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AIRCRAFT RELIABILITY

AIR TRANSPORTAION AND AIRCRAFT MAINTENANCE (AE1012). AIRCRAFT RELIABILITY. Y.K.Sinha Rajalakshmi Engineering College. Topics to be covered. Aircraft reliability The maintenance schedule & its determinations Condition monitoring maintenance Extended range operations (EROPS) & ETOPS

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AIRCRAFT RELIABILITY

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  1. AIR TRANSPORTAION AND AIRCRAFT MAINTENANCE (AE1012) AIRCRAFT RELIABILITY Y.K.Sinha Rajalakshmi Engineering College

  2. Topics to be covered • Aircraft reliability • The maintenance schedule & its determinations • Condition monitoring maintenance • Extended range operations (EROPS) & ETOPS • Ageing aircraft maintenance production

  3. What is reliability ? • Reliability is a broad term that focuses on the ability of a part, assembly or system to perform its intended function • Mathematically speaking, assuming that the part, assembly or system is performing its intended function at time equals zero (T0),reliability can be defined as the probability that an item will continue to perform its intended function without failure for a specified period of time (T0+ TS) under stated conditions.

  4. T0 TS

  5. TS T0

  6. Definition of Reliability Reliability is the probability that a part, assembly, or system will perform its intended function in a stated condition or environment for a predetermined length of time without failure.

  7. components.

  8. Equipment failure Most equipment failures have no relationship to length of time in-service. Most failures are unpredictable. But if you detect a future failure early, you can handle it most cost effectively before it becomes a breakdown

  9. Equipment degradation

  10. Condition Monitoring

  11. Reliability Programme A Reliability Programme is an event reporting system based on performance values experienced under actual conditions. It provides a means of measuring the performance of aircraft systems and components and comparing the performance to predetermined levels of acceptable performance. An event reporting system and data analysis permits the rapid identification of adverse trends. If the systems and components do not meet established levels, an alert is issued and an investigation is initiated to assess the problem and initiate a programme of corrective actions.

  12. COLLECTION • Pilot Reports • Delays & Cancellations • Component Removals • Inspection Findings • Shop Findings • Power Plant Data • Structural Data Flight Statistics • OMT / QAR Data DATA DISPLAY,REPORTS ANDANALYSIS • Statistical Reports • Trend Monitoring • Fleet Campaign • Validation Study • Historical Data CORRECTIVE ACTION AND ANALYSIS • Modify Maintenance Process • Modify Maintenance Tasks • Service Bulletin Modifications • Correct Maintenance Procedures • Modify/Correct Shop Procedures • Escalate/Reduce Intervals • Adjust Inventory Levels

  13. Reliability Programme Advantages • Improved management of airworthiness • Effectiveness of maintenance programmes • Provides visibility for cost control • Optimizes management of fleet performance • Timely database sustains the fleet vital statistics • Supports technical efficiency of the Operations Control Center • It provides the tools for reliability analysis of aircraft structures.

  14. Reliability Programme Disadvantages • Lack of data discipline provides mis-information • The larger the fleet operation the larger the computing resources required • Data must be consistent and accurate to be meaningful.

  15. Reliability theory • Reliability is the probability that a device continues to perform a particular function over a particular period of time and under stated conditions. • Let R denote the reliability of a component, and let F be the rate of failure, then R + F = 1 • R dependent on the failure-free operation.

  16. Reliability (ctd) • In reliability theory it is customary to assume a constant failure rate. Then we typically express reliability R, the probability of survival to time t, in the form: R = e-t = e -t/T where T = mean time between failures, or mean time to failure whichever is most appropriate in the circumstances.

  17. Reliability formulae • Consider the situation where a system is composed of several subsystems whose reliability is known, the terms being compatible. • There may be parallelism, interconnections of various kinds, etc. • Two common methods of interconnection are important - in series and in parallel.

  18. Connection in series • Let R1, R2, R3, ..., Rn denote the reliability of components, and F1, F2, F3, ..., Fn denote the corresponding failure rates. • Then the system operates only if all the components themselves operate. • The overall reliability of the system is R where R = R1 x R2 x R3 x ... x Rn

  19. Connection in parallel • In this case the system operates if at least one of the components operates. • The relevant formula is then: F = F1 x F2 x F3 x ... x Fn or (1 - R) = (1 - R1) x (1 - R2) x (1 - R3) x ... x (1 - Rn)

  20. Combination

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