AMO Chapter 1

Aerospace Engineering – ATO - MRO

Airline Maintenance Operations

AE4-442

Dr. Adel A. Ghobbar

E-mail: [email protected]

COURSE NOTES 2012-13

Airline Maintenance Operations, AE4-442 Glossary of Terms

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GLOSSARY OF TERMS

A/C Aircraft

AAIB Air Accidents Investigation Branch

AAN Airworthiness Approval Note

AC Alternating Current

ACJs Advisory Circulars-Joint

ADs Airworthiness Directives

ADD Acceptable Deferred Defects

ADI Average inter-Demand Interval

ADL Allowable Deficiency List

AEA Association of European Airlines

AET Acoustic Emission Testing

AMJ Advisory Material-Joint

AMO Approved Maintenance Organisation

AMS Approved Maintenance Schedule

ANO Air Navigation Order

AO Airline Operator

AOC Air Operator’s Certificate

AOG Aircraft-On-Ground

APU Auxiliary Power Unit

ASEMC Avionics Systems Engineering and Maintenance Committee

ASPL Advance Spares Provisioning List

ATA Air Transport Association

ATC Air Traffic Control

AUR Aircraft Utilization Rate

AWO All-Weather Operations

BAe British Aerospace

BCAR British Civil Airworthiness Requirements

BOM Bill Of Materials

CAA Civil Aviation Authority

CAR Civil Air Regulation

CC Carrying Cost


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CM Condition-Monitoring

CMA Component Maintenance Assembly

CMM Component Maintenance Manual

CMR Certificate of Maintenance Review

C of A Certificate Of Airworthiness

COL Component’s Overhaul Life

CPA Critical Path Analysis

CRS Certificate of Release to Service

CSDB Common Source Data Base

CV2 Square Coefficient of Variation on Demand

DMC Direct Maintenance Costs

EASA European Aviation Safety Agency

ECAC European Civil Aviation Conference

ECT Eddy Current Testing

EDI Electronic Data Interchange

EIP End Item Plans

EOQ Economic Order Quantity

EPP Economic Part-Period

EMSG European Maintenance System Guide

FAA Federal Aviation Administration

FAR Federal Aviation Regulation

FHs Flying Hours

FIM Fault Isolation Manual FLs Flying Landings

FOD Foreign Object Damage FOQ Fixed Order Quantity FSN Fast, Slow and Non-moving

GE General Electric

HFACS Human Factors Analysis & Classification System

HML High, Medium, Low

HT Hard-Time

HVL Half Value Layer

IATA International Air Transport Association

IC Item Cost


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ICAO International Civil Aviation Organisation

IFSDs In Flight Engine Shout Downs

IMC Indirect Maintenance Costs

IPC Illustrated Parts Catalogues

IPD Initial Provisioning Data

IPP Incremental Part-Periods

IPPA Incremental Part-Period Algorithm

JAA Joint Aviation Authorities

JAR Joint Aviation Requirements

JIT Just In Time

LAMS Light Aircraft Maintenance Schedule

LFL Lot For Lot

LOX Liquid Oxygen

LPD Logistic Planning Document

LPT Liquid Penetrant Testing

LRU Line Replaceable Units

LS Lot-Size

LT Lead Time

ME Maintenance Extension

MEL Minimum Equipment Lists

MHs Man-Hours

MMEL Master Minimum Equipment List

MOI Magneto Optic Imaging

MOQ Minimum Order Quantity

MPT Magnetic Particle Testing

MSO Maintenance Service Organizations

MRB Maintenance Review Board

MRO Maintenance Repair and Overhaul

MRP Material Requirements Planning

MS Master Schedule

MSG Maintenance Steering Group

MSI Maintenance Significant Items

MSR Maintenance Support Resources

MTBF Mean Time Between Failure


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MTBO Mean Time Between Overhaul

MTBR Mean Time Between Removal

MTBUR Mean Time Between Unscheduled Removal

MTWA Maximum Total Weight Authorised

NAA National Aviation Authorities

NDE Non-Destructive Evaluation

NDE Non-Destructive Examination

NDI Non-Destructive Inspection

NDT Non Distractive Testing

NEC National Electrical Code

NFF No Fault Found

NPA Notice of Proposed Amendment

NPRM Notice of Proposed Rule-Making

NTSB National Transportation Safety Board

OC On-Condition

OC Ordering Cost

OEM Original Equipment Manufacturers

PFA Popular Flying Association

PH Planning Horizon

PMA Parts Manufacturer Approval

PMP Primary Maintenance Process

P&W Pratt & Whitney

QA Quality Assurance

QC Quality Control

RCM Reliability Centred Maintenance

RD Research and Development

ROP Re-Order Point

R-R Rolls Royce

RSPL Recommended Spares Provisioning Listing

RT Radiographic Testing

SB Service Bulletin

SC Service Check

SDE Scarce, Difficult and Easy to Procure

SES Single Exponential Smoothing


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SKUs Stock Keeping Units

SMI Scheduled Maintenance Inspections

SPL Seasonal Period Length

SS Safety Stock

SSI Structural Significant Items

TAT Turn Around Time

TFL Technical Flight Log

TICC Technical Information & Communications Committee

TMC Total Maintenance Cost

TT Thermography Testing

USAF United State Air Force

UT Ultrasonic Testing

UV UltraViolet

VE Visual Examination

VED Vital, Essential and Desirable

VLA Very Light Aircraft

WASG World Airlines and Suppliers Guide

WCDR Weighted Calculation of Demand Rates

Technical Definitions

Aircraft capacity

The payload available within aircraft.

Aircraft daily utilisation

The average daily flying hours for one in-service aircraft (of a given fleet). Daily

utilisation is computed by dividing the total flying hours accumulated by the fleet in a

reporting period by the number of in-service aircraft days in the same period.

Aircraft downtime

That time the aircraft is on the ground i.e. total time less flying time.


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Aircraft in-service

Total aircraft available days divided by total days of the period.

Average flight time

Total Flying hours divided by number of landings.

Aircraft Kilometres

Aircraft kilometres are calculated by multiplying the number of flights performed by the

stage distance.

Aircraft operating cycle

A completed take-off and landing sequence, including touch and go landings.

Bench check

A functional check of an item in the shop to determine whether or not the item may be

returned to service or whether it requires adjustment repair or overhaul.

Block flying hours

The number of hours incurred by an aircraft from the moment it first moves for a flight

until it comes to rest at its intended blocks at the next point of landing or returns to its

departure point prior to take-off.

Break down spares

Spare parts held in stores for use as replacement parts when components are

disassembled.

Capacity available in hangars or workshops

The maximum number of units that can be held in the hangars or workshops at any

overtime. This number takes into accounts the amount of working space required per

unit.

Check

An examination to verify the functional capability or physical integrity of an item.


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Defect

Any confirmed abnormal condition of an item, whether or not this could result eventually

in a failure.

Downtime maintenance

The interval between the time an item or aircraft is made available for preventive or

corrective maintenance until the item or aircraft is returned to or considered available for

service use. Parts, sub-assemblies or units, which perform a distinctive function

necessary to the operation of a system.

Essentiality

Essentiality has different target of demand probabilities. These show that when the

percentage of demand goes up the essentiality gets stronger, and the larger the fleet size

the less the percentage of spare parts needed.

Failure

The inability of an item to perform within previously specified limits.

Ferry flight

A non-revenue flight made to position aircraft for any reason (Technical for example).

Flying hours (airborne)

The accumulated time intervals between wheels-off to wheels-on. (Same as flight time).

Ground facility

Consists of hangars, workshops, stores, administration and welfare buildings required for

maintenance of aircraft.

Ground support equipment

Equipment required on the ground to support the operation and maintenance of the

aircraft and all its airborne equipment.

Hours out-of-service

The number of elapsed hours that an aircraft is not available for operation when

scheduled to be available.


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Interchangeable

An interchangeable part, sub-assembly, or unit meets or exceeds required functional and

structural specifications for a given application. It has the same mounting provisions;

overall dimensions and connections may vary provided that installation does not require

work or modification.

Job card

A card issued to a workman giving details of the work to be done. Usually contains

provision for recording start and completion times and the estimated target or standard

times.

Line maintenance

Routine inspection and malfunction rectification performed on route and base stations

during transit, turn around, or night-stops.

Log entries

Any entry in the aircraft technical log relating to real or suspected unserviceability,

whether entered by flight crew or ground engineer.

Maintenance man-hours

A measure of maintenance cost often used by operators is the ratio of maintenance man-

hours to aircraft flying hours. This is useful for first estimates in budgeting, and is also

used as a target in military aircraft procurement contracts.

Maintenance planning

The activity which organises the work before physically doing it, planning creates a

concept and detailed program to achieve stated maintenance objectives.

Passenger Tonne Kilometres

Are calculated by multiplying the weight of passengers un-lifted on each stage flight by

the stage distance (Tonne = 1000 kilogrammes).

Sample inspection

The monitoring and/or withdrawal of selected items from services to establish their

condition at predetermined progressive intervals.


