7.12 Transmissions Flashcards
What is the primary function of a gear?
The transmission of power through motion.
What leads to stress and wear in a gear system?
Motion within the gear system.
What should be periodically examined in gears?
All gears for cracks, chipped teeth, and the presence of pitting or excessive wear.
What are causes for rejection and replacement of a gear?
Deep pit marks and excessive wear on gear teeth.
How can minor scratches and abrasions on a gear surface be removed?
Using a fine abrasive cloth.
What is not acceptable on a gear surface?
Deep scratches or scoring.
What must be checked and maintained to ensure proper gear mesh?
Correct gear backlash.
What is essential for improving the life and performance of a gear?
Understanding how to inspect, report, and document the conditions of the gear.
What usually causes gear failure or premature wear?
Excessive backlash and/or poor lubrication.
What can cause gears to corrode?
Exposure to corrosive conditions and moisture in the lubricant.
What results from a complete breakdown or lack of lubrication?
Overheating of the gear.
What does normal wear on gear teeth result in?
A polished appearance over the tooth’s entire surface.
What are the types of gear wear discussed?
Overload wear, pitting & spalling, cracking and breakage, interference wear, abrasive wear.
What occurs during overload wear?
Metal is removed from the gear surface by sliding action, causing micro-welds and deformations.
What causes pitting and spalling in gears?
Thin oil films and high temperatures.
What usually causes cracking in gears?
A failure in the heat treatment process or improper machining.
What is interference wear caused by?
Misalignment of gears or mating of the teeth.
What causes abrasive wear on gear teeth?
Scratching and scoring from particles in the lubricant.
What is a wear pattern in gears?
The prints that one set of gear teeth leaves on another set when they mate.
How can wear patterns be examined?
Before final assembly, during service, during overhaul, and after a failure.
What is used to establish tooth contact patterns before assembly?
Prussian blue.
What is the purpose of gear backlash?
To prevent gears from jamming and to provide lubricant space.
What is minimum backlash?
Occurs when all tolerances give the shortest centre distance and the thickest teeth.
What is maximum backlash?
Occurs when all tolerances give the greatest centre distance and the thinnest teeth.
How can backlash be measured in a gear train?
By locking one end of the gear train and measuring the limits of movement at the other end.
What is the total backlash in a four-wheel gear train if each gear has 0.001 mm backlash?
0.003 mm.
What are chain assemblies required to be inspected for?
Chain assemblies are required to be inspected at specified intervals as per the requirements of the aircraft maintenance manual.
What is the primary inspection of a chain assembly focused on?
The primary inspection is to ensure the chain passes smoothly over the sprockets.
What should be done if the chain does not pass over the sprocket smoothly?
A deeper inspection is required to ascertain the problem.
What does a secondary inspection of a chain assembly check for?
A secondary inspection is for wear which requires a load being applied to determine if the chain has stretched or worn.
What is a typical percentage limit of deflection/elongation for a loaded chain?
A typical percentage limit of deflection/elongation ranges from 1.5% to 3% when the chain is loaded with the correct tension.
What additional factors must be inspected on the chain?
The chain must also be inspected for damage, cleanliness, adequacy of lubrication, and absence of corrosion.
What should be done if the inspection reveals signs of corrosion or defects in the chain?
If the inspection reveals the chain shows signs of corrosion or other defects, it must be replaced.
What care must be taken when adjusting the tension of a chain with turnbuckles?
Care must be taken to ensure that the chain is not twisted during adjustment.
What should be done when a chain is 5% worn?
Replace the chain when 5% worn.
What is the probable cause of pin galling?
Inadequate lubrication.
What is the correction for pin galling?
Reduce load or chain drive speed and provide proper chain lubrication.
What causes tight joints in a chain?
Dirt or foreign substance packed in joints, corrosion or bent pins.
What should be done to correct tight joints?
Clean and re-lubricate the chain or replace the chain.
What causes hooked sprocket teeth?
Excessive chain wear.
What should be done if sprocket teeth are hooked?
Replace the chain and the sprocket.
What causes abnormal protrusion or turned pins?
Excessive internal friction caused by high loading and inadequate lubrication.
What is the correction for abnormal protrusion or turned pins?
Replace the chain, improve lubrication and eliminate overload conditions.
What causes cracked plates due to fatigue?
Loading beyond the chain’s dynamic capacity.
What should be done if there are cracked plates due to fatigue?
Replace the chain with a chain of larger dynamic capacity or eliminate high load condition.
What is the cause of fractured plates due to tension?
High overload.
What should be done if there are fractured plates due to tension?
Replace the chain and correct the cause of overload.
What causes arc-like cracked plates due to stress corrosion?
Severe rusting or exposure to acidic or caustic medium.
What should be done if there are arc-like cracked plates due to stress corrosion?
Replace the chain and protect from hostile environment.
What causes enlarged holes in a chain?
High overload.
What should be done if there are enlarged holes in the chain?
Replace the chain and correct cause of overload.
What causes a rusted chain?
Exposure to moisture, water in lubricant, or inadequate lubrication.
What should be done if the chain is rusted?
Replace the chain and protect from moisture, change the chain lubricant, and improve chain lubrication.
What is the main role of a sprocket?
The main role of a sprocket is to convert rotary motion into linear motion or vice versa.
What materials are commonly used to manufacture sprockets?
Common materials include alloy, hard fibre material, and plastic.
What can a visual inspection of a sprocket determine?
A visual inspection can determine if the sprocket has worn beyond its limits.
What should be checked during a sprocket inspection?
Look for worn teeth and misalignment.
What is required during the inspection of drive belts and pulleys?
All drive belts and pulleys are required to be inspected during scheduled maintenance inspections.
What defects must be inspected for in drive belts?
Inspect for wear and degradation, cracking and splitting, chipping and fraying.
What causes cracking and splitting in drive belts?
Cracking and splitting can be caused by slipping of the belt.
What should be done if defects are found in drive belts?
All defects require belt or pulley replacement.
How is belt tension tested?
The tension can be tested by pushing on the belt in an unsupported location and observing the deflection.
What should be referenced to check the belt tension?
Reference must always be made to the relevant AMM.
What should be done if the belt is too loose?
Loosen the tension bolt on the mounting bracket and adjust the pulley until the correct tension is achieved.
