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Notion Press
Old No. 38, New No. 6

McNichols Road, Chetpet
Chennai - 600 031
First Published by Notion Press 2016

Copyright © Haguma Timothee 2016
All Rights Reserved.
ISBN 978-1945825-99-6
This book has been published with all efforts taken to make the material error-free after the
consent of the author. However, the author and the publisher do not assume and hereby disclaim
any liability to any party for any loss, damage, or disruption caused by errors or omissions, whether
such errors or omissions result from negligence, accident, or any other cause.
No part of this book may be used, reproduced in any manner whatsoever without written permission
from the author, except in the case of brief quotations embodied in critical articles and reviews.
Contents
Preface ix
Abstract xi
1. BASICS OF AIRCRAFT MAINTENANCE MANAGEMENT 1

1.0. INTRODUCTION 1
1.1. ROLE OF ENGINEER 2
1.2. ROLE OF THE MECHANIC 2
1.3. TWO TYPES OF MAINTENANCE 3
1.4. KEY CONCEPTS 3
1.5. ESTABLISHING A MAINTENANCE PROGRAM 4
1.6. DEVELOPMENT OF MAINTENANCE PROGRAMS 6
1. On-condition maintenance 8
2. Condition Monitoring 9
3. Hard Time Process 10
1.7. GOALS OF MAINTENANCE 17
1.8. MAINTENANCE PROGRAM CONTENT 19
1.9. OBJECTIVES OF MAINTENANCE 19
1.10. AVIATION INDUSTRY CERTIFICATION REQUIREMENTS 21
1. Type Certificate 21
2. Operator’s Certificate 22
3. A Certificate of Airworthiness 23
4. Production Certificate 23
1.11. AVIATION INDUSTRY INTERACTION 24
Conclusion 25
2. DOCUMENTATION AND TECHNICAL DIRECTORATES 26

2.0. INTRODUCTION 26
2.1. DOCUMENTATION FOR MAINTENANCE 26
2.1.0. Types of Documentation 27
Contents
2.1.1. Manufacturer’s documentation 27

2.1.2. Regulatory Documentation 30
2.1.3. Airline Generated Documentation 31
2.2. ATA DOCUMENTS STANDARDS 33
2.3. REQUIREMENTS FOR MAINTENANCE PROGRAM 35
2.4. SUMMARY OF FAA REQUIREMENTS 41
2.5. ADDITIONAL MAINTENANCE PROGRAM REQUIREMENTS 42
2.6. THE MAINTENANCE AND ENGINEERING ORGANIZATION 44
2.6.1. Maintenance Engineering Organization chart 45
2.6.2. General Groupings 45
2.6.3. Manager Level Functions 47
A. Technical services Directorates 47
B. Aircraft Maintenance Directorate 50
C. Shop Maintenance Directorate 51
D. Material Directorate 52
E. Maintenance program evaluation department 53
2.7. TECHNICAL SERVICES 55
2.8. ORGANIZATIONAL STRUCTURE AND THE TECHNICAL POLICIES AND
PROCEDURES MANUAL 57
2.9. ENGINEERING ORDERS PREPARATION 60
Conclusion 61
3. PRODUCTION PLANNING AND TECHNICAL TRAINING 62

3.1. PRODUCTION PLANNING AND CONTROL 62
3.1.1. Forecasting 63
3.1.2. Production Planning 64
3.1.3. Production Control 67
3.1.4. Feedback for Planning 69
3.1.5. Organization of Production Planning and Control 69
3.2. TECHNICAL PUBLICATIONS 69
3.2.1. Functions of Technical Publications 70
3.2.2. Airline Libraries 73
3.2.3. Control of Publications 73
3.2.4. Document Distribution 74
3.3. TECHNICAL TRAINING 74
3.3.1. Training organization 75
vi
Contents
3.3.2. Training for Aviation Maintenance 75

3.3.3. Maintenance Resources Management 77
3.3.4. Airframe Manufacturer’s Training Courses 78
3.3.5. Airline Training Courses 79
3.3.6. Computer Support 80
3.3.7. Computer program Modules 82
3.3.8. Selecting a Computer System 83
Conclusion 84
4. MAINTENANCE ACTIVITIES AND TECHNICAL SHOPS 85

4.1. LINE MAINTENANCE ON AIRCRAFT 85
4.2. MAKEUP OF LINE 86
4.3. FUNCTIONS OF CONTROL MAINTENANCE 86
4.4. LINE MAINTENANCE OPERATIONS 90
4.5. AIRCRAFT LOGBOOK 91
4.6. RAMP AND TERMINAL OPERATIONS 92
4.7. OTHER LINE MAINTENANCE ACTIVITIES 94
4.8. LINE STATION ACTIVITIES 95
4.9. MAINTENANCE CREW SKILLS REQUIREMENTS 95
4.10. MORNING MEETING 96
4.11. HANGAR MAINTENANCE ON AIRCRAFT 96
4.11.1. Introduction 96
4.11.2. Organisation of Hangar Maintenance in Space Requirements 98
4.11.3. Maintenance Support Shops 103
4.11.4. Ground Support Equipment 103
4.11.5. Hangar Maintenance Activity-A Typical “C” check 104
4.12. MAINTENANCE AND OVERHAUL SHOPS (OFF -AIRCRAFT) 106
4.12.1. Types of Shops 107
4.12.2. Operations of overhaul shops 109
4.12.3. Shop Data Collection 109
4.13. MATERIEL SUPPORT 110
4.13.1. Organization and function of materiel: The Materiel Directorate 110
4.14. MAINTENANCE AND ENGINEERING (M&E) SUPPORT MATERIEL 112
Conclusion 113
vii
Contents
5. QUALITY ASSURANCE AND MAINTENANCE SAFETY

REGULATIONS 114
5.1. REQUIREMENT FOR QUALITY ASSURANCE (QA) 115
5.1.1. Quality Audits 119
5.1.2. ISO 9000 Quality Standards 124
5.1.3. Technical Records 125
5.1.4. Main Functions of Quality Assurance 126
5.2. QUALITY CONTROL 127
5.2.2. Quality control organization 127
5.2.3. Quality Control Inspector’s Qualifications 128
5.2.4. Basic inspection policies 129
5.2.5. Difference between FAA, CAA, ICAO, EASA and JAA 130
5.3. RELIABILITY 132
5.3.2. Definition of reliability 133
5.3.3. Types of reliability 133
5.3.4. Aircraft Reliability Program 134
5.3.5. Administration and management of risk 138
5.4. MAINTENANCE SAFETY 139
5.4.1. Industrial Safety 140
5.4.2. Safety Regulations 141
5.4.3. Maintenance Safety Program 142
5.4.4. General Responsibilities for Safety 143
5.4.5. General Safety Rules 145
5.4.6. Accident and Injury Reporting 147
Conclusion 148
Bibliography 149
List of Abbreviations 155
viii
Chapter 1
Basics of Aircraft Maintenance Management
1.0. INTRODUCTION
Maintenance of aircraft is a comprehensive, on-going process. The entire aircraft needs
to be examined, maintained, and have the necessary parts replaced to uphold the safety
standards mandated by the Federal Aviation Administration. Aircraft are required to be
maintained after a certain period of calendar time or flight hours or flight cycles.
This chapter will deal with some of the routine maintenance tasks performed by an
Aircraft Maintenance Team including cleaning aircraft and components, application
of corrosion prevention compound, lubricating parts, draining and troubleshooting
fuel systems, checking and servicing hydraulic and pneumatic systems, replacing
components, inspecting for general wear and tear.
Aircraft maintenance is a newer field of working in avionics, which deals with
electronic systems. These parts are vital for navigation and communications, and
include radar, instruments, computer systems, radio communications, and global
position systems (GPS).A strong knowledge of wiring and technical skills is required for
working in avionics maintenance.
Definition of and reasons of Maintenance setups

