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Module 11 Richard > 11.2 Airframe Structures - General > Flashcards

11.2 Airframe Structures - General Flashcards

1
Q

What must be done if a defect is found on an aircraft

A

It must be noted in the logbook so it can be rectified with an approved drawing

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2
Q

What type of loads do structural members usually carry

A

End loads rather than side loads

Tension or compression rather than bending

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3
Q

Rather than taking structural loads what qualities are required from fairings and cowlings

A

They need to have a neat appearance and streamlined shape

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4
Q

Every part of the aircraft must be planned to take the load to be imposed on it what is this process called

A

Stress analasys

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5
Q

To ensure the aircraft structure is capable of taking all of the stresses it will experience in flight what is done in the initial design phase

A

Fail safe load transfer, damage tolerance and fatigue indexing

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6
Q

What does the fail safe method rely on

A

Duplication of certain structural members. If one fails the other will take the load

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7
Q

What is the damage tolerance method

A

Requires an assessment to see if the damage sustained will lead in failure

This method is old and outdated

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8
Q

What is a further method of damage tolerance

A

By using crack limited joints. The joints will limit the spread of cracks

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9
Q

What is fatigue known as

A

Fracturing after a series of cyclic loads, may be much less than the ultimate load

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10
Q

What are the 3 categories of aircraft structure

A
  • Primary structure
  • Secondary structure
  • Tertiary structure
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11
Q

What are the characteristics of the primary structure

A

Critical load baring structure. Requires immediate repair if damaged as it can affect the structural integrity of the aircraft

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12
Q

What are the characteristics of the secondary structure

A

Not load baring and the failure of a secondary structure would not affect the structural integrity of the aircraft

These consist of things like access panels and require repair as soon as possible

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13
Q

What are the characteristics of a tertiary structure

A

Not load baring and do not make up an integral part of the airframe. They consist of things like wing root fairings and landing gear fairings

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14
Q

What are the 5 main structural units of an aircraft

A
  • The fuselage
  • The wings
  • The stabilisers
  • Flight control surfaces
  • The landing gears
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15
Q

What main structural members make up an aircrafts structure

A

Stringers, frames, bulkheads, ribs, skin and other members

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16
Q

How are structural members fixed together

A

With brackets, rivets, bolts, screws and nuts which add strength to the fuselage

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17
Q

What are structural members designed to do

A

Carry a load or resist stress

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18
Q

How is stress created

A

By the internal force of a substance which opposes or resists deformation

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19
Q

What are the 6 major types of stress that can effect aircraft structure

A
  • Tension
  • Compression
  • Torsion
  • Shear
  • Bending
  • Hoop stress
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20
Q

Give the definition of tension

A

Stress that resits the forces trying to pull it apart

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21
Q

How do you calculate tensile strength

A

Divide the load (in pounds) with by the cross sectional area

The result is PSI

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22
Q

What is the definition of compression

A

Stress that resists a crushing force. Causes aircraft parts to be squeezed together

Usually measured in PSI

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23
Q

What type of stress is torsion

A

A twisting stress. For example when the rudder is deflected

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24
Q

What is shear stress

A

Unaligned forces pushing one part of a body in one direction and another part in the opposite direction

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25
Q

What is bending stress

A

A combination between compression and tension.

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26
Q

When an aircraft is pressurised what type of load is it under

A

Differential loading

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27
Q

What are the two side effects of differential loading

A

One causes the compartment to stretch longitudinally and the other causes the circumference of the compartment to expand

This is known as hoop stress

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28
Q

What are the zones of the aircraft

A

Primary areas of aircraft such as the fuselage, wings and engines

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29
Q

In what units do Boeing measure their zones

A

Imperial in inches

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30
Q

What are the reference lines called on Boeing aircraft

A

Body stations, body buttock lines and body water lines

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31
Q

Where is the body station

A
  • A vertical plane at right angle to the body centreline

- Measured from a point in front of the aircraft (jig)

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32
Q

What is the abbreviation of body station

A

BS

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33
Q

What are the body buttock lines

A

Vertical planes parallel to the fuselage centreline

Body buttock line 0 is the body centreline

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34
Q

What is the abbreviation of Body Buttock line

A

BBL
For right - R BBL
For left - L BBL

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35
Q

What are the body water lines

A

Water lines are horizontal planes at right angles to the body stations and body buttock lines

Body waterline 0 is bellow the fuselage

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36
Q

Where is the reference line used for installation on components and equipment used by the manufacturer

A

Along the top surface of the floor beams

37
Q

On Boeing aircraft what are the wing coordinates used

A
  • The wing reference plane
  • Wing buttock lines
  • Wing stations
38
Q

On Boeing aircraft what are nacelle coordinates divided in to

A
  • Nacelle stations
  • Nacelle buttock lines
  • Nacelle water lines
39
Q

Where is nacelle station 0 on Boeing aircraft

A

In front of each forward engine mount

40
Q

On Boeing aircraft what are the horizontal stabiliser coordinates

A
  • The stabiliser chord plane
  • Buttock lines stations
  • Leading edge stations
  • Elevator stations
41
Q

What is the horizontal stabiliser reference plane

A

The plane through the leading edge and trailing edges of the stabiliser aerofoil

42
Q

On Boeing aircraft what coordinates is the vertical stabiliser split in to

A
  • Fin stations
  • Waterlines
  • Leading edge stations
  • Rudder stations
43
Q

