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AGK > AGK Systems - lesson 1 > Flashcards

AGK Systems - lesson 1 Flashcards

1
Q

What’s the cause of most stress on a shorthaul aircraft?

A

Pressure cycles

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2
Q

What is the pressure on the fuselage created by pressurising the cabin?

A

8 - 9 psi

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3
Q

What is the time of useful consciousness at 36,000

A

30 - 60 seconds

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4
Q

What document sets the standards for normal, utility, aerobatic and commuter aeroplanes

A

CS 23

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5
Q

What document sets the standards for turbine powered large aeroplanes.

A

CS 25

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6
Q

What is the purpose of the certification standards?

A

“to ensure that an acceptable safety level for equipment and systems as installed on the aeroplane”

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7
Q

What is the principle behind certification?

A

The more catastrophic the consequences of failure would be, the less likely it must be that it can happen

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8
Q

From the certification standards:
Define:
Fail safe

A

In the event of a failure the component remains safe.

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9
Q

From the certification standards:
Define:
Safe life

A

Components are designed to survive a specific design life with a chosen reserve

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10
Q

Safe life can be measured in

A

Cycles
Landings
Calendar duration

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11
Q

Safe life requires components to have a good design life over a ___________ period.

A

predictable

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12
Q

Fail safe: Describe what is mean by multiple load paths.

A

A system that allows duplication of anything critical.

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13
Q

Describe damage tolerance

A

The ability of a structure to sustain defects safely until repair can be effected

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14
Q

Stress is the internal force per unit area inside a structural component as a result of

A

external loads

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15
Q

What is the equation for stress?

A

Stress = Load / original cross sectional area

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16
Q

Describe ‘Strain’

A

The deformation caused by stress on a material, given as a change in dimension percentage of original.

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17
Q

Forces imposed by maneuvering ark known as

A

dynamic loads

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18
Q

If you see ‘yaw damper’ in a question it refers to

A

Dutch roll

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19
Q

Rudder ratio control will refer to

A

the reducing requirement for the rudder at high speed

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20
Q

What type of load would build up very slowly over time or remain more or less constant over a period of time. For rxample, the loads when stationary on the ground

A

Static loads

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21
Q

What type of load would be described as loads which re-occur and rise and fall in magnitude. Vibration which occurs in rapidly changing frequencies, especially in turbine engines, is a good example of cyclic loading.​

A

Cyclic loads

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22
Q

Name 5 types of loads and stress

A

Tension
Compression
Torsion
Shear
Bending

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23
Q

If a material returns to original shape is shows _______ properties

A

Elastic

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24
Q

If a material will permanently deform it shows _______ properties

A

Plastic (plasticity)

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25
Q

Aluminium possesses both elastic and ______ properites

A

plastic

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26
Q

In metals, plastic deformation leads to?

A

buckling component, permanent deformation.​

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27
Q

Elastic range followed by plastic range. Which would be normal operating range for an aircraft?

A

Elastic range

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28
Q

If you see skin wrinkling or buckling then the structure is as likely to have experienced which force?

A

compression

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29
Q

If you see pulled rivets then you are likely to see the structure has experienced which force?

A

Tension

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30
Q

Where would you expect the largest bending moment?

A

Wing root

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31
Q

Wing bending relief in the air is countered by

A

Fuel and engine in/on the wings

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32
Q

When would maximum stress on the wing occur?

A

Empty wing tanks.

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33
Q

Why would you use centre tank fuel first?

A

Reduce the wing bending
You are reliant on fuel pumps for the centre tank

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34
Q

In flight top of the wing is being compressed while bottom is in tension however when on the ground:

A

top tension
bottom compression

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35
Q

Transport cat aircraft have a load factor derived by what multiplier on the load limit
“factor of safety”

A

1.5

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36
Q

Limit load value is

A

2.5g

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37
Q

Ultimate load value

A

3.75g

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38
Q

Two identical aircraft on the same mission. One has a 1% greater mass. What is the effect on airframe fatigue

A

5%

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39
Q

Each airframe as a fatigue life calculated by manufacturer based on

A

hours flown
number of load cycles

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40
Q

The reason for derated / reduced thrust take off is for

A

Direct operating costs of the engine

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41
Q

Failure is more likely under what type of loading​?

