Availability Analysis of a Military Turbojet Engine
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TECHNICAL ARTICLE—PEER-REVIEWED
Availability Analysis of a Military Turbojet Engine R. Ragupathy . R. K. Mishra
Submitted: 30 April 2019 / Published online: 11 June 2019 ASM International 2019
Abstract Availability analysis has been performed on a military turbojet engine using commercially available reliability software. Failure data of the engine over a period of 7 years are considered. The failures/defects are categorized, and then analysis is performed for the major defects. Weibull model is used to analyze the availability of the engine highlighting the possible areas for improvement for the enhancement of engine availability. Keywords Availability Defect analysis Aircraft on ground Mean time to failure Time between overhaul Abbreviations AGB Accessory gear box AOG Aircraft on ground ARU Average rate of usage CCOC Combustion chamber outer casing DI Defect investigation FOD Foreign object damage MCD Magnetic chip detector MTTF Mean time to failure MTTR Mean time to repair NC Not confirmed TBO Time between overhauls
R. Ragupathy R. K. Mishra (&) Regional Centre for Military Airworthiness (Engines), Bangalore, India e-mail: [email protected]
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Introduction Turbojet engines are used worldwide by armed forces for various lightweight fighter-bomber and trainer applications. They are in service for decades and form the backbone of any military command. The nature of their application leads them to operate at extreme conditions and often unscheduled during training and combat modes. Rapid throttle excursions and ‘‘g’’ load variations during different maneuvers cause high cyclic stresses on engine components and unusual demands on engine accessories [1]. Ingress of hot gases from fired missile or from engines of other aircrafts during formation flight or even volcanic gases sometimes generates flow distortion, turbulence and instability in the engine leading to abnormality in performance [1–3]. As a result, a number of engines develop snags forcing premature withdrawal from service and affecting the flight management. Non-availability of engines for service leads to ‘‘aircraft on ground’’ (AOG), a situation not favorable for any armed force. More AOG is an indication of lack of preparedness for any emergency and warlike situation. Therefore, analysis of ‘‘availability’’ of engines for service is an important aspect of fleet management so that appropriate remedial measure can be put in the system. In the present paper, an attempt is made to analyze the availability of a military turbojet engine using commercially available reliability software ‘‘Reliasoft Weibull??7’’ [4]. The failures/defects of this engine are categorized into different groups, and then analysis is performed for the major defects. Weibull model is used to analyze the availability of the engine highlighting the possible areas for improvement for the enhancement of engine availability. Improvement in maintainability and
J Fail. Anal. and Preven. (2019) 19:814–820
reliability leads to a better availability of aeroengines. Howev
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