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Aircraft Maintenance Management Module
Aircraft Maintenance Introduction
General definition
Maintenance cost is broadly defined as the sum of incurred labour, material costs and various overheads otherwise known as indirect maintenance costs. The labour is normally a process time controlled and productivity related where certain tools such as lean processes or “Six sigma” can be employed to enhance productivity and consequently improve consumed labour.
The material element is dependant on negotiated supplier’s contracts and products reliability programs.
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1. Aircraft Maintenance Cost Philosophies & Economics The maintenance costs represent 10-20% of the
worldwide airlines direct operating costs. These costs
are growing in view of introduction of new more
expensive material, highly sophisticated repair
schemes especially those associated with structural
parts and core Engine parts, and increasing labour
costs.
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Boeing suggests that there are many other influencing
factors to the maintenance costs such as Aircraft
utilisation, Environment and Age. Furthermore,
Airlines influence costs of its operations and
maintenance support practices; similarly component
Manufactures influence product support and
reliability.
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The Airlines overall maintenance costs are categorised
as Controllable and Non Controllable Costs. The
controllable cost element is further split into
contractual and non contractual costs. The contractual
cost elements are either outsourced or accomplished
In-house depending on potential benefits or savings in
the short or long runs.
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Thus it is of extreme importance to understand all
elements of airlines maintenance costs and contain
such costs where practicable through introduction of
processes and manpower improvements, enhanced
training and optimisation of maintenance interval
requirement for both ON/OFF aircraft maintenance in
liaison with the OEMs.
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The Airline industry currently under tremendous
pressure in light of the current downturn reducing
demand especially on premium cabin, hence the
competition which resulted in fares reduction and
subsequently low yields than breakeven costs.
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2. Maintenance Costs (Direct /Indirect) Breakdown The Maintenance costs are the sums of total costs pertain
to Direct and Indirect Maintenance. Per IATA, Direct
Maintenance comprises the following, by Cost segment:
- Airframe, Engines and component maintenance. And
by cost element: Labour, Material and Outside repair
Where, Indirect Maintenance includes the Overheads
costs.
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Boeing elaborates on these definitions further as follows:
- Direct Maintenance Cost is, the direct airframe and Engine maintenance which consist of the labour and material required to perform service, repair, modification, restoration, inspection, test, and troubleshooting tasks during on-airplane and shop maintenance activities.
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Maintenance Overhead consists of maintenance supervision, maintenance training, maintenance planning, unallocated labour costs, rentals and Utilities.
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We have to understand the elements that comprise the
Direct Maintenance Cost (DMC) and Indirect
Maintenance Cost (IMC). The breakdown of these
costs is:
2.1 Direct maintenance costs
2.2 Indirect maintenance costs
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2.1.1 ON aircraft maintenance
This type of maintenance is normally carried out
during the scheduled aircraft checks as defined by the
Manufacturer’s MPD documents where an extensive
part of Labour Man-hours is expended as compared to
materials consumed such as filters, oil, greases,
fittings and minor structural parts.
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Additionally, allotted portion of check time is dedicated to tests, inspection, minor airframe corrections and components removals which are due for routine maintenance. IATA as shown in Figure (1) below refer to this maintenance category as 1st Level Maintenance costs segments that include Airframe and Engines Labour, materials and subcontracted work.
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Maintenance Cost Task Force 20097
1- Direct Maintenance Cost OverviewAirframe /
On Aircraft- Labor- Material- Subcontracted
Engine
- Labor- Material- Subcontracted
Component /Off Aircraft- Labor- Material- Subcontracted
1st Level : Total Cost during period
Labor (MH)- routine- non routine- modifications- cabin ...
Material- P/N- Quantity- Cost ...
Detailed listing- P/N- Quantity- MTBUR- Repair Cost ...
Per Remove- MSN- ETT- Repair Cost ...
2nd Level : Cost per Maintenance Event
1. Maintenance Cost Breakdown
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Aircraft Maintenance Costs - Guest Lecture - Cranfield University - March 2009 - CSMAM - Ref. D09005085 -Issue 1
Aircraft Maintenance Costs in Perspective
Direct operating cost Indirect operating cost
Life cycle cost
Total operating cost Disposal cost
Cash operating cost
Financial
Fuel and oil
Landing & Navigation fees
Direct maintenance cost
Crew
Insurance
Passenger services
Marketing and sales
Indirect maintenance cost
Other
2.1.2 OFF Aircraft Maintenance This is normally carried out away from aircraft on Engines
and components in either In house or outsourced overhaul
shops as these costs comprise expended labour, material,
testing and modifications.
The above two categories are generally split as per below
percentages.
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The ON aircraft Maintenance checks are further summarised as
follows:
1. Aircraft Transit checks- this is a normal minor check that
occurs every flight where walk around is conducted by the
Engineers to detect any obvious damage and/or discrepancy
which my obstruct aircraft despatch or serviceability for further
flights. Also aircraft Log books will be reviewed to clear or
defer all recorded snags.
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1. Aircraft Service or Weekly checks- This check is a little
more extensive hours are expended in general visual
inspections and overall Aircraft condition. Minor
modification (Engineering Orders) can be conducted and
additional defects clearances which require extended times
can be accomplished during this check.
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1. Aircraft “A” checks- This is a routine MPD check that
occurred almost every three months or 500 flight hours
with various tasks scheduled for accomplishment. Few
access panels, Engine cowlings and other doors will be
opened to perform certain visual inspections and
rectifications.
