AC Systems Flashcards
CS For Airworthiness
CS23 - Small Commuter AC
CS25 - Large Turbine AC 5300kg
Safe Life
To not suffer catastrophic failure in AC expected life cycle
If it does fail there will be no catastrophic damage
Flying hour/Cycles/TO/LD/Pressurisations
Fail Safe
Redundancy alternate component for the load path
+ Backup for critical component
- Costs/POF/Weight
Damage Tolerance Structure
Spreading Load over larger area
Crack arresting features limit spread of cracks
+ eliminates extra structure
CS Standards Focus Points?
Design
Build Materials
Build Quality
Manufacturing standards
Stress
Internal force per unit inside component from external loading (press or stress)
- distorting in skin
- missing rivets
- wrinkles
Strain
Deformation caused by stress
Types of stress
- tension (apart)
- compression (together)
- torsion (twisting)
- sheer (parallel)
Wing in flight
Compression on top of wing
Tension under wing
Excessive compression & tension
Compression - buckling/wrinkling
Tension - pulled rivets
Dynamic load
Quick build up due to flight conditions
Manoeuvring and change in g load.
Severe
Static Load
Constant/slow build up
Weight of wheel on ground on ac wings
Bending Load + relief?
Greatest at wing roots
Weight + dynamic forces by lift
Weight management
Staying within loading g limit
MZFM limit keep wing root within limits
Load alleviation - rigid
Cyclic Loads
Alternating loads at difference phases of flight
Pressurisation
Design limit + design ultimate load
Max load set by designer in service
DLL x 1.5
Wing Spars
Main structural loading
Withstand torsional/bending loads
Fatigue
Failure at a load less than steady applied load.
- weight
- size of loads
- tensions loading
F LIFE - # cycles for metal to fail at certain stress
Corrosion
Disintegration of metals
Oxidation
Electrolytic - dissimilar metals EP contrast
Black oil from rivets = corrosion
Stress Corrosion
Fatigue + corrosion
Corrosive conditions under tensile loads
Delamination
Decrease in composite structure strength
- difficult to detect
- bubbled skin
- hair line cracks
- changes in sound when tapping
Hard time
Removed at intervals
Serial numbers/Part Numbers
Scheduled maintenance
On-Condition
Inspected and monitored
Removed in fails visual inspection
Composite
Two or more materials to give rise to unique structural properties
Matrix - epoxies/polyester
Fibres - glass/carbon/armaid
Matrix spread load between fibres
Advantage/disadvantage of composite
Retain properties at elevated temps
High strength
Stiffness
Costly
Labour intensive
Hard to maintain
Careful electrical bonding required
Delamination
