Aircraft Structures Repair I
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Transcript of Aircraft Structures Repair I
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7/30/2019 Aircraft Structures Repair I
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UNIVERSITI KUALA LUMPUR - MALAYSIAN INSTITUTE OF AVI ATION TECHNO LOGY
AIRCRAFT STRUCTURES REPAIRAIRCRAFT STRUCTURES REPAIR
AAB 31003AAB 31003
UNIVERSITI KUALA LUMPUR
Malaysian Institute of Aviation
Technology
UNIVERSITI KUALA LUMPUR - MALAYSIAN INSTITUTE OF AVI ATION TECHNO LOGY
AIRCRAFT STRUCTURES REPAIR
AIRCRAFT STRUCTURES REPAIRAIRCRAFT STRUCTURES REPAIR
AAB 31003AAB 31003Chapter IChapter I
Ir. Abu Zaid Bakar
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AIRCRAFT STRUCTURES REPAIRAIRCRAFT STRUCTURES REPAIR
AAB 31003AAB 31003
Overview
1. General Structures
2. Construction Method
3. Structure AssemblyTechnique & Protection
4. Airframe Symmetry
5. Fuselage, Door, Engine
Mount, Nacelle & Landing
Gear Attachment
6. Wings & Stabilizer
7. Window &
Windscreen8. Inspection of
Aircraft Structures
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AIRCRAFT STRUCTURES REPAIRAIRCRAFT STRUCTURES REPAIR
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AIRCRAFT
LIGHTER THAN AIR HEAVIER THAN AIR
AIRSHIPS BALLONS POWER DRIVEN NON-POWER DRIVEN
GLIDER (SAIL PLANES)AEROPLANE HELICOPTER
LANDPLANE AMPHIBIANSEAPLANE
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Beam A member subject to bending, where carry load at right angle to their length. A
beam may be simply supported at the end. The support may be a little way from
the ends or it may be supported at one end only, where it is called cantilever. Examples, I-beam, T-beam, Z-beam
Application: Spar, Floorboard Structures
Strut Member taking a compression load. Examples: Landing gear strut, Wing strut.
Tie
Member taking a tensile load Examples: Landing gear beam
Strain x / x
Stress Force per unit area. F/A
General Structures
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Torsion
Member or circular cross section subject to twisting couples or torques. Examples: torque tube,
Bending
A cantilever beam having a downward force at the end. The beam is deflected downward, upper
section of the beam is having tension and lower section of the beam is under compression
Compression
Any structure when under compression is when the forces in that structure are pointed towards
the centre of the structure
Tension
Any structure when under compression is when the forces in that structure are pointed outwards
from the centre of the structure
Fatigue
The tiredness of the structure after had undergone cyclic loading
General Structures
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General Structures
Stress Riser
Hoop Stress
Different in pressure between inside and outside of the pressurised area
of the aircraft. (Circumferential stress)
Shear
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Primary Structures
All major components of the aircraft. The failure of which in flight or ground
manoeuvres would likely to cause catastrophic structural collapse or loss of controlof the aircraft.
Secondary Structures
Includes all portions of the aircraft which would normally be regarded as primary
structure but which unavoidably have such reserve strength over design
requirements that appreciably weakening may be permitted without risk of failure.
It also include structure which if damage would not impair the safety of the aircraft.
Tertiary StructuresInclude all portions of the structure in which stresses are low, but which for various
reasons cannot be omitted from the aircraft.
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Wing Box
Ribs
Longerons
Bulkhead
Aft Spar
Forward Spar
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Damage ToleranceDamage tolerance is related to fatigue, crack propagationand fail-safe design.
The structural engineers primary responsibility to ensurethe design to have adequate strength and rigidity atminimum weight.
3 components to determine the fatigue life of a givenstructure are:
i) material selectionii) stress level
iii) number of cycle to be tolerated at various stress level
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Damage ToleranceTo ensure aircraft will perform satisfactory, the structure is designed for the
main four failure modes:
Static ultimate strength (incld. Yield strength requirement)
Fatigue life of the structure (crack initiation)
Fatigue life of the damaged structure (inspection interval)
Static residual strength of the damage structure
Essential consideration to the development of the damage tolerance design
Material Selection
Fastener Load Distribution
Ultimate Design Cut-off Stress
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Fail Safe
A structure in which failure of a particular part is
compensated for by another part, that is able tocarry the loads, for a limit period of time.
Is achieved through material selection, properstress levels, and multiple load path structural
arrangements which maintain high strength inthe presence of a crack or damage
A C A S C S AAIRCRAFT STRUCTURES REPAIR
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Example of Fail Safe Criteria
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Stress Cycle
The stress cycle is the stress-time function which is repeatedperiodically and identically.
Load Spectrum
A collection of data of the load exposure of a structure. Examples
are gust, maneuvers, landing impact, ground roll, climb, cruise,
decent, etc.
Damage Tolerance
AIRCRAFT STRUCTURES REPAIRAIRCRAFT STRUCTURES REPAIR
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Stress Cycle
Fmax Maximum Stress
Fmin Minimum Stress
Fa Alternating Stress = (Fmax - Fmin)/2 Fm Mean Stress = (Fmax + Fmin)/2
R = stress ratio = Fmin/Fmax
Fmax
Fa
Fm
Fmin
Cycle (N)
Stress (F)
Stress
Range
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Load Spectrum
Altitude
Speed
Gross Weight
Range
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Requirements
BCAR has specify the safety factor for the structural
parts in aircraft to be 1.5 ( if a part has a working loadof 100 pounds, it must be designed to carry 100 x 1.5
= 150 pounds of load.
FAA ?
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THANK YOU