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Module 13 EASA Part 1 > 13.16 Landing Gear > Flashcards

13.16 Landing Gear Flashcards

(107 cards)

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1
Q

Apart from supporting the aircraft on the ground, what are the secondary functions of the undercarriage (UC)?

A

Support the aircraft in a stable attitude
Provide mobility on the ground
Absorb landing loads
Dampen out noise and vibration during taxiing
Steering
Braking

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2
Q

What is a tricycle UC?

A

Two main UC units and one nose UC unit (standard)
Variations of the above apply

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3
Q

What are the main advantages of tricycle UC?

A

Pilots view during taxiing, landing and take–off is virtually unobstructed
Layout of the UC units give forward stability
Maximum braking efficiency can be utilised

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4
Q

What are the disadvantages of tricycle UC?

A

Stability and CofG can be affected during maintenance operations
CofG must remain within area bounded by UC units otherwise structure becomes unbalanced

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5
Q

Where are the ideal strength points in a) the fuselage and b) the wing?

A

a) adjacent to a frame or juncture of a frame or stringer

b) adjacent to the mainspar or juncture of a rib or spar

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6
Q

What is a structural fuse?

A

Points between the landing gear and wing spar attachments

Strong enough to handle normal operating loads

Designed to fail under excessive loads before damage to the primary structure can occur

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7
Q

What are the advantages of fixed UC?

A

Simple

Less weight

Less maintenance

Lower cost

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8
Q

How should a damaged/overheated wheel be approached?

A

Do not approach until the tyre has cooled to an ambient temperature

Approach at an oblique angle in the direction of the tyre shoulder

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9
Q

What are the two main types of wheel assembly?

A

Removable flange

Split hub

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10
Q

In the two main types of wheel assembly, how is sealing achieved when used with tubeless tyres?

A

Use an o–ring seal

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11
Q

What are the 3 methods of heat dissipation?

A

Wheels are vented and flared

Heat shields may be installed around the brake unit

Axle fans may provide a cooling flow of air through the wheel

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12
Q

What wheel component can prevent explosion due to overheated wheel brakes and how do they work?

A

Thermal fuse plugs

Melt to release the tyre pressure when their temperature exceeds a set figure

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13
Q

What type of bearings are wheels usually mounted on to?

A

Tapered roller bearings

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14
Q

What action should be taken if any wheel tie bolt is found to be defective?

A

The wheel should be removed and the complete set renewed

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15
Q

What is the area of a tyre called where the carcass plies are located?

A

Sidewall

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16
Q

How are Radial plies laid in relation to the direction of rotation?

A

90° to the direction of rotation

Each successive layer laid at the same angle

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17
Q

What is the purpose of the chine in a nosewheel tyre?

A

Deflect water and slush to the side and away from intakes

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18
Q

What are the awl vents and how are they identified?

A

Identified by green or grey painted spots

Vents which pierce the sidewall and allow nitrogen or air trapped during the tyre’s manufacturing process to percolate through the carcass plies

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19
Q

What should the red spot or triangle on a tyre be aligned with on the wheel?

A

Tubed tyres – Heavy spot of the tube

Tubeless tyres – Heavy point of the wheel assembly

On both occasions may be the inflation valve

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20
Q

What is tyre creep?

A

Tendency of the tyre to move relative to the wheel

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21
Q

What allowance is made to the tyre pressure when it is subjected to the weight of the aircraft?

A

4%

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22
Q

What action should be taken if a cold tyre is found to be 5% below loaded inflation?

A

Any tyre between 5% and 10% below loaded inflation pressure should be reinflated to the correct pressure

Checked at the next daily check

Rejected if 5% below again

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23
Q

What action should be taken if a tyre on a multi–wheel UC has run flat?

A

All tyres on that UC should be scrapped

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24
Q

What is the maximum oxygen content of a tyre?