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1. Aircraft “C” checks- within this check the aircraft is grounded
for an extended time where many routine MPD tasks will be
carried out. As majority of access panels are opened, a detailed
visual inspection will be carried out on airframes linkages,
structural fittings and main systems (such as oil, hydraulic and
fuel) functional or leak checks and major components defect
rectification. The interior cabin such as seats will be removed
fro refurbishment. Galleys and toils will receive servicing and
repairs.04/21/23 Aircraft Maintenance Module 21
1. Heavy Aircraft checks or “D” checks as some airlines
call it. The aircraft will undergo a detailed visual
inspection almost in every area including main structure
where a NDT and application of special die pent rants will
be carried out to detect possible skin cracks. Within the
cabin the primary structural parts removed for corrosion
treatment especially galleys, floor panels and seat main
frames.
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OFF Aircraft Maintenance
The OFF aircraft Maintenance are further summarised
as follows:
a) Engine Repair and Overhaul Maintenance – during aircraft operations, The Engines are the most stressed items where every time the aircraft takes off, Engines parts rotate at a very high speed with thrust causing certain wear to such parts at an accelerated pace. Engine internal parts especially turbine and combustion chambers are manufactured from special materials in order to withstand the high temperatures and pressure put on the engine during operations.
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Hence, the maintenance is often significant and expensive and that is the reason where majority of airlines outsource engine maintenance to OEMs/MROs to alleviate the burden off airlines from investment in development of such highly sophisticated overhaul shops with special required repairs.
Normally the Engine initial shop visits expenses from Aircraft induction to maturity is relatively less expensive than aging Engine maintenance as main LLP parts requires replacement then and such parts impose a high cost to the Engine Maintenance.
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In general terms, the difference between engine and airframe
maintenance is that Engine material costs will exceed 80% of
the total maintenance while airframe maintenance will
equally share labour and material by 50/50%.
The Engine performance maintenance costs optimisation is
measured by the time it stays on wing as achieved by the
continuous OEM development causing less removals and
subsequently lower maintenance costs.04/21/23 Aircraft Maintenance Module 25
1. Component Repairs, Modifications, and
Replacements This maintenance includes normal scheduled and unscheduled
components repairs to restore its serviceable condition. The parts are often categorised into rotables, repairable and expendables whereby a multiple number of repairs/resets is possible to rotables parts and considered as assets for the airline.
The maintenance costs associated with this part depend significantly on whether these can be repaired In house or outsourced. This decision highly depends on two factors, the Turn around time and the Warranty aspect.
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In other words, if the OEM TAT is reasonable, then it is quite
sensible to despatch such components for repairs outside under
warranty without spending much hassle to develop such
capability and waste Engineers energy on warranted
components especially during the initial five years from
Aircraft induction. There are occasions where rotables or
repairable parts are scrapped due to economic conditions
BER ,i.e. Where the Repair cost exceeds the 65% threshold of
the unit cost04/21/23 Aircraft Maintenance Module 27
In-Direct Maintenance Costs
2.2 Indirect Maintenance Costs
The Indirect maintenance cost or otherwise known as Overhead
cost is defined as the sum of all labour and material costs for
support services which add to the total maintenance of the
aircraft. The elements of IMC include the overhead costs of but
not limited to, Facilities, Stores, Equipment, administration,
Engineering technical services, Materials management and Engg
training.
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The IMC costs vary significantly amongst airlines subject
together with organisational structure and the level of
In/outsourcing plus work efficiencies.
Therefore The IMC costs fall within the category of
controllable airline maintenance costs but this factor
cannot be controlled nor quantified by Aircraft
manufacturers.
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The use of automation and sophisticated control system
especially in the tech records, planning and materials
management, drastically reduce the labour requirement
and size of these support services departments and
subsequently slash the IMC costs.
Therefore, the IMC costs overheads need to be reviewed
frequently to envisage possibility of introducing processes
improvements. 04/21/23 Aircraft Maintenance Module 30
The ideal tool for this exercise would be Six Sigma which
looks at the work environment to analyse the adopted
processes, then propose solutions for the purpose of
working smarter and cut inefficiencies (Turner 2005).
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Operating Cost Breakdown
10% - 25%Ownership CostOwnership Cost
Cash Airplane RelatedOperating Cost
(CAROC)
Cash Airplane RelatedOperating Cost
(CAROC)
• Fuel• Cockpit crew• Cabin crew• Maintenance• Landing• Navigation • Ground handling
• Depreciation• Financing (airplane and
introductory investment)• Operating lease cost• Hull insurance
Passenger Related
Cost
Passenger Related
Cost
Cargo Related
Cost
Cargo Related
Cost
• Food• In flight services• Handling• Baggage
handling • Commissions • Reservations
and sales• Advertising
• Handling• Commissions • Reservations
and sales• Advertising
System Related
Cost
System Related
Cost
• Airplane general and administrative
• Passenger general and administrative
• Cargo general and administrative
Total Operating Cost(TOC)
Total Operating Cost(TOC)
Airplane RelatedOperating Cost
(AROC)
Airplane RelatedOperating Cost
(AROC)
System RelatedOperating Cost
System RelatedOperating Cost
Payload RelatedOperating Cost
Payload RelatedOperating Cost
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