Aerospace Aerospace Engineerin Engineerin g Reasons for Reasons for Maintenance Maintenance 06/06/22 1 ► ► Reasons for Maintenance To keep performance, reliability and availability within design limits at minimum cost. ◙ Deterioration with age – examples are fatigue, wear and corrosion. ◙ Chance failure – examples are tyre burst, excess structural loads. ► ► Processes that affect an aircraft
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Aerospace Aerospace EngineeringEngineering Reasons for MaintenanceReasons for Maintenance
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► ► Reasons for MaintenanceTo keep performance, reliability and availability within design limits at minimum cost.
◙ Deterioration with age – examples are fatigue, wear and corrosion.◙ Chance failure – examples are tyre burst, excess structural loads.
► ► Processes that affect an aircraft
Aerospace Aerospace EngineeringEngineering Some TerminologySome Terminology
Availability is the probability that a system will be able to perform its required function at a specified instant in time.
Reliability the ability of a system or component to perform its required functions under stated conditions for a specified period of time.
Maintainability is the probability that a failed system can be made operable in a specified period of time (Kapur and Lamberson, 1977)
Aerospace Aerospace EngineeringEngineering Mechanisms of FailureMechanisms of Failure
Some of failure mechanisms in aircraft and systems equipments :◦Material failure◦Parameter drift◦Leakage◦Contamination◦Software failure◦Electromagnetic Interference◦Fraud
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Aerospace Aerospace EngineeringEngineering Cause of FailureCause of Failure
Common areas linked to causes of failures: ◦Design Manufacturing ◦Maintenance ◦Purchasing ◦Operator ◦Quality system ◦Data ◦Sabotage or enemy action
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Aerospace Aerospace EngineeringEngineering Sources of FailureSources of Failure
Categories illustrate some less obvious potential basic sources of failure:◦ Ignorance -a designer, manufacturer, maintainer or operator
is unaware of the risk in the decision he is making or the activity he is undertaking.
◦ Lack of data -a sub-category of ignorance but one over which the maintenance system has some control.
◦ Negligence (Clause)-While the individual or organisation is aware of the correct action, this is not carried through. Errors can be made through inattention. The extreme case is wilful negligence which may be chargeable as criminal negligence.
◦ Poor planning -lack of adequate planning can trigger a chain of circumstances leading to a system failure
◦ Sabotage or enemy action (bad Action)-where deliberate hostile action is involved.
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Aerospace Aerospace EngineeringEngineering
FORM OF AIRCRAFT FORM OF AIRCRAFT MAINTENANCEMAINTENANCEConsist of;
Difference between time of departure reals and programs
• If difference > 15 min Delay
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Airlines Operating CostAirlines Operating Cost
LCC (Life Cycle Cost) : Total operating cost over the life of the aircraft or engine
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Airlines Operating CostAirlines Operating Cost
TOC (Total Operating Cost) which sometimes called cost of ownership) [TOC = DOC + IOC]
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Airlines Operating CostAirlines Operating Cost
IOC (Indirect Operating Cost) : Other costs beyond DOC such as Marketing, Passenger services, Aircraft handling and Administration
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Airlines Operating CostAirlines Operating Cost
DOC = DMC + IMC + Fuel + Landing and navigation fees + Flight crew expenses + Insurance depreciation + Financing of aircraft and spares
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Airlines Operating CostAirlines Operating Cost
DMC (Direct Maintenance Cost) : Productive labour and material consumed to maintain the aircraft
IMC (Indirect Maintenance Cost) : Other costs attributed to maintenance such as administration, engineering, training, supervision, amortisation of tools and facilities