11.2.a Structures General Flashcards

1
Q

What philosophy are modern structures developed with?

A

Stressed skin

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2
Q

What is PSE?

A

Principle Structural Elements

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3
Q

What are Principle Structural Elements?

A

The part of the aircraft that contributes significantly to carrying flight, ground, or cabin pressure loads.

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4
Q

What are some of the PSE’s?

A

Wings
Horizontal Stab
Vertical Stab
Canard
Forward wing
Winglets
Pressurised areas

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5
Q

How are aircraft strength requirements specified?

A

In terms of the max loads expected in service and max load plus safety factor.

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6
Q

What is a flight load?

A

The maximum loads expected in service.

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7
Q

What is an ultimate limit load?

A

Flight limit loads multiplied by a factor of safety.

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8
Q

Where is the criteria found for limit loads of large aircraft?

A

CS-25

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9
Q

What are the five forces acting on an aircraft?

A

Torsion
Tension
Shear
Bending
Compression

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10
Q

What is torsion?

A

Stretch

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11
Q

What is compression?

A

Squeeze

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12
Q

What is torsion?

A

Twist

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13
Q

What is shear?

A

One layer moving opposite to the other.

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14
Q

What is bending?

A

Combination of tension and compression.

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15
Q

What are the three categories of structure?

A

Primary
Secondary
Tertiary

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16
Q

What is primary structure?

A

Any part that should it fail lead to loss of control or catastrophic failures and harm.

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17
Q

What are some examples of primary structure?

A

Wing spars
Engine Mounts
Fuselage frames

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18
Q

What is an SSI?

A

Structurally significant item.

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19
Q

What is secondary structure?

A

Non-primary structural components such as ribs, stringers and segments of skin.

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20
Q

What is secondary structure less prone too?

A

Weakening without facing failure risks.

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21
Q

What is tertiary structure?

A

Remaining components of the aircrafts framework.

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22
Q

What kind of stuff comes under tertiary structure?

A

Fairings
Fillets
Support brackets

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23
Q

What does the document FAA AC 23-13A evaluate?

A

Fail safe load transfer
Damage tolerance
Fatigue indexing

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24
Q

What is a fail safe design?

A

Duplication of structural methods to ensure if one fails then the other will take the load.

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25
Q

What is the disadvantage of fail safe designs?

A

They add weight.

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26
Q

What is the modern version of fail safe?

A

Damage tolerance.

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27
Q

What is safe life concept?

A

Prediction of how long a structure can remain in service.

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28
Q

How is the safe life indicated?

A

As a number of cycles or hours.

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29
Q

What is the safe life given to the structure?

A

1/3 of the max calculated hours.

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30
Q

What does the damage tolerance concept require?

A

Evaluation of the structure.

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31
Q

What does damage tolerance testing look like?

A

Repeated static and dynamic load tests, which demonstrate that the structure can withstand the loads expected in service plus a factor of safety.

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32
Q

What is another type of damage tolerant structure?

A

Multiple load path concept.

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33
Q

How does multiple load path concept work?

A

Large, heavy, and highly stressed members are avoided. Small members carry the loads, each supporting only a small percentage of the total.

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34
Q

What are crack limiting joints?

A

Specially designed structure that will limit the spread of cracks but ensure they can be detected.

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35
Q

What are the five main structural units?

A

Fuselage
Wings
Stabilisers
Flight Control surfaces
Landing Gears

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36
Q

How are the primary dimensions of an aircraft calculated?

A

There are defined zones, reference points, lines and planes.

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37
Q

What are the reference planes?

A

Vertical
Horizontal
Longitudinal

38
Q

What are the 8 major zones of an aircraft?

A

100-800

39
Q

What is zone 100?

A

Lower fuse

40
Q

What is zone 200?

A

Upper fuse

41
Q

What is zone 300?

A

Empennage

42
Q

What is zone 400?

A

Power plant

43
Q

What is zone 500?

A

Left wing

44
Q

What is zone 600?

A

Right Wing

45
Q

What is zone 700?

A

Landing gear

46
Q

What is zone 800?

