning

A

Locked tyre skidded over runway, generating friction heat and steam, lifting tyre off runway

125
Q

What does a properly inflated tyre have a deflection of

A

32% (good tread wear)

Over inflated - less than 32%

Under inflated - more than 32%

126
Q

If the tyre is deflated more than 45% how much heat is generated

A

More than 3 times normal heat

127
Q

Why is under inflation worse than over inflation

A

Excessive stress, ply separation and weakening of carcass

128
Q

How much is the pressure reduced by when not under load

A

4%

129
Q

How much does the tyre pressure change for every 3 Celsius

A

1%

130
Q

When is the tyre worn on tyres with a centre groove

A

When middle groove is no longer visible over length of 10cm or more

131
Q

How many times can an aircraft fly when a tyre has reaches its normal wear limit

A

15 times

132
Q

When must a tyre be removed if a chevron cut is more than

A

8mm deeper than the bottom of the nearest groove

133
Q

What are tyre bulges caused by

A

Overheating in tread area

134
Q

Where can you find the wheel interface (transmission unit)

A

On the axle of the wheel

135
Q

What do the pistons change in a brake piston housing

A

Hydraulic brake pressure into load

136
Q

What is an advantage of a self sealing coupling in a break piston housing

A

Do not have to bleed the brakes after installation

137
Q

What is the purpose of the adjuster in brakes

A

Responsible for brake clearance and compensate for brake wear

138
Q

What does the torque tube do in the brake

A

Transmits the torque of the stator disks to the piston housing

(Done by splines)

139
Q

What does the heat pack in the brake consist of

A

Rotors and staters

When brake pressure is applied friction between these give braking effect

140
Q

What are the advantage of carbon packs over steel packs

A

Around a third lighter, less wear and can withstand much higher temperatures

141
Q

What are the allowable temperature limits of carbon and steel heat packs after a rejected take off

A

Carbon: 2500-3000 Celsius

Steel: 1500-2000 Celsius

142
Q

What are the disadvantages of carbon to steel heat packs

A

More expensive

However can be recycled (2 used can be made in to 1 new one)

143
Q

What is the metal drive block for on carbon heat packs

A

Protects the carbon disk during installation on the axle and wheels are being installed on brake unit

144
Q

What gives a visual indication of the overall wear of the heat pack

A

Wear indicator pin (Pack does not have to be removed)

Fully worn when pins align with bracket

145
Q

How many landings does 1mm of pin length correspond to on brakes

A

20-30

146
Q

What must be ensured when checking for brake wear

A

Parking brake is on

Brakes are cold

147
Q

What do the brake pedals operate on large aircraft with power braking

A

A metering valve (more pressure to brakes)

148
Q

What is differential braking

A

Independently operating left hand or right hand brakes

149
Q

What are the brake pedals connected via

A

Connection rods

150
Q

What hydraulic system normally powers the normal brake metering

A

4 (1 as backup)

151
Q

What does in flight braking do

A

Stops rotation movement of the wheels during retraction

Generates high Gyro movement

152
Q

What is the BSCU

A

Braking Steering Control Unit

Controls normal braking, automatic braking, in flight braking, anti skid, nose wheel steering and temperature monitoring

153
Q

What does the brake pressure transducer do

A

Limits the brake pressure in proportion to brake pedal travel

154
Q

What gives the artificial feel at the brake pedals

A

Master cylinder

155
Q

What powers the parking brake when the hydraulic power is switched off

A

Accumulator pressure

If that decreases then restored with electrical pump

156
Q

When does the anti skid automatically turn off

A

When the aircraft is below a certain speed ( e.g. 10 KTS)

Avoids danger of releasing brakes when not wanted

157
Q

What is the brake release signal for each wheel

A

2 sets of 4 green lines

158
Q

Why would and automatic brake system be used

A

Reduce delay between touchdown and application of brakes (Less than 1 second)

Each second delay reduces stopping distance by 60m

159
Q

How much increase of drag do speed brakes give

A

40-80%

160
Q

When are the speed brakes applied (% of aircraft weight on wheels)

A

65%-90% weight on wheels

161
Q

What does the servo valve do for the brakes

A

Sends pressure to the brakes

162
Q

What does the deceleration rate depend on

A

Runway length

163
Q

What rate of deceleration is selected when a blue light illuminates

A

Medium deceleration, auto braking system armed

164
Q

What colours are 0-4 and 5-9 for brake temp

1-100 Celsius) (9-865 Celsius

A

0-4 white

5-9 amber above 300 Celsius

165
Q

How is temperature of wheel brakes measured

A

Thermocouple

166
Q

How are brakes cooled

A

Electrically driven cooling fan

3 phase motor

167
Q

What are micro switches

A

Switch devices that can open and close an electrical circuit at very high speeds

168
Q

What do 3 greens indicate

A

Landing gear is down and locked

Amber light - gear in transit and not locked

Module 11 Richard (19 decks)

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