Syllabus1.Aircraft Maintenance and Maintained Systems2.Reliability and Rates of Failure3.Redundancy4.Failure Interactions5.Risk Analysis and Error Reduction in Aircraft

Maintenance6.Aircraft Maintenance Programme Management

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ME4504: A

ircraft Maintenance M

anagement

At the end of this course, you will have a goodunderstanding of the fundamental principles of aircraftreliability and maintenance engineering, and beequipped with practical knowledge of mandatoryairworthiness requirements and aircraft maintenance.

Aviation Safety

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The Number One Priority of Aviation

Like most industries, the aviation industry also ratessafety as the No. 1 priority (while ensuring profitability). Forthe aviation industry, this claim is not just hot air.To enable the highest level safety and continuoussafety improvement, a safety culture is relentlesslychampioned and cultivated. Technology, systems,standards and policies for safety and reliability havebeen put in place and practiced to support this goal.

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Aviation SafetyIn 2013, Aviation is the safest way of travel in the world. At anaccident rate of 4.2 per 1 million departures*, an average personhas too fly 365 days per year for 652.3 years before an accident isexpected to occur.

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Global Accident Rate (per million departures). Courtesy of ICAO State of Global Aviation Safety report 2013

Worldwide Traffic Volume (millions of departure). Courtesy of ICAO State of Global Aviation Safety report 2013

Aviation was not always thissafe. This is partly achieved byhighly regulated, proper aircraftmaintenance system.

*Accounts only for schedule passenger air services.

(Just unfortunate that there are on average 85,500departures per a day).

Be Careful with Statistics

Lets look at it this way.

At 31.2 million departures per year, thistranslates to an average of 85,500departures per a day. Hence, 1 milliondepartures would be made in 11.7 days.

Therefore, on average, globally, 4.2accidents occurred every 11.7 days, oralternatively, 1 accident somewhere in theworld per 2.78 days. This does not soundso great, but it is good compared to all othermodes of civil transportations.

6At an accident rate of 4.2 per 1 million departures, an averageperson has too fly 365 days per year for 652.3 years before anaccident is expected to occur. This is true if this is the only aircrafttaking-off, departing each day.

If a statistic sounds too good to be true, you have to question it because there is good chance that it is not.

What is Safety?

To reduce injury rates and losses, one must reduce the number ofdefects and subsequent failures. To reduce failures and defects,the probability of Survival (i.e. Reliability) must be increased,safety culture and reliability must be improved.Safety is achieved by Reliability Management.

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Safety and Reliability Go Hand in HandA safe industry is a reliable industry, and a reliable industry willalso be a safe industry.To ensure a safe civil aviation industry, the ICAO and theworldwide civil aviation authorities establish and regulateairworthiness standards and recommended practices, such thatno aircraft can be operated on unless in a certified airworthy state.

Safety: the state of being safe, freedomfrom the occurrence or risk of injury,danger, or loss.

Continuing AirworthinessAirworthiness means an aircraft (1) meets its typedesign and (2) is in a condition for safe operation.Continuing Airworthiness is the process of maintainingthe aircraft in a state for safe air operation (airworthy)at all times.

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Continuing Airworthiness is a shared responsibility by the Owner / Operator and Maintenance persons, with the ultimate responsibility to the Owner / Operator….by FAR 91

The aircraft must be the same as thatdescribed in the type certification,supplementary TC, and any approvedalternations (no illegal modifications!)

Performed all Airworthiness Directives Manufacturer Service Bulletins Inspections and maintenance Repair any accidental damages according to

repair manual and/or manufacturer advice.

Continuing Airworthiness

Proper aircraft maintenance is essential for keeping aircraft andaircraft parts in optimal condition, and ensuring the safety of pilots,crew, and passengers.

Certified repair stations and maintenance technicians performmaintenance and inspections on aircraft. The state’s civil aviationauthority (such FAA of the US, ESAS of the EU, CAD of HK) isresponsible for certifying the repair stations and aircraft maintenancetechnicians (AMTs).

In the US, repair stations are certified under FAR Part 145. AMTs arecertified under FAR Part 65 for the US.

In the US, FAA FAR Part 43 details the standards regarding themaintenance, preventative maintenance, and alterations of aircraftand aircraft articles and systems.

9For the aircraft to be airworthiness, the operator, aviationsuppliers and facilities must meet the airworthinessstandards and comply with aviation regulations, and holdairworthiness certification licenses before operating on theaircraft.