Aircraft maintenance is defined as the overhaul, repair, inspection or modification of
an aircraft or aircraft component. Maintenance may include such tasks as ensuring
compliance with Airworthiness Directives or Service Bulletins. The maintenance of
aircraft is highly regulated, in order to ensure safe and correct functioning during flight.
National regulations are coordinated under international standards, maintained by
bodies such as the International Civil Aviation Organization (ICAO). The maintenance
tasks, personnel and inspections are all tightly regulated and staff must be licensed for
the tasks they carry out.
According to Harry A. Kinnson, (2012), the industry definition of maintenance
generally includes those tasks required to restore or maintain an aircraft’s systems,
components, and structures in an airworthy condition.
Maintenance is required for three principal reasons:
i. Operational to keep the aircraft in a serviceable and reliable condition so as to
generate revenue.
ii. Value Retention: To maintain the current and future value of the aircraft by
minimizing the physical deterioration of the aircraft throughout its life.
Fundamentals of Aircraft Maintenance Management
iii. Regulatory Requirements: The condition and the maintenance of aircraft are
regulated by the aviation authorities of the jurisdiction in which the aircraft is
registered.
Such requirements establish standards for repair, periodic overhauls, and alteration
by requiring that the owner or operator establish an airworthiness maintenance and
inspection program to be carried out by certified individuals qualified to issue an
airworthiness certificate (Civil aviation department Hong Kong, 2014).
Historically in the early days of aviation, owners and engineers concerning with
in-flight failures and component reliability developed maintenance Schedules to help
prevent costly occurrences. As aviation grew and scheduled air transport arrived,
safety, reliability and economics became important in order to attract passengers. It
became apparent that to achieve a controlled balance between safety and economics,
Regulatory Authorities needed to ensure minimum standards were maintained and a
level playing field existed for fair competition between operators.
What to maintain, when to maintain and how to maintain, are the keys to the
content of the Maintenance Schedules and a system was developed for Operators,
Manufacturers and Regulators to share experience and knowledge on these very issues
for new aircraft being developed. Some Commercial Air Transport operators may choose
to maintain their aircraft in accordance with a Maintenance Programme. This is a ‘real
time system’ which consists of a Maintenance Schedule and a whole group of review
and management procedures to ensure that it remains realistic and effective.
1.1. ROLE OF ENGINEER

One of the first sources of confusion, particularly among those who are not engineers
or scientists, is the distinction between science and engineering. The primary role
of science is to develop knowledge and understanding of the physical universe. An
important distinction is that this pursuit of knowledge may occur largely without
regard to societal need or to societal implications. The direction of scientific research
has been described by some as curiosity-based research which is not necessarily driven
by the values of society. Societal values resulting priorities do not necessarily define
the bounds, direction or scope of scientific curiosity. This is not a criticism of science,
for such is the nature of “inquiring.” Furthermore, it is often not possible to determine
relevance of a particular field of scientific inquiry to the future needs of society.
Role of engineer occurs in reduction of entropy, when the designer has produced
what he or she believes is the optimum system when the boss, who is responsible
for budget asks, “how much will it cost to build this?” The designer has meticulously
calculated these widgets can be mass produced for $ 1230 each “Great he says boss.”
Now redesign it so we can build it for under a thousand dollars, that means redesign
usually with reduced tolerance, cheaper materials, and unfortunately more entropy,
more entropy translates it into maintenance required, the designing engineer’s primary
concern ,then is to minimize the entropy of the system.
1.2. ROLE OF THE MECHANIC

The mechanic such as technician, repairer, or maintainer, on the other hand, has a
different problem. One important point to understand is that entropy not only exists
in a very system, the entropy of a system is always increasing .That means that the
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design-in level of perfection will not be permanent. Some components will deteriorate
from the use and some will deteriorate from lack of use. Misuse by operator or user may
also cause some premature deterioration or degradation of the system or even out right
damage .This deterioration or degradation of the system represents an increase in total
entropy of the system .Therefore, while the engineer’s job is to minimize the entropy
of the system during design, the mechanic’s job is to combat the natural, continual
increase in the entropy of the system during its operational lifetime.
It is the engineer’s responsibility to design the system which as high a degree of
perfection as possible within reasonable limits. The mechanic responsibility, on the
other hand, is to combat the continual increase in entropy during the operational
lifetime of the equipment.
1.3. TWO TYPES OF MAINTENANCE

i. Unscheduled maintenance: This element provides procedures, instructions, and
standards for the accomplishment of maintenance tasks generated by the inspection
and scheduled maintenance elements, pilot reports, failure analyses, or other
indications of a need for maintenance. Procedures for reporting, recording, and
processing inspection findings, operational malfunctions, or abnormal operations
such as hard landings, are an essential part of this element. A continuous aircraft
logbook can serve this purpose for occurrences and resultant corrective action
between scheduled inspections. Inspection discrepancy forms are usually used
for processing unscheduled maintenance tasks in conjunction with scheduled
inspections. Instructions and standards for unscheduled maintenance are normally
provided by the operator’s technical manuals.
The procedures to be followed in using these manuals and for recording and certifying
unscheduled maintenance are included in the operator’s procedural manual (civil
aviation requirements,1992).
ii. Scheduled Maintenance: This element concerns maintenance task performed at
prescribed intervals. Some accomplish concurrently with inspection task that are
apart from the inspection elements and may be included in the same schedule. Other
tasks are performed independently. The scheduled tasks include replacement of
life limited items, components requiring replacement for periodic overhaul, special
inspections such as X-rays, checks or tests on condition items etc. Special work
forms can be provided for accomplishing these tasks or they can be specified by a
work order or some other documents.
1.4. KEY CONCEPTS

The field of Aircraft Maintenance Management has enormous key concepts to be
elaborated as below:
i. Reliability
The level of perfection can also be referred to as the reliability of the system. The
designed in level of perfection is known as the inherent reliability of that system. This
as good as the system gets during real world operation. No amount of maintenance
can be performed to increase the system reliability any higher than this inherent
level. However it is desirable for the operator to maintain this level of reliability at
all times.
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ii. Redesign
The system can be designed to higher level of perfection that is a higher level of
reliability with a corresponding decrease in total entropy. During this redesign, new
components, new materials, or new techniques may have been used to reduce the
natural entropy of the system. In some cases a reduction in man-made entropy may
result because the designer applied tighter tolerances attained improved design
skills or changed the design philosophy.
Although the designers have reduced entropy of the system, the system will
deteriorate. It is quite possible that the rate of deterioration will change from the
origin design depending upon numerous factors, thus, the slope of the curve
may increase, decrease or stay the same. Whichever is the case the maintenance
requirements of the system could be affected in some way. At a given point in time,
a component or system is either functioning or it has failed, and that the component
or system operating state changes as time evolves. A working component or system
will eventually fail. The failed state will continue forever, if the component or system
is non-repairable. A repairable component or system will remain in the failed state
for a period of time while it is being repaired and then transcends back to the
functioning state when the repair is completed.
This transition is assumed to be instantaneous. The change from a functioning
to a failed state is failure while the change from a failure to a functioning state is
referred to as repair. It is also assumed that repairs bring the component or system
back to an “as good as new” condition. This cycle continues with the repair-to failure
and the failure-to-repair process; and then, repeats over and over for a repairable
system.
iii. Failure Rate Patterns
There are three patterns of failures for non-repairable items, which can change with
time. The failure rate or hazard rate may be decreasing, increasing or constant.
a. Decreasing Failure Rate or Non-repairable Items
A decreasing failure rate (DFR) can be caused by an item, which becomes less
likely to fail as the survival time increases; this is demonstrated by electronic
equipment during their early life or the burn-in period. This is demonstrated
by the first half of the traditional bath tub curve for electronic components or
equipment where failure rate is decreasing during the early life period.
b. Constant Failure Rate or Non-repairable Items
A constant failure rate (CFR) can be caused by the application of loads at a
constant average rate in excess of the design specifications or strength. These
are typically externally induced failures.
c. Increasing Failure Rate or Non-repairable Items
An increasing failure rate (IFR) can be caused by material fatigue or by strength
deterioration due to cyclic loading. Its failure mode does not accrue for a finite
time, and then exhibits an increasing probability of occurrence.
1.5. ESTABLISHING A MAINTENANCE PROGRAM