A

5% by volume

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25
What affect will a rise of 3°C have on tyre pressure?
Approximately 1% change in pressure
26
Describe the 3 forms of aquaplaning?
Dynamic Viscous Reverted rubber
27
What are the advantages of a multi–wheel UC?
Easier to stow when retracted Provide greater safety (burst tyre is not so critical) Easier to handle during maintenance (wheels are smaller) Increasing brake efficiency (brake units on every wheel) Weight of aircraft is spread
28
What is the purpose of the bogie hop damper/tilt jack?
Means of positioning the bogie beam at a suitable angle for retraction and landing Acts as a damper unit
29
What component of the bogie maintains the weight force on the rear wheels during braking?
Equaliser rods/compensating rods
30
What might be the result of lack of lubrication on a bogie UC?
Corrosion or Hydrogen embrittlement
31
What is the purpose of the torque links on a nose UC assembly?
Prevent rotation of the lower strut within the upper strut Limit extension of the lower strut within the upper strut
32
How can nosewheel shimmy be prevented on larger aircraft?
Using twin nosewheels, each attached to a 'live' axle Shimmy dampers Twin actuator steering system restriction of flow
33
Why must the nose UC be centred?
Must align with the wheel bay once the weight has been removed or damage would occur when the UC is retracted
34
How are nose UCs usually centred (non-steerable)?
Centring cams are located inside the shock absorber With weight off, oleo strut is extended by gas pressure within the strut Sliding cam contacts the fixed cam and slides along it In so doing, rotates the nose gear into a straight ahead direction
35
What are the 2 main types of oleo pneumatic shock absorber?
With separator Without separator
36
How does the shock absorber with separator achieve rebound restriction?
When landing, oil in the outer cylinder lifts the flutter plate and passes freely into the lower cylinder When the compressed gas expands, oil flows back to the outer cylinder but spring now closes the flutter plate Flow of oil is now restricted therefore speed of extension is limited
37
How is correct extension of an oleo ascertained during daily servicing?
Check daily against the centre of gravity/loading graphs provided in the approved maintenance manual
38
What is the general order of replenishing an oleo strut?
Dispel gas Drain old oil Recharge oil Recharge gas
39
How are normal taxying loads cushioned?
Cushioned by gas pressure and dampened by the limited flow of fluid through the orifice
40
Levered suspension struts are more likely to use what type of oleo?
Small liquid spring shock absorber
41
What must friction brakes do?
Convert kinetic energy into heat Provide drag (retarding force) Disperse heat
42
How is a working clearance maintained in the brake pack when the brakes are released?
Springs in the adjuster assemblies move the pressure plate back to maintain a working clearance and permit free rotation of the wheel
43
What condition should the brakes be in to measure the wear pin?
Brakes need to be applied
44
What effect would air in the brake hydraulic system have?
Degrade the performance of the brakes Sluggish or less effective due to sponginess
45
What colour coding relates to brake overheat on an EICAS display?
White
46
Where can Maxeret mechanical anti–skid units be mounted?
Either rim driven or axle mounted
47
In the electronic anti–skid system, what outputs do an AC speed sensor and DC speed sensor produce?
AC – DC voltage proportional to the frequency of the current produced DC – voltage output directly proportional to the rotational speed of its armature
48
What are the schematic components of an electrical anti–skid system?
Wheel transducer Control box Anti–skid control valve Annunciator Brake units
49
In a retractable UC, what braces the shock absorber a) longitudinally and b) laterally?
a) rear or drag bracing strut b) side bracing strut (may also provide a means of retraction)
50
What is the purpose of the 'walking beam'?
Serves to reduce the reaction force going into the aircraft structure from the actuator
51
On a British aircraft, what would 3 red lights indicate on an UC position indicator?
UC is in transit
52
How is an up selection of the UC prevented when the aircraft is on the ground?
Safety device Spring–loaded plunger retains the selector in the down position and is released by operation of a solenoid Electrical power to the solenoid is controlled by WOW switch on shock absorber strut Electrical power is therefore only restored on takeoff
53
From which service does a hydraulic steering system receive its main operating pressure?
Mainly UC down line (emergency supply from a hydraulic accumulator)
54
How is a steerable nose leg centred before retraction?
Inner cylinder in each steering jack is connected to the landing gear UP Supplied with fluid under pressure when the landing gear is selected UP Steering jacks thus extend equally to centralise the nose wheel
55
What does the flow of fluid between the 2 steering jacks enable?
Allowing the aircraft to be towed, or the nosewheel to return to the central position after a turn has been initiated with the steering wheel
56
What slows down the rate of lowering of the UC?
Restrictor valves
57
What 3 conditions would give a red landing gear position and warning indication?
Doors are 'not closed' with the landing gear in the up position Any engine throttle is retarded to idle position with the landing gear in the up position During landing gear transit; or when any landing gear is not in the position that corresponds to the position of the landing gear control handle
58
What condition would give an aural warning?
An unsafe condition 1. Landing gear not down and locked, engine is at idle, aircraft below predetermined speed (can be silenced) 2. Landing gear not down and locked, flaps extended beyond the approach position for landing (cannot be silenced)
59
What is the main method of attachment of landing gear?
Pivot point called a trunnion
60
What are the disadvantages of a retractable UC?
Increased weight of additional moving parts More complicated design Additional maintenance
61
What is the melting point for the following thermal fuse plugs: Red Green Yellow
Red – 155 °C Green – 177 °C Yellow – 199 °C
62
What is a 'live' axle with regards to a nose wheel?
When the axle itself rotates within bearings in the nose wheel leg
63
What are the regions of a tyre?
Crown Shoulder Sidewall Bead
64
