Aviation Maintenance Aviation Maintenance ManagementManagement

Aviation Maintenance Aviation Maintenance ManagementManagement

Why We Have to Do MaintenanceChapter 1

January 28

1871 — The last balloon to leave Paris during the Persian siege takes off with orders for the French fleet to bring food and supplies to replenish the French capital, an armistice having been signed.

The flight of the General “Cambronne” ends a period of almost exactly 5 months during which the advantages of balloons were put to efficient use.

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January 28

1945 — The Burma Road is reopened.

THIS DAY IN AVIATIONTHIS DAY IN AVIATIONTHIS DAY IN AVIATIONTHIS DAY IN AVIATION

January 28

1945 — The USAAF 8th AF observed its 3rd birthday with a 1,000 plane raid on Germany.

THIS DAY IN AVIATIONTHIS DAY IN AVIATIONTHIS DAY IN AVIATIONTHIS DAY IN AVIATION

Aviation Maintenance ManagementAviation Maintenance ManagementAviation Maintenance ManagementAviation Maintenance Management

Introduction Design & The Role of the Engineer Role of the Mechanic Types of Maintenance Reliability & Redesign Failure Rate Patterns Other Maintenance Considerations Summary

IntroductionIntroductionIntroductionIntroduction Schedule pressures, parts shortages,

equipment deficiencies, regulatory and agency compliance inspections, union pressures etc..

Technology advancements and diverse equip require perpetual training

Parts issues – no parts, cannibalization, aircraft on ground, weather conditions

Personnel issues – financial, family, substance abuse, late, no-show, vacations, trng, meetings – impact (touch labor)

Unscheduled Maintenance

Managerial ChallengesManagerial ChallengesManagerial ChallengesManagerial Challenges Aircraft out of service impacts –

crew training and readiness Lost of revenue (no passengers – and maint/labor

costs) Loss of customer loyalty (customer is price based)

Intent of course not to make you an expert maintenance manager but to expose you to the various influences and the functions and techniques of the job

Knowledge is power

Modern Day Aircraft MaintenanceModern Day Aircraft MaintenanceModern Day Aircraft MaintenanceModern Day Aircraft Maintenance

Aircraft require preventive or corrective maintenance at frequent intervals

Kind of operation; environmental conditions; storage facilities avail; age and construct of aircraft

Maintenance Man-hours per Flying hour (MMH/FH)

Cost to maintain a particular type of aircraft

Modern Day Aircraft MaintenanceModern Day Aircraft MaintenanceModern Day Aircraft MaintenanceModern Day Aircraft Maintenance

Cost of ownership – fuel, wash, oil, tires etc… Scheduled maintenance

Goal is to correct any deficiency before it occurs Checks cost money – labor and parts, fluids costs and

loss of passenger revenue when not flying Total up all Maintenance associated costs

subtract from revenue from aircraft and you get profit or loss

Design & Role of EngineerDesign & Role of EngineerDesign & Role of EngineerDesign & Role of Engineer

We can design perfect systems on paper but we can not build perfect systems in the “real” world

Nothing is perfect Good, Fast, Cheap

A design engineer may be limited from making the perfect system by technology or the state of the art within any facet of the design effort

Limited by ability, technique or economics Economics may force a redesign with reduced tolerances,

cheaper materials and gap between: perfect and “perfect” realism

Role of the MechanicRole of the MechanicRole of the MechanicRole of the Mechanic

For the mechanic the gap between “perfect” & “perfect” realism always changes & predominantly for the worse

Components or systems tend to wear out from use or lack there of (time or environmentally related)

Misuse may cause premature deterioration or degradation of the system or even outright damage

The engineer’s responsibility is to design the system with as high degree of perfection within reasonable limits/constraints

The mechanic’s responsibility is to combat the gap between ideal & realism during the operational lifetime of the equipment

Two Types of MaintenanceTwo Types of MaintenanceTwo Types of MaintenanceTwo Types of Maintenance

Preventive Maintenance (PMs) Performed at regular intervals – to prevent deterioration of the system

to an unusable level and to keep it operational – often referred to as:

Scheduled Maintenance Performed – daily, every flight, every 200 flight hours, or every 100

cycles (takeoff & landings)

Unscheduled Maintenance Various, unpredictable intervals maintenance actions are required to

restore a system that may require extensive testing, troubleshooting, adjusting, replacement, restoration, or complete overhaul of parts or subsystems

Maintenance DefinedMaintenance DefinedMaintenance DefinedMaintenance Defined Cost of Ownership and scheduled maintenance

are 2/3 of equation Unscheduled Maintenance – random failures Reliability studies have led to MTBF (Mean Time

Between Failure) – components / system guesstimated reliability factor

Induced failures – FOD, damage from servicing vehicles, maintenance malpractices

Inherent failures – delamination of composites, substandard bearings, inefficient seals etc.

