Gear Wear Pattern Analysis

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Questions and Answers

What can happen if a pulley is out of line?

It can cause wear to both the pulley and the cable (correct)

It can increase the lifespan of the cable

It can improve the efficiency of the cable system

It can make the pulley turn more freely

What is the primary purpose of pulley guards?

To increase the speed of the pulley

To reduce friction between the pulley and cable

To reduce the noise of the pulley

To prevent the cable from jumping out of the groove (correct)

Why are control chains used in aircraft control systems?

Because they are lighter than cables

Because they can provide a relatively large amount of force to operate (correct)

Because they are cheaper than cables

Because they are easier to install

What is the purpose of studying the pattern of contact left on the teeth of gears?

To set up the correct shimming or assembly relationship Signup and view all the answers

What is unique about the manufacturing of aircraft control chains?

They are manufactured to closer tolerance and have more rigorous inspection criteria Signup and view all the answers

What is an indication of normal wear on the teeth mating surfaces?

A polished surface on the tooth face Signup and view all the answers

During an overhaul, what is examined to determine acceptability for further service?

The wear pattern on the gear teeth Signup and view all the answers

What is the benefit of regular inspection of pulley bearings, bolts, and bushings?

It can ensure the serviceability of the pulley Signup and view all the answers

What can happen if a pulley is not equipped with a guard?

The cable may jump out of the groove Signup and view all the answers

What is the heel of a helical bevel gear?

The larger-width outer end of the gear Signup and view all the answers

What type of chains are typically used in aircraft control chains?

Roller type Signup and view all the answers

What is the purpose of chain keepers in aircraft control chains?

To stop the chain from coming off the sprockets Signup and view all the answers

Which side of the tooth is under pressure during normal operation?

Drive side Signup and view all the answers

What are the three parameters used to size chains?

Pitch, width, and roller diameter Signup and view all the answers

What can the wear pattern examination reveal after a gear or assembly failure?

The cause of the failure Signup and view all the answers

Why are non-reversible chains connected using end fittings?

To allow the chain to be fitted in one direction only Signup and view all the answers

What is the purpose of chain guards in aircraft control chains?

To prevent the chain from coming adrift when tension is reduced Signup and view all the answers

What should be done to the chain before checking for wear or damage?

Clean the chain Signup and view all the answers

What is the formula to calculate the chain elongation percentage?

Extension (%) = (M - (X × P)) × 100 Signup and view all the answers

What is the consequence of excessive tension on the chain?

It causes the chain rollers to bind on the sprocket teeth Signup and view all the answers

What should be done if the chain elongation is greater than 2%?

Replace the whole chain Signup and view all the answers

How is the chain tension checked?

By applying a specified load and measuring the deflection Signup and view all the answers

What is a common consequence of inadequate chain storage?

Chain corrosion or kinking Signup and view all the answers

What is a criterion for rejecting a chain?

All of the above Signup and view all the answers

What is the primary role of sprockets in many aircraft systems?

To convert rotary motion into linear motion and/or linear motion into rotary motion Signup and view all the answers

What is the purpose of an idler sprocket in a chain system?

To support the chain run Signup and view all the answers

What determines the gearing ratio of a chain system?

The number of teeth on the drive sprocket and the driven sprocket Signup and view all the answers

What is the correct way to store chains?

Cleaned, dried, and coiled without twisting Signup and view all the answers

What is the purpose of sighting along the length of a suspended chain?

To check for kinks or twists Signup and view all the answers

What are sprockets usually made from?

Depending on the application, steel, alloy, hard fibre material, or plastic Signup and view all the answers

Study Notes

Chain Maintenance

To check for elongation, apply a specified load to the chain, measure the length, and calculate the extension using the formula: Extension (%) = (M - (X × P)) × 100 / (X × P)
Replace the whole chain if elongation is greater than 2%, as it can compromise its strength
Chain tension is checked by measuring chain deflection under a given load

Chain Tensioning

Chain tensioning is adjusted using turnbuckles or adjustable sprockets
The chain should be tightened enough to remove any backlash
Too much tension causes the chain rollers to bind on the sprocket teeth

Criteria for Chain Rejection

The chain section is elongated by more than 2%
Any links are stiff or jammed
Any part of the chain is kinked or twisted
Any plates are cracked, worn, or corroded
Any rollers are cracked, worn, corroded, or jammed

Chain Storage

Correct storage of chains is important to minimize the possibility of corrosion or kinking of the links
Chains should be cleaned, dried, and soaked in light lubricating oil before storage
Chains should be coiled without twisting and checked for kinks or twists

Pulleys and Belt Inspection

Pulleys should turn freely when the control cables are moved
If a pulley is out of line, it causes wear to both the pulley and the cable
Mountings for pulleys should be corrected and the cable carefully examined for wear
Wear of pulley bearings, bearing bolts, and bushings should be checked for serviceability regularly

Chain Introduction

Control chains are found in a number of applications in aircraft control systems
Chains are made up of multiple links and can be joined together to make an endless loop
Chains can be of a terminating type – a single length with a start and finish
Chains are manufactured to closer tolerance and have more rigorous inspection criteria

Chain Components

Chain keepers, similar to cable guards, stop the chain from coming off the sprockets
Chains have drive and idler sprockets and a method of maintaining the tension of the assembly
Chain link assembly consists of rollers, bushes, and inner link plates
Pins are mounted in the outer plates, which are clamped together to join the whole assembly

Chain Sizing

Chains are sized according to pitch, width, and roller diameter
Non-reversible chains are joined or connected using end fittings similar to cable terminals
Chain guards can be fitted to sprockets to prevent the chain from coming adrift when tension is reduced

Chain Inspection

Chains need to be assessed regularly for wear, corrosion, and distortion, including elongation
It is always best to clean the chain before checking for wear or damage

Sprockets

Sprockets are used in many aircraft systems and in a variety of different applications
Sprockets are usually made from steel, alloy, hard fibre material, or plastic
Their primary role is to convert rotary motion into linear motion and/or linear motion into rotary motion
Sprockets act as support for the chain in the form of an idler sprocket

Idler Sprocket

An idler sprocket is a non-driving sprocket used to support the chain run
Sprocket teeth are spaced to align with the chain pitch
The number of teeth on the drive sprocket compared to the number of teeth on the sprocket being driven determines the gearing ratio of the chain system

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Description

Learn how to analyze the wear pattern on gear teeth to determine the condition of the gear assembly and identify potential issues. This quiz covers the techniques used to examine gear wear, including the normal wear patterns and signs of abnormal wear.