A maintenance program combines the maintenance and inspection functions used to
fulfill an operator/applicant’s total maintenance needs. A state’s regulations normally
4
require that an operator must have a maintenance program adequate to perform the
work and qualified competent persons to certify the maintenance and to monitor
performance.
Terminologies
i. Airworthiness: A condition in which the aircraft, airframe, engine, propeller,
accessories, and components meet their type design and are in a condition for safe
operation.
ii. Inspection: The routine performance of inspection tasks at prescribed intervals.
The inspection must ensure the airworthiness of an aircraft, up to and including its
overhaul or life-limits.
iii. Scheduled (routine) maintenance: The performance of maintenance tasks at
prescribed intervals.
iv. Unscheduled (Non-routine) Maintenance: The performance of maintenance tasks
when mechanical irregularities occur. These irregularities are categorized as to
whether or not they occur during flight time.
v. Structural Inspection: A detailed inspection of the airframe structure that may
require special inspection techniques to determine the continuous integrity of the
airframe and its related parts.
vi. Program Requirements: Basic requirements of a maintenance program which will,
include the following:
1. Inspection
2. Scheduled Maintenance
3. Unscheduled Maintenance
4. Overhaul and Repair
5. Structural Inspection
vii. Manuals: Instructions and standards for unscheduled maintenance should be in the
operator or applicant’s technical manuals. The manuals must contain procedures to
be followed when using these manuals and recording scheduled and unscheduled
maintenance.
viii.Approval: Maintenance programs are approved by issue of ‘operations specifications’
or by direct approval of the Maintenance program document. The approved
document should describe the scope of the program and reference manuals and
other technical data. Details of the program must also be included in the operator/
applicant’s manual.
ix. Operator or Applicant’s Organization: The operator/applicant must have an
organization adequate to carry out the provisions of the maintenance program. If
the work is to be performed outside of the operator/applicant’s organization, the
contractor must meet the same requirements. In determining the adequacy of the
organization, the following must be considered:
1. The complexity of the organization
2. The aircraft
3. The experience of the personnel
4. The number of personnel
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1.6. DEVELOPMENT OF MAINTENANCE PROGRAMS

a. Introduction: Maintenance is as old as the world. From the ancient times every
industry has to survive by maintaining its equipment in proper conditions. Under
the economic pressure most airlines currently experiences, there is no margin to
do too much or not enough of maintenance. Customers’ demands high regularity,
punctuality and safety. It is all about finding a balance in the maintenance program
to be able to control costs and to deliver what the customers expect. To actively
work with the maintenance program and to continuously evaluate the same is of
these reasons utterly important.
b. Maintenance Program History: In the early days of aviation maintenance programs
were developed primarily by pilots and mechanics. They assessed an aircraft’s needs
for maintenance based on their individual experiences and created programs that
were simple and devoid of analysis.
The introduction of the airlines as a new method of transport demanded new
regulations and broader involvement of the Regulatory Authorities in maintenance
requirements. During this era not only were regulations put in place but programs
were started to monitor reliability and safety.
The entry of the large jet aircraft B707 and DC-8 (DC-8 also known as the
McDonnell Douglas DC-8) in the fifties focused public attention on the need for
safer and more reliable aircraft. The aircraft manufacturer became the source
of maintenance program development. Time limitations were established for
maintenance and the entire aircraft was periodically disassembled, overhauled, and
reassembled in an effort to maintain the highest level of safety. This was the origin
of the first primary maintenance process referred.
c. Maintenance Steering Group (MSG) Approach: In 1968 the Maintenance Steering
Group (MSG) was created with a mandate to formulate decision logic process used
for development of the initial scheduled maintenance requirements for new aircraft.
The group was composed of participants from various aviation bodies, including
the Air Transport Association (ATA), airlines, aircraft manufacturers, suppliers, and
Federal Aviation Administration (FAA) representatives.
That same year representatives of the steering group developed “MSG-1 -
Maintenance Evaluation and Program Development”, which for the first time used
a decision-logic diagram to develop the scheduled maintenance program for the
new Boeing 747 aircraft. Both hard-time and on-condition processes were used for
development of the aircraft’s routine maintenance tasks. In 1970, MSG-1 is updated
to MSG-2 to make it applicable for later generation aircraft (L 1011 and DC-10), and
at the same time the methodology introduces a third primary maintenance process
defined as Condition-Monitoring (CM). Under Condition-Monitoring no services
or inspections are scheduled to determine integrity or serviceability, however the
mechanical performance is monitored and analysed. For example, a given operating
characteristic of the equipment is trended and compared with known “normal”
operating levels. An acceptable range is established with either upper and/or lower
limits, or some maximum or minimum level. As long as the trend data remain inside
the acceptable level, any variation is considered to be normal. When the trend line
intersects the “unacceptable” limit, removal of the unit is required to prevent a
failure in the future.
6
A characteristic of Condition-Monitoring is that it is not considered a preventive

maintenance process; the process allows failures to occur, and the failure modes of
conditioned-monitored items are considered not to have a direct adverse effect on
operating safety.MSG-2 decision logic was subsequently used to develop scheduled
maintenance programs for the aircraft of the 1970s. Maintenance tasks were derived
from one of three processes:
1. Hard-Time,
2. On-Condition,
3. Condition-Monitoring or some combination of the three Processes.
In 1979 the Air Transport Association (ATA) task force sought to improve on
MSG-2 to address a new generation of advanced technology aircraft (B757 & B767).
Additionally, the task force identified a number of shortcomings in MSG-2 decision
logic, key among them: MSG-2 did not differentiate between maintenance being
done for safety reasons versus economic reasons.
An MSG-2 program became very unwieldy and difficult to manage because it
required so many components to be individually tracked. MSG-2 did not effectively
deal with the increased complexity of aircraft systems. MSG-2 did not address
regulations related to damage tolerance and fatigue evaluation of structures; these
are currently accounted for in Corrosion Prevention and Control Programs (CPCP)
and requirements mandated through an Aging Aircraft maintenance program.
The work of the Air Transport Association of America (ATA) task force led to the
development of a new, task-oriented, maintenance process defined as MSG-3. The
process adopted a decision tree methodology with the primary purpose of:
a. Separating safety-related items from economic.
b. Defining adequate treatment of hidden functional failures.
Under MSG-3 logic, activities are assessed at the system level rather than the
component level .In other words, if it can be demonstrated that the functional failure
of a particular system had no effect on operational safety, or that the economic
repercussions were not significant, there was no need for a routine maintenance
activity. Although there is no actual in-service operational data available when
the MSG-3 process begins for a new aircraft, there is much historical data on the
performance of similar components and systems used in earlier designs, as well as
test data from the manufacturer and component vendors. It’s the actual in-service
reliability data of similar components and systems that drives the task and interval
decisions. Another principal benefit from the MSG-3 process is that it generally
produces higher safety standards. This is primarily due to the greater degree of
intelligent approach to maintenance in terms of selecting tasks that are effective.
The approach results in far less maintenance tasks, which minimizes the infant
mortality effect associated with excessive maintenance.
Studies in Human Factors clearly identified correlation between excessive
maintenance and induced incidents, or accidents, resulting from preventive
maintenance through replacement and overhaul of components (Mr. Shannon P.
Ackert, 2010)
Today, MSG-3 is the only game in town for commercial airplane manufacturers.
According to Advisory Circular AC-121-22A, FAA policy states that the latest
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MSG analysis procedures must be used for the development of routine scheduled
maintenance tasks for all new or derivative aircraft. It is the only methodology
accepted by the airworthiness authorities. MSG-3 has also been adopted by most
major business jet manufacturers, with the encouragement of the National Business
Aviation Association (NBAA).
Drawbacks of MGS-2
i. Does not take the economic view into the considerations. Simply maintains
aircraft safety at any cost
ii. Does not treat hidden failures to pilots: electric and electronic failures, fatigue
inside the structure, etc.
iii. Is a bottom-up approach requiring more staff
iv. The definitions in MSG-2 contradicts themselves
v. Does not take the modern corrosion prevention approach into account
Advantages of MSG-3
i. Top-down process
ii. Reduced maintenance costs
iii. Fewer maintenance tasks
iv. Some tasks are carried out for economic reasons and others for safety reasons
v. Eliminates emotions
d. Process Oriented Maintenance
The process oriented maintenance is developed for aviation using decision logic
procedures developed by air transport association of America. The maintenance
steering group (MSG-2) process is bottom up approach whereby each unit (system,
component or appliance) on the aircraft is analysed and assigned to one of the
primary maintenance processes, Hard Time, On-condition or Condition monitoring.
In general, hard time means the removal of an item at predetermined interval
usually specified in either so many flight hours or so many flight cycles. In some
cases the hard time interval may be in calendar time. On-condition means that
the item will be checked at specified intervals (in hours, cycle or calendar time) to
determine its remaining serviceability. Condition monitoring involves the monitoring
of failure rates, removal rates, etc. to facilitate maintenance program. (Harry A.
Kinnson, 2012).
The three oriented maintenance processes are discussed below in detail:
1. On-condition maintenance
“On-condition” means fit and forget, or don’t do anything until a failure occurs.
The above interpretations of “on-condition” maintenance may cause operational
surprises, which could not only prove very costly, but also jeopardise the safety
of an aircraft and its occupants.
The majority of aircraft mechanical components do not fail abruptly, but give
some warning or sign of the fact that they are about to fail. These warnings
or signs are called Potential Failures, and are defined as identifiable physical
conditions which indicate that a functional failure is about to occur or is in the
process of occurring. The amount of warning given by different potential failures
8
varies from microseconds to decades. Longer warning intervals mean greater

