AFS PT1

Question 1

Describe safe life design philosophy. (021.01.01.01)

Answer 1

The minimum life it is known that no catastrophic damage will occur. Can be recorded as: flying hours, cycles of landing gear, aircraft pressurisations, and calendar basis.

Question 2

Describe fail-safe design philosophy. (021.01.01.01)

Answer 2

A structure in which a failure of a particular part is compensated by an alternative load path. This ensures an adjacent part can carry the load for a limited time period, normally up to the next periodic inspection, without any catastrophic consequences. Example: in wing attachments.

Question 3

Describe damage tolerant design philosophy. (021.01.01.01)

Answer 3

This eliminates the extra structural members from fail-safe designs by spreading the loading structure over a larger area. Hence the structure is designed so that damage can be detected during normal inspection cycles before a failure occurs.

Question 4

What is the purpose of redundancy, duplication or triplication. (021.01.01.01 & 021.01.01.02)

Answer 4

Redundancy, or duplication or triplication, eliminates the possibility of complete system failure. It allows for the function of a component to be taken over by another component in the event of failure. Example: multiple hydraulic systems.

Question 5

What EASA certification specification is required for different types of aeroplanes? (Normal, utility, aerobatic, commuter aeroplanes and larger aeroplanes)
(021.01.01.02)

Answer 5

CS-23: normal, utility, aerobatic and commuter

CS-25: larger aeroplanes

Question 6

What are the steps to aircraft specification? (021.01.01.02 - complementary information)

Answer 6

Familiarisation (manufacture presents project).
Establishment of certification program (EASA & manufacture define & agree on means to achieve compliance).
Compliance demonstration (manufacture demonstrates compliance of its product with regulatory requirements).
Issue of approval (EASA closes the investigation & issues certificate).

Question 7

How are aircraft certified? (021.01.01.02)

Answer 7

Aircraft must obtain a type certificate from the responsible aviation regulatory authority, such as EASA for the EU and some non-EU countries. The certificate is issued after certification specifications are met, and covers aspects such as design, material quality and build quality.

Question 8

Define stress and strain. (021.01.02.01)

Answer 8

Stress - internal force per unit area inside a structural part as a result of external loads. Can be broken down into tensile (stretching), compression and torsion. Stress=Force/Area.
Strain - deformation caused by the action of stress on a material. Will only happen when the force reaches a certain magnitude. Strain=Extension/Original Length.

Question 9

Explain how stress and strain are always present in an aircraft structure? (021.01.02.01)

Answer 9

There are 4 forces acting on an aircraft:
Weight - always present, varies with the force of gravity during manoeuvres.
Lift - generated when taking off and airborne, tends to bend wings upwards.
Drag - acts on components such as landing gear, bends them backwards.
Thrust - will produce forward loads on the airframe.

Question 10

Describe static loads, when it occurs, and how a pilot can affect its magnitude. (021.01.02.01)

Answer 10

Constant and builds slowly. Will occur on the grounds. Pilots should not exceed maximum operating weights.

Question 11

Describe dynamic loads, when it occurs, and how a pilot can affect its magnitude. (021.01.02.01)

Answer 11

Build quickly due to changes in flight conditions. Produced when an aircraft is manoeuvred, and can induce loads on other parts of the aircraft. Pilots should manoeuvre within authorised load factor boundary.

Question 12

Describe cyclic loads, when it occurs, and how a pilot can affect its magnitude. (021.01.02.01)

Answer 12

Occur repeatedly at regular or irregular intervals and can be static or dynamic. Safe life of components determines the number of cycles that would lead to failure. Pilots and maintenance planners should ensure load cycles are not exceeded.

Question 13

Describe effects of corrosion. (021.01.03.01)

Answer 13

The metal is converted into metallic compounds, which reduces the ability of the metal to withstand forces, and can lead to earlier than planned structural failure.

Question 14

Define corrosion. (021.01.03.01)

Answer 14

Most metals are unstable, and corrosion is the tendency of the metal to return to a stable state, similar to the metallic ore from which it originated.

Question 15

What are the signs of corrosion which may be visible on a walk around inspection? (021.01.03.01)

Answer 15

Bumps or blisters on paint.
Discolouration of paint.
Signs of grey/white powder on aluminium, reddish on ferrous material.
Cracking.

Question 16

What are the signs of airframe stress? (021.01.02.01)

Answer 16

Loose rivets.
Cracking in aircraft falsework.
Fuel leaks from the wing fuel tanks.
Stress and fatigue cracks on components.

Question 17

Where is the risk of corrosion increased? (021.01.03.01)

Answer 17

Tropical, industrial and marine environments.
Lowest risk in arctic, rural and inland environments.
Corrosion is also more likely on older aircraft.

Question 18

How can the affect of corrosion be minimised? (021.01.03.01)

Answer 18

Keeping the aircraft in a hangar.
Apply corrosion inhibitors.
Regular aircraft washing.
Engine compressor washes.
Regular removal and application of paint surface.
Increased maintenance inspections.
Early intervention.

Question 19

What fluids on board an aircraft are corrosive? (021.01.03.01)

Answer 19

Hydraulic fluids.
Engine oils.
Chemical toilet fluids.
De-icing fluids.
Fluids carried for transportation.

Question 20

Explain fatigue, and its affects on an aircraft. (021.01.03.01)

Answer 20

Fatigue is the weakness in a structure caused by repeated variations of stress, and causes the structure to fail at a load less than it would for a steadily applied load. Failing load depends on the number of cycles experienced.

Question 21

Explain hard-time or fixed-time maintenance. (021.01.05.01)

Answer 21

An item must be removed from service before its scheduled maintenance period.
Time between overhaul (TBO).
Time between replacement (TBR).
Items dismantled, reconditioned, or replaced.

Question 22

Explain on-condition maintenance. (021.01.05.01)

Answer 22

Uses an inspection or functional check to determine an items performance.
Continual monitoring.
Specified time intervals.
Standard determines if it should be replaced or not.