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Seat-Kilometres Available

Are calculated by multiplying the number of seats available for sale on each stage flight

by the stage distance. Seats not available for the carriage (transport) of passengers

because of the weight of fuel or other load are excluded.

Seat-Kilometres Used

Are calculated by multiplying the number of revenue passengers carried on each stage

flight by the stage distance.

Scheduled maintenance

Maintenance performed to retain an item in a serviceable condition by systematic

inspection, detection, prevention of failures, replacement of wear-out items, adjustment,

calibration, cleaning, etc.

Technical cancellation

Elimination of a scheduled trip because of a known or suspected malfunction and/or

defect.

Unscheduled maintenance

Maintenance performed to restore an item to a satisfactory condition by correction of a

known or suspected malfunction and/or defect.

A Alpha

B Bravo

C Charlie

D Delta

E Echo

F Foxtrot

G Golf

H Hotel

I India

J Juliet

K Kilo

L Lima

M Mike

N November

O Oscar


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P Papa

Q Quebec

R Romeo

S Sierra

T Tango

U Uniform

V Victor

W Whisky

X Xray

Y Yankee

Z Zulu

Airline Maintenance Operations, AE4-442 Chapter One

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Chapter One: Airworthiness and its Regulation

1.1 Maintenance Philosophies and Concepts

Introduction

Any airline or organization that operates aircraft for transporting passengers or cargo has

the prime responsibility to maintain its aircraft in safe and airworthy condition.

Aircraft maintenance programs vary from one operator to another. The airlines develop

their maintenance programs in accordance with their operational, commercial, and

technical requirements. Government regulations, route structures, availability of

manpower, and facilities are also taken into consideration.

Objectives

The objective of this course is to explain theory and practice of aircraft maintenance and

to provide general guide lines for the development of suitable aircraft maintenance

programs.

Definitions

Aircraft maintenance is divided into line and base maintenance depending on where it is

performed, and into minor and major maintenance depending on how long it takes to

perform it.

Line Maintenance

Line maintenance is performed at line stations or at the flight line of an airline’s base

station. Line maintenance normally consists of routine tasks with low intervals like

servicing, cleaning, refuelling, and light inspections. Non-routine line maintenance may

range from the replacement of a black box to an engine change. Line maintenance is

“Departure Oriented”. It will be restricted as to the work that has to be performed and

tend to defer any time consuming items to the next base visit. The manpower and

facilities at line stations are usually limited so maintenance tasks must also be

accordingly limited.


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Based Maintenance

Based maintenance is performed at an airline’s maintenance base. It is “Fix-Oriented”

because the base has the manpower and facilities to perform all kinds of aircraft

maintenance work.

Minor Maintenance

Minor maintenance can be performed in 24 hours or less. It normally includes the routine

maintenance work up to the A-Check and the resulting non-routine tasks. Depending on

the maintenance program in use, minor maintenance may also include some “C-Check”

tasks. It is performed at line stations or at a maintenance base.

Intermediate Maintenance

Intermediate maintenance comprises of tasks of a “C-Check” nature requiring ground

times of up to 7 days. Lower or higher interval tasks may be included to optimize task

accomplishment and the available ground time.

Major or Heavy Maintenance

Maintenance work that requires an aircraft down-time of more than 7 days is considered

major or heavy maintenance. It includes structural inspections and repairs, repainting,

cabin refurbishment, and major modifications. Heavy maintenance is performed at a

maintenance base.

1.2 Maintenance Program Development

1.2.1 Maintenance Theory

Current maintenance theory can best be understood by taking a brief look at the historical

development of aircraft maintenance theories.

During the nineteen thirties it was believed that mechanical parts wear out, that wear-

outs cause failures, and that failures degrade safety. This belief led to the periodic

disassembly of everything from engines to structures and radio sets. The operating time

of the aircraft controlled all maintenance activities. Scheduled overhaul “Hard-Time,

HT” (as it is called today) was the only recognized primary maintenance process.


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Shortly after World War II, a second primary maintenance process was recognized. It

was called “On-Condition, OC” maintenance because it permitted the use of periodic

condition checks instead of scheduled overhauls. This process was mainly applied to

known wear items like brakes and tires.

Neither of the two processes fully accommodated the new components which were

introduced on the jet aircraft during the sixties. The airlines analyzed the behaviour of

hundreds of components during millions of flight hours and finally discovered that the

reliability of complex assembles – (as opposed to burn-cell items) – does not decrease

with increasing age. Preventive maintenance processes like Hard-Time and On-Condition

therefore could not be used as a means to ensure their continued reliability. The right way

to maintain these complex assemblies turned out to be a third primary maintenance

process called “Condition-Monitoring, CM”.

In the early seventies, when wide-body jets were introduced, aircraft maintenance theory

had arrived at its current form. It states:

1. Mechanical parts wear out over a wide range of time.

2. Part reliability is a function of its inherent design. Most designs include redundancy

that prevents failures from having an effect on safety.

3. Good and adequate maintenance assures that a part is as reliable as its initial

design.

4. More than adequate maintenance does not improve reliability. However less than

adequate maintenance can degrade part reliability.

5. Basic engineering changes are required to improve inherent reliability.

6. There are only three primary maintenance processes: HT, OC, and CM.

7. The function, failure mode, and failure effect of a unit can be used in a logical

manner (MSG-2) to arrive at the minimum preventive maintenance requirement to

protect inherent reliability.

1.2.2 Primary maintenance process, PMP

The three primary maintenance processes recognised by the CAA/EASA and FAA are;

hard-time, on-condition, and condition-monitoring. In general terms, the first two both


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involve actions directly concerned with preventing failure, whereas condition monitoring

does not. However, the condition monitoring process would be expected to lead to

preventive action if shown to be necessary. These categories of component maintenance

are defined as follows:

Hard-time, HT

This is defined as a preventive process in which known deterioration of an item is limited

to an acceptable level by the maintenance actions carried out periodically according to

time in service. This time may be calendar time, the number of cycles, or the number of

landings. The prescribed actions normally include servicing, full or partial overhaul

and/or replacement according to the instructions in relevant documentation so that the

item is restored to suitable condition for use for a further specified period. HT requires

that a component be overhauled after a pre-set usage time, regardless of the component’s

condition, and assumes a relationship between failure and age. Today, Hard-Time items

rarely make up more than two or three percent of all scheduled maintenance tasks.

Engine disks, flap links, and landing gear parts are typical Hard-Time replacement items.

The individual Hard-Times are determined by the manufacturer during endurance tests or

by the airline as a result of its operational experience. The Hard-Time intervals usually

apply to the total life of the parts or until the overhaul of the units.

On-condition, OC

This is also a preventive process, but one in which the item is inspected or tested at

specified periods to an appropriate standard in order to determine whether it can continue

in service. The inspection or test may reveal a need for servicing action. The fundamental

purpose of OC is to remove an item before its failure in service. It is not a philosophy of

‘use until failure’. OC requires checks and tests of components at fixed intervals, with

parts such as wires, bulbs, brackets, covers and bearings etc, being replaced during

overhaul.

Typical examples of On-Condition applications are NDT tests for hydraulic and

pneumatic systems, Borescope checks on internal engine parts, and visual inspections on

structural items. It is important that these inspections are repeated at regular intervals.

The length of the intervals is fairly short at the beginning and then gradually increasing

as service experience becomes available. Some people wrongly refer to units without


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inspection or overhaul interval as being “On-Condition” when they are not. Such units

are part of the Condition-Monitoring process. OC maintenance is like HT – a preventive

maintenance process – and depends on a fixed inspection interval.

Condition monitoring, CM

This is not a preventive process, having neither hard-time nor on-condition elements, but

one in which information on items is collected from operational experience, then

analysed and interpreted on a continual basis as a means to implement corrective

procedures.

It is convenient here to classify information, z, into two classes; namely, direct

information and indirect information. Direct information is where z measures a variable

which directly determines failure, for example the thickness of a brake pad, or the wear

in a bearing. Indirect information z on the other hand provides associated information

which is influenced by the component condition, but is not a direct measure of the failure

process, for example, an oil analysis or a vibration frequency analysis. In both cases, the

point of concern is to predict, given information z, the subsequent and conditional failure

time distribution as an input to modelling maintenance practice.

CM is accomplished by appropriate means available to an operator for finding and

resolving problem areas. These means range from notices of unusual problems to special

analysis of unit performance. All electronic components and most of the complex

electrical or mechanical units are normally part of the CM process.

Table1.1 summarises the overhaul control category, and Table 1.2 listing of primary

maintenance processes overhaul components.


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Category Maintenance Action Requirements / Restrictions

Hard-Time Overhaul/Replace item at specified time

interval.

Overhaul will ‘zero time’ the item.

On-Condition

- OC checks at specified time intervals.

- Regularly scheduled collection of OC data.

Overhaul required when item exceeds

specified limits for OC check or OC data.

- OC check must give reasonable

assurance of satisfactory operation

until the next check.

- OC data must ascertain continuing

airworthiness and/or show reliability

degradation – failure imminence.