maintenance task intervals.
Maintenance tasks or inspections/checks used to detect potential failures,
and consequently to avoid a total functional failure, are called “on-condition”
maintenance tasks. This is because items are left in service on the condition that
they “continue” to meet a desired physical condition and performance standards.
The process of “on-condition” maintenance is applied to items on which
a determination of their continued airworthiness can be made by visual
inspection, measurements, tests or other means without disassembly inspection
or overhaul. The condition of an item is monitored either continuously or
at specified periods. The item’s performance is compared to an appropriate
standard to determine if it can continue in service. These appropriate standards
may relate to, but are not limited to, cleanliness, cracks, deformation, corrosion,
wear, pressure or temperature limits, looseness or even missing fasteners,
and are published in the applicable approved data of the aircraft or aircraft
component.
“On-condition” maintenance means an inspection or functional check that
determines an item’s performance and may result in the removal of an item
before it fails in service. It is not a philosophy of fit until failure or fit and forget.
For example, an upper or lower limit of an indicated parameter such as a
fluid pressure or monitoring of upper limits of solids content in a lubricant may
indicate a component’s wearing condition, etc. Failure of an item to continue to
meet the specified standard will indicate that further maintenance actions are
necessary.
At specific periods, the condition of an item may require a sound technical
judgement to determine that a malfunction or failure of the item will not occur
prior to the next scheduled inspection.
According to an extensive international study conducted in the aviation
industry, as much as 89 per cent items can benefit from “on-condition”
maintenance tasks. That is why, at present, the majority of maintenance tasks
listed in the manufacturer’s maintenance schedules/checks are “on-condition”
tasks.
Depending on the maintenance system in force, compliance with “on-condition”
maintenance tasks is mandatory if listed in the manufacturer’s maintenance
schedules/checks or Schedule 5 of Civil Aviation Regulations (CARs) 1988.
2. Condition Monitoring
Condition Monitoring is a process for systems, components, or appliances
that have neither hard time nor on-condition maintenance as their primary
maintenance process. It is accomplished by appropriate means available to
an operator for finding and solving problem areas. The user must control the
reliability of systems or equipment based on knowledge gained by analysis of
failures or other indications of deterioration.
Condition monitoring is the process of monitoring a parameter of condition
in machinery, in order to identify a significant change which is indicative of a
developing fault. It is a major component of predictive maintenance. The use of
condition monitoring allows maintenance to be scheduled, or other actions to
9
be taken to prevent failure and avoid its consequences. Condition monitoring

has a unique benefit in that conditions that would shorten normal lifespan can
be addressed before they develop into a major failure. Condition monitoring
techniques are normally used on rotating equipment and other machinery such
as pumps, electric motors, internal combustion engines, and presses, while
periodic inspection using non-destructive testing techniques and fit for service
evaluation are used for stationary plant equipment such as steam boilers, piping
and heat exchangers.
3. Hard Time Process
A hard time component is a component that requires a specific action at a specific
interval like overhaul, refurbishment, bench check, etc. per the manufacturer’s
recommendations.
Requires that an accordance with the carrier’s service. This is a preventive
primary maintenance appliance or part be periodically overhauled in maintenance
manual or that it be removed from (Shannon P. Ackert, 2010).
Hard-time processes mandated that all components be taken out of service
when they reached a specified age, expressed as the number of operating flight
hours, flight cycles, calendar time, or other stress units since new or since last
shop visit. Removed units were routed to repair centers and effectively zero-
timed, whereby the operating age was restored to a unity of zero by means of an
overhaul.
In 1960 representatives from both the Federal Aviation Administration and
the airlines formed a task force to investigate the capabilities of preventive
maintenance. Two major discoveries resulted from their investigation:
1. Scheduled overhaul has little effect on the overall reliability of complex
equipment unless the equipment has a dominant failure mode.
2. There are many items for which there is no effective application for scheduled
hard-time maintenance. The findings of the task force led to the development
of a second primary maintenance process defined as On-Condition (OC). On-
Condition requires that an appliance or part be periodically inspected or
checked against some appropriate physical standard to determine whether it
can continue in service.
The purpose of the standard is to remove the unit from service before failure
during normal operation occurs. Example of an OC process is measurement of
brake wear indicator pins; compare brake wear condition against a specified
standard or limit. Brake wear will vary considerably among operators.
Due to operational conditions, however the wear indicator pin on-condition
check will help attain near maximum usage out of each set of brakes.
Maintenance Program Enhancement Process
Following entry into service, the aircraft manufacturer’s regularly works with the
Industry Steering Committee to improve the efficiency of the maintenance tasks
that operators use to create their scheduled maintenance programs.
Improvements are based on the aircraft manufacturer’s analysis of in-service
data collected from the worldwide fleet.
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The maintenance program enhancement process requires that the aircraft

manufacturer and operators work together to identify tasks within the maintenance
review board report (MRBR) that can be optimized. For each identified maintenance
task, the aircraft manufacturer reviews the data and analyses the positive and
negative in-service results.
Once the analysis is complete, the aircraft manufacturer makes a recommendation
for each individual task under review and presents to the Industry Steering Committee
(ISC). Accepted changes are submitted for regulatory approval and incorporated
into both the maintenance review board report (MRBR) and the maintenance
planning document (MPD), which is issued to the operators for inclusion in their
own scheduled maintenance program.
e. Maintenance Task Development
MSG-3 is the current method used for developing the scheduled maintenance tasks
and intervals which will be acceptable to the:
i. Regulatory authorities,
ii. Operators
iii. Manufacturers
The remaining maintenance, that is non-scheduled or non-routine maintenance,
consists of maintenance actions to correct discrepancies noted during scheduled
maintenance tasks.
For each potential failure cause, the MSG-3 guidelines provide task oriented
logic to determine the appropriate scheduled maintenance tasks. A Task Oriented
Program consists of specific tasks, selected for a given functional failure consequence
based on actual reliability characteristics of the equipment they are designed to
protect.
Tasks are selected in a hierarchy of difficulty and cost, from lowest to highest.
Depending on the consequence of failure of safety, operational, economic, hidden
safety and hidden non-safety, a single or combination of tasks will be selected. The
following is the generic list of tasks to be selected:
a. Lubrication Servicing: meant for maintaining inherent design capabilities.
b. Operational/Visual Check: a failure finding task to determine if an item is fulfilling
its intended purpose.
c. Functional Check or Inspection functional checks: are quantitative checks to
determine if one or more functions of an item perform within specified limits.
There are three levels of inspections to determine if an item is fulfilling its
intended purpose as the following:
i. General Visual Inspection (GVI)
ii. Detailed Inspection (DI)
iii. Special Detailed Inspection (SDI)
iv. Restoration: reworking, replacement of parts or cleaning necessary to return
an item to a specified standard.
v. Discard: the removal from service of an item at a specified life limits.
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Maintenance Review Board

