propeller

Question 1

many types of damage cause propellers to what

Answer 1

fail or become not airworthy

Question 2

according to FAA data, majority of propeller failures occur where

Answer 2

blade at the tip region, usually within several inches from the tip

Question 3

what is often times the reason of failure in the tip region

Answer 3

crack initiator such as a pit, nick, or gouge

Question 4

other possible locations of blade failure

Answer 4

any portion of a blade, including the mid-blade, shank, and hub, particularly when nicks, scratches, corrosion, and cracks are present

Question 5

one of the principal causes of loss of airworthiness in propellers

Answer 5

corrosion

Question 6

external corrosion where poses a serious problem

Answer 6

metal blades, hubs, and other components

Question 7

where does internal corrosion exist

Answer 7

where moisture may collect in internal cavities such as hubs, blade clamps, and pitch control mechanisms

Question 8

three distinct types of corrosion on metal propeller components

Answer 8

surface corrosion, pitting, intergranular corrosion

Question 9

The loss of surface metal due to chemical or electro-chemical action with visible oxidation products usually having a contrasting color and texture to the base metal.

Answer 9

surface corrosion

Question 10

generally results when the corrosion protection on a metal surface has been removed by erosion or by polishing.

Answer 10

surface corrosion

Question 11

what is not recommended when dealing surface corrosion

Answer 11

removing paint and corrosion protection, such as when polishing blades

Question 12

consists of visible corrosion cavities extending inward from the metal surface

Answer 12

pits

Question 13

They can grow on the surface, under decals, or under improperly installed de-ice boots.

Answer 13

pitting

Question 14

Occurs in grain boundaries

Answer 14

intergranular corrosion

Question 15

may be the result of the continued presence of moisture such as under a decal, in a fastener hole, or where anodize and paint protective barriers have been lost

Answer 15

intergranular corrosion

Question 16

a form of intergranular corrosion that occurs more often in forgings or rolled sheets, and less often in castings. sometimes visible as metal flaking and cracks on a blade leading edge

Answer 16

exfoliation

Question 17

When propeller blades are bent, twisted, or cocked, they will not be properly aligned with each other in operation.

Answer 17

face, leading edge, or twist misalignment

Question 18

vibration may cause what

Answer 18

loss of thrust

Question 19

The level of vibration can be severe and depending on the severity of the misalignment, could lead to what

Answer 19

catastrophic failure

Question 20

A sharp, notch-like displacement of metal usually found on leading and trailing edges. All nicks are potential crack starters

Answer 20

nick

Question 21

The loss of material from blade surface by the action of small particles such as sand or water and is usually present on the leading edge close to the tip. This damage destroys the blades’ corrosion protection, which might lead to blade failure

Answer 21

erosion

Question 22

These terms describing surface damage are found in Appendix 1, Glossary of Common Propeller Terms.

Answer 22

scratches, gouges, cuts, and scoring

Question 23

When found anywhere in a propeller, cracks are cause for its immediate removal and detailed inspection. will grow over time, perhaps very rapidly, and eventually lead to failure

Answer 23

cracks

Question 24

can be harmful, depending on their size, location, and configuration. cause local stress risers around their perimeter and at the bottom under the surface.

Answer 24

dents

Question 25

how do you repair dents

Answer 25

removing material, not filling dents

Question 26

may be indicated by a small burned and melted area on the blade, a trail of small pits along the blade, or may show no indication at all

Answer 26

lightning strike

Question 27

what is affected when the damage from a lightning strike is severe

Answer 27

strength of the blade material itself, damaging blade bearings or other internal components

Question 28

since lightning requires specialized equipments, this is used to check for magnetism in steel components

Answer 28

gauss meter

Question 29

A propeller may have been exposed to an overspeed condition and give no indication of the event. However, the event may have severely damaged the propeller due to the dramatic increase in centrifugal loads.

Answer 29

overspeed

Question 30

if suspected of having operated in an overspeed condition, what should one do?

Answer 30

it should be removed and sent to a propeller repair station to be inspected for elongation of bolt holes, dimension changes, or other signs of stress

Question 31

can include a broad spectrum of damage, from no visible damage, to a small nick, to severe ground impact damage

Answer 31

foreign object strike

Question 32

why is a conservative approach in evaluating the damage required?

Answer 32

possibility that there may be hidden damage that is not readily apparent during a superficial, visual inspection

Question 33

On rare occasions, propellers have been exposed to this such as hangar or engine fire

Answer 33

fire damage or heat damage

Question 34

propellers with fire damage are normally what

Answer 34

retired

Question 35

may have a lower temperature threshold for potential damage.

Answer 35

composite propeller blades