How is bias ply constructed with regards to the centreline or direction of rotation?
Between 30° and 60° angles Successive plies are laid with the cord angles opposite to each other to provide balanced carcass strength
65
What does ply rating indicate?
Strength of the tyre
66
Why is creep a particularly dangerous issue in tubed tyres?
May move the inner tube far enough to tear out the inflation valve, causing sudden deflation of the tyre
67
How might a creep indication be given without a creep mark?
Red triangle or red spot indicating the tyre light spot would be positioned at the wheel inflation valve and could provide an indication of creep
68
What should be used when inflating a tyre for pressures above 100 psi?
Screw–on connector
69
What should be done with a tyre which is more than 10% below loaded inflation pressure at ambient temperature?
Rejected together with the companion tyre on the same axle
70
What should happen if a tyre has been under load while in a deflated condition?
Tyre removed from the aircraft
71
What should happen if a tyre has been taxied while in a deflated condition?
The deflated tyre and its axle companion should be scrapped
72
How might the heavy side of a tube be marked?
With a red or yellow band approximately 10mm wide
73
Following tyre inflation after tyre and wheel assembly, what should be used and why?
Safety cage Prevent injury to the operator
74
What are the three stages of venting of a tubeless tyre after tyre and wheel assembly?
First stage – Fairly rapid but ceases after 20 minutes Second stage – Slow seepage lasting several hours Third stage – Continuing process resulting from normal permeation of nitrogen through the inner lining
75
When must the testing of tubeless tyres be carried out after tyre and wheel assembly?
After the first stage of venting has ceased
76
When carrying out a duration pressure test, when should the tyre be rejected?
Loss exceeds 10%
77
When carrying out a duration pressure test, what should happen when the loss of pressure is less than 10%?
Re–inflated to the original pressure and checked in 12 hours
78
How long should a duration pressure test last in total?
24 hours
79
How might concussion of a tyre occur?
Heavy impact on, for example, a stone during touchdown
80
How is concussion detected externally?
Dark stain on the tyre or very slight bulge where the rubber is bruised
81
How is concussion detected internally?
A diagonal line or a 'star', dark in colour, at the point where the impact occurred
82
What must be ensured when removing tubed tyres from split wheels?
Completely deflated before any attempt is made to remove loose members
83
What is the expected error of 'stick' type gauges?
Up to 4%
84
What is the expected error of 'dial–type' gauges?
1/2% within the range of pressures specified for light aircraft and older types of transport aircraft
85
How should tyres be stored?
Vertically upright Two–thirds of the tyre should be stored above the support tubes and one–third below
86
How should tyre tubes be stored if the original wrapping is not available?
Slightly inflated and stored inside tyres of appropriate size
87
What is the shelf life of tyres and tubes?
Provided they are kept in ideal storage conditions, 7 years from the date of manufacture
88
What depth of water could cause dynamic aquaplaning?
1/10 inch"
89
Explain reverted rubber aquaplaning?
Friction caused by skid increases the temperature of the tyre, causing rubber particles to build up at the rear of the tyre contact area Forms a 'seal' delaying the escape of water Water boils and is converted to steam which lifts the tyre off the surface of the runway
90
What other name might the bogie hop damper/tilt jack have?
Bogie levelling strut
91
How is any unevenness of the runway compensated for?
By the tilt jack allowing the bogie to pivot about the bottom of the main shock absorber
92
In a shock absorber with separator, what does the lower cylinder piston head contain which normally covers holes drilled through the head?
Spring loaded flutter plate
93
What can the number of charging points tell you about the type of shock absorber you have?
With separator – separate charging points for the oil and gas
94
How does the shock absorber without separator achieve rebound restriction?
Using a metering pin When the gas expands after initial landing and having been compressed Oil flow is restricted through the metering pin and so slows the speed of extension
95
What are the conditions for when a tyre must be inflated with nitrogen?
Braked wheels of aircraft over 5700 kg MTWA on retractable UC
96
Where are the wear pins located on a brake unit and what do they do?
Attached to the pressure plate and protrude through the torque plate Amount of wear which has taken place in the disc pack
97
What might the wear indicator pin also be known as?
Retraction pin
98
What would the emergency hydraulic system not be connected to with regards to brakes?
Anti–skid device
99
How is the parking brake applied?
Both brake pedals are depressed and the parking brake handle pulled
100
What is a brake debooster and what is their principle of operation?
Pressure reducing valves Pressure differential being generated by an area differential
101
In a Maxeret mechanical rim driven anti–skid unit, by how much will the flywheel overrun the drum when the wheel is beginning to skid?
Up to a maximum of 60° relative to angular movement
102
In a Maxeret mechanical axle driven anti–skid unit, by how much will the flywheel overrun the drum when the wheel is beginning to skid?
30°
103
What are the pre–requisites for the operation of an electronic brake anti–skid control system?
Anti–skid is selected ON Undercarriage is down Ground sensing in ground mode Wheels are spinning at a predetermined RPM eg 30 knots and above
104
What is a DC wheel speed sensor?
Small permanent magnet direct current generator whose voltage output is directly proportional to the rotational speed of its armature
105
On a British manufactured aircraft, what does 'no lights' visible on the UC position indicator show?
UC is locked up
106
Why is the hydraulic steering system supplied from the UC down line?
Ensures that the steering system is only in operation when the nose UC is down
107
In a steerable nosewheel, when is castoring allowed?
When the steering wheel is released Control valve returns to neutral under the action of its centring springs Nose wheel is free to castor

Module 13 EASA Part 1 (20 decks)

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