7.12 Transmissions

Question 1

What is the primary function of a gear?

Answer 1

The transmission of power through motion.

Question 2

What leads to stress and wear in a gear system?

Answer 2

Motion within the gear system.

Question 3

What should be periodically examined in gears?

Answer 3

All gears for cracks, chipped teeth, and the presence of pitting or excessive wear.

Question 4

What are causes for rejection and replacement of a gear?

Answer 4

Deep pit marks and excessive wear on gear teeth.

Question 5

How can minor scratches and abrasions on a gear surface be removed?

Answer 5

Using a fine abrasive cloth.

Question 6

What is not acceptable on a gear surface?

Answer 6

Deep scratches or scoring.

Question 7

What must be checked and maintained to ensure proper gear mesh?

Answer 7

Correct gear backlash.

Question 8

What is essential for improving the life and performance of a gear?

Answer 8

Understanding how to inspect, report, and document the conditions of the gear.

Question 9

What usually causes gear failure or premature wear?

Answer 9

Excessive backlash and/or poor lubrication.

Question 10

What can cause gears to corrode?

Answer 10

Exposure to corrosive conditions and moisture in the lubricant.

Question 11

What results from a complete breakdown or lack of lubrication?

Answer 11

Overheating of the gear.

Question 12

What does normal wear on gear teeth result in?

Answer 12

A polished appearance over the tooth’s entire surface.

Question 13

What are the types of gear wear discussed?

Answer 13

Overload wear, pitting & spalling, cracking and breakage, interference wear, abrasive wear.

Question 14

What occurs during overload wear?

Answer 14

Metal is removed from the gear surface by sliding action, causing micro-welds and deformations.

Question 15

What causes pitting and spalling in gears?

Answer 15

Thin oil films and high temperatures.

Question 16

What usually causes cracking in gears?

Answer 16

A failure in the heat treatment process or improper machining.

Question 17

What is interference wear caused by?

Answer 17

Misalignment of gears or mating of the teeth.

Question 18

What causes abrasive wear on gear teeth?

Answer 18

Scratching and scoring from particles in the lubricant.

Question 19

What is a wear pattern in gears?

Answer 19

The prints that one set of gear teeth leaves on another set when they mate.

Question 20

How can wear patterns be examined?

Answer 20

Before final assembly, during service, during overhaul, and after a failure.

Question 21

What is used to establish tooth contact patterns before assembly?

Answer 21

Prussian blue.

Question 22

What is the purpose of gear backlash?

Answer 22

To prevent gears from jamming and to provide lubricant space.

Question 23

What is minimum backlash?

Answer 23

Occurs when all tolerances give the shortest centre distance and the thickest teeth.

Question 24

What is maximum backlash?

Answer 24

Occurs when all tolerances give the greatest centre distance and the thinnest teeth.

Question 25

How can backlash be measured in a gear train?

Answer 25

By locking one end of the gear train and measuring the limits of movement at the other end.

Question 26

What is the total backlash in a four-wheel gear train if each gear has 0.001 mm backlash?

Answer 26

0.003 mm.

Question 27

What are chain assemblies required to be inspected for?

Answer 27

Chain assemblies are required to be inspected at specified intervals as per the requirements of the aircraft maintenance manual.

Question 28

What is the primary inspection of a chain assembly focused on?

Answer 28

The primary inspection is to ensure the chain passes smoothly over the sprockets.

Question 29

What should be done if the chain does not pass over the sprocket smoothly?

Answer 29

A deeper inspection is required to ascertain the problem.

Question 30

What does a secondary inspection of a chain assembly check for?

Answer 30

A secondary inspection is for wear which requires a load being applied to determine if the chain has stretched or worn.

Question 31

What is a typical percentage limit of deflection/elongation for a loaded chain?

Answer 31

A typical percentage limit of deflection/elongation ranges from 1.5% to 3% when the chain is loaded with the correct tension.

Question 32

What additional factors must be inspected on the chain?

Answer 32

The chain must also be inspected for damage, cleanliness, adequacy of lubrication, and absence of corrosion.