No defect – A-799 or fault within tech data limits (require expenditure of maintenance resources)

Reliability & RedesignReliability & RedesignReliability & RedesignReliability & Redesign

Reliability “A measure of the probability that an item will survive to a

specified operating age or time, under specified operating conditions, without a failure”

no amount of maintenance can be performed to increase the systems inherent level of designed in-level of perfection

Redesign When the reliability decreases & a higher level of “perfection”

is desired – redesign may take place Needs to be weighed if the performance improvement justifies

more maintenance & thus the increase in maintenance costs – ideally the opposite is true

Failure Rate Patterns (MTBF)Failure Rate Patterns (MTBF)Failure Rate Patterns (MTBF)Failure Rate Patterns (MTBF)

All systems or components fail at the same rate or exhibit the same patterns of wear out and failure

The maintenance performed is related to those rates and failure patterns (Table 1-1 pg. 10)

“Infant mortality” – early high failure rate in component’s life

“getting the bugs out” Causes” poor design, improper parts, incorrect usage etc..

These characteristics of failure make it necessary to approach maintenance in a systematic manner to reduce peak periods of unscheduled maintenance

Several techniques have been designed to combat this:

Three Maintenance Management Three Maintenance Management TechniquesTechniquesThree Maintenance Management Three Maintenance Management TechniquesTechniques

Three Maintenance Management Techniques Equipment redundancy, line replaceable units, &

minimum aircraft dispatch requirements Equipment Redundancy

Duplicate systems – primary and a backup (radios, navigation devices, flight control systems, computers)

Instrumentation within cockpit can signify status Line Replaceable Units (LRUs) – black boxes

Designed to allow easy removal and replacement to reduce out of service timer of aircraft

Three Maintenance Management Three Maintenance Management TechniquesTechniquesThree Maintenance Management Three Maintenance Management TechniquesTechniques

Master Minimum Equipment List (MMEL) Lists ALL equipment for the aircraft model – list is tailored to its

MEL

Minimum Equipment List (MEL) List of equipment that the aircraft may be inoperative

but still allowed to fly as long as it does not affect the safety & operation of flight – Tailored to mission

Determined by manufacturer and sanctioned by the regulatory authority (FAA)

Three Maintenance Management Three Maintenance Management TechniquesTechniquesThree Maintenance Management Three Maintenance Management TechniquesTechniques

Minimum Equipment List (MEL) Concept of the MEL is to allow the deferral of

maintenance without upsetting mission requirements Maintenance must be performed within some set of

guidelines (1, 3, 10, or 30 days or cycles required) depending on operational requirements of the system

Pilot may always require or defer maintenance per the MEL

Maintenance MUST abide by decision…. (his call) “Takes a college education to break it & a high school

education to fix it.”

Minimum Equipment List (MEL)Minimum Equipment List (MEL)Minimum Equipment List (MEL)Minimum Equipment List (MEL)

Dispatch Deviation Guide (DDG) Instructions for maintenance not necessary obvious to the

mechanic – tying up cables, capping off connectors, taking circuit breakers out to prevent inadvertent power-up of equipment during flight while maintenance is being performed and any other precautionary steps that need to be taken

Configuration Deviation List (CDL) List of information of equipment or panels etc. that may be missing

or added per that aircraft model

All lists can be found in the aircraft logbook

3 techniques help minimize the workload and reduce service interruptions due to maintenance

SummarySummarySummarySummary The purpose of aircraft maintenance is to ensure the

aircraft will remain airworthy throughout its operational life

Still haven’t reached perfection even with advances in technology

3 maintenance techniques help manage maintenance actions

Not all aircraft maintenance activities will be organized or operated in the same manner but the programs and activities will be the same