Condition -

Monitoring (No

overhaul control)

- No scheduled overhaul or repair.

- Item is operated to failure.

- Failure must have no direct adverse

effect on flight safety.

- Hidden functions must have regularly

scheduled verification tests.

- Data collection / evaluation program

required for overhaul surveillance.

Table 1.1 - Overhaul control category summary.

1.3 The development of a Maintenance Steering Group, MSG

In mid-1968, representatives of various airlines developed the “Handbook MSG-1,

Maintenance Evaluation and Program Development,” which included decision logic and

inter-airline/manufacturer procedures for developing a maintenance program for Boeing

747 aircraft. It was subsequently decided that experience gained on the 747 project

should be applied to all newly developed aircraft. In order to do this, the decision logic

was updated and certain procedures specific to the 747 were deleted. That universal

document resulted in MSG-2. In mid-1979, the Air Transport Association, ATA, with the

intention of further updating procedures, formed a task force to analyse MSG-2 and make

recommendations for change and improvements. These revisions were published by the

ATA and approved by the FAA in late 1993 as an acceptable method for developing

scheduled maintenance requirements for new model transport-category aircraft. This is

known as MSG-3.

1.3.1 MSG-2 Decision Logic

Airline / Manufacturer Maintenance Program Planning Document MSG-2, dated March

25, 1970 shows in detail how the maintenance theory is being used to determine the


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essential scheduled maintenance requirements for a new airplane. Systems, components,

structures, and engines are put through the MSG-2 Decision Logic to find:

1. Which tasks can be done?

2. Which tasks must be done in order to prevent adverse effects on operating safety

and to assure the availability of hidden functions.

3. Which tasks should be done for economic value?

The final result is a list of preventive maintenance tasks divided into Hard-Time and On-

Condition tasks, and another list of those items that require no scheduled maintenance

and therefore included in the Condition-Monitoring process.

1.3.2 MSG-3 Decision Logic

Airline/Manufacturer Maintenance Program Planning Document MSG-3, dated October

1980 is the present day standard to determine the essential scheduled maintenance

requirements for new airplanes. MSG-3 includes detailed decision logic for assigning

tasks and task intervals to all aircraft systems and components.

Quite often, airlines operate a fleet of aircraft that are divided between both MSG-2 and

MSG-3 decision logic programs. Generally, all new aircraft manufactured today will

follow the MSG-3 concept in contrast to older aircraft continuing with the older

philosophy of MSG-2

Implementation of the recommendations generated through MSG-3 analysis is the major

role of an airline operator in developing a maintenance program. The accuracy and clarity

of the MSG-3 process provides a smooth transition for the airline to determine its

manpower, parts, tooling, ground equipment, and other related requirements. MSG-3 is

based on a consistent and rigorous application of questions for each aircraft component.

It is decision tree analysis at work. The first question MSG-3 asks is: “What’s the

consequence of a specific hardware/component failure for the entire aircraft?” Once this

consequence is assessed, MSG-3 offers a choice of applicable tasks and evaluates each

one’s effectiveness. Once a task is chosen, its frequency is patterned after frequencies

adopted for similar hardware. If no comparison can be made, a conservative frequency is

initially adopted and adjusted as experience is gained.


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This work resulted in the recognition of a third, primary maintenance process called

condition-monitoring, a process applying to components with specific design

characteristics but not involving hard-time or on-condition checks.

Task Descriptions

The MSG-3 assigned task categories are shown in Table 1.3 as follows:

Lubrication and Servicing To maintain the inherent design capabilities to reduce rate of

functional deterioration.

Operational Check Verification/Certification of operation which does not require

quantitative tolerances (acceptance).

Functional Check Verification of an item against quantitative standard within

specified limits.

Restoration

Replacement or restoration of an item to specified standard

on or off the aircraft by cleaning or up to overhaul. Item must

show functional degradation at an identifiable age of same

components.

Discard

Removal from service of an item at a specified life limit. The

item must show functional degradation at an identifiable age

and a large proportion of the units must survive to that age.

No-Task Items which have no safety effect. These items follow the

CONDITION-MONITORING logic per MSG-2

Combination

For items which functional failure has a safety effect. When

any of the previous tasks does not fulfill requirements, a

combination of tasks must be used in analyzing the proper

maintenance prerequisites.

Table 1.3 - The MSG-3 assigned task categories.

1.4 Aircraft Maintenance Scheduled Programs

After the MSG-2 & MSG-3 decision logic has been used to determine all preventive

maintenance tasks and their intervals, the maintenance program itself can be developed.

At this point it must be remembered that the maintenance requirements are only one of

several factors which shape the form of a maintenance program. Commercial,

operational, and economical needs must also be considered.


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The aircraft maintenance workload is generated through a continuous airworthiness

maintenance program. These programs include: aircraft inspections which deal with

routine inspection, minor services and tests performed on the aircraft at prescribed

intervals; scheduled maintenance that includes replacement of life-limited items, periodic

overhauls and special inspection, and unscheduled maintenance which is usually

generated by inspections, pilot reports and failure analysis.

In order to perform the maintenance work, production maintenance is organized into

three levels. The first level is the first line, which deals with inspection, testing and

minor maintenance tasks. The second line maintains major tasks, e.g. overhaul and

replacements of limited-life equipment. The third line or depot maintenance is used for

major jobs, which cannot be handled by the first and second lines.

The following sections show what can be considered the framework of a typical program

for an average airline.

1.4.1 Classes of Maintenance Stations

From the standpoint of the maintenance function, a major carrier normally divides its

many stations served into different classes of stations. For example, in descending order

of capability, they include:

1. Maintenance base

2. Major stations

3. Service stations

4. Other stations

Maintenance Base

Is generally conceded to be the largest, most adaptable (versatile), and best-equipped

facility in the system. It is the overhaul and modification centre for the carrier’s entire

fleet and it has the capability of repairing nearly all of the components. Few components

must be returned to the manufacturer or sent to outside agencies for reconditioning.

Major Stations

Include the carrier’s large hub cities. These stations have relatively large numbers of

maintenance people and extensive facilities. They also maintain the largest assignments

of spare parts, mainly supplied by the maintenance base. In general, these stations are


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capable of rendering complete line maintenance requirements of specific types of

equipment.

Service stations

Are large stations served by the carrier but not located at major hub cities with large

banks of connecting flights. These stations are well equipped and well staffed with line

maintenance personnel, but less so than the major stations.

Other stations

Throughout the system might be designated Class 1, Class 2 and Class 3.

Class 1 stations might have only sufficient numbers of licensed people to assure

maintenance coverage for each flight prior to departure. Minimal facilities and

spare parts for performing the assigned work would be provided.

Class 2 stations might have just enough mechanics and facilities to do routine

servicing, such as engine heating, de-icing, aircraft moving, and the lightest of

maintenance on specific equipment.

Class 3 stations might include smaller cities where there are no licensed

maintenance people. They are, therefore, never scheduled to perform

maintenance work and their aircraft servicing is limited to work that has no

effect upon airworthiness, mainly cargo and passenger handling. Ordinarily,

they deal only with through trips or turnaround flights.

1.4.2 Types of Maintenance

A carrier generally divides aircraft maintenance and servicing work into different levels

of inclusiveness and intensity. Arranged in ascending order, these might include en-route

service, terminating pre-flight check, service check, maintenance check, and overhaul.

Fuelling is a separate operation, and while it can be done at the time of a check, it is not a

part of the check.

Generally the headquarters staff controls the routing into stations for maintenance.

Engineering and maintenance, working with the local CAA/EASA, establishes the

frequencies and the content of the checks and overhauls.

i. En route service is performed whenever a flight operates through any of the

major, service, or Class 1 stations. It involves a visual check of the exterior

(external) with particular attention to indications of fuel or oil leaks and


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obvious discrepancies, such as worn or flat tires, low shock struts, or fuselage

or wing damage. It may also include interior and exterior cleaning, depending

upon need and available ground time.

ii. Terminating pre-flight checks are performed as scheduled when a flight

terminates at a major, service, or Class 1 station, at least every 24 hours. This

check encompasses the same work as en route service plus such additional

items as checking of engine oil supply; checking of engine inlet and exhaust

areas for signs of deterioration; checking of landing gear and tires (for wear,

inflations, fluid quantities, and so forth); checking of exterior lighting; and

checking and servicing of cabin water system, lavatories, oxygen systems,

flight recorder, and batteries and auxiliary power units, as necessary. This

check is a six-to-twelve-man-hour job, depending upon the type of aircraft.

iii. Service checks are performed at major, service, or designated Class 1 stations

(those that are qualified to handle them) at predetermined frequencies. The

stations performing this check must be approved by the EASA for the type of

aircraft involved. A service check might be performed after an aircraft logs

up to 150 hours’ flight time. A service check encompasses the items included

in the terminating pre-flight checks and en route service plus a considerable

volume of more intensive maintenance. This includes inspection and

servicing of cabin compressors, hydraulic units, seat installations, restroom

installation, buffet installations, cockpit equipment, interior lighting,

windows, and so forth. It also includes examination of certain structural

members, checking of fuel sumps1 for water or contamination, and any

special work that might be deemed necessary by the line service engineering

and line maintenance organization. A service check may require as much as

35 to 60 man-hours.

iv. A maintenance check is the most lavish attention an airplane gets between

overhauls. Each maintenance check requires a full day to complete and it

consumes from 400 man-hours on the smallest jet to 1,300 man-hours on the

biggest. It covers virtually every system and component of the aircraft.