Continuing Airworthiness 10

FAA Airworthiness certificate example

Certified repair stations

Certified maintenance technicians

Safe and ready for flight

Approved aircraft maintenance programs

Aircraft Maintenance

and evaluation programs

Hong Kong Aviation RequirementAirworthiness Requirements of the Hong Kong Civil Aviation Department – Hong Kong Aviation Requirement (HKAR)

HKAR-HTSO Hong Kong Technical Standard Orders Hong Kong Airworthiness Notices HKAR-1 Airworthiness Procedures HKAR-2 Administrative & Guidance Material HKAR-21 Certification of Aircraft and Related Products,

Parts and Appliances, and of Design and Production Orgs. HKAR-66 Licensing of Maintenance Personnel HKAR-145 Approved Maintenance Organisations HKAR-147 Approved Maintenance

Training/Examinations HKAR-183 Representatives of the Director-General HKAR-MMEL/MEL Master Minimum Equipment … CAD 418 Condition Monitored Maintenance: an

Explanatory Handbook CAD 452 - Aircraft Maintenance Schedules and

Programmes Information and Guidance CAD 748 Aircraft fuelling and fuel installation management

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Aircraft Maintenance System

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Beyond The RegulationsAircraft maintenance is one of the most important factorsinfluencing the success of an airline. “Only when the fleet is ina technically excellent state of care can the flying operationsbe run safely, punctually and profitably”, Lufthansa Technik.

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Maintenance program cost can range from 10 to 30 percentof the operating cost of an airline. It is in the operator’sinterest to know the details about maintenance in order tominimize maintenance cost. Cost effective preventiveactions are necessary to improve profitability.

Airline Maintenance CostBased on an Exclusive Benchmark Analysis of FY2012 available data by IATA’s Maintenance Cost Task Force*, the key airline maintenance costs were found as follow. Airline maintenance cost was on average 12% of the total

operating cost. The average maintenance cost was $1,014 per flight hour,

$2,547 per flight cycle and $ 3.4 Mill. per aircraft.

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*Airline Maintenance Cost Executive Commentary (FY2012 data)http://www.iata.org/whatwedo/workgroups/Documents/AMC-ExecComment-FY12.pdf

Engine maintenance remained the highest cost segment. It is on average 41% of direct maintenance cost.

Administrative and professional staff, overhead costs on average were 21% of total costs.

Impact of Failures / AccidentsFailure has far reaching effects on a company.In a minor accidents / incidents, Availability / Operation schedule Reputation Profitability Dissatisfied customers Idle employeesIn major accidents, Long lasting emotional traumas due to serious injuries and loss

of lives of staff and passengers Profits becoming losses Reduced value of investment in plant and equipmentIt has been found, the impact of aviation accidents is not merelywithin the company and those directly involved. Serious aircraftaccidents have long term negative impact on the entire industry.

Not all failure can be prevented, but the prevention of failuresreduces the occurrence of accidents. Proper maintenance isthe key in preventing technical failures.

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Accidents Due to Maintenance Errors 1Japan Airlines Flight 123 (12/08/1985): a scheduled domestic JapanAirlines passenger flight from Tokyo International Airport to OsakaInternational Airport, Japan. A Boeing 747SR crashed killing 15 crewmembers and 505 passengers on board.

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China Airlines Flight 611 (25/05/2002): The Boeing 747-209Boperating between Taipei and Hong Kong disintegrated in mid-air andcrashed into the Taiwan Strait, killing all 225 people on board. The in-flight break-up was caused by improper repairs to a tail-strike on theaircraft 22 years earlier.

The aircraft was involved in a tail-strike incident 7 years earlier. Thesubsequent repair of the bulkheaddid not conform to the approvedrepair methods - the bulkhead gaveway, losing all four hydraulicsystems and the vertical stabilizer.

China Southwest Airlines Flight 4509 (24/02/1999): a flight fromChengdu to Wenzhou crashed into a field while on approach toWenzhou Airport, killing all 61 passengers and crew members onboard. Air crash investigation found that incorrect locknuts had beeninstalled in the elevator operating system, which spun off during theflight, leaving the elevator uncontrollable

Accidents Due to Maintenance Errors 2

Tuninter Flight 1153 (06/08/2005): an ATR 72Tuninter Airlines (today known as TunisAirExpress) international flight from Bari Italy toDjerba Tunisia, ditched into the MediterraneanSea near the city of Palermo. 16 of the 39people on board died. The accident caused byengine fuel exhaustion due to the installation ofwrong fuel quantity indicators - one designed forthe ATR 42 was installed in the larger ATR 72.

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The Importance of Aircraft Maintenance

Proper aircraft maintenance is essentialfor keeping aircraft and aircraft parts inoptimal condition, to ensuring the safetyof pilots, crew, and passengers, and tomaintain and to continuously improve thehigh level of safety of aviation.

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Purpose of Maintenance

To meet continuing airworthiness Restore efficiency, safety and

reliability to design levels whendeterioration has occurred.

