11.2 AIRFRAME STRUCTURES Flashcards
1
Q
What are the 3 structural classifications
A
- primary structure
- secondary structure
- tertiary structure
2
Q
Explain secondary structure
A
- non-primary structural components
- less prone to weakening
- e.g. fuselage stringers
3
Q
Explain primary structure
A
- If structure fails, can lead to a very bad consequence
- e.g. engine mounts
4
Q
Explain tertiary structure
A
- lightly stressed components
- e.g. fairings, support brackets etc
5
Q
What does it mean by fail-safe
A
- back-up protection despite failure
- once failure occurs it is no longer ‘fail safe’
- will require frequent inspections
6
Q
What does it mean by safe-life
A
- Prevent catastrophic failure
- structure is serviceable approx 1/3 of max calculated operating hours
7
Q
What does it mean by damage tolerance
A
- repeated static + dynamic load tests
- ensures that even with damage it remains within the operational life
- reliant on visual inspection to find damage
8
Q
What is included in the zonal identification system
A
- major zones
- sub-major zones
- zones
9
Q
100
A
Lower half of fuselage
10
Q
200
A
Upper half of fuselage
11
Q
300
A
Empennage (aft fuselage and horizontal and vertical stabilisers)
12
Q
400
A
Power plants and the struts
13
Q
500
A
Left wing
14
Q
600
A
Right wing
15
Q
700
A
Landing gear and LG doors
16
Q
800
A
Doors
17
Q
For smaller aircraft the 2nd digit in the sub-major zones is between
A
1-6
18
Q
For larger aircraft the 2nd digit in the sub-major zones is between
A
1-9
19
Q
Usually the sub-major zones on the right hand side are even or odd
A
Even
20
Q
Usually the sub-major zones on the left hand side are even or odd
A
Odd
21
Q
What digit is the zone and how are they numbered
A
- 3rd digit
- FWD to AFT, INBOARD to OUTBOARD, BOTTOM to TOP
22
Q
Explain body stations or fuselage stations
A
- vertical plane at right angle to body centreline
- distance measured from a point in front of nose
23
Q
Explain buttock lines
A
Vertical planes parallel to body centre line (longitudinal)
24
Q
Explain waterlines
A
-horizontal planes, right angle to body buttock lines (horizontal)
25
What is tension
Resists forces which pull it apart
26
What is compression
- shorten/squeeze
27
What is torsion
- stress causes twisting
28
What is shear
-resists one layer of material to slide over adjacent layer
29
What is the stress calculation
- Force/cross-sectional area
30
What is bending
Combination of compression and tension
31
Explain Hoop stress
- pressure exerted circumferentially on skin
- hoop stress = 2(axial axis)
(twice value of longitudinal stress)
32
Where are drain holes located
- various positions of aircraft’s lower fuselage
33
What are ‘bilge-like’ valves
- Prevent loss of air during aircraft pressurisation
Valve open = depressurised
Valve closed = pressurised
34
When interior cabin is depressurised is the spring loaded ‘bilge like’ valve open or closed
Open
35
What must be ensured when flammable vapour or water is present
Ventilation
36
What does easy access to locate system components result in
- saves time and lowers maintenance cost
37
What are installed securely but with ease of removal in mind
Cockpit indicators
38
What does lightning strike caused by direct damage look like
- burned surface/melted
39
What does lightning strike caused by indirect damage look like
- damage to the electrical system and equipment
40
A lightning strike usually causes small damage approximately —mm in diameter
3mm
41
What is the hole diameter of a high intensity lightning strike
6mm
42
Most common area for lightning strikes?
- nose
- trailing edges
43
What is bonding
Same electrical current potential (low resistance path)
44
What is grounding
To maintain a constant electrical potential between aircraft and ground
45
How do you prevent the build up of static charges
Bonding
46
What does the frames do in the airframe construction
- give cross-sectional shape (often circular)
- give shape and provide strong attachment points
47
What are bulkheads and what is its function
- give shape to fuselage
- pressure bulkheads used to contain pressure
- fireproof bulkheads used to seal and isolate fires
48
Main difference between bulkheads and grommet
Bulkheads- cannot put hand through
Grommet - can put hand through
49
What are Longerons
Main longitudinal member of fuselage/nacelle
50
Primary bending loads are taken by
- stringers
- longerons
- bulkhead
Longerons
51
What are Longerons supplemented by
Stringers
52
Explain stringers
-smaller and lighter than longerons
- carry loads along their length
- used for skin attachment
53
What is the function of clips/cleats?
Help transfer the pressure loads from the skin
54
What is the clips/cleats attached to
Skin to frame and stringer
55
Explain doublers
-reinforced skin that requires extra strength
- often found around doors or windows
56
What are some types of doublers known as
Crack stoppers
57
What are struts
-load bearing components that primarily hand compression forces
- transmit loads from one part of fuselage to another
58
What are struts made out of
- lightweight materials such as aluminium or composite material
59
Explain ties
- handle tension forces
- typically made from high strength materials like steel or titanium
60
What construction are floorboards
- honeycomb composite
61
What usually carries tension loads during pressurisation
Floor beams
62
What are the 2 types of fuselage construction
- truss type
- monocoque type
63
Explain truss type
Carries both tension and compression loads
64
Explain true monocoque construction
- Frame assemblies and bulkheads give fuselage shape
- skin carries primary stress
65
Explain semi-monocoque construction
- loads shared between skin and framework
- ‘known as stressed skin structure’
66
What is the wing box supported by
Heavy frames and a ‘keel beam’
67
Aircraft’s empennage contains vertical and horizontal stabilisers (T or F)
T
68
What is type 1 for special coatings
Water repellent coating
69
What is type 2 for special coatings
Heavy duty corrosion preventive compound
70
What are the 3 aircraft cleaning methods
- wet washing
- dry washing
- polishing
71
What type of wash removes oil, grease, dirt, carbon deposits etc
Wet washing
72
What type of wash removes dirt and small accumulation of dirt
Dry wash
73
Explain polishing
- removes oxidisation and corrosion
- restore colour and make brighter
74
How are acrylic windows cleaned
- windows must be washed with warm water and soap
- polish with cloth