A

Doors

47
Q

The second digit of the zone code is what range for small aircraft or large aircraft?

A

1-6 for small
1-9 for large

48
Q

On a fuselage how are the coordinates identified?

A

By body, fuselage stations or water lines and butt lines.

49
Q

What is meant by BS or FS?

A

Body station or Fuse station

50
Q

How is the body station measured?

A

From a datum in front of the nose.

51
Q

What are the butt lines?

A

Vertical planes parallel to the body centreline plane.

52
Q

What is the body butt line 0?

A

Centreline

53
Q

What are body waterlines?

A

The horizontal planes at right angles to the butt lines.

54
Q

Where are wing stations measured from?

A

Either a butt line reference point or from wing rib 1.

55
Q

What are component stations used for?

A

Various components such as flying controls.

56
Q

What is tension measured in?

A

Newtons in ISU or Pounds force in imperial

57
Q

How do you calculate tensile strength?

A

Load of material divided by cross sectional area

58
Q

What is shear strength usually equal to or less than?

A

Tensile or compressive strength.

59
Q

How is stress created?

A

When a material is subject to force.

60
Q

What is bending stress a combination of?

A

Compression and tension

61
Q

What is hoop stress?

A

The pressure on a cylinder outwards from the centre on the circumference.

62
Q

For any given pressure, what will the hoop stress be?

A

Twice the value of the longitudinal stress.

63
Q

What is strain a ratio of?

A

Deformation of a material caused by stress.

64
Q

How is strain calculated?

A

Change in length divided by the original length.

65
Q

What is fatigue?

A

Cyclic or alternate loads.

66
Q

What is effective drainage and ventilation crucial for?

A

Preventing fluids becoming trapped.

67
Q

How do fluids get to the drain holes?

A

System of longitudinal and cross drain paths.

68
Q

How is loss of pressure prevented from drain holes?

A

Bilge like valves are used.

69
Q

What must be ventilated to permit vapour to evaporate?

A

Any cavity in structure that may have flammable vapour or water.

70
Q

Where are ventilation requirements found?

A

CS-25

71
Q

How is the fittings, attachments and space decided for instruments?

A

Type
Cost
Usage
Serviceability

72
Q

How must LRU’s be placed?

A

Quickly fitted and removed.

73
Q

How is an aircraft protected from lightning strike?

A

Bonding
Earths
External skin

74
Q

If an aircraft is hit by lightning it is important too…?

A

General walk around
Find signs of damage

75
Q

What two types of damage do you get from lightning strikes?

A

Direct
Indirect

76
Q

What is direct damage?

A

Surface is burnt, melted, or show signs of metallic distortion.

77
Q

What is indirect damage?

A

Damage to the electrical system and equipment that was caused by large transients on the wiring.

78
Q

If a lightning strike has caused a system malfunction what is there a requirement for?

A

Full inspection of the defective system.

79
Q

What does a lightning strike normally look like?

A

Small circular melt or scorch marks approx 3mm in diameter.

80
Q

What other things are inspected in a lightning inspection?

A

Fuel system valves
IDG
Hyd fittings
Radio
Nav

81
Q

What is bonding?

A

Joining two electrical conductors together.

82
Q

What is grounding?

A

Process of electrically connecting conductive objects to structure or return path.

83
Q

What is the aim of boding?

A

Preventing build up of static charges and minimising the risk of electrical arcing and interference with on-board electronic systems.

84
Q

How is hardware used for bonding selected?

A

Mechanical strength
Current
Ease of installation

85
Q

When installing grounds what conditions apply?

A

Must be separated (AC/DC/shields)
No more than 4 on one stud
Dual grounds must be installed in fuel vapour areas

86
Q

How is composite structure bonded?

A

They have an aluminium mesh in the layers.

87
Q

What is composite direct bonding?

A

Exposing the mesh and mounting equipment directly onto it.

88
Q

What is indirect composite bonding?

A

Exposing the mesh and installing a wire or connector.

89
Q

When testing a bond lead contact point what max ohms must be seen?

A

0.025

90
Q
A