A

tensile

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42
Q

Failures first start at points where stress is ____________

A

concentrated

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43
Q

Maximum stress is experienced at

A

sharp corners or ridges​

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44
Q

Combination of corrosive condition and steady tensile load​ is known as

A

stress corrosion

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45
Q

Alloys must possess a number of qualities including:​

A

Elasticity ​
Plasticity​
Stiffness ​
Strength. ​

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46
Q

Common materials used for aircraft include:​

A

Aluminium
titanium
magnesium alloys
steel​

May include added lithium, magnesium, manganese, silicon, zinc​

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47
Q

Alloy of copper and nickel with small amount of Magnesium and Iron. High resistance to corrosion, low coefficient to expansion and very strong. Used in Jet exhaust pipes​

describes what?

A

Monel

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48
Q

In composite structures you can choose where to lay the fibres for what reason

A

adds strength to where you need it

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49
Q

A composite is?

A

Combination two or more organic / inorganic components

50
Q

Advantages of composites:

A

Light, strong, stiff, durable, resistant to corrosion and fatigue​

Excellent strength to weight ratio​

Can be moulded into complex shapes​

51
Q

Disadvantages of Composites

A

Hard to inspect for flaws ​

May absorb moisture which freeze causing delamination​

Expensive to produce​

Difficult to repair​

Not as tolerant to damage as aluminium​

Not naturally electrically conductive​
-Tendency to heat up and delaminate when struck by lightning​

Quickly eroded by sand and hail – must be protected on leading edges.

52
Q

Ways to protect from corrosion

A

Painting – Aesthetics, branding, good corrosive and UV resistance – periodical repaint required​

Anodising – suited to alloys, provides a hard wearing coloured coating​

Powder coating – suited to alloys, hard wearing zinc coating, may be coloured​

Polishing – Useful for Aluminium, Chromium and Stainless Steels – encourages natural hardened surface layer​

Bedding compounds – used between dissimilar materials to prevent Galvanic corrosion – typically a Zinc Chromate paste​

53
Q

Sources of corrosion

A

Any fluid leaks.

54
Q

There are two types of maintenance method:​

A

Hard time maintenance​ - fixed
On condition maintenance​ - variable

55
Q

Define:
Redundancy

A

duplicating critical parts so should one fail the other can still perform the task

56
Q

Define:
Stress and Strain

A

always present within the structure – static and dynamic​

57
Q

Define:
Static loads

A

on the ground – weight and gravity​

58
Q

Define:
Dynamic loads

A

in flight – vary in magnitude according to manoeuvres and atmospheric conditions​

59
Q

Define:
Greatest stress

A

wings and wing roots – inspect during pre-flight for cracks, popped rivets buckled skin or structural distortion​

60
Q

Define:
Corrosion

A

weakens a structure and creates a point where stress fractures can form​

Rust – ferrous based materials​

Oxidation – Aluminium and alloys (white powdery residue)​

61
Q

Marine and humid environments pose greatest threat of ?

A

Corrosion

62
Q

Define:
Fatigue

A

increased risk where corrosion is present, high number of cycles, hard manoeuvring and/or low maintenance​

63
Q

Define:
Hard Time Maintenance

A

fixed intervals – Time, cycles – cannot be exceeded – A Check or D Check

64
Q

Define:
On condition Maintenance

A

as required – brakes, tyres, wipers, lights

65
Q

Define:
Composite structure

A

combination of 2 or more organic / inorganic materials​

66
Q

Define:
Fibre Reinforced Plastic (FRP)

A

Typically Carbon or Kevlar construction with polymer resin

67
Q

Define:
Glass Reinforced Plastic (GRP)

A

Fibreglass – glass strands impregnated with resin – Epoxy or Poly Vinyl​

68
Q

Limits on airframe:​

A

Maximum Structural Ramp Mass – the maximum permissible mass before the aircraft commences taxi​

Maximum Structural Take-Off Mass – the maximum permissible mass at the start of the take-off run​

Maximum Zero-Fuel Mass – Maximum mass of the aircraft without usable fuel​

Maximum Structural Landing Mass – the maximum mass on landing, in normal circumstances. ​