Question 33

What should be done if the inspection reveals signs of corrosion or defects in the chain?

Answer 33

If the inspection reveals the chain shows signs of corrosion or other defects, it must be replaced.

Question 34

What care must be taken when adjusting the tension of a chain with turnbuckles?

Answer 34

Care must be taken to ensure that the chain is not twisted during adjustment.

Question 35

What should be done when a chain is 5% worn?

Answer 35

Replace the chain when 5% worn.

Question 36

What is the probable cause of pin galling?

Answer 36

Inadequate lubrication.

Question 37

What is the correction for pin galling?

Answer 37

Reduce load or chain drive speed and provide proper chain lubrication.

Question 38

What causes tight joints in a chain?

Answer 38

Dirt or foreign substance packed in joints, corrosion or bent pins.

Question 39

What should be done to correct tight joints?

Answer 39

Clean and re-lubricate the chain or replace the chain.

Question 40

What causes hooked sprocket teeth?

Answer 40

Excessive chain wear.

Question 41

What should be done if sprocket teeth are hooked?

Answer 41

Replace the chain and the sprocket.

Question 42

What causes abnormal protrusion or turned pins?

Answer 42

Excessive internal friction caused by high loading and inadequate lubrication.

Question 43

What is the correction for abnormal protrusion or turned pins?

Answer 43

Replace the chain, improve lubrication and eliminate overload conditions.

Question 44

What causes cracked plates due to fatigue?

Answer 44

Loading beyond the chain's dynamic capacity.

Question 45

What should be done if there are cracked plates due to fatigue?

Answer 45

Replace the chain with a chain of larger dynamic capacity or eliminate high load condition.

Question 46

What is the cause of fractured plates due to tension?

Answer 46

High overload.

Question 47

What should be done if there are fractured plates due to tension?

Answer 47

Replace the chain and correct the cause of overload.

Question 48

What causes arc-like cracked plates due to stress corrosion?

Answer 48

Severe rusting or exposure to acidic or caustic medium.

Question 49

What should be done if there are arc-like cracked plates due to stress corrosion?

Answer 49

Replace the chain and protect from hostile environment.

Question 50

What causes enlarged holes in a chain?

Answer 50

High overload.

Question 51

What should be done if there are enlarged holes in the chain?

Answer 51

Replace the chain and correct cause of overload.

Question 52

What causes a rusted chain?

Answer 52

Exposure to moisture, water in lubricant, or inadequate lubrication.

Question 53

What should be done if the chain is rusted?

Answer 53

Replace the chain and protect from moisture, change the chain lubricant, and improve chain lubrication.

Question 54

What is the main role of a sprocket?

Answer 54

The main role of a sprocket is to convert rotary motion into linear motion or vice versa.

Question 55

What materials are commonly used to manufacture sprockets?

Answer 55

Common materials include alloy, hard fibre material, and plastic.

Question 56

What can a visual inspection of a sprocket determine?

Answer 56

A visual inspection can determine if the sprocket has worn beyond its limits.

Question 57

What should be checked during a sprocket inspection?

Answer 57

Look for worn teeth and misalignment.

Question 58

What is required during the inspection of drive belts and pulleys?

Answer 58

All drive belts and pulleys are required to be inspected during scheduled maintenance inspections.

Question 59

What defects must be inspected for in drive belts?

Answer 59

Inspect for wear and degradation, cracking and splitting, chipping and fraying.

Question 60

What causes cracking and splitting in drive belts?

Answer 60

Cracking and splitting can be caused by slipping of the belt.

Question 61

What should be done if defects are found in drive belts?

Answer 61

All defects require belt or pulley replacement.

Question 62

How is belt tension tested?

Answer 62

The tension can be tested by pushing on the belt in an unsupported location and observing the deflection.

Question 63

What should be referenced to check the belt tension?

Answer 63

Reference must always be made to the relevant AMM.

Question 64

What should be done if the belt is too loose?

Answer 64

Loosen the tension bolt on the mounting bracket and adjust the pulley until the correct tension is achieved.