Maintain design level efficiency,safety and reliability of equipment.

To collect information for design andreliability improvements.

To accomplish aircraft maintenanceat safe level at minimum cost.

To uphold aircraft resell value

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Aircraft maintenance involves inspect, overhaul, repair and componentsreplacement of aircraft, to ensure that the aircraft and its systemsremain airworthy throughout its design life or Aircraft Life Extension

Main purpose of the Aircraft maintenance program:

Aircraft Maintenance Programme20

DefinitionsMaintenance is all activities involved in keeping a system’sequipment in working order and up to standards.A maintenance schedule is a detailed plan of what is to bemaintained on an aircraft and how often.A maintenance programme is the maintenance schedule plus theprocedures and policies, and tools (Reliability programme forexample) designed for continuous review and planning ofmaintenance activities and schedule, and analyses of the statisticaldata collected. A maintenance programme allow aircraftmaintenance to be accomplish at safe level and at minimum cost.

Maintenance ProgramAn aircraft shall not fly unless it has been maintainedin accordance with an approved maintenance program(approved by the state/country of registration).

The airworthiness requirement of Hong Kong onContinuing Airworthiness and Maintenance of Aircraftcan be found in the following CAD documents: Hong Kong Aviation Requirements HKAR-1 Sub-

section 1.6 CAD 452 – Approval of Aircraft Maintenance

Schedules CAD 418 – Condition Monitored Maintenance: An

explanatory handbook

In general, the maintenance program consist of: Maintenance Schedule Reliability programme

*In other states, similar documents can be found and obtained from the state’s civil aviation authority.

Maintenance Programme 22From management and planning view point, the maintenance of aircraft is differentiated into: Departure check Pre-flight check/Post flight check Daily (Service check) Weekly A check: 500 Flight Hours (FH) C check: 2500 FH D check: 6-10 YearsIn terms of requirement on servicingequipment and maintenance facility, theabove checks and maintenance slots aredifferentiated into: line maintenance Base maintenance and overhaul

Line and Base Maintenance23

Removal or installation of landing gear tires. Servicing of landing gear wheel bearings. Replacement of defective safety wiring / split pins. Replacement of seats. Carrying out an inspection of a flight control

system that has been assembled, adjusted, repaired, modified or replaced.

Line maintenance is minor, scheduled andsometimes unscheduled maintenance work thatcan be carried out on the aircraft at the airportgate or apron with minimal tool requirements. Linemaintenance usually means that the aircraft keepsto its usual schedule. The frequency can be pre-flight, daily, weekly and A checks, which arenormally carried out over night. The aircraft is thenavailable by the next morning for its scheduledservice. Line maintenance is includes:

Base Maintenance: Maintenance tasks fallingoutside the criteria for Line Maintenance areconsidered to be Base Maintenance. The C andD Checks are base maintenance checks. Dueto the comprehensive nature of these 2 checks,they are also known as Heavy maintenance.The C-Check is carried out about every one anda half to two years will take several days, whichrequiring a large majority of the aircraft'scomponents to be inspected, replaced andrepaired. The C-Check needs substantialground facilities.

The D-Check is also known as Overhaul. Theaircraft is taken out of service for 6-8 weeks.During the D-Check, the aircraft is stripped fromits paint, taken apart completely, inspected,tested, repaired, parts replaced, modified andthen put back together. The D-Check is thebiggest maintenance event for any aircraft.

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Reliability Programme 25Maintenance Programme based on Maintenance Steering Group(MSG) logic or containing Condition Monitoring tasks shouldcontain a Reliability Programme. see Appendix No. 1 of HKAR-1 Sub-section 1.6-2 There is guidance in CAD 418 on what constitutes a Reliability Programme.

The data which is gathered through maintenance and reliabilityprogramme is believed to be a measure of the effectiveness ofthe maintenance and the maintenance programme that is appliedto the aircraft.

A low incidence of technical findings is one way by whichdetermination can be made that the maintenance is effective.

The reliability programme entails collation and analysis of dataentered from in-service activities of the aircraft, its systems andsub-components. The primary purpose is to monitor the failurelevel and to identify poor performance whether as a result ofquality or maintenance issue.

Reliability ProgrammeTypically, on a monthly basis, and minimum of six month basis,the operator will review: Technical Log entries component failures (in particular - cause of failure) Delays Ground Incident Reports Mandatory Occurrence Reports (MORs) findings from task cardsWith the purpose of looking for trends, variations or areas ofdeterioration that can be addressed by taking some kinds ofpreventative maintenance action.

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The skill of being able to understand and analysisreliability (or failure) data is paramount in AircraftMaintenance Engineering.