Generally only the major stations are equipped to perform maintenance

1 a hole or container, especially in the lower part of an engine, into which a liquid that is not needed can flow


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checks. Maximum times between maintenance checks might be as high as

875 flight hours for a B-727 or 500 flight hours for a B-737. Maintenance

checks for each type of aircraft are planned so that the workload involved in

each particular check is about the same. The bulk of the jobs are repeated

during every check. Some, however, are required less frequently and thus are

scheduled only for certain checks.

1.4.3 Overhaul of Airframes

The basic document used in formulating the overhaul plan of a major carrier’s jet fleet is

the work report prepared by the engineering department for maintaining the structural

integrity of the particular aircraft. When this document is approved by the CAA/ EASA,

it becomes a part of the operations specifications, which detail the requirements for

continuous airworthiness. Compliance is not only desirable but also mandatory.

A separate work report covers the entire structure, the landing gear, and all control

surfaces of each jet aircraft type by zones. It spells out the kind of inspection each item is

to receive and designates the frequency or interval of inspections.

A carrier’s structural-integrity program thus provides the framework upon which each

airframe overhaul is constructed. Other jobs, some related, others not, constitute or

comprise the body of the overhaul.

1.4.4 Overhaul of Engines and Other Components

In general, overhauls of engines, their accessories, and other components are handled in

much the same manner. Components are brought in when either operating time or

condition requires it, and the overhaul returns them to specifications laid down by

engineering and the manufacturer. A large part of engine overhaul is made up of repair

and reconditioning operations, as it is usually beneficial, both economically and from the

standpoint of reliability, to reuse seasoned/tested components when they can be reworked

to approved specifications.

Scheduled engine changes are planned so as to minimize shipping costs and transit times

and avoid special routing of aircraft. All scheduled big-jet engine changes are handled at

the carrier’s major base, and all others at compromise locations where routing is

convenient and labour is available. When practical, engine changes are made during

maintenance check or airframe overhaul.


© A A Ghobbar 13

1.4.5 Type of Aircraft Overhaul Checks

To conform with CAA/ EASA guidelines, some companies have adopted maintenance

policies that call for routine inspections at least every four days. The first major check

(denoted as ‘A’ check), mandated by the CAA/ EASA, occurs every 200 flight hours, or

about once a week. ‘A’ checks involve a visual inspection of all major systems such as

landing gear, engines, and control surfaces. ‘B’ checks are performed every 600 to 1500

flight hours, and entail a thorough visual inspection plus lubrication of all moving parts

such as horizontal stabilizers and ailerons. ‘C’ and ‘D’ checks are done about once every

one to four years respectively, and require taking the aircraft out of service for up to a

month at a time.

There is no hierarchy of importance in maintenance checks. All tasks are important at

their interval or they would not be required. But there is a hierarchy of check frequency

and ground time. Starting with an “A” check, each higher check type demands more

ground time and is performed less frequently as shown on Table 1.4. Intervals and

ground time vary considerably depending on the type of aircraft and the type of

operations involved.

Interval Flight Hours Ground Time

“A” Check 200 to 500 8 to 16 Hours

“B” Check 600 to 1500 16 to 36 Hours

“C” Check 2000 to 5000 48 Hours and more

Table 1.4 - A, B, and C checks intervals.

"D" check or heavy maintenance visit; after a number of years of operation, some major

work needs to be done on transport aircraft. During a down time of anywhere from four

to eight weeks such major tasks as paint renewal, cabin refurbishment, control surface

removals, and internal structural inspections are performed. The total package is called a

“D Check” or if the package content is varying, a “Heavy maintenance Visit”.

1.4.6 Non-Routine Maintenance

There is rule-of-thumb which claims that each hour of routine maintenance generates one

hour of non-routine maintenance. While this is not always true, it is true enough to serve

as an indication of how many non-routine maintenance hours can normally be expected.


© A A Ghobbar 14

Non-routine maintenance results from malfunctions, pilot complaints, and maintenance

squawks/complain.

Aircraft modifications are another source of non-routine maintenance work. Depending

on the size and the urgency of the modifications they will be performed together with any

scheduled check or in some case during an extended special aircraft down time.

1.4.7 Maintenance Program Selection

The selection of the right maintenance program depends on the aircraft operations and

the maintenance manpower situation at hand. More specifically it can be said that the

following factors favour/help the selection of a program which consists of a small

number of large work packages:

1. Available spare aircraft.

2. Large number of aircraft participating in the program.

3. Non-scheduled operations.

4. High aircraft utilization.

5. Long range operations.

6. Variation in utilization varies with calendar seasons.

7. Maintenance work performed outside the airline.

8. Flexible manpower situation.

9. Single and centrally located maintenance base.

The other extreme – a large number of progressively performed small checks is favoured

by the following conditions:

1. No spare aircraft.

2. Small number aircraft participating in the program.

3. Scheduled operations.

4. Short-haul operations.

5. Low aircraft utilization.

6. Several locations available for performing maintenance work.

7. High cost of manpower necessitating manpower equalization.


© A A Ghobbar 15

Many airlines will find themselves with a mix of conditions that will pull their

maintenance programs away from the extremes towards the typical “A”, “B”, “C”, and

“D” Check programs. The final selection usually reflects one overriding priority – the

need for manpower equalization or the high cost of aircraft-out-of-service time.

1.4.8 Modification to Aircraft

'Modification' means the alteration of an aircraft/aircraft component in conformity with

an approved standard. Modifications are changes to aircraft and their equipment or

substitution of parts. All modifications affecting airworthiness must be approved by the

CAA/ EASA and must comply with EASA PART applicable at the time of original

certification. Modifications often involve design changes; aircraft operators possess

limited design authority, so the modification is usually devised by the manufacturer.

Nature of modifications

The European EASA classes modifications as either minor or major:

1. Minor modifications regarded by the EASA as relatively unimportant may be

designed, embodied and certified by an approved organisation or licensed aircraft

maintenance engineer. Minor modifications, which are more important, require

approval by the EASA directly or by an approved design organisation.

Modification approval requires a form detailing the modification, its applicability

and relevant drawings or specifications. A Civil Modification Record or work done

must be kept; the CAA/ EASA may inspect this as required.

2. Major modifications require a more extensive approval process by the

CAA/EASA including a Certificate of Design (Modification) and the issue of an

airworthiness approval note (AAN) by the CAA/ EASA. A civil modifications

record of these must also be kept.

Mandatory modifications of UK origin

Modifications considered essential to the airworthiness of the aircraft are classed as

Mandatory and identified by a CAA/ EASA Airworthiness Directive (AD) number.

Initial notification of the modification to all operators and maintenance organisations is

by a service bulletin (SB) or technical news sheet published by the approved

organisation. If higher priority is needed, publication by mail or similar means is used.


© A A Ghobbar 16

The CAA/ EASA then issues an emergency airworthiness directive to all operators of the

aircraft type and to CAA/ EASA Safety Regulation Group Area and Overseas Offices.

Mandatory modifications and inspections of foreign origin

For aircraft of foreign origin, modifications or inspections considered as mandatory by

their airworthiness authority are automatically classed as mandatory by the CAA/ EASA

for such aircraft operated in the UK, unless the CAA/ EASA specifically rules to the

contrary/opposite.

Modification record book

This must be kept and maintained for all UK registered aircraft over 2730 kg MTWA.

The owner/operator is responsible for keeping this up to date.

Mandatory reports

An operator or commander of every public transport aircraft registered in the UK who

makes, repairs or overhauls an aircraft, or who signs a certificate of maintenance review

or of release to service shall make a report to the CAA/ EASA of any incident, defect, or

malfunction to the aircraft or its equipment which would endanger the aircraft or its

occupants.

1.4.9 Contract Maintenance

Many of the newer carriers do not have a maintenance base capable of performing major

aircraft overhauls. Maintenance by their own personnel is often limited to en route

service and terminating pre-flight checks. All major maintenance is contracted with a

major or national carrier and performed at the latter’s maintenance base or at a major

station where equipment and personnel are available. Also, it is not uncommon for

carriers of all sizes to contract maintenance service work either with another carrier or

with a private maintenance firm at those stations that receive a limited number of flights.

Firms like Aircraft Services International provide minor maintenance services as well as

other functions, such as cleaning aircraft, baggage handling, and aircraft fuelling, at

small, medium, and large hubs for carriers with infrequent service.


© A A Ghobbar 17

Sub-contracting Maintenance

Many airlines contract out work which may be more economically performed either by

manufacturers, other airlines or overhaul agencies – since the capital investment in test

facilities, manpower and accommodation may not be justifiable within the airline for the

volume of components in the fleet and those held as spares. Equally, when justifiable,

airlines may set up such facilities as required, and perform the work for other airlines.