The primary purpose of a Maintenance Review Board (MRB) is to assist the regulatory
authorities to determine the initial scheduled maintenance requirements for new or
derivative types of transport category aircraft. The MRB report is used as the basis
from which an operator develops its own continuous airworthiness maintenance
program. MSG-2,-3, or the MRB report is not intended to be used as a controlling
document for an operator’s program after the initial program is established. One
of the specific reasons MSG-3 was created was to eliminate the confusing process-
oriented maintenance programs. This eliminated confusion associated with various
interpretations of condition monitoring, on-condition, and hard time, and the
difficulties encountered when attempting to determine what maintenance was being
accomplished to an item that carried one of the process labels. The goal of MSG-2
and -3 is to produce a scheduled maintenance program that maintains the inherent
level of safety and reliability of the aircraft.
Principal maintenance inspectors (PMI) should allow and encourage their
assigned operators to utilize the less confusing MSG-3 task-type terminology in
the maintenance time limitations document rather than the MSG-2 process-type
terminology. PMIs should also inform their operators of the following program and
report changes:
An operator may change a process-oriented maintenance program to a task-
oriented maintenance program by changing the words in the maintenance time
limitations document to reflect the actual task being performed. This is not considered
to be an MSG-2 to -3 conversions since no analysis is being accomplished.
A manufacturer may change an MSG-2 MRB report to an MSG-3 MRB report by
analysing all maintenance significant items in accordance with MSG-3 logic. Since
there are significant differences between MSG-2 and -3, the MRB Policy Board
believes there is no appropriate formula to change an MRB report from one logic
to the other. The MSG-3 analysis must be accomplished to allow the result to be
identified as an MSG-3 MRB report.
The Current MSG Process – MSG-3
Hearing the acronym MSG might make some think of the preservative in some
take-out food. But in the maintenance world, MSG-3 is the root of all inspection
schedules in a process starting before an aircraft enters service. Here is a look at
this fascinating process and how manufacturers and operators work to achieve the
end result.
The method that aircraft manufacturers, operators and regulators use to develop
the manufacturer’s initial maintenance schedule, as part of the work towards aircraft
certification, is beyond the ken of many in the hands-on maintenance world. It is
often a multi-year process, involving the application of rigorous logic, the analysis
of reams of data and the interaction of multiple administrative bodies.
All the more reason to know more about aviation’s Maintenance Steering
Group-3, or MSG-3, process; it starts before an aircraft enters service, when there
is no in-service operational data, and continues through the life of the type. MSG-3
practitioners are the Industry Steering Committee (ISC) working groups. Working
group members, who are specialists in the various aircraft systems, interact with
members of the manufacturer’s design group and receive data from the manufacturer,
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such as mean time between failures. But it is the working group members who do
the detailed analysis and generate proposed scheduled maintenance tasks. The
working group member’s representatives of the manufacturer and operators present
their results to the ISC, which approves it. Representatives of the regulators attend
industry steering committee ISC meetings as advisers.
The final output of the ISC for a new aircraft is the Maintenance Review Board
Report (MRBR), which outlines the recommended minimum initial maintenance
requirements. This document is then approved by the FAA, as the MRB chairman
for a U.S. aircraft.
Although there is no actual in-service operational data available when the ISC
process begins for a new aircraft, there is much historical data on the performance
of similar components and systems used in earlier designs, as well as test data
from the manufacturer and component vendors. “It’s the actual in-service reliability
data of similar components and systems that drives the interval,” according to Ray
Smith, a Boeing technical principal and the co-chairman of the 787 ISC.
MSG-3 stresses a top-down approach to analysis that starts at the highest
manageable level and looks at the consequences of that failure, explains Dave
Nakata, vice president of Empower MX, an MSG-3 consulting service.
If MSG-3 analysis shows that a certain functional failure would jeopardize
operational safety, and couldn’t be rectified by any of the hierarchy of standard
tasks within the specified logic, then redesign of the item in question would be
mandatory. Application of MSG-3 logic to the emerging Boeing 787-8 aircraft, for
example, has led to mandatory design changes in flight control and lightning/
High-Intensity Radiated Field (HIRF) protection systems, Smith, Boeing technical
principal and the co-chairman of the 787 ISC said.
MSG-3 is the only game in town for commercial airplane manufacturers. According
to Advisory Circular AC-121-22A, FAA policy states that the “latest MSG analysis
procedures must be used for the development of MRBRs for all new or derivative
aircraft.” It is the “only methodology accepted by the airworthiness authorities,”
states JörgCoelius, section manager for maintenance programs with Lufthansa
Technik. Although Maintenance Repair and Overhaul (MROs) are executors rather
than decision makers in the MSG-3 community, LHT is knowledgeable. It helped
develop MSG-3-based maintenance programs for Southwest Airlines, Alaska Airlines
and Lufthansa.
FAA stresses the safety aspects of MSG-3. The methodology helps improve
safety by addressing hidden functional failures. “Maintenance-significant items are
addressed at the system level instead of at the parts level.” MSG-3 also helps improve
maintenance efficiency, FAA notes, by eliminating redundant and ineffective tasks.
There is usually a substantial cost reduction in hard time component removal and
replacement.
The agency also praised MSG-3’s thoroughness. The methodology focuses on
aircraft systems and the loss of system function s, FAA said.
i. It considers hidden failures, plus one additional failure, in the decision logic,
identifies three consequences of a loss of function (safety, operational, and
economic),
ii. Identifies safety tasks,
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iii. Identifies scheduled maintenance tasks

MSG-1 and 2, by contrast, focused on parts and part failure rates, considered
only one failure in the decision logic and didn’t identify any tasks it was process-
oriented rather than task-oriented.
MSG-3 has also been adopted by most major bizjet manufacturers, with the
encouragement of the National Business Aviation Association (NBAA). Bombardier
was the first proponent, but Gulfstream, Embraer, Cessna and Dassault Falcon
Jet, among others, have embraced the methodology. One can argue that the bizjet
original equipment manufacturers (OEMs) were better off under the old approach,
which stressed hard time and on-condition maintenance. They had a steady revenue
stream based on predictable parts replacement intervals.
B787
The MSG-3 process for the 787-8 started in 2005 and the FAA approved the
scheduled maintenance program in 2008. While 787-8 activities will continue
through flight test and the life of the airplane, Industry Steering Committee (ISC)
work regarding the 787-9 is expected to get under way in October 2009.
The 787 ISC included seven working groups: systems; electrical and avionics;
lightning and High-intensity Radiated Fields (HIRF); power plant; flight controls
and hydraulics; structural; and zonal, says Lynne Thompson, Boeing’s director of
maintenance engineering.
It’s often said that MSG-3 is a task-oriented system, so analysis engineers go
through a prescribed logic sequence, asking questions, depending on the category
of the failure under consideration. A task is then selected to identify or rectify the
failure.
A working group’s system-level thought process concerning loss of hydraulic
pressure, for example, might go as follows: How might hydraulic pressure be lost
for the right, left or centre hydraulic system? Via an operational pump, failed valve,
leak in tubing, etc.
What tasks are required that is applicable and effective to ensure that the
hydraulic system is maintained to the level of reliability that the manufacturer
designed and certified the system to operate at? Then those tasks would be added to
the scheduled maintenance program if approved by the Industry Steering Committee
(ISC).
With MSG-3, “you’re looking at the results of the failure instead of worrying about
the failure, itself,” Nakata says. System-level analysis of an hydraulic functional
failure, for example, might focus on the failure of the hydraulic distribution system
and its consequences. Even this might not rise to the level of a safety impact if the
aircraft, as is common today, has multiple redundant hydraulic systems. In the
context of design redundancy, MSG-3’s top-down approach, which starts at the
system level and eventually works down to the component level, results in fewer
maintenance tasks, Coelius, section manager for maintenance programs with
Lufthansa Technik pointed out.
The MSG-3 document provides logic “trees” for systems and power plant analysis,
structural analysis, zonal analysis and lightning/HIRF analysis. In the systems
power plant diagram, for example, the decision logic divides possible failure effects
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into five categories, depending on whether the functional failure is evident to the
flight crew. These are:
i. evident safety,
ii. evident operational,
iii. evident economic,
iv. hidden safety and
v. hidden non-safety. The tasks resulting from the evident safety and hidden safety
categories are the most critical ones.
f. Maintenance Program Documents
The MRB Report outlines the initial minimum scheduled maintenance/inspection
requirements to be used in the development of an approved continuous airworthiness
maintenance program. The Maintenance Planning Document (MPD) document
contains all the MRB requirements plus mandatory scheduled maintenance
requirements that may only be changed with the permission of the applicable
airworthiness authority. These supplemental inspection tasks are detailed in
the aircraft’s Certification Maintenance Requirement (CMR) and Airworthiness
Limitation (AWL) documents.
i. Certification Maintenance Requirements (CMR)
A CMR is a required periodic task established during the design certification
of the airplane as an operating limitation of the Type Certificate (TC). CMRs
usually result from a formal, numerical analysis conducted to show compliance
with catastrophic and hazardous failure conditions. A CMR is intended to detect
safety significant latent failures that would, in combination with one or more
other specific failures or events, result in a hazardous or catastrophic failure
condition. Example of a CMR task is performing a visual inspection of the elevator
tab rods and mechanism every 2,000 flight cycles.
ii. Airworthiness Limitations (AWL)
They are regulatory approved means of introducing inspections or maintenance
practices to prevent problems with certain systems. Mandatory replacement
times, inspection intervals and related inspection procedures for structural safe-
life parts are included in the AWL document, and are required by the regulatory
authorities as part of the Instructions for Continued Airworthiness.
iii. Operators Approved Maintenance Program
The Maintenance Program Documents (MPD) scheduled maintenance tasks
should not be considered as all-inclusive. Each individual airline has final
responsibility to decide what to do and when to do it, except for those maintenance
requirements identified as “Airworthiness Limitations” (AL) or “Certification
Maintenance Requirements” (CMR).
Additional requirements in the form of Service Letters, Service Bulletins
and Airworthiness Directives are the responsibility of the individual airline
to incorporate. Maintenance tasks recommended in engine, APU, and vendor
manuals should also be considered the most common requirements that make
up an Operator’s Approved Maintenance Program (OAMP).
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g. Maintenance Interval Defined

