17.6.3 Blade Damage Assessment

Question 1

What can cause damage to propeller blades during flight?

Answer 1

Objects such as stones, dirt, and birds can strike against the propeller blades and hub, causing bends, cuts, scars, nicks, scratches, or other defects.

Question 2

What happens if a defect in a propeller is not repaired?

Answer 2

Local stresses may develop, potentially causing a crack to form, which can lead to the failure of the propeller or hub.

Question 3

What are the two categories of propeller blade damage?

Answer 3

Damage can be classified as airworthy or unairworthy.

Question 4

What is ‘airworthy damage’?

Answer 4

Airworthy damage can be repaired in the field and does not affect flight safety characteristics.

Question 5

What is ‘unairworthy damage’?

Answer 5

Unairworthy damage exceeds the limits of airworthy damage and requires more extensive repairs.

Question 6

What is a crack in the context of propeller damage?

Answer 6

An irregular shaped separation within a material, usually visible as a narrow opening at a surface.

Question 7

What does ‘debond’ refer to in propeller damage?

Answer 7

A separation of the metal erosion shield from the composite material in the blade.

Question 8

What is delamination?

Answer 8

An internal separation of the layers of composite material.

Question 9

What is a depression in propeller damage?

Answer 9

A surface area where the material has been compressed, but not removed, by contact with a sharp object.

Question 10

What does ‘distortion’ mean in relation to propellers?

Answer 10

An alteration of the original shape or size of a component.

Question 11

What is exposure in terms of propeller damage?

Answer 11

A condition in which material is left open to the action of the elements.

Question 12

What is a gouge?

Answer 12

A small surface area from which material has been removed by contact with a sharp object.

Question 13

What is impact damage?

Answer 13

Damage that occurs when the propeller blade or hub assembly strikes or is struck by an object.

Question 14

What is a scratch in propeller terminology?

Answer 14

The removal of paint and a small amount of material not exceeding 0.5 mm.

Question 15

What is a nick?

Answer 15

A small indent or notch, not deeper than 0.5 mm.

Question 16

What is a split in a composite blade?

Answer 16

A delamination of a composite blade extending to the blade surface, typically found near the trailing edge or tip.

Question 17

What is a dent?

Answer 17

A hollow or mark left by impact, blow, or pressure.

Question 18

What is erosion in the context of propeller damage?

Answer 18

A gradual wearing away or deterioration due to the action of air contaminations like sand and dust.

Question 19

What is corrosion?

Answer 19

A gradual wearing away due to a chemical action.

Question 20

What is fatigue in propeller blades?

Answer 20

Fatigue failures typically occur near the blade tip but can happen in other areas when damage is ignored.

Question 21

What should be inspected during a propeller inspection?

Answer 21

Inspect each whole blade, not just the leading edge, for erosion, scratches, nicks, and cracks.

Question 22

Where can airworthy damage limits be found?

Answer 22

In AMM ATA chapter 61 of the related aircraft.

Question 23

What is the primary method of propeller inspection?

Answer 23

Visual inspection, which includes using touch and other senses along with visual cues.

Question 24

What is a tap test?

Answer 24

A method to inspect composite blades for delaminations and debonds by tapping with a metal coin.

Question 25

What is penetrant inspection?

Answer 25

A method using fluorescent penetrant to detect small surface cracks on propeller blades.

Question 26

What is ultrasonic inspection?

Answer 26

A method using sound waves to detect flaws on or below the surface of the component being tested.

Question 27

What is eddy current inspection?

Answer 27

A method that generates and measures an electric field to detect flaws at or slightly below the surface.

Question 28

What is magnetic particle inspection?

Answer 28

A method useful for finding cracks and imperfections at or near the surface of ferrous parts.

Question 29

What is erosion in propeller blades?

Answer 29

The loss of material from the blade surface due to the action of small particles, typically near the leading edge.

Question 30

What are the three types of corrosion in metal propellers?

Answer 30

Surface corrosion, pitting, and intergranular corrosion.

Question 31

What is surface corrosion?

Answer 31

The loss of surface metal due to chemical action, usually visible with oxidation products.

Question 32

What is pitting in propeller damage?

Answer 32

Visible corrosion cavities extending inward from the metal surface, which can lead to cracks.

Question 33

What is intergranular corrosion?

Answer 33

Corrosion occurring in grain boundaries, often due to moisture retention.

Question 34

What is impact damage in propellers?

Answer 34

Damage from a foreign object that can range from no visible damage to severe ground impact damage.

Question 35

What special problems do wood or composite propellers face?

Answer 35

They can suffer from internal damage due to small strikes, leading to delamination or microcracks.

Question 36

What should be checked in wooden propellers?

Answer 36

Look for glue line debonding, warping, and loss of protective coating.

Question 37

What can clogged drain holes in propellers cause?

Answer 37

They can lead to moisture retention, causing further damage.