Chapter 1 - Airframe Designs And Materials

Question 1

CS-23

Answer 1

Sets standard for normal, utility and commuter aircraft.

Question 2

CS-25

Answer 2

Applies to turbine powered large aircraft (Around 5,800kg +)

Question 3

Certification Standards focus on what 4 points?

Answer 3

• Aircraft Design
• Build Materials
• Build Quality
• Manufacturing Standards

Question 4

What is a ‘Safe-Life’?

Answer 4

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.

Question 5

How is ‘Safe-Life’ measured?

Answer 5

• Flight Hours.
• Pressurisation Cycles.
• Landings.
• Calendar Duration.

Question 6

What is ‘Fail-Safe’?

Answer 6

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.

Question 7

3 Hydraulic Pumps is an example of….

Answer 7

Redundancy (Failsafe)

Question 8

Benefits of ‘Fail Safe’?

Answer 8

• Always a backup for critical component failures.

- Prevents major structural failure (In most cases).

Question 9

Negative(s) of ‘Fail Safe’?

Answer 9

• More weight on aircraft
• Reduced Performance
• Higher Costs

Question 10

An example of Damage Tolerance?

Answer 10

Crack-arresting features

Prevents a crack from spreading and compromising the structural integrity of the aircraft (Duplicate Load Paths).

Question 11

What are the 4 main types of stresses?

Answer 11

• Tension (Pulling) Causes pulled rivets.
• Compression - Causes Wrinkling
• Torsion (Twisting)
• Shear - (2 forces acting in parallel from each other)

Question 12

What is the definition of Strain (AGK)?

Answer 12

Deformation of the component caused by stress on the component.

Question 13

Bending of the wing will cause…

Answer 13

• Compression

- Tension

Question 14

Stress formula?

Answer 14

Stress = Force / Area

Question 15

What can cause dynamic loads?

Answer 15

-Load Factor changes when the aircraft is manoeuvring.

Rapid manoeuvring causes advanced stress.

Question 16

What is defined as ‘Static Loads’?

Answer 16

When the aircraft is on the ground and not moving.

Landing gear pushing up the wings and fuselage

Question 17

What is meant by ‘Cyclic Loads’?

Answer 17

Stress caused on the aircraft by pressurisation.

Every time the aircraft pressurises and climbs, the cabin bulges.
METAL FATIGUE

Question 18

What is the risk of having low amounts of fuel? (Other than starvation)

Answer 18

The aircraft uses fuel as a counter balance to lift in the wings.
- Without this counter balance the stress on the wing roots increases.

Question 19

What part of the aircraft sees the most stress?

Answer 19

The wing roots.

All the twisting, pulling and compression from the fuel, engines and lift.

Question 20

What is ‘MRM’?

Answer 20

Maximum Ramp Mass

Maxed authorised movement weight on the ground.

Question 21

What is ‘MZFM’?

Answer 21

Maximum Zero Fuel Mass

Cannot exceed it. Will most likely cause structural failure of the wing root.

Question 22

What is ‘MSTM’?

Answer 22

Maximum Structural Takeoff Mass

Max weight that the structure of the aircraft can takeoff with.

Question 23

What is ‘MSLM’?

Answer 23

Maximum Structural Landing Mass

Max weight for landing that the structure can handle without getting damaged.

Question 24

What are the signs of Stress/Damage?

Answer 24

• Signs of deterioration / distortion
• Loose / Missing rivets or screws.
• Wrinkles or bubbles in the skin/paint.

Question 25

Black ‘oily’ fluid is coming out from under the rivets. What does this mean?

Answer 25

- The rivets are corroding.

Question 26

What does ‘Elastic Deformation Limit’ mean?

Answer 26

How far a component can be stretched and still return to its original shape.

Question 27

What is meant by ‘Plastic’?

Answer 27

The object will NOT go back to its original position after stretching.

Question 28

How do you calculate Ultimate Load Factor?

Answer 28

Ultimate Load = Limit Load x 1.5

Question 29

What percentage of their load limit can a wing take?

Answer 29

150%

Question 30

What is ‘Fatigue Life’?

Answer 30

The number of cycles for a metal to fail at a certain stress.

Question 31

Measures to avoid fatigue?

Answer 31

- Avoid rough manoeuvring - Avoid Turbulence - Not flying with excessive amounts of fuel / payload. - Designs to last (Rounded Windows).

Question 32

Characteristics of a good material?

Answer 32

- High Density - High Strength - High stiffness - Good common resistance - Good fatigue resistance - Ability to withstand High Temp - Easy to manufacture - Cheap - Lightweight - Electrical Conductor

Question 33

What is a Alloy?

Answer 33

2 or more different metals blended together to provide ideal properties.

Question 34

What is the makeup of Duralumin

Answer 34

Copper, Manganese & Magnesium

Question 35

What is a ‘Composite Material’?

Answer 35

Made from 2 or more constituent materials with significantly different physical or chemical properties. When combined the properties of the material change. - Layered Materials.

Question 36

Advantages of using Composite Materials?

Answer 36

- Make flexible/complex shapes. - Lighter. - High strength. - High stiffness. - Resistant to corrosion. - High strength to weight ratio.

Question 37

Disadvantages of using Composite Materials?

Answer 37

- 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.

Question 38

What happens when lightning strikes Alloys?

Answer 38

Should pass through aircraft | Pin holes at entry and exit points.

Question 39

What happens if lightning strikes Composite?

Answer 39

Potential explosion of materials at the exit point.

Question 40

What is ‘Delamination’?

Answer 40

When the layers of composite start to separate. | Significantly reduces the strength of the structure.

Question 41

How can we identify Delamination?

Answer 41

- Bubbles on the skin of the aircraft. - Hair-line cracks. - Changes in sound when tapping structure.

Question 42

What is the definition of ‘Corrosion’?

Answer 42

The disintegration of an engineered material into it’s constituent atoms.

Question 43

What is ‘Oxidisation’ corrosion?

Answer 43

Chemical reaction of the metal with the air. | Causes breakdown of metal surfaces.

Question 44

What is ‘Electrolytic’ Corrosion?

Answer 44

Corrosion caused by electric current between two metals in an electrolytic environment.

Question 45

What is ‘Stress Corrosion’?

Answer 45

Fatigue and corrosion that occurs in the materials under high tensile loads.

Question 46

What is ‘Hard Time Maintenance’?

Answer 46

Maintenance based on defined limit for individual components and structures. Items are removed from service BEFORE their safe life expires.

Question 47

What is ‘On Condition Maintenance’?

Answer 47

Replacement based on condition instead of wear limit.

Question 48

Pitting and discolouration can be a sign of…..?

Answer 48

Corrosion.

Question 49

What is ‘Wet-Layup’?

Answer 49

Honeycomb material, filled with resin.

Question 50

Fibre, matrix and core combined together are an example of…..

Answer 50

Advanced Composites.

Question 51

Salt-laden areas promote ______ therefore, planes must be cleaned regularly.

Answer 51

Corrosion