Contract and Pool Maintenance

Maintenance and pool contracts refer to agreements between airlines to do maintenance

for each other. Airlines with low frequency of flights into some of their stations should

consider contract or pool maintenance for these stations.

While the cost per maintenance man-hour and material will be higher for contracted

maintenance, the total direct maintenance cost per airplane flight hour may be lower.

This is especially true for smaller airlines and airlines with a lengthy / in-frequent route

structure.

Currently some airlines have agreements whereby one airline may do the entire engine

overhaul, another airline will overhaul most of the components and a third airline will

accomplish all the structural inspection. Extensive pooling of airplanes, engines and

component overhaul plus spares pooling is now accomplished by several groups of

airlines such as the ATLAS group (Alitalia, Tap, Lufthansa, Air France, and Swiss Air),

and the KSSU group (KLM, SAS, Swiss Air, UTA)

1.5 Aircraft Maintenance Certificates

The concept of Airworthiness, defined as “the continuing capability of the aircraft or

component part to perform in a satisfactory manner through a range of operations

determined by the CAA or FAA, and the flight operations for which it was designed”.

Each aircraft off the line receives an airworthiness certificate attesting to the fact that it

conforms to the type certificate and is safe to fly.

Before we start discussing those certificates, let's first review their authorities

The International Civil Aviation Organisation, ICAO

The Chicago Convention of 1944 set up ICAO, founded in 1947, to promote agreement

between nations in aviation. One of the ICAO functions is to promote international


© A A Ghobbar 18

standards and recommended practices for air safety; these are written in the Annexes to

the Convention. Annexe 8 covers Airworthiness of Aircraft, giving broad standards to be

enforced by national authorities.

The United Kingdom is a member of ICAO. The UK national authority for airworthiness

is the Civil Aviation Authority (CAA).

United Kingdom Civil Aviation Authority, CAA

- The CAA is responsible for the control of airworthiness for all aircraft registered

in the UK. During design and manufacture it monitors aircraft to ensure that they

comply with its regulations, and at the end of this process the aircraft type is

certificated for the appropriate use.

- ‘Continuing Airworthiness’ is the term used by the CAA to describe its activities,

which include the regulation of civil aircraft maintenance.

- There are six aircraft certification categories classified by UK CAA:

i. Transport Category (Passenger)

ii. Transport Category (Cargo)

iii. Aerial Work Category (includes balloons)

iv. Private Category

v. Special Category

vi. Permit to Fly

- ‘Permit to Fly’ aircraft are those not eligible for a normal C of A, and include

micro-lights, homebuilt and restored aircraft. Rules for their maintenance are

simplified, and renewal of permits is done either directly by the CAA or devolved

to a suitable volunteer organisation, such as the Popular Flying Association (PFA).

- Special Category aircraft are those not fully meeting current requirements, usually

prototypes.

- Private Category aircraft exceeding 2,730 kg (was 6,000 Ib) maximum total

weight authorised (MTWA) do not require an approved maintenance schedule;

these are usually business aircraft kept by large companies. Aircraft and


© A A Ghobbar 19

helicopters below 2,730 kg MTWA are covered by the light aircraft maintenance

schedule (LAMS); this is a simplified scheme with a three-year cycle.

- The CAA lays great stress on the need for adequate recording and analysis of work

done on aircraft, since it is through such data that the CAA can check the

adequacy of this work.

- Recording of maintenance work is required by law, so that accident investigation

may be carried out.

- The CAA receives all foreign manufacturers’ service bulletins (SBs), and reviews

the information to decide whether the classification is appropriate for aircraft on

the UK register.

Federal Aviation Administration, FAA

In April 1967, the Federal Aviation Agency became the Federal Aviation Administration

and was incorporated into the new Department of Transportation, which had been

established to give unity and direction to a coordinated national transportation system.

The FAA’s basic responsibilities remain unchanged, however. While working with other

administrations in the Department of Transportation in long-range transportation

planning, the FAA continues to concern itself primarily with the promotion and

regulation of civil aviation to ensure safe and orderly growth.

1.5.1 Certificate of Airworthiness, C of A

An aircraft must have a current C of A in order to fly; this is issued under the law of the

country in which the aircraft is registered. The UK C of A becomes invalid if the aircraft

is ‘repaired, replaced, removed, overhauled, or modified in manner not approved by the

CAA’, or ‘any inspection, or modification classified as mandatory by the CAA that

ensures the aircraft remains airworthy has not been carried out’. When the C of A is

issued, the category of use is also specified. For large civil aircraft this will normally be

Transport Category (Passenger) or Transport Category (Cargo); thus a cargo aircraft is

not allowed to carry passengers.


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1.5.2 The Air Operator’s Certificate, AOC

Aircraft registered in the UK must fly on public transport in accordance with the terms of

the Air Operator’s Certificate (AOC) granted by the CAA. This signifies that the holder

is considered to be ‘competent/capable to secure the safe operation’ of the specific

aircraft detailed on the AOC. For this purpose, the CAA evaluates the organisation, staff,

training, equipment and maintenance practices of the operator.

1.5.3 Certificate of Maintenance Review, CMR

Aircraft and their equipment registered in the UK for transport or aerial work must have

a valid certificate of maintenance review (CMR) which states the date on which the

review was carried out and the date on which the next review is due as specified in the

approved maintenance schedule (AMS) or associated approved document.

The certificate records the current maintenance status of the aircraft against the

maintenance schedule and any modifications or inspections required by the CAA. The

issue of certificates of release to service and all technical log defects, including the

rectification or deferment of these defects, are also noted.

The CMR does not have to coincide with any particular maintenance activity, but must

‘not exceed’ time limits for a review. These are specified in the AMS. The CMR as

issued should state the period of validity and include the signature of the person

authorised to issue the certificate.

1.5.4 Certificate of Release to Service, CRS

The ANO 1989 Article 11 requires that an aircraft registered in the UK and issued with a

C of A shall not fly without a certificate of release to service (CRS) being issued

following:

- Overhauls, repairs, replacements, modifications and mandatory inspections.

- Maintenance to the relevant AMS

- Work on radio equipment or survival craft done on the aircraft.

The CRS as issued must be signed in all the relevant work categories for the work done.

For a set of inspections or tests contained in a check specified in the AMS, a single CRS

is sufficient. Those signing must be satisfied that all work has been properly carried out

using the correct and up to date manuals, drawings, specifications, recommended tools

and test gear, and in a suitable working environment.


© A A Ghobbar 21

1.5.5 Authorised Release Certificate (Form EASA 1)

This is an internationally recognised import/export parts release document issued by

organisations specifically approved for the purpose. The certificate signifies that the part

has been manufactured or overhauled in compliance with the requirements and

specifications called for by the aircraft constructor. It is the duty of an operator to verify

that all parts received have the appropriate release documents.

1.5.6 Renewal of the Certificate of Airworthiness

The aircraft must have been maintained to an approved schedule. An inspection must be

carried out by a qualified person to determine the amount of work needed to ensure the

airworthiness of the aircraft. Checks must be made to ensure that it conforms to the Type

Certificate Data Sheet and the Flight Manual. Any mandatory modifications and

inspections as called for by the EASA must be carried out.

1.5.7 Certification of modifications

All modification incorporation work must be supervised either by an approved

organisation or by a licensed aircraft maintenance engineer in the appropriate category.

Before a certificate of release to service is issued, it should be confirmed that the correct

drawings and literature for the modification have been used and that the modification has

been correctly carried out, tested and inspected.

1.6 The Applications of Joint Aviation Requirements

1.6.1 Joint Aviation Authorities, EASA

The Joint Aviation Authorities (EASA) are an associated body of the European Civil

Aviation Conference (ECAC) representing the civil aviation regulatory authorities of a

number of European States who have agreed to co-operate in developing and

implementing common safety regulatory standards and procedures. This co-operation is

intended to provide high and consistent standards of safety and a “level playing-field” for

competition in Europe. Much emphasis is also placed on harmonising the EASA

regulations with those of the USA.


© A A Ghobbar 22

We used to be

JAR Joint Airworthiness Requirements

With an

AASC Airworthiness Authority Steering Committee

We are now


Producing

JAR Joint Aviation Requirements

With the idea of later becoming more integrated in a


1.6.2 Joint Aviation Requirements, JAR

- The Civil Airworthiness Authorities of certain European countries have agreed

common comprehensive and detailed airworthiness requirements (referred to as the

Joint Airworthiness Requirements, JAR) with a view to minimising Type

Certification problems on joint ventures, to facilitate the export and import of

aviation products, and make it easier for maintenance carried out in one European

country to be accepted by the Civil Aviation Authority in another European

country.

- A principal objective of the EASA is to develop and adopt Joint Aviation

Requirements (JAR’s) in the fields of aircraft design and manufacture, aircraft

operations and maintenance, and the licensing of aviation personnel. The eventual

aim is to produce a system in common with the USA FAR codes, so that national

variations in the certifying of new aircraft will disappear.