How are the vertical and horizontal stabiliser stations identified on Airbus

A

They are called horizontal stab stations and vertical stab stations

44
Q

What zone is 100

A

Bottom of the fuselage

45
Q

What zone is 200

A

Top half of fuselage

46
Q

What zone is 300

A

Vertical and horizontal stabiliser

47
Q

What zone is 400

A

Power plant and struts

48
Q

What zone is 500

A

Left wing

49
Q

What zone is 600

A

Right wing

50
Q

What zone is 700

A

Landing gear and landing gear doors

51
Q

What zone is 800

A

Doors

52
Q

What is done to make a more accurate description of an object rather than just zone number

A

Major zones are broken down in to sub major zones for more precise location

53
Q

If two or more access panels are in the same zone what is done to identify each one

A

A letter is used after zone numbers

54
Q

How is the lower half of the pressurised fuselage drained

A

By using a system of valved drain holes

55
Q

How are fluids directed to the drain holes in the lower pressurised fuselage

A

Through a system of longitudinal and cross-drain paths through the stringers and frame shear clips

56
Q

What is used to prevent the loss of pressure through drain holes

A

Bilge- like valves are fitted

They are spring loaded

57
Q

What is the most basic form of lightning protection

A

The exterior almost all metal structure. It acts as a shield protecting internal areas from lightning and electrical systems from electromagnetic interference

58
Q

What must be done after a lightning strike has happened

A
  • General walk around and find out damaged area and discharge
  • If damage is found a detailed inspection is required and must be documented
59
Q

What two types of damage do lightning strikes usually result in

A

Direct damage - Surface is burned or melted or shows signs of metalic distortion at two or more points

Indirect damage - Large electrical transients on the wiring which may cause damage to the electrical systems equipment

60
Q

What type and size of mark will a lightning strike usually cause

A

A small circular melt mark approx 1/8 inch diameter

61
Q

What might other signs of lightning strike be

A

Burned or discoloured skin or rivets

62
Q

What are the lightning strike conditional inspection examines these areas

A
  • External surfaces
  • Static discharges
  • Fuel system valves
63
Q

What are the most likely places for lightning strikes to occur

A

Fuselage nose section and the aerofoil trailing edge tips

64
Q

What components could a high intensity lightning strike damage

A
  • Fuel valves
  • Generators
  • Power feeds
  • Electrical distribution systems
65
Q

Why are aircraft bonded

A
  • To minimise radio and radar interference
  • To eliminate fire hazard by preventing spark between two metallic components at different potentials
  • To minimise damage from lightning strikes
  • To provide a low resistance return path for single wire electrical systems
  • To aid effectiveness of shielding
66
Q

As long as protective coatings have been removed from components which bonding leads are attached what should the resistance not exceed when checked

A

A resistance no greater than 0.025 Ohms

67
Q

What conditions apply when installing grounds

A
  • Grounds must be separated AC, DC shields
  • There must be no more than 4 terminals on 1 stud
  • In a fuel vapour area dual grounds must be installed
68
Q

What is grounding

A

Grounding is the process of connecting systems and the shields of shielded cables to the aircraft metallic structure at pre-designated points

69
Q

What is a longeron

A

Main longitudinal member of a fuselage or nacelle

70
Q

What is a tie rod (tension rod)

A

Member taking a tensile load

71
Q

What is a strut

A

A member taking a compression load

72
Q

What is a spar

A

The main spanwise member of an aerofoil. Frequently consists of an upper and lower boom separated by a web

73
Q

What is a stringer

A

A stiffener which assists with sheet materials to carry loads along their length.

With integral construction they are machined or etched out of the skin panel

74
Q

What is ‘safe life’

A

The period in which It is considered that a failure of a component is extremely unlikely.

75
Q

What is a crack stopper

A

A reinforcing member usually placed at right angles to the path of an anticipated crack which will reduce the rate of further propagation

76
Q

What is static loading

A

Loads imposed on an aircraft when stationary

77
Q

What are the two types of fuselage construction

A
  • Truss Type

- Monocoque type

78
Q

What is truss type

A

Rigid framework made up from members such as beams, struts and bars to resist deformation by applied loads.

Usually light aircraft covered in fabric. Tubular fame welded

79
Q

What is the biggest problem with monocoque constructions

A

Since no bracing members are present the skin has to be strong enough to take all of the stress.

Strength the weight is the issue

80
Q

What is the main advantage of the semi monocoque construction

A

The structure can take a lot of stress or damage and still maintain enough strength to hold together

81
Q

What are floorboards constructed from

A

A honeycomb composite construction

82
Q

What is the empennage attachment

A

Similar to the wing box but for the horizontal and vertical stabilisers

83
Q

What is the purpose of engine nacelles

A

The contain the engine components and provide a streamlined enclosure

84
Q

When are bolts most commonly used on aircraft

A

When high strength is needed. If high strength is not needed then screws are used as a replacement

85
Q

What are the 3 main types of surface protection

A
  • Pretreatment
  • Paint coatings
  • Special coatings
86
Q

What would a pretreatment consist of

A
  • Increase corrosion resistance of the metal by chemical or electrochemical procedures
  • Give a good surface for paint coatings
87
Q

What would paint coatings consist of

A
  • Primer: Increases corrosion resistance

- Top coat: Adds to the surface protection and then provides good finishing qualities

88
Q

Why are special coatings used and what are used

A

They are used on materials or places that require extra or more intensive corrosion resistance

  • Type 1: Water repellant coating usually made from silicone free materials
  • Type 2: Heavy duty corrosion preventative compound, i.e. Greases available in various grades
89
Q

What is the purpose of surface cleaning

A

To remove dirt or oil for inspection and maintenance purposes

Module 11 Richard (19 decks)

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