Airframe Design and Materials Flashcards
(39 cards)
Minor Failure
Probable
10^3
Major Failure
Remote
10^5
Hazardous Failure
Extremely Remote
10^7
Catastrophic Failure
Extremely Unprobable
10^9
Safe Life
The life of an aircraft which it will not suffer catastrophic failure.
May be used during a declared number of cycles or flight hours.
Fail Safe
The load is carried by other components if a part of the structure fails.
The limited amount of time that an aircraft can carry a failed load.
Can be carried until the next periodic inspection.
“PARALLEL LOAD PATHS”
Damage Tolerant structure
Load is spread over a large area.
Bending
The total combination of tension, compression and shear.
Tension
The outer edge stresses.
Can cause pulled rivets.
Compression
The inner edges squeezing together.
Shear
Occurs across the structure as forces try and tear it.
Stress
The internal force per unit area inside structural part, as a result of external loads
Strain
- The quantifiable effects of stress
- The Deformation caused by the action of stress on a material
Buckling
Deformation occurring to a thin sheet after compressive forces.
What is a Stringer used for?
L shape metal that is bonded to skin.
Will PREVENT BUCKLING
Design Limit Load CS25
The maximum load the designer expects the aircraft to experience in service.
2.5g
Ultimate load = 2.5g x 1.5 = 3.75g
Dynamic Load
Builds up quickly due to changes in flight conditions.
Produced when manoeuvring
Can be severe.
Static Load
Build up slowly, fairly constant
When does maximum stress occur at the wings?
Maximum stress occurs with empty wing tanks
What provides bending relief at the wing roots?
Ailerons
Fuel in wings
Underslung engines.
What does the Wohler Curve exhibit?
Relationship between stress and cycles to Failure
Stress Corrosion
Combination of stress & corrosion.
Causes by fatigue.
Unpredictable and quick
What determines the number of cycles to failure?
The amplitude or size of load
Define an Alloy
A combination of two or more metals providing properties we didn’t have previously