69
Q

Aircraft designs utilise either:

A

High wing, low wing, high or mid-set tail plane and T-tail

70
Q

Typically the following apply:​

A

Arc welding – ferrous metals of high grade (thickness)​

Mig welding (Metal Inert Gas) – lower grade metals and uses a gas to protect the weld – Argon usually​

Tig welding (Tungsten Inert Gas) – Aluminium and alloys (including Stainless Steel) – uses Argon as an Inert gas shroud

71
Q

Principal components of the semi-monocoque design are:​

A

Aircraft skin - provides aerodynamic shape, carrying a portion of the load ​

Formers/frames - define the shape ​

Stringers - run longitudinally and help to withstand skin buckling​

Longerons - the main longitudinal load-carrying members​

Bulkheads - provide structural partitions inside the fuselage​

Firewall - a fire resistant bulkhead

72
Q

What semi-monocoque construction element run longitudinally to Withstand buckling?

A

Stringers

73
Q

Define:
Aircraft skin

A

provides aerodynamic shape, carrying a portion of the load

74
Q

Define:
Formers/frames

A

define the shape

75
Q

Define:
Stringers

A

run longitudinally and help to withstand skin buckling​

76
Q

Define:
Longerons

A

the main longitudinal load-carrying members

77
Q

Define:
Bulkheads

A

provide structural partitions inside the fuselage

78
Q

Define:
Firewall

A

a fire resistant bulkhead

79
Q

A single machined piece of aluminium forms skin and stringer-like structure​, what are the advantages?

A

No need for rivets and other attachment methods saving a great deal of weight​

Ideal for wet wings where structure of wing itself used to form a fuel tank cell – no rivet holes!​

80
Q

Most fuselage cross-sections are circular or almost circular in shape This is done for two reasons:​

A

Ensures that air flow will not separate at moderate angles of attack or sideslip​

More easily withstands the loads imposed by pressurisation.​

81
Q

The oval type cross section fuselage, results in:​

A

Lower manufacturing cost​

Greater capacity resulting in increased revenue​

Better options for cargo loading and unloading​

82
Q

Define:
The Pressure Hull​

A

Section of fuselage between forward and rear pressure bulkheads​

83
Q

The pressure hull experiences:​

A

Axial stress acts along the longitudinal axis ​

Hoop stress acts radially across the fuselage cross section​

84
Q

Cyclic stress experienced every time cabin is pressurised so the pressure hull has a fatigue life, measured in ______ ______

A

flight cycles​

85
Q

There are three types of wing design:​

A

The cantilever wing​
The semi-cantilever wing​
The externally braced wing​

86
Q

Describe a cantilever wing

A

All high speed jet transport aircraft have cantilever wings because struts create too much drag.​
737

87
Q

Describe a semi-cantilever wing

A

A semi-cantilevered wing has some supporting external struts​

eg. C172

88
Q

Describe an externally braced wing?

A

An externally braced wing has external supporting struts and bracing wires ​

.​eg. Cessna 152

89
Q

Describe a wing spar

A

Is the main span-wise structural member of the wing​

Withstands bending loads and supports the weight of the wing on the ground​

Large or very long wings may have more than one spar​

Typically constructed either as box section or as an I beam​

90
Q

Describe a wing rib

A

Provide aerodynamic shape​

Allow the stressed skin to be attached to the wing structure and transfer the loads into the spar​

91
Q

Describe a stringer

A

Combine with ribs to share loads and transfer load to spars​

92
Q

Stressed Skin​

A

Provides the smooth aerodynamic outer cover and withstands tension and compression stresses​

93
Q

Chord line vs chord

A

Chord line - the line
Chord - a length

94
Q

Define:
Wet wing:

A

Internal wing spaces can form an integral fuel tank​

If it’s using existing structure then it’s ‘integral’

95
Q

Define:
Torsion box

A

With multiple spar designs the spars are linked together to form a torsion box​

The torsion box is very rigid, resistant to twisting and greatly adds to wing strength​

96
Q

Define:
Wingbox

A

Section between the wings. It connects to wings and fuselage

97
Q

The wing experiences torsional stresses for two reasons:​

A

When the engines are mounted on the wing their thrust line tends to cause twisting forces on the wing structure​
-Therefore, engines are positioned forward of the wing​

Stresses caused by the difference between the positions of the centre of gravity (CG), and the centre of pressure (CP) ​

98
Q

What does moving the CofG forward on the wing help to prevent?