- Much of the stimulus for this is, of course, the Single European Act, which has

taken effect since 1993. This establishes the free movement within the EC of

goods, services, staff and capital. Thus aircraft and parts should be easily movable

for sale, lease and operation with no administrative burdens. Maintenance work

should be possible in any EC country; technicians, engineers and flight crew must

be able to transfer between countries.


© A A Ghobbar 23

- The Regulation section has technical study group to investigate into specific areas.

The Certification section has certification terms for each new aircraft type; these

also handle the continuing airworthiness of the type. Thus there are teams for new

types built and operated in Europe such as the A320, A330, A340, Do.328 etc., and

also for aircraft not built in Europe but operated on European registers, such as

Boeing 747-400, McDonnell Douglas MD-11, Boeing de Havilland Dash 8.

1.6.3 Operator’s Responsibility, EASA PART-OPS

Ensure the airworthiness of the aeroplane by:

- Accomplishment of pre-flight inspections

- Rectification to an approved standard of any defect and damage affecting safe

operation.

- All maintenance in accordance with approved programme.

- Analysis of the effectiveness of the maintenance.

- Accomplishment of operational or airworthiness directives and mandatory

requirements.

- Embodiment of modifications in accordance with an approved standard and for

non-mandatory modifications, the establishment of an embodiment policy.

- Ensure that the Certificate of Airworthiness for each aeroplane operated remains

valid.

1.6.4 Approved Maintenance Organisations, EASA PAR T-145

EASA PART-145 specifies the requirements for organisations that maintain

commercially used aircraft and components of such aircraft. Many maintenance

organisations have already obtained a EASA PART-145 approval from their local EASA

authority. Quite often this was not a simple process. The requirements are not always

clear and they need to be translated to the practical situation within the company. Also,

the requirements change regularly. Since the first publication in 1991, EASA PART-145

has been amended several times and new amendments are still issued. Therefore, up to

date knowledge of the EASA PART-145 requirements is and remains important (see

Figure 1.1).


© A A Ghobbar 24

Figure 1.1 - EASA PART Flowchart.

EASA PART 145.1 General

a. No aircraft when used for Commercial Air Transport may fly unless a

certificate of release to service has been issued by an organization for

maintenance carried out on the aircraft or an aircraft component intended for

fitment to such an aircraft.

b. No organization may certify for release to service an aircraft used for

Commercial Air Transport unless either approved in accordance with this

EASA PART-145.

c. No organization may certify for release to service an aircraft component

intended for fitment to an aircraft used for Commercial Air Transport unless

either approved in accordance with this EASA PART-145.

d. A maintenance organization approval may be granted for maintenance activity

varying from that for an aircraft component to that for a complete aircraft or

any combination thereof.

EASA PART 145.40 Equipment, tools and material

a. The EASA PART-145 approved maintenance organization must have the

necessary equipment, tools and material to perform the approved scope of

work.

b. Where necessary, tools, equipment and particularly test equipment must be

controlled and calibrated (the degree of quality or excellence of tools) to

standards acceptable to the EASA full member Authority at a frequency to

ensure serviceability and accuracy. Records of such calibrations and the

standard used must be kept by the EASA PART-145 approved maintenance

organization.


© A A Ghobbar 25

EASA PART 145.45 Maintenance data

When new types of aircraft are introduced, the manufacturer normally provides the

airline with initial provisioning data, IPD, e.g. advance spares provisioning list, ASPL,

recommended spares provisioning list, RSPL, and logistic planning document, LPD.

These references for initial provisioning usually indicate the main base float required to

maintain aircraft. The original equipment manufacturers, OEM, also provide overhaul

manuals for components fitted to the aircraft, which enable an assessment of the piece

parts required based on reliable information, and specified component operation and life

limits. The cost of operating older aircraft will continue to decline because parts

availability becomes greater and the price for those parts becomes less. The survey

results in Figure 1.2 showed the following courses of action taken:

● In most cases companies asked the manufacturer for initial provisioning data, IPD,

when new aircraft were introduced, or they used their own experience of previous

types of the same aircraft to calculate the quantity of parts required.

● As this question is more appropriate for airline operators than maintenance service

organizations 14% of those maintenance companies believed that this question did

not apply to their business, either because they carried out other operator's aircraft

maintenance, or because they believed the manufacturer's data was not reliable.

These companies did not operate flights or own their own fleet.

Figure 1.2 - Changing the fleet size or adding new type of aircraft.

55%

96%

22%

0%

34%

77%

13% 14%

0%

20%

40%

60%

80%

100%

120%

Experience of previous types Consultation withmanufacturer

Consultation with otheroperators

Not applicable

Course of Action

% O

f Res

pons

es

Airline Companies

Maintenance Organizations


© A A Ghobbar 26

The EASA PART-145 approved maintenance organization must hold and use applicable

current maintenance data in the performance of maintenance including modifications and

repairs. Applicable means relevant to any aircraft, aircraft component or process

specified in the EASA PART-145 approved maintenance organization’s approval class

rating schedule and any associated capability list. For the purposes of EASA PART-145

applicable maintenance data is;

1. Any applicable requirement, procedure, airworthiness directive,

operational directive or information issued by the EASA or EASA full

member Authority.

2. Any applicable airworthiness directive issued by a non-EASA

Authority or non-EASA full member Authority where said Authority

is the original type certificate Authority.

3. Any applicable data, such as but not limited to, maintenance and repair

manuals, issued by an organization under the approval of the EASA

full member Authority including type certificate and supplementary

type certificate holders and any other organization approved to publish

such data by the said Authority.

4. The EASA PART-145 approved maintenance organization must

establish procedures that ensure that if found, any inaccurate,

incomplete or ambiguous procedures, practices, information or

maintenance instructions contained in the maintenance data used by

maintenance personnel is recorded and notified to the author of the

maintenance data.

5. The EASA PART-145 approved maintenance organization must

ensure that maintenance data controlled by the organization is kept up

to date. In the case of operator/customer controlled and provided

maintenance data, the EASA PART-145 approved maintenance

organization must show that either it has written confirmation from the

operator/customer that all such maintenance data is up to date or it has

work orders specifying the amendment status of the maintenance data

to be used or it can show that it is on the operator/customer

maintenance data amendment list.


© A A Ghobbar 27

EASA PART 145.47 Production Planning

a. The EASA PART 145 approved maintenance organization must have a

system appropriate to the amount and complexity of work to plan the

availability of all necessary personnel, tools, equipment, material,

maintenance data and facilities in order to ensure the safe completion of the

maintenance work.

b. The planning of maintenance tasks, and the organizing of shifts, must take

into account human performance limitations.

c. When it is required to hand over the continuation or completion of a

maintenance action for reasons of a shift or personnel changeover, relevant

information must be adequately communicated between outgoing and

incoming personnel in accordance with a procedure acceptable to the EASA

full member Authority.

EASA PART 145.55 Maintenance records

a. The EASA PART-145 approved maintenance organization must record all

details of work carried out in a form acceptable to the EASA full member

Authority.

b. The EASA PART-145 approved maintenance organization must provide a

copy of each certificate of release to service to the aircraft operator, together

with a copy of any specific approved repair/modification data used for

repairs/modifications carried out.

c. The EASA PART-145 approved maintenance organization must retain a copy

of all detailed maintenance records and any associated maintenance data for

two years from the date the aircraft or aircraft component to which the work

relates was released from the EASA PART-145 approved maintenance

organization.

EASA PART 145.60 Occurrence reporting

a. The EASA PART–145 approved maintenance organization must report to [its'

EASA full member Authority and the organization responsible for the design

of the aircraft or aircraft component] any condition of the aircraft or aircraft

component, identified by the EASA PART–145 approved maintenance


© A A Ghobbar 28

organization that [has resulted or may result in an unsafe condition] that could

seriously hazard the aircraft.

b. The EASA PART-145 approved maintenance organization must establish an

internal occurrence reporting system acceptable to the EASA full member

Authority to enable the collection and evaluation of such reports including the

assessment and extraction/removal of those occurrences to be reported under

subparagraph (a) above. The procedure shall identify adverse trends,

corrective actions taken to address deficiencies and include evaluation of all

known relevant information relating to such occurrences and a method to

circulate the information as necessary.

EASA PART 145.85 Changes to the approved maintenance organization

The EASA PART-145 approved maintenance organization must notify the EASA full

member Authority of any proposal to carry out any of the following changes before such

changes take place to enable the EASA full member Authority to determine continued

compliance with this EASA PART-145 and to amend, if necessary, the approval

certificate, except that in the case of proposed changes in personnel not known to the

management beforehand, these changes must be notified at the earliest opportunity.

1. The name of the organization.

2. The location of the organization.

3. Additional locations of the organization.

4. The accountable manager. ('Accountable manager' means the manager

who has corporate authority for ensuring that all maintenance required

by the customer can be financed and carried out to the standard

required by the EASA full member Authority).