Maintenance means the preservation, inspection, overhaul, and repair of aircraft,
including the replacement of parts. The purpose of maintenance is to ensure that the
aircraft remains airworthy throughout its operational life. Although maintenance
requirements vary for different types of aircraft, experience shows that most
aircraft need some type of preventive maintenance every 25 hours or less of flying
time, and minor maintenance at least every 100 hours. This is influenced by the
kind of operation, climatic conditions, storage facilities, age, and construction of
the aircraft. Maintenance manuals are available from aircraft manufacturers or
commercial vendors with revisions for maintaining your aircraft.
i. Inspections
The interval depends generally upon the type of operations in which the
aircraft is engaged. Some aircraft need to be inspected at least once every 12
calendar months, while inspection is required for others after each 100 hours of
operation. In other instances, an aircraft may be inspected in accordance with
an inspection system set up to provide for total inspection of the aircraft on the
basis of calendar time, time in service, number of system operations, or any
combination of these.
All inspections shall follow the Manufacturer Maintenance Manual including
the Instructions for Continued Airworthiness concerning inspection intervals,
parts replacement, and life-limited items as applicable to your aircraft.
ii. Annual Inspection
Any reciprocating-engine powered or single-engine-turbojet/turbo propeller
powered small aircraft (12,500 pounds and under) flown for business or pleasure
is required to be inspected at least annually by an FAA certificated A&P mechanic
holding an Inspection Authorization (IA), or an FAA certificated repair station
that is appropriately rated, or the manufacturer of the aircraft. The aircraft may
not be operated unless the annual inspection has been performed within the
preceding 12 calendar months. A period of 12 calendar months extends from any
day of a month to the last day of the same month the following year. However,
an aircraft with the annual inspection overdue may be operated under a special
flight permit issued by the FAA for the purpose of flying the aircraft to a location
where the annual inspection can be performed.
iii. 100 Hour Inspection
Reciprocating-engine powered and single-engine-turboprop/turbojet powered
aircraft (12,500 pounds and under) used to carry passengers for hire or used for
flight instruction, shall be inspected within each 100 hours of time in service by an
FAA certified A&P mechanic, an FAA certified repair station that is appropriately
rated, or the aircraft manufacturer. An annual inspection is acceptable as a
100-hour inspection, but the reverse is not true.
iv. Other Inspection Programs
The annual and 100-hour inspection requirements do not apply to large (over
12,500 pounds) airplanes, turbojet, or turbo propeller-powered multiengine
airplanes, or to airplanes for which the owner or operator complies with the
progressive inspection requirements.
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v. Altimeter System Inspection

It is required that the altimeter, encoding altimeter, and related system be tested
and inspected in the preceding 24 months before operated in controlled airspace
under Instrument Flight Rules.
Transponder Inspection: requires that before a transponder can be used, it
shall be tested and inspected within the preceding 24 months.
vi. Preventive Maintenance
The Federal Aviation Regulations (FAR)’s list approximately two dozen relatively
uncomplicated repairs and procedures defined as preventive maintenance.
Certificated pilots, excluding student and recreational pilots, may perform
preventive maintenance on any aircraft owned or operated by them that are
not used in air carrier service. These preventive maintenance operations are
listed in FAR Part 43, Appendix A, under Major Alterations, Major Repair, and
Preventive Maintenance. FAR Part 43 also contains other rules to be followed in
the maintenance of aircraft.
vii. Repairs and Alterations: All repairs and alterations of standard airworthiness
certificated aircraft are classed as either major or minor. FAR Part 43, Appendix
A, describes the alterations and repairs considered major. Major repairs or
major alterations shall be approved for return to service on FAA Form 337, Major
Repairs and Major Alterations, by an appropriately rated certificated repair
station, an FAA certificated A&P mechanic holding an Inspection Authorization,
or a representative of the Administrator. Minor repairs and minor alterations
may be approved for return to service with a proper entry in the maintenance
records by an FAA certificated A&P mechanic or an appropriately certificated
repair station.
viii. Letter Check Maintenance Program
The ‘A’ checks are packaged into a sequence of A1-A12, each with a corresponding
interval of 500 flight hours. The A-Check cycle is therefore completed at the A12
check at 6,000 FH. The ‘C’ checks are packaged into a sequence of C1 – C12,
and are due every 18 months. In addition, there is a primary heavy structural
check (D-Check) due every 144 months. This structure maintains alignment of
the A-checks with the C-checks, and the C-checks with the D-check. Effectively
all maintenance tasks are in phase at the last check of the cycle.
ix. Phased Maintenance Program
The A-checks are scheduled every 500 flight hours; however there will be no
clear cycle of A-checks (A1, A2, A3, A4, and so on) where all tasks are in phase
at the last check of the cycle. Under this structure, tasks are often continuously
added/revised as the aircraft ages. The C-Check program consists of continuous
C-checks whereby every sixth check is the heaviest (C6, C12, C18, etc) because
it captures the 1C, 2C, 4C, and 6C tasks.
1.7. GOALS OF MAINTENANCE

To achieve standard goals of maintenance program, we need to identify those goals to
be employed. The Air Transport Association of America (ATA) points out five goals of
maintenance program, the FAA airframe manufacturers and the airlines repeat these
goals throughout their own literature.
17
These goals were developed in conjunction with establishment of initial maintenance

program when new airplane model was been developed, these goals are not sufficient
for a good, effective maintenance program at the operators. For this in service activities,
five goals of maintenance program are established:
i. To ensure the realisation of the inherent safety and reliability levels of the
equipment.
ii. To restore safety and reliability to their inherent levels when deterioration has
equipment.
iii. To obtain information necessary for adjustments and optimization of the
maintenance program when these inherent levels are not met.
iv. To obtain information necessary for design improvement of those items whose
inherent reliability proves inadequate.
Other Goals of Maintenance

Eventually all mechanical components or equipment will fail the whole purpose then of
maintenance is to not only recognize this fact but to cope with it in the most effective
way.
The essential purpose of Aircraft Maintenance is to either return a defective system or
component to serviceability or to maintain the aircraft system, component or structure
in an airworthy condition.
The primary reasons for aircraft maintenance could be considered to be the following:
a. To keep the aircraft in a serviceable and reliable condition so that may continue
to serve its useful purpose.
b. To ensure that all regulatory requirements remain fully in compliance within the
concept of delivering continuing airworthiness.
c. To ensure that the asset value is protected.
Maintenance has come a long way since the early days when maintenance programs
owed more to the perception of the maintenance needs, as opposed to the analysed
and justified needs. In addition the role of the regulator was also minimal, and in part
developed as a result of events, incidents and accidents. During the end of the first half
of the 20th century regulations began to strengthen and the aircraft manufacturer was
seen as the appropriate source of the maintenance program development.
The early attempts at effective maintenance , in the 1960’s, saw time limits developed
which resulted in aircraft being progressively dismantled, in what became known as
Hard Time primary maintenance.
All hard time components were then routed through an overhaul process and after an
appropriate restoration process were considered as zero timed. Following investigations
into the effectiveness of the Aircraft Maintenance Process, by both the FAA and several
airlines, a number of determinations were made.
The first was that in reality schedule overhaul did not have a particular impart on
the reliability of a component unless there was a dominant failure mode evident.
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1.8. MAINTENANCE PROGRAM CONTENT

