Chapter 3

Definitions, Goals, and Objectives

Maintenance Defined• Airline:

• “Those actions required for restoring or maintaining an item in a serviceable condition,

• Including servicing, repair, modification, overhaul, inspection, and determination of condition”

Maintenance Defined• Moubray – Industrial consultant

• “Ensuring that physical assets continue to do what their users want them to do”

• FAA• “Inspection, overhaul, repair, preservation,

and replacement of parts”

• Hessberg – Chief mechanic – Boeing 777• “Action necessary to sustain or restore the

integrity and performance of the airplane• Includes inspection, overhaul, repair,

preservation, and replacement parts”

Maintenance Defined• Kinnison

• “Process of ensuring that a system continually performs its intended function at its designed-in level of reliability and safety”

• Definition implies servicing, adjusting, replacement, restoration, overhaul, and anything else needed to ensure proper and continual operations of the system or equipment

Inherent Reliability– Degree of reliability depends on:

• Design characteristics• Process used for determining maintenance

requirements

– Inherent reliability is not• The length of time an item will survive with no

failures

– Inherent reliability is • Level of reliability the item will exhibit when it

is protected by preventative maintenance and adequate servicing and lubrication

Aviation Word Pairs• Verification/Validation

– Verification• Written test/procedure• When read and understood by a

knowledgeable person• Is correct, adequate, and acceptable for the

purpose for which it was intended

– Validation• Written test/procedure has been performed• By an appropriate trained maintenance person• Understandable, adequate, and proven to

accomplish the intended purpose

Aviation Word Pairs• Operational check/Functional check

– Operational check• “Task to determine if an item is fulfilling its

intended purpose”– Operate equipment, system, or component as usual – Determine whether or not it is useable for its

intended purpose

– Functional check• “Quantitative check to determine if each

function of an item performs within specified limits”

– Equipment, system, or component has been checked

– Using necessary equipment/tools to measure certain parameters for accuracy

Aviation Word Pairs• Functional failure/Potential failure

– Functional failure• “Inability of an item to meet a specific

performance standard”

– Potential failure• “Detectable condition which shows a

functional failure is imminent or could happen very soon”

Aviation Word Pairs• Goals/Objectives

– Goals• “Point in time or space where you want a level

of accomplishment”

– Objectives• “Action or activity you employ to achieve a

specific goal”

Airline Maintenance Goals• Airline purpose

– Move people/goods from one place to another

– (For profit)• Maintenance organization

– Support the unit’s operation– “Deliver airworthy vehicles to the flight department

in time to meet the flight schedule”– “Deliver these vehicles with all necessary

maintenance actions completed or properly deferred”

Airline Maintenance Goals• FAA

– Requires maintenance to be done at specified intervals and to accepted standards• Deferrals

– Lack of parts, time constraints, etc– In accordance with MEL– No further extension can be granted

Maintenance Program Content• Manual

– 2 groups of tasks• Scheduled tasks

– Accomplished at specified intervals

• Non-scheduled tasks– Conducted after scheduled tasks– Reports of malfunctions– Data analysis

– Efficient program• Schedule only tasks necessary to meet stated

objectives• Do not schedule additional tasks

– Increases costs without reliability increase

Maintenance Objectives• 4 objectives identified by ATA

– Developed during initial maintenance program with a new airplane model

– Book adds additional objective

Maintenance Objectives• Objective 1

– Ensure the realization of the inherent safety and reliability levels of the equipment• Scheduled maintenance tasks• Developed by

– Equipment manufacturer– Airline maintenance organization– Third-party maintenance company– Industry-supported organization

Maintenance Objectives• Objective 2

– Restore safety and reliability to their inherent levels when deterioration has occurred• Unscheduled maintenance tasks

– Troubleshooting actions– Removal/replacement of parts/components– Performance of tests/adjustments

• Developed by– MSG process– Contained in manufacturer’s maintenance manual

Maintenance Objectives• Objective 3

– Obtain the information necessary for adjustment and optimization of the maintenance program when these inherent levels are not met• Operator adjusts/optimizes program

– Investigates if failure/removal rates too high– Quality of maintenance performed– Inferiority of parts/components– Inadequacy of maintenance processes/procedures– Maintenance intervals inadequate

Maintenance Objectives• Objective 4

– Obtain the information necessary for design improvement of those items whose inherent reliability proves inadequate• Cannot achieve desired level of reliability

– Deficiency in design– Coordinate with other operators/manufacturers– Could be joint effort

• Result - redesign

Maintenance Objectives• Objective 5

– Accomplish these objectives at a minimum total cost, including costs of maintenance and the cost or residual failures• Don’t do more maintenance than required

– Meet inherent levels of safety and reliability

• Cost of modifications too high– May not be justified unless– Measureable increases in performance justify the

cost