AGK Systems - Design and materials

Question 1

According to FAA regulations, at what number of hours and cycles should an aircraft be withdrawn?

Answer 1

34,000 hours or 34,000 cycles.

Question 2

What do CS23 and CS25 regulate?

Answer 2

CS23 - sets standard for normal, utility, aerobatic and commuter aeroplanes.

CS25 - Applies to turbine powered large aeroplanes.

Question 3

What is the purpose of certification standards?

Answer 3

To ensure that an acceptable safety level fir equipment and systems are installed.

Question 4

What 4 terms are set by CS23 and CS25 regarding design philosophy based knowledge redundancy and maintenance?

Answer 4

Fail safe - in event of failure, component remains safe.
Safe life - Components are designed to survive a specific design life with a chosen reserve.
Damage tolerance - ability for a structure to sustain defects safely.
Fault tolerant - enables a system to continue operating, possibly at a reduced level.

Question 5

Formula for stress.

Answer 5

Force/Area

Question 6

What is strain?

Answer 6

Deformation caused by stress.

Question 7

What are dynamic loads?

Answer 7

Forces imposed by manoeuvring. Build up and subside very quick.

Question 8

What are static loads?

Answer 8

Build up slowly over time.
remain constant over a period of time e.g on the ground.

Question 9

What are cyclic loads?

Answer 9

Loads which reoccur and rise and fall in magnitude.
Vibration which rapidly changes rpm is an example.

Question 10

What do yaw dampers and rudder ratio change?

Answer 10

Manage aerodynamic loads.

Question 11

What are the 5 types of stress?

Answer 11

Tension - Pulled outwards
Compression - Pushed inwards
Torsion - twisting
Shear - unaligned forces acting on one part of the body in one direction, and another part of the body in the opposite direction.
Bending - Compression inside bend, tension outside.

Question 12

What pre-flight checks are done to check for structural damage?

Answer 12

Check for skin buckling.
Check for pulled, loose or missing rivets.
Check for cracks.

Question 13

Consequences of compression of the wing?

Answer 13

Skin wrinkling or buckling.
Tension causes pulled rivets.

Question 14

What is a bending load?

Answer 14

Wing root experiences a large bending moment.
On ground, static force of landing gear acts upwards on wing.
Airborne, weight acts downwards on the wing - bending relief.

Question 15

What is the ultimate load and limit?

Answer 15

Limit load - 2.5g
Ultimate load - 3.75g
‘factor of safety’ for ultimate load is derived by 1.5 times limit load.

Question 16

Explain fatigue.

Answer 16

Repeat cycles of stress create cracks in metal.
Fatigue life based on number of hours flow and number of cycles.

Question 17

What design factors affect fatigue?

Answer 17

Tensile loading.
concentrated stress points.
Sharp corners and ridges experience the most.

Question 18

What is stress corrosion?

Answer 18

Interactions caused by fatigue and corrosion.
Metals under stress corrode quicker.

Question 19

What properties should the materials have?

Answer 19

Good fail-safe design.
Resistance to fatigue.
Elastic.
Stiff.
Strength.

Question 20

What materials are used for aircraft?

Answer 20

Aluminium, titanium, magnesium alloys and steel. As well as composite materials such as carbon.

Question 21

Aluminium.

Answer 21

Less dense than steel, corrosion resistantm quite weak.

Question 22

Duralumin.

Answer 22

Age hardened alloy, strong, 95% aluminium.
4% corrosion which increases strength but also corrosion.

Question 23

What is ACLAD?

Answer 23

Aluminium alloy sheets formed over a duralumin core. Improves corrosion resistance.

Question 24

Other materials that are used, and there properties.

Answer 24

Honeycomb materials - replacing rivets.

Question 25

What are composites?

Answer 25

Combination of 2 or more organic/inorganic components.
One material is used as matrix to hold everything, other provides reinforcement in the form of fibres.
Common matrix materials - epoxy resin, polyamide.
Reinforcement materials - glass, boron, carbon Kevlar.

Question 26

What are fibre reinforced plastics?

Answer 26

material laid out in a mold which is cured (high temp and pressure). strength, stiffness and flexibility can be adjusted.

Question 27

What is composite delamination?

Answer 27

materails start to seperate, happens due to stress or impacts. Weakens the structure.

Question 28

What is a carbon tow?

Answer 28

bundle of thousands of carbon fibres. used in composite materails to proivde strength. Used in fuesalages, wings, tail.

Question 29

What the 2 maintenance methods?

Answer 29

Hard time maintenance, On condition maintenance.