AGK Systems Flashcards
Minor failure conditions ?
May be probable
Major failure conditions ?
Must be no more frequent than remote
Hazardous failure conditions ?
Must be no more frequent than extremely remote
Catastrophic failure conditions ?
Must be extremely improbable
Safe life concept ?
Requires structures to have an explicitly stated lifespan within which no catastrophic structural damage may occur under safe operation
Safe-life concept can be measured in ?
Flight hours
Pressurisation cycles
Landings
Calendar duration
Fail safe design ?
Critical areas have multiple load paths, designed to provide redundancy. This ensures if one fails an alternate path can carry all load through duplicate.
Fail safe design examples
Wing spar attachments
Tail plane attachment
Engine fittings
Cabin windows
Fail safe design disadvantages ?
Weight penalty consumption
Corrosion
Fatigue
Damaged tolerance design?
Some excess weight can be avoided if the are damage tolerant, these structures have crack arresting features.
What is load ?
An external force applied to a component that causes stress, which leads to deformation, know as strain
4 main stress types ?
Tension
Torsion
Compression
Shear
Dynamic loads are ?
Imposed by manoeuvring and can change very fast.
Rapid build up can cause severe stresses on materials.
Static loads … ?
Build up slowly or remain constant
Cyclic loads ?
During flight loads change and alternate rapidly, components experience compression and tension changes.
Can cause metal fatigue which can lead to structural failure
Overstress ?
Can lead to structural failure and any suspected OS must be investigated.
Areas prone to stress ?
Spar lines
Wing horizontal and vertical attachments
Roots
A/C skin
Load limit on transport A/C
2.5 g
Ultimate load limit is (+50%)
So 3.75g
Risk of fatigue increases with ?
Corrosion
High number of flight cycles
Hard manoeuvring
Poor maintenance practices
How is fatigue detected ?
Visual inspection during walk around
Corrosive conditions and steady tensile load can produce metal fatigue, also known as ?
Stress corrosion
Max ramp mass ?
Max mass authorised for manoeuvring on the ground
Max take off mass ?
Mass at which the pilot is allowed to take off
Max zero fuel mass ?
Mass of A/C and all it’s contents excluding the weight of useable fuel onboard
Max landing mass ?
Maximum mass at which A/C is permitted to land
Fatigue can be reduced by ?
Reduced cycles
Avoiding coarse manoeuvres
Avoiding turbulence
Not flying with excess fuel/payloads
Corrosion ?
Disintegrates the smooth surface of metal.
Creates a natural starting point for fatigue cracks
Corrosion is more likely ?
Over warm, salty water
How should corrosion be dealt with ?
Repaired, primed and re-painted
Corrosion indicators ?
Brown/reddy discolouration
Aluminium forms a grey powder
Potential Al mixes ? (Alloy)
Cu
Mg
Mn
Composite Mats are made from ?
Two or more materials with different chem of physical properties, combined to produce the best of both, components remain separate
Composite fibres can comprise ?
Kevlar (aramid)
Carbon (graphite)
Glass bonded with
Resin
Filler
Matrix is ?
Material the supports the fibres, and bonds them together.
Composite mats adv ?
Better power to weight ratio
Lighter
Fibres can be aligned to provide best load qualities.
Corrosion resistant
Composite mats disadv ?
Hard to inspect flaws
Doesn’t conduct well
Expensive
Less damage tolerant
Lighting impacts on composite mats ?
Can result in explosion of material at exit point
Lighting strikes on alloys ?
Tend to leave pinholes at entry and exit (little damage)
Hard time maintenance ?
Is predictable
A definite time limit in component before it has to be replaced
(Could be-
Calendar time
Landings
Cycles
Flight hours)
On condition maintenance is ?
Periodic inspection of components, post check a component is either replaced or continues in service.
(Checked once an issue arrises)
Fuselage structure type is ?
Monocoque (she’ll)
Or
Semi-monocoque (shall over frames and ribs)
How are structure components fixed ?
Bolting
Riveting
Bonding
Welding
Frames … ?
Define the shape
Stiffeners, stringers and longerons …?
Provide the base for the skin
Cross beams …?
Support floor panels
A secondary overlapping material layer is called a …?
Doubler
Where are pressurised bulk heads ?
Eitherend of the fuselage
Structural and non structural ones are in between
Fuselage shapes include ?
Circular
Oval
Double-bubble
Rectangular
What stress does the pressure hull experience …? (Everything in between pressure bulkheads)
Hoop and axial stress