5. The facilities, equipment, tools, material, procedures, work scope and

certifying staff that could affect the approval.

1.6.5 Approved of Maintenance Training Organisatio ns, EASA PART-147

Purpose of EASA PART-147

To lay down the requirements for the approval of maintenance training organisations and

training.


© A A Ghobbar 29

EASA PART 147.1 General

a. This EASA PART–147 prescribes the requirements to be met by

organisations seeking approval to conduct approved training / examination of

certifying staff as specified in EASA PART–66.

b. Approved basic training is required by EASA PART–66 to qualify for the

maximum reduction in total maintenance experience specified in EASA

PART–66.

c. To qualify for the sub-paragraph (b) approved basic training the organisation

must be approved by a EASA full member Authority.

d. An organisation may not be approved to conduct only examinations.

EASA PART 147.15 Applicability

a. Maintenance training organizations located in EASA full member States may

be granted approval when in compliance with this EASA PART–147.

b. Maintenance training organizations located in a non-EASA full member State

or non-EASA member State may be granted approval if the EASA full

member Authorities are satisfied that there is a need for such approval.

EASA PART 147.30 Facility requirements

a. Facilities must be provided which ensure protection from the prevailing

weather elements and of overall size to cope with all planned training and

examination on any particular day.

b. Fully enclosed accommodation separate from other facilities must be provided

for the instruction of theory and the conduct of knowledge examinations as

necessary.

c. The sub-paragraph (b) accommodation environment must be maintained at a

light, noise and temperature/humidity level such that students are able to

concentrate on their studies or examination as appropriate, without undue

distraction or discomfort.

d. In the case of basic training course, basic training workshops and/or

maintenance facilities separate from training classrooms must be provided for

practical instruction appropriate to the planned training course, except that

arrangements may be made with another organisation to provide such

workshops and/or maintenance facilities. When another organisation is used

to provide workshops and/or maintenance facilities, a written agreement must


© A A Ghobbar 30

be made with such organisation specifying the conditions of access and use of

the basic maintenance workshops and/or maintenance facilities. The EASA

full member Authority and EASA standardization teams will require access to

any such contracted organisation and the written agreement must specify this

access.

e. Office accommodation must be provided for instructors, knowledge

examiners and practical assessors of a standard to ensure that they can prepare

for their duties without undue distraction or discomfort.

f. Secure storage facilities must be provided for examination papers and training

records. The storage environment must be such that documents remain in

good condition for the EASA PART–147.55 retention period. The storage

facilities and office accommodation may be combined subject to adequate

security.

g. A library must be provided containing all current technical material

appropriate to the scope and level of training undertaken.

EASA PART 147.35 Personnel requirements

a. The maintenance training organization must contract sufficient staff to

plan/perform knowledge and practical training, conduct knowledge

examinations and practical assessments in accordance with the approval,

except that when another organisation is used to provide practical training and

assessments, such other organisations’ staff may be nominated to carry out

practical training and assessments.

b. The experience and qualifications of instructors, knowledge examiners and

practical assessors must be established as being to a standard acceptable to the

EASA full member Authority.

EASA PART 147.40 Records of instructors, examiners and assessors

a. The maintenance training organization must maintain a record of all

instructors, knowledge examiners and practical assessors. These records

should reflect the experience and qualification, training history and any

subsequent training undertaken.

b. Terms of Reference must be drawn up for all instructors, knowledge

examiners and practical assessors. Any limitation of the scope of authority of


© A A Ghobbar 31

the individual, particularly those staff designated in EASA PART–147.35(b),

must be clearly indicated.

c. Instructors, knowledge examiners and practical assessors must be provided

with a copy of their Terms of Reference.

EASA PART 147.45 Instructional equipment

a. Each classroom must have sufficient presentation equipment of a standard that

ensures students can easily read presentation text/drawings/diagrams and

figures from any position in the classroom. Presentation equipment should

include representative synthetic (artificial, mock) training devices to assist

students understanding of the particular subject matter where such devices are

considered beneficial for such purposes.

b. The basic training workshops and/or maintenance facilities must have all tools

and equipment necessary to perform the approved scope of training.

c. The basic training workshops and/or maintenance facilities must have an

appropriate selection of aircraft, engines, aircraft parts and avionic equipment.

d. The aircraft type training facilities must have an example of the appropriate

aircraft type except that synthetic training devices may also be used when the

EASA full member Authority is satisfied that such synthetic training devices

ensure good training standards.

EASA PART 147.55 Records

The maintenance training organisation must keep all student training, examination and

assessment records for at least 5 years following completion of the particular student’s

course.

EASA PART 147.75 Changes to the EASA PART 147 approved maintenance

training organization

a. The EASA PART–147 approved maintenance training organisation must

notify the EASA full member Authority of any proposed changes to the

organisation that affect the approval before any such change takes place to

enable the EASA full member Authority to determine continued compliance

with this EASA PART–147 and to amend if necessary the approval

certificate.


© A A Ghobbar 32

b. The EASA full member Authority may prescribe the conditions under which

the EASA PART–147 approved maintenance training organization may

operate during such changes unless the EASA full member Authority

determines that the approval should be suspended.

c. Failure to inform the EASA full member Authority of such changes may

result in suspension or abolish of the approval certificate backdated to the

actual date of the changes.

EASA PART 147.105 Approved aircraft type/task training

Aircraft type training may be sub-divided in airframe type training, power-plant type

training, or avionic systems type training. A EASA PART-147 approved maintenance

training organization may be approved to conduct airframe type training only, power-

plant type training only or avionics systems type training, if acceptable to the Authority.

1.6.6 Approved of Certifying Staff EASA PART-66 (E ngineer Licensing)

EASA PART 66 is a new EASA rule introducing qualification requirements for

Certifying Staff. Certifying Staff are those personnel authorised to release an aircraft to

service after maintenance work in a EASA PART 145 Approved Maintenance

Organisation (AMO).

Licence Structure

EASA PART-66 is a harmonised set of requirements for the qualification of aircraft

maintenance staff by the issue of an Aircraft Maintenance Licence. Whilst this licence is

intended to be used as the basis for a EASA PART-145 Approved Maintenance

Organisation to issue a Certification Authorisation, the “basic” element of the licence

may be considered as providing a qualification in aircraft maintenance that demonstrates

the achievement of an underpinning level of knowledge and competence. EASA PART-

66 does not yet cover aircraft below 5700kg but it is intended that light aircraft will be

included eventually under Category B3.

The licence is divided broadly between Mechanical and Avionic trade disciplines

although in view of the various technologies and combinations applicable to certain

aircraft the Mechanical licence category is further subdivided. In addition there are

various levels within the licence, which allow the holder to be authorised to perform

certain roles within line and/or base maintenance. These reflect different levels of task


© A A Ghobbar 33

complexity and are supported by different standards of experience and knowledge. An

individual may hold a combination of licence categories. The three levels within the

licence are:

Category A Line Maintenance Certifying Mechanic

Category B1 Line Maintenance Certifying Technician (Mechanical)

Category B2 Line Maintenance Certifying Technician (Avionic)

Category C Base Maintenance Certifying Engineer

Category A is intended to be the basis for Limited Authorisations allowing an

experienced and knowledgeable mechanic to be authorised to certify certain simple

inspections and routine tasks. It is not intended that the Category A licence is used alone

to support line maintenance activities. The Category A licence does not carry any type

ratings but, following appropriate task training within a EASA PART-147 or EASA

PART-145 approved organisation, may be used as the basis for a certification

authorisation for certain prescribed tasks.

The Category A Licence is divided into sub-categories; however there is no avionic

specific sub category A since the majority of the tasks are either mechanical or electrical

in nature. Personnel who have either existing experience or are taking a course of

approved training which is of an avionic bias may still qualify for Category A in an

appropriate sub category subject to variations in experience or knowledge requirements

which apply in such cases. The sub categories for Category A - Line Maintenance

Certifying Mechanic are:

Sub category A1 - Aeroplanes Turbine

A2 - Aeroplanes Piston

A3 - Helicopters Turbine

A4 - Helicopters Piston

Category B will be the mainstay (foundation) licence qualification for aircraft

maintenance staff under the EASA PARTs. Category B licences are available in both

mechanical and avionic disciplines with sub categories as for Category A. Although

primarily for line maintenance use at Technician level, it is intended that certain base

maintenance staff who do not issue a Certificate of Release to Service, but who

contribute to the final CRS issue by the Category C engineer, will also be required to

hold a Category B1 or B2 licence.


© A A Ghobbar 34

The sub categories for Category B Line Maintenance Certifying Technician/Base

Maintenance Technician are:

Sub Category B1.1 - Aeroplanes Turbine

B1.2 - Aeroplanes Piston

B1.3 - Helicopters Turbine

B1.4 - Helicopters Piston

Category B2 - Avionics (no further sub division)

Category B1 is mechanically orientated and covers aircraft structure, airframe systems,

engines and propellers or rotors as appropriate. The licence holder will also be able to

certify all electrical work including power and distribution systems and control and

indication systems for systems within their privileges. Additionally a capability for

authorisation for the replacement of avionic line replaceable units may be held.