The Advanced Technology attachment document cited below discussed what a
maintenance program should be. The maintenance program consists of two groups of
tasks: a group of scheduled tasks to be accomplished at specified intervals a group of
non- scheduled tasks which results from conducting the scheduled tasks, from a report
of malfunctions, and from data analysis. An efficient program is one which schedules
only those tasks necessary to meet stated objectives. It does not schedule additional
tasks which will increase maintenance cost without a corresponding increase in
reliability protection.
Thus a maintenance program consists of scheduled maintenance tasks to keep
equipment and systems in top operating condition, unscheduled maintenance tasks to
address in service failures, a continuing analysis and surveillance activity to optimize
the total maintenance effort by improving the maintenance program or requesting
redesign of equipment and an effort to minimize maintenance cost.
1.9. OBJECTIVES OF MAINTENANCE

Maintenance management is the process of overseeing maintenance resources so that
the organization does not experience downtime from broken equipment or waste money
on inefficient maintenance procedures. The following are the objectives of maintenance:
1. To reduce Cost
The cost is the primary factor of firms, especially in a highly competitive industry.
Researchers mention unsatisfactory global sourcing costs. Airline operations directly
affect the costs of the products or services and their purchase price. These costs
are generated directly or indirectly from the supply chain. Consequently, higher
costs and prices decrease airline competitiveness. Therefore, having a setup of
maintenance or replacement will reduce the cost of airlines that may occur during
downtime.
However, the process analysis or cost-reduction strategy provides insights into
the inefficiencies which exist within current processes and place more emphasis on
demand pull-type processes which require forecasting operational schedules.
Nevertheless, aircraft fuel is the most important issue to airlines cash flow. It
is the highest operating cost portion (26.5%) of the total cost. Airlines separately
manage fuel cost and maintenance. Aircraft climb technique results in a 5 per cent
fuel saving.
2. To manage time of operations
Time refers to maintenance time and material procurement lead time. Maintenance
time is the job-processing time since the service was requested by a customer up to
completely fulfilling that requirement. Procurement lead time begins from an order
issued until the part’s arrival at the promised location. Lead times include transport
time, custom clearance time, and other unexpected delays. Moreover, the supplier
relationship possibly affects procurement lead time.
When there is proper aircraft maintenance, practical operations are continuously
performed in both parallel and serial fashions.
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3. To improve Quality
Aircraft parts must be manufactured by factories, which are officially approved by the
civil aviation organization of the state. Also, inspection, repair, altering, or overhauls
of aircraft parts must performed by an approved factory. The worldwide-accredited
auditors are the Federal Aviation Administration (FAA) and the European Aviation
Safety Agency (EASA). The Department of Civil Aviation (DCA) of Thailand is also
an approved auditor for repairing factories, which are located in Thailand. On the
other hand, the quality of aircraft maintenance is related to approval organization.
Airlines trust FAA/EASA-certified repair stations as top quality and DCA-certified
repair station as lower quality. However, both FAA/EASA and DCA are acceptable
as explained in ICAO annex 6. Thus, aircraft maintenance improves its quality
under degradation.
4. To maintain Reliability
Langford explained the meaning of reliability as “the probability that a system
will perform its intended function for a specified interval under stated conditions”
and expressed as an equation as follows: where = probability that the system
will successfully perform as required over the interval of time. The longer mean
time between failures (MTBF) results in higher reliability. In order to increase
aircraft reliability, maintenance managers must reduce aircraft downtime due to
maintenance, which is related to aircraft-part-procurement lead time and repairing
time.
The failure rate dictates the frequency of unscheduled corrective maintenance or
repair of a system affected by random malfunction. Low reliability indicates frequent
failures, which trigger more frequent corrective maintenance. Consequently, the
reliability can be improved by enhancing maintenance support in forms of facilities,
skilled technicians, tools, and supporting stocks of spare components, and repair
parts. Increased system reliability based on high-quality components can greatly
extend the intervals of operation between failures and eliminate or minimize
corrective maintenance support requirements.
5. To ensure Maintainability
The maintainability measures ability of a system to be restored to a specified level
of operational readiness within defined intervals with the use of the aforementioned
facility, and equipment resources. The maintainability is related to scheduled and
unscheduled maintenance. Maintainability refers to ease and speed at which any
maintenance activity can be carried out on any equipment. Maintenance can be
measured by mean time to repair (MTTR). It is a function of equipment design, and
maintenance task design including use of appropriate tools, jigs, work platforms,
and so forth. Once a piece of equipment has failed, it must be possible to get it back
into an operating condition as soon as possible.
6. To ensure aircrafts Availability
Availability measures the readiness of a system to fulfil its assigned function.
Airlines try to obtain high utilization to maximize their income. The aircraft must
be available before next scheduled flight; otherwise, the flight delay may be costly.
Maintenance managers must predict unforeseen troubles and pre plan materials,
skilled technicians, and facilities. They seek possible solutions for minimizing
aircraft-maintenance times which results in maximized availability. Thus, aircraft
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availability relates to flight hours per period. Higher flight hours (lower ground time)
results in higher availability.
7. To realize Flexibility/Replace Ability
Operation managers frequently experience problems of material shortage or
malfunction of equipment. Flexibility is an ability of production plant or service
provider by which he switches the planned operation to another process or solution
to meet the customer expectation. Supply chain flexibility is an ability to reconfigure
the supply chain and alter the supply of product in line with customer demand. It
is composed of two dimensions:
a. Resource flexibility which refers to a resource that can be applied to a range
of alternative uses with low costs and low difficulties are associated with the
switching from one resource to another as well as a short time is required for the
switch,
b. Coordination flexibility is a flexibility of process that redefines product strategies
in reconfiguring the chain of resources to produce the product, and re-deploy
those resources needed to produce the product.
1.10. AVIATION INDUSTRY CERTIFICATION REQUIREMENTS

