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Fleet-level Reliability of Multiple Repairable Units: a Parametric Approach using the Power Law Process
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
Saab Aerotech.
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
2014 (English)In: International Journal of Pedagogy, Innovation and New Technologies, ISSN 0973-1318, E-ISSN 2392-0092, Vol. 10, no 3, p. 239-250Article in journal (Refereed) Published
Abstract [en]

The application of parametric reliability analysis methods for repairable units, such as Power law process, is quite clear and straightforward for a single repairable unit. However, in practice, the analyst needs to know the reliability characteristics of units at a fleet level. The application of parametric reliability analysis methods at the fleet level, even if it is limited in scope, is quite complex. The aim of this paper is to describe the use of the power law process for multiple repairable units with differing reliability characteristics, to predict the expected number of failures at fleet level. The empirical data used in the paper are based on field data gathered during the operational life of two types of multi repairable units used in the Swedish military aircraft system FPL 37 Viggen from 1977 to 2006. The paper performs the trend test using TTT-based MIL-HDBK-189 and Laplace tests, and assesses the equality of shape-parameters for the intensity function of the power law process for multiple units. Estimation of the scale- and shape-parameters using maximum likelihood estimation is also performed. The parametric approach using power law process was found to yield relatively accurate estimations of number of failures, compared to empirical data

Place, publisher, year, edition, pages
2014. Vol. 10, no 3, p. 239-250
National Category
Other Civil Engineering
Research subject
Operation and Maintenance
Identifiers
URN: urn:nbn:se:ltu:diva-5236Local ID: 347bf29f-5ff6-45b2-b316-767cd1a4a291OAI: oai:DiVA.org:ltu-5236DiVA: diva2:978110
Note
Validerad; 2014; 20130817 (aliahm)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
In thesis
1. Part-out Based Spares Provisioning and Management: A Study for Aircraft Retirement
Open this publication in new window or tab >>Part-out Based Spares Provisioning and Management: A Study for Aircraft Retirement
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The operation and maintenance phase of a complex technical system may deal with strategicdecisions for asset retirement and end-of-life management. When a fleet of aircraft reachesthe retirement phase, the operation of remaining fleet should still be kept at a defined level ofavailability. Obviously, the provisioning of spares is a key issue to support the maintenanceand operation of the remaining fleet. The best practice within the aviation industry is to re-usethe spares of retired aircraft to support the operational fleet. This is referred to parting-out.The purpose of the research conducted for this thesis has been to develop decision supportmethodologies, models and tools for the management of a sustainable part-out-based sparesprovisioning for an aircraft fleet during its retirement period. The proposed methodology willbe used to support the retirement process of aircraft fleet and enhance the organisation’scapability of making efficient and cost-effective decisions concerning the re-use of spare partsduring the retirement period. To achieve the purpose of this research, literature studies, casestudies, algorithm development and simulations have been conducted. Empirical data havebeen collected through document studies, interviews, and the perusal of archival records fromSaab Support and Services AB. The data analysis performed for this research has been basedon theories and methodologies within reliability analysis, cost modelling, spares forecasting,stock provisioning and decision making, in combination with the best practices implementedby the aviation industry for the end-of-life management and retirement of aircraft.In the present thesis, part-out-based spares provisioning (PBSP) program is proposed to utiliseretired aircraft units effectively as spare parts. The proposed approach is illustrated andverified through a case study performed on the “Saab-105” military aircraft fleet withinSwedish air force fleet. A PBSP programme is proposed, associated management activitiesare described, the key decision criteria are presented, and a functional framework for aneffective PBSP is suggested. The proposed PBSP program provides a foundation for furthermeasures and tasks to be performed within the retirement period, such as terminatingmaintenance contracts, discarding internal maintenance capabilities, reviewing stocks, scalingdown administrative processes (e.g. spares procurement and obsolescence monitoring), etc.An important part of the PBSP programme is the reliability analysis of multiple repairableunits, and this has been investigated, using parametric and non-parametric reliabilityapproaches. The aim is to identify a practical approach for estimation of the future sparedemand at fleet level. Furthermore, a set of computational models and search algorithm havebeen developed for the identification of applicable termination times, of both the parting-outprocess and the maintenance and repair actions performed on the units. This includestermination of the parting-out process (PO), the sending of parted-out units directly to storage(POS), and repair actions performed on the units received at the repair shops owing tocorrective (CM) and preventive (PM) maintenance, as well as the parted-out units that need tobe repaired (POM). The feasible termination alternatives are compared with regard to theirrespective costs and the most cost-effective solutions are identified.The results of the research study show that a PBSP programme can yield large reductions inmaintenance and spares procurement costs, while supporting operation of existing fleet athighest required availability. It also contributes positively to implement a green supply chainduring the retirement phase. The methodology and approaches introduced within the thesiscan be applied in other civil applications, such as energy, mining, process industry andtransportation sectors.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2017
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keyword
Aircraft retirement, End-of-life management, Parting-out, Part-out-based spares provisioning, Reliability analysis, Repairable units, Spare parts provisioning
National Category
Civil Engineering
Research subject
Operation and Maintenance
Identifiers
urn:nbn:se:ltu:diva-66224 (URN)978-91-7583-990-5 (ISBN)978-91-7583-991-2 (ISBN)
Public defence
2017-11-21, F1031, Luleå tekninska universitet, Luleå, 09:30
Opponent
Supervisors
Available from: 2017-10-24 Created: 2017-10-23 Last updated: 2017-11-24Bibliographically approved

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