Category B2 is avionic biased, covering ATA Chapters 22 - Autoflight, 23 -

Communications, 31 - Instruments, 34 - Navigation and 45 - Central Maintenance

Computers and confers privileges similar to those of the mechanical technician to cover

electrical power and distribution and control and indication systems associated with

avionic systems.

Category C licence is considered more of a qualification related to the management of

maintenance during base maintenance. It is not a licence which allows the holder to

perform detailed inspections, diagnosis and replacements which collectively make up a

base maintenance input. The Category C certifier will be supported by appropriately

qualified B1 and B2 technicians who carry out these tasks and who verify and sign that

they have been completed properly. The Category C licence is intended to be used to

certify the process of maintenance, built upon the experience and knowledge of the

individual and their ability to manage the input. As such, the route to qualification may

be either from a mechanical or avionic background as a Category B1 or B2 licence holder

or the equivalent position in base maintenance, a base maintenance technician.

An alternative qualification path is available based on a qualification at degree level in an

appropriate discipline acceptable to the Authority. Acceptance will take into

consideration the university which issued the degree and the course content and may be

restricted to degrees issued within EASA member states. The degree by itself does not


© A A Ghobbar 35

meet the whole qualification as there are additional experience and examination

requirements to be satisfied. Graduates may not hold a Category B1 or B2 licence

without meeting the three years minimum maintenance experience required for that

Category.

Aircraft Type Endorsements

Holders of EASA PART-66 Aircraft Maintenance Licences in Category B1, B2 and C

may apply for inclusion or addition of an Aircraft Type Rating subject to meeting certain

requirements. These are the completion of a EASA PART-147 Approved Type Training

Course on that type, covering the subjects appropriate to the licence category being

endorsed and those topics listed in EASA PART-66.45. A minimum period of practical

experience is required on the aircraft type prior to application.

Logbooks and Records

Whilst not mandatory, the CAA advises all candidates to maintain log books or records

on a progressive basis to support any subsequent licence application. Entries should be

made periodically to show periods of work, the nature of the work, the aircraft type

involved and such records should be countersigned by a suitable referee who may be a

supervisor, quality manager or EASA PART-66 licence holder. For aircraft type ratings,

a record of the tasks undertaken on the type being applied for will allow the CAA to

consider the applicant’s practical experience in relation to the requirements of EASA

PART-66.45. The Authority may request details of a candidate’s experience for perusal.

International Developments

EASA PART 145 contains an exemption to the effect that certifying staff working in non

EASA based approved maintenance organisations will not be required to comply with

EASA PART 66. This exemption is based on the fact that it is impractical to impose a

complex standard like EASA PART 66, with all its social and educational implications

to countries who already have their own qualification system.

However, in order to ensure equivalent standards and fair competition, EASA PART 145

required the foreign EASA PART 145 organisations to demonstrate that their

qualification system is comparable to EASA PART 66. If it is not comparable, then the

EASA will impose and publish additional conditions to ensure equivalence.


© A A Ghobbar 36

It should be noted that an increasing number of non-EASA countries are adopting EASA

PART 66 as their national qualification standard for certifying staff. This of course will

facilitate the demonstration of equivalence.


© A A Ghobbar Page 36

Table 1.2 - A summary of KLM-uk workshop overhaul components.

# Component description Part

number

Aircraft

type

Quantity

per aircraft

Fleet

size

Maintenance

processes

Period

MTBO

Period

MTBR

Repair

TAT

Time

series

1 Air Conditioning Unit 2203480-2 Fokker 100 2 17 HT 2000 FHs 854 FHs 20 MHs 95 - 99

2 Alternator Unit No 406-3 Fokker 27 2 16 HT 2500 FHs 1250 FHs 20 MHs 92 - 94

3 Battery - Ultra pure 4078-8 Fokker 50 2 9 HT 1000 FHs 12 Weeks 5 MHs 95 - 00

4 Battery - distilled water 4608-1 Fokker 100 2 17 HT 1000 FHs 12 Weeks 5 MHs 94 - 00

5 Battery - Lead Acid 40678-2 ATR-72 1 5 HT 1000 FHs 12 Weeks 5 MHs 98 - 00

6 Brake Assembly (Heat Pack) AH 52220 Fokker 27 4 16 CM 750 FLs 700 FLs 20 MHs 89 - 95

7 Brake Assembly (Brake Unit) AH 52220 Fokker 27 4 16 CM 5000 FLs 1200 FLs 25 MHs 89 - 95

8 Brake Assembly Unit AHA 2174-5 BAe 146 4 13 HT 9600 FLs 1500 FLs 24 MHs 90 - 99

9 Brake Assembly Unit 5011809-2 Fokker 100 4 17 CM 2500 FLs 2500 FLs 24 MHs 94 - 99

10 Brake Assembly Unit 5007996-1 Fokker 50 4 9 HT 3600 FLs 1200 FLs 18 MHs 95 - 99

11 Brake Control Valve AC 61348 Fokker 27 2 16 HT 6600 FHs 3420 FHs 10 MHs 89 - 94

12 Combustion Chamber RK 49159A Fokker 27 2× 7 16 CM 1200 FHs 1200 FHs 28 MHs 92 - 95

13 DC Generator 30E02-21G1 Fokker 27 2 16 HT 2500 FHs 1104 FHs 28 MHs 92 - 94

14 Drag Strut Unit 200261001 Fokker 27 2 16 HT 12000 FLs 3620 FLs 30 MHs 89 - 94

15 Inverter Assembly 1518-8-C Fokker 27 2 16 HT 2700 FHs 617 FHs 17 MHs 92 - 94

16 Lock Strut Unit 200260001 Fokker 27 2 16 HT 12000 FLs 4510 FLs 45 MHs 89 - 94

17 Main Undercarriage Unit 200223001 Fokker 27 2 16 HT 12000 FLs 2882 FLs 250 MHs 89 - 94

18 Main Wheel Overhauled 5008131-5 Fokker 100 4 17 HT 2500 FLs 1007 FLs 12 MHs 92 - 00

19 Main Wheel Tyre Changed 5008131-5 Fokker 100 4 17 CM 500 FLs 226 FLs 11 MHs 92 - 00

20 Main Wheel Overhauled 5007995-1 Fokker 50 4 9 HT 3500 FLs 1516 FLs 7 3/4 MHs 95 - 00

21 Main Wheel Tyre Changed 5007995-1 Fokker 50 4 9 CM 700 FLs 316 FLs 4 3/4 MHs 95 - 00

22 Main Wheel Overhauled AHA 1489 BAe 146 4 13 HT 1600 FLs 1245 FLs 10 MHs 90 - 00

23 Main Wheel Tyre Changed AHA 1489 BAe 146 4 13 CM 400 FLs 229* FLs 4 MHs 90 - 00

24 Main Wheel Overhauled AHA 1890 ATR-72 4 5 HT 1800 FLs 1600 FLs 6 MHs 98 - 99

25 Main Wheel Tyre Changed AHA 1890 ATR-72 4 5 CM 450 FLs 133 FLs 6 MHs 98 - 00

26 Maxaret Anti Skid Unit AC 63538 Fokker 27 2× 2 16 HT 4000 FLs 4000 FLs 16 MHs 89 - 94

27 Nose Undercarriage Unit 200490001 Fokker 27 1 16 HT 12000 FLs 3588 FLs 250 MHs 89 - 94

28 Nose Undercarriage Unit 201071001-3 Fokker 100 1 17 HT 20000 FLs 11495 FLs 220 MHs 96 - 00

29 Nose Wheel Overhauled 5008133-1 Fokker 100 2 17 HT 1250 FLs 1000 FLs 4.5 MHs 93 - 00

30 Nose Wheel Tyre Changed 5008133-1 Fokker 100 2 17 CM 250 FLs 122 FLs 3.5 MHs 93 - 00

31 Nose Wheel Overhauled 5007998 Fokker 50 2 9 HT 2500 FLs 906* FLs 3.5 MHs 95 - 00

32 Nose Wheel Tyre Changed 5007998 Fokker 50 2 9 CM 500 FLs 232 FLs 2.5 MHs 95 - 00

33 Nose Wheel Overhauled AHA 1349 BAe 146 2 13 HT 1100 FLs 1100 FLs 5 MHs 90 - 00

34 Nose Wheel Tyre Changed AHA 1349 BAe 146 2 13 CM 275 FLs 161 FLs 2 MHs 90 - 00

35 Nose Wheel Overhauled AH 54474 ATR-72 2 5 HT 1200 FLs 527 FLs 6 MHs 98 - 00

36 Nose Wheel Tyre Changed AH 54474 ATR-72 2 5 CM 300 FLs 135 FLs 3 MHs 98 - 00

HT, hard time; CM, condition monitored; FHs, flying hours; FLs, flying landings; MHs, man-hours; TAT, turn around time.

* Overhaul at every 5th tyre change; MTBO, mean time between overhaul; MTBR, mean time between removals.

AMO Chapter 1

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