The aviation industry is the most heavily regulated of all the transportation modes, with
the exception of certain requirements for a business license and licensing of the vehicles
and drivers one can enter the taxicab business quite easily but aviation industry is
complex with plenty of rules and regulations.
1. Type Certificate
This certificate is applied for by the designer of the vehicle once the basic design has
been determined.
A type certificate is issued to signify the airworthiness of an aircraft manufacturing
design. The certificate is issued by a regulating body, and once issued, the design
cannot be changed. The certificate reflects a determination made by the regulating
body that the aircraft is manufactured according to an approved design, and that
the design ensures compliance with airworthiness requirements. The regulating
body compares design documents and processes to determine if the design meets
requirements established for the type of equipment. Requirements established by
a regulating body typically refer to Minimum Operating Performance Standards
(MOPS) and related documents such as DO-178 series, DO-160 series and DO-254
series, which are developed jointly by Radio Technical Commission for Aeronautics
(RTCA, Inc.) and European Organization for Civil Aviation Equipment (EUROCAE).
Once issued, the aircraft “type” meets appropriate requirements. The determination
process includes a step called “First Article Inspection”, for it and for each of its
subassemblies. This is a quality control assessment whereas those prior to it are
part of quality assurance.
With respect to “cannot be changed”: When an air framer wants to change
something it has two options; one is to request a Supplemental Type Certificate
(STC), the other is to create an entirely different design. The choice is determined
by considering whether or not the change constitutes a new design i.e. introduces
risk not considered in the first design. If the manufacturer believes the change
doesn’t introduce new risk the manufacturer typically requests an STC. This is less
21
expensive. If the regulatory authority agrees with the rationale for choosing STC,
the STC is granted.
The type certificate (TC) implies that aircraft manufactured according to the
approved design can be issued an Airworthiness Certificate. Examples of regulatory
authorities are the Civil Aviation Authority (CAA), the Federal Aviation Administration
(FAA) and the European Aviation Safety Agency (EASA). To meet those requirements
the aircraft and each sub-assembly must also be approved. For example, in the U.S.
these sub-assemblies must meet requirements in the applicable Technical Standard
Order (TSO). To meet those requirements the design documents are examined for
compliance with the applicable Minimum Operating Performance Standards (MOPS)
applicable to that sub-assembly. MOPS are published by RTCA, Inc. When aircraft
are produced to meet a given TC, each one need not be tested as rigorously but the
confidence demonstrated by the Type Certificate is conferred, when the aircraft has
been assigned an Airworthiness Certificate.
2. Operator’s Certificate
An air operator’s certificate (AOC) is the approval granted by a national aviation
authority (NAA) to an aircraft operator to allow it to use aircraft for commercial
purposes. This requires the operator to have personnel, assets and system in place
to ensure the safety of its employees and the general public. The certificate will
list the aircraft types and registrations to be used, for what purpose and in what
specific area at airports or geographic region.
The requirements for obtaining an AOC vary from country to country, but are
generally defined as:
a. Sufficient personnel with the required experience for the type of operations
requested,
b. Airworthy aircraft, suitable for the type of operations requested,
c. Acceptable systems for the training of crew and the operation of the aircraft
(Operations Manual)
d. A quality system to ensure that all applicable regulations are followed,
e. The appointment of key accountable staff, who are responsible for specific safety
critical functions such as training, maintenance and operations,
f. Carriers Liability Insurance for Airlines: Operators are to have sufficient insurance
to cover the injury or death of any passenger carried
g. Proof that the operator has sufficient finances to fund the operation
h. The operator has sufficient ground infrastructure, or arrangements for the supply
of sufficient infrastructure, to support its operations into the ports requested.
i. The certificate is held by a legal person who resides in the country or region of
application for European Aviation Safety Agency (EASA).
As an AOC shows the acceptance of the relevant NNA of the operators personnel,
infrastructure and procedures, it holds value. In most jurisdictions an AOC may
be sold or acquired to prevent the arduous process of gaining regulator acceptance
for a new AOC. This can allow failed airlines to be sold as a going concern and then
more easily changed into another business. This has occurred with FLYi airline’s
AOC being bought by Northwest Airlines to start Compass Airlines, now a feeder
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airline for Delta Air Lines marketed as Delta Connection, and also with Strategic
Airlines purchasing the AOC, staff and routes of the failed OzJet airlines.
According to the United States Department of Transportation, the Federal
Aviation Administration is to maintain an airline air carriers operating certificate in
the category of fitness an air carrier must maintain the following three standards:
adequate financing, competent management, a willingness to comply with applicable
laws, and regulations which include at least 75 % of airlines controlling voting
equity must be held by US citizens.
3. A Certificate of Airworthiness
A Certificate of Airworthiness or an airworthiness certificate is issued for an aircraft
by the national aviation authority in the state in which the aircraft is registered.
The airworthiness certificate attests that the aircraft is airworthy insofar as the
aircraft conforms to its type design. Each airworthiness certificate is issued in one
of a number of different categories. A certificate of airworthiness is issued when
the aircraft is registered in the name of the owner. Thereafter, a yearly currency
fee is payable to renew the Certificate of Airworthiness. If this fee is not paid when
due, the certificate expires and the owner must apply again for this certificate to
be issued, the Certificate of Airworthiness can only be issued when a certificate of
release to service from the maintenance facility declares that the maintenance due
has been carried out and the aircraft is then certified as being airworthy. In the USA,
Australia and some other countries, each airworthiness certificate is classified as
either a Standard Airworthiness Certificate or a Special Airworthiness Certificate.
A standard airworthiness certificate is an airworthiness certificate issued for
an aircraft by the national aviation authority in the state in which the aircraft
is registered. A standard airworthiness certificate is one of the certificates that
are mandatory if an aircraft is to be used in commercial operations. In the USA,
Australia and some other countries, a standard airworthiness certificate is issued
in one of the following categories.
4. Production Certificate
A production certificate refers to an approval document issued by the Federal
Aviation Administration to manufacture duplicate aircraft products.
The administrator of the Federal Aviation Administration issues a production
certificate authorizing the production of a duplicate of an aircraft, aircraft engine,
propeller, or appliance for which a type certificate has been issued when the
administrator finds the duplicate will conform to the certificate. On receiving an
application, the administrator inspects, and requires testing of a duplicate to
ensure that it conforms to the requirements of the certificate. The administrator
can include in a production certificate terms required in the interest of safety.
Production under type certificate

Production under type certificate authorizes the manufacture of a product under the
FAA-approved type design for up to 6 months after the type certificate is issued.
This type of production requires the FAA to increase its level of involvement. Due to
limited FAA resources, there may be delays in the FAA’s ability to conduct airworthiness
inspections and to issue airworthiness approvals. Except as otherwise authorized, the
23
FAA will discontinue its conformity and airworthiness inspections after 6 months from
the date the type certificate was issued.
How to obtain authorization for production under type certificate

It is needed to obtain production approval under type certificate as part of type certificate
and separate application is not required.
The manufacturer is required to make each manufactured product available to
the FAA for an airworthiness inspection. The FAA issues the necessary airworthiness
documentation for each manufactured product that conforms to its FAA-approved type
design data. The manufacturer is required to maintain, at the place of manufacture, the
technical data and drawings necessary for the FAA to make its determination whether
the product and its articles conform to the type design.
Delivery Inspection
For the operator and owner of a new aircraft, it is very important that the aircraft is
inspected and checked during the assembly and acceptance phases.
SR Technics offers delivery inspection on the final assembly line, as well as at the
delivery centre. Services consist of all inspections from the start of assembly up to
delivery to the owner and operator, and include:
a. Monitoring and review of all production documentation, customer quality
logbooks and aircraft inspection reports
b. Preparation and review of all documentation required to start the customer
acceptance checks at the delivery centre
c. Close cooperation with the customer and liaison with the manufacturer’s delivery
team during all stages of aircraft acceptance
d. Daily review of technical and quality log books to ensure that the critical path is
adhered to during the delivery phase
e. Liaison with delivery-, quality-, test flight- and customer inspection managers, as
well as ferry flight coordinators, to ensure smooth and on time delivery
Certification of Personnel
Personnel certification regulations have been grouped in two categories, flight
crewmembers and other than flight crewmembers. The category of “other than flight
crew members” includes mechanics, control tower operators, and parachute riggers.
From the beginning of the current activities to revise the mechanic portion of the rule, it
has been the contention of all parties concerned, including the FAA, that maintenance
personnel should have a separate, standalone rule. In the current environment of
complex and constantly evolving aviation technology, it is necessary to have a dedicated
rule that focuses solely on the maintenance personnel that serve the aviation industry.
1.11. AVIATION INDUSTRY INTERACTION

The aviation industry is comprised of aircraft manufacturers, and vendors of parts,
systems, accessories for the aircraft, airline operators, third party maintenance
organizations, trade associations, such as the Air Transport Association of America
and the International Air Transport Association (IATA), flight crew, cabin crew, and
24
mechanics unions and regulatory authorities. This integrated group of professionals

is constantly working together to develop and improve aviation both technically and
operationally. This is somehow unique compared to other transport modes. This
continuous quality improvement (CQI) concept was in effect in the commercial aviation
field long before it became standard procedure in other areas.
Conclusion
Proper aircraft maintenance is essential for keeping aircraft and aircraft parts in optimal
condition, and ensuring the safety of pilots, crew, and passengers. Airline and airport
industry should keep Maintenance, Repair and Overhaul (MRO) setups for smooth flow
of flight operations and for the sake of running the operations profitably at minimum
cost of maintenance.
25

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Notion Press

Old No. 38, New No. 6

First Published by Notion Press 2016

1. BASICS OF AIRCRAFT MAINTENANCE MANAGEMENT 1

2. DOCUMENTATION AND TECHNICAL DIRECTORATES 26

2.1.1. Manufacturer’s documentation 27

3. PRODUCTION PLANNING AND TECHNICAL TRAINING 62

3.3.2. Training for Aviation Maintenance 75

4. MAINTENANCE ACTIVITIES AND TECHNICAL SHOPS 85

5. QUALITY ASSURANCE AND MAINTENANCE SAFETY

Basics of Aircraft Maintenance Management

Definition of and reasons of Maintenance setups

1.1. ROLE OF ENGINEER

1.2. ROLE OF THE MECHANIC

1.3. TWO TYPES OF MAINTENANCE

1.4. KEY CONCEPTS

1.5. ESTABLISHING A MAINTENANCE PROGRAM

1.6. DEVELOPMENT OF MAINTENANCE PROGRAMS

A characteristic of Condition-Monitoring is that it is not considered a preventive

varies from microseconds to decades. Longer warning intervals mean greater

be taken to prevent failure and avoid its consequences. Condition monitoring

The maintenance program enhancement process requires that the aircraft

Maintenance Review Board

iii. Identifies scheduled maintenance tasks

g. Maintenance Interval Defined

v. Altimeter System Inspection

1.7. GOALS OF MAINTENANCE

These goals were developed in conjunction with establishment of initial maintenance

Other Goals of Maintenance

1.8. MAINTENANCE PROGRAM CONTENT

1.9. OBJECTIVES OF MAINTENANCE

1.10. AVIATION INDUSTRY CERTIFICATION REQUIREMENTS

Production under type certificate

How to obtain authorization for production under type certificate

1.11. AVIATION INDUSTRY INTERACTION

mechanics unions and regulatory authorities. This integrated group of professionals

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