A

Flutter

99
Q

Because the CG and CP don’t act through the same point on the wing, they form a couple which tends to twist the wing around its ________ ____

A

flexural axis

100
Q

Some torsional stress can be relived by carefully designing the position the engines and the fuel tanks to move the ________ ____ closer to the centre of pressure. ​

A

flexural axis

101
Q

Manufacturers employ a range of methods to prevent flutter on aircraft wings:​

A

Chord wise and span wise positioning of masses ​

Engines are pylon mounted ahead of the wing CG​

Fuel is stored in integral wing tanks that are towards the front of the wing ​

The wing is designed with good torsional stiffness​

An addition to torsional stiffness the wing displays bending flexibility​

The ability to absorb vertical loads​

102
Q

What can the crew do to reduce chances of flutter?

A

carry out correct fuel balancing procedures in flight

103
Q

The Empennage

A

Provide longitudinal stability from horizontal stabiliser and longitudinal control from the rudder​

Directional stability from the vertical stabiliser and directional control from the rudder​

Caution must be applied during take-off and landing to prevent a ‘tail strike’​

This will cause detrimental damage to the airframe – accidents have been attributed to damage caused to the aft pressure bulkhead by a tail strike.​

104
Q

T-Tail
2 good
2 bad

A

Move the tail out of the downwash from the main wing

Provide a good glide ratio, and are more efficient on low speed aircraft​

More likely to enter a deep stall and are more difficult to recover from a spin​

Must be of a stronger construction and therefore heavier than conventional tails.​

105
Q

What is control surface flutter

A

Flutter is the rapid oscillation of a flight control surface due to imbalances​

106
Q

Control surface Flutter is primarily caused by an interaction of

A

aerodynamic forces
inertia forces
elastic properties of the control surface​

107
Q

How do we prevent control surface flutter?

A

mass balancing

108
Q

What material is often used for aircraft floors?

A

ALUHEX – provides an extremely light, yet strong material, which is used on aircraft floor panels, walls, doors, hatches and skins​

109
Q

Explosive blow-out bung in the cabin floor

A

Prevents the cabin floor from collapsing in the event of cargo area decompression.

110
Q

If a door has to open outwards what can be employed to keep it closed.

A

Outward opening doors require an inflatable seal or rubber cuff to make them air-tight.

111
Q

Flight deck windows must (CS25):​

A

Have excellent optical qualities​

Be sealed securely to withstand cabin pressurisation forces​

Withstand the stresses imposed by temperature difference​

Withstand significant impacts without breaking​

Have a de-ice / anti-ice facility​

112
Q

A windscreen is made up of
and why

A

Windscreen panels are made up of two transparent plies​

Interlayer absorbs impact loads and prevents the glass from fragmenting.​

113
Q

CS 25 requires aircraft equipped with direct vision window​ to have what properties

A

Designed either to slide back or to open inwards​

Large enough to be used as a means of emergency escape.

114
Q

Hydraulic systems transmit power to ______ locations ​

A

remote ​

115
Q

Typical uses for hydraulics in large aircraft include:​

A

Landing gear and wheel brakes​
Nose wheel steering​
Primary flight controls​
Spoilers​
Flaps​
Speed brakes​
Engine thrust reversers.​

116
Q

In a hydraulic system is important to understand that Pressure is generated though what?

A

a resistance to flow! ​

117
Q

A hydraulic pump generates what?

A

flow (not pressure)

118
Q

In a hydraulic system we don’t really care about ______ pressure.

A

static

119
Q

Oil is incompressible.
true/false

A

true

120
Q

According to Pascal’s law the pressure induced by a 500lb load on oil enclosed in a cylinder is felt as ____lb of static pressure at every point in the oil.​

A

500lb

121
Q

Force =

A

force = pressure x area

122
Q
A

AGK (17 decks)

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