Chapter 1 - Airframe Designs And Materials Flashcards
CS-23
Sets standard for normal, utility and commuter aircraft.
CS-25
Applies to turbine powered large aircraft (Around 5,800kg +)
Certification Standards focus on what 4 points?
- Aircraft Design
- Build Materials
- Build Quality
- Manufacturing Standards
What is a ‘Safe-Life’?
The time frame within the aircraft will comfortably sustain safe operations - Within the ‘Life span’.
Or
The amount of time where, no catastrophic damage will occur from regular operations.
How is ‘Safe-Life’ measured?
- Flight Hours.
- Pressurisation Cycles.
- Landings.
- Calendar Duration.
What is ‘Fail-Safe’?
Redundancy for failure.
If the structural integrity of the aircraft is at risk, then there needs to be a backup which can support the aircraft FULLY.
Critical areas have ‘multiple load paths’ should one fail, another option is available.
3 Hydraulic Pumps is an example of….
Redundancy (Failsafe)
Benefits of ‘Fail Safe’?
- Always a backup for critical component failures.
- Prevents major structural failure (In most cases).
Negative(s) of ‘Fail Safe’?
- More weight on aircraft
- Reduced Performance
- Higher Costs
An example of Damage Tolerance?
Crack-arresting features
Prevents a crack from spreading and compromising the structural integrity of the aircraft (Duplicate Load Paths).
What are the 4 main types of stresses?
- Tension (Pulling) Causes pulled rivets.
- Compression - Causes Wrinkling
- Torsion (Twisting)
- Shear - (2 forces acting in parallel from each other)
What is the definition of Strain (AGK)?
Deformation of the component caused by stress on the component.
Bending of the wing will cause…
- Compression
- Tension
Stress formula?
Stress = Force / Area
What can cause dynamic loads?
-Load Factor changes when the aircraft is manoeuvring.
Rapid manoeuvring causes advanced stress.
What is defined as ‘Static Loads’?
When the aircraft is on the ground and not moving.
Landing gear pushing up the wings and fuselage
What is meant by ‘Cyclic Loads’?
Stress caused on the aircraft by pressurisation.
Every time the aircraft pressurises and climbs, the cabin bulges.
METAL FATIGUE
What is the risk of having low amounts of fuel? (Other than starvation)
The aircraft uses fuel as a counter balance to lift in the wings.
- Without this counter balance the stress on the wing roots increases.
What part of the aircraft sees the most stress?
The wing roots.
All the twisting, pulling and compression from the fuel, engines and lift.
What is ‘MRM’?
Maximum Ramp Mass
Maxed authorised movement weight on the ground.
What is ‘MZFM’?
Maximum Zero Fuel Mass
Cannot exceed it. Will most likely cause structural failure of the wing root.
What is ‘MSTM’?
Maximum Structural Takeoff Mass
Max weight that the structure of the aircraft can takeoff with.
What is ‘MSLM’?
Maximum Structural Landing Mass
Max weight for landing that the structure can handle without getting damaged.
What are the signs of Stress/Damage?
- Signs of deterioration / distortion
- Loose / Missing rivets or screws.
- Wrinkles or bubbles in the skin/paint.
Black ‘oily’ fluid is coming out from under the rivets. What does this mean?
- The rivets are corroding.
What does ‘Elastic Deformation Limit’ mean?
How far a component can be stretched and still return to its original shape.
What is meant by ‘Plastic’?
The object will NOT go back to its original position after stretching.
How do you calculate Ultimate Load Factor?
Ultimate Load = Limit Load x 1.5
What percentage of their load limit can a wing take?
150%
What is ‘Fatigue Life’?
The number of cycles for a metal to fail at a certain stress.
Measures to avoid fatigue?
- Avoid rough manoeuvring
- Avoid Turbulence
- Not flying with excessive amounts of fuel / payload.
- Designs to last (Rounded Windows).
Characteristics of a good material?
- High Density
- High Strength
- High stiffness
- Good common resistance
- Good fatigue resistance
- Ability to withstand High Temp
- Easy to manufacture
- Cheap
- Lightweight
- Electrical Conductor
What is a Alloy?
2 or more different metals blended together to provide ideal properties.
What is the makeup of Duralumin
Copper, Manganese & Magnesium
What is a ‘Composite Material’?
Made from 2 or more constituent materials with significantly different physical or chemical properties.
When combined the properties of the material change.
- Layered Materials.
Advantages of using Composite Materials?
- Make flexible/complex shapes.
- Lighter.
- High strength.
- High stiffness.
- Resistant to corrosion.
- High strength to weight ratio.
Disadvantages of using Composite Materials?
- Hard to inspect for flaws (Elastic so doesn’t deform)
- May absorb moisture and delamify.
- Can be expensive
- Less damage tolerant
- Requires immediate repair
- Does not conduct electricity.
What happens when lightning strikes Alloys?
Should pass through aircraft
Pin holes at entry and exit points.
What happens if lightning strikes Composite?
Potential explosion of materials at the exit point.
What is ‘Delamination’?
When the layers of composite start to separate.
Significantly reduces the strength of the structure.
How can we identify Delamination?
- Bubbles on the skin of the aircraft.
- Hair-line cracks.
- Changes in sound when tapping structure.
What is the definition of ‘Corrosion’?
The disintegration of an engineered material into it’s constituent atoms.
What is ‘Oxidisation’ corrosion?
Chemical reaction of the metal with the air.
Causes breakdown of metal surfaces.
What is ‘Electrolytic’ Corrosion?
Corrosion caused by electric current between two metals in an electrolytic environment.
What is ‘Stress Corrosion’?
Fatigue and corrosion that occurs in the materials under high tensile loads.
What is ‘Hard Time Maintenance’?
Maintenance based on defined limit for individual components and structures. Items are removed from service BEFORE their safe life expires.
What is ‘On Condition Maintenance’?
Replacement based on condition instead of wear limit.
Pitting and discolouration can be a sign of…..?
Corrosion.
What is ‘Wet-Layup’?
Honeycomb material, filled with resin.
Fibre, matrix and core combined together are an example of…..
Advanced Composites.
Salt-laden areas promote ______ therefore, planes must be cleaned regularly.
Corrosion
