Application of modern maintenance systems in General Aviation

Transcription

1 CÍGER Andrej 1 Application of modern maintenance systems in General Aviation INTRODUCTION Nowadays, aviation is a highly sophisticated and complex system, despite the fact that aviation is one of the youngest from the transport sectors. The concept of maintenance is closely related to aviation from its beginnings. The existence of two world wars has brought very rapid technological development. The concept of maintenance and its application gained significantly in importance. Air frames became very complex and contained a large number of components and systems. It was necessary to develop methods for controlling parts in order to maintain the necessary level of safety, minimized the level of economic burden, and to ensure smooth and no-failure operation. Competences associated with maintaining the required parameters were passed on to qualified aviation technicians and maintenance organizations. The whole process is supported by valid legislation, maintenance systems and standards in the field of continuing air worthiness of aircraft and aircraft components. The aim is to implement so-called progressive methods of maintenance management, when the aircraft and its individual units, aggregates and components are continuously monitored and on these basis the maintenance cycles and individual acts are directed in compliance with established requirements. In addition to these maintenance procedures, it is necessary to deal with maintenance of special technical aviation equipment which the University of Zilina has in the form of AEROLAB 1. In this case it is necessary to take into account the airworthiness and interoperability of built-in special facilities for scientific and research purposes, and this is also set up maintenance procedures in accordance with valid legislation. 1 EVOLUTION OF MAINTENANCE At the beginning of this article it is necessary to define the basic terms closely linked to the maintenance. Maintenance is the process of maintaining or restoring the specified operating characteristics to maximize lifetime of device or system. Fatigue is a mechanism that is often described on the verge of assumptions and hypotheses. In principle this is a mechanical and physical degradation, or degradation of chemical properties of the wear caused by external factors. Reliability is a general characteristic of the product on a predetermined time to perform the required functions for maintaining operational product parameters of the technological requirements. Reliability define sub-properties such as reliability, durability, serviceability, availability etc. Technical requirements defined set of specifications, technical and operational characteristics of the product, further its methods of operation, maintenance and repair. Lifetime is a characteristic of the product to perform the required functions to limiting state established technical requirements. Its expression is various such as the number of hours, cycles, or function of calendar time during which it could be overhauled couple of time. Reliability is superior to the concept of lifetime. Achieve the desired service life is a prerequisite or demonstrating reliability. Reliability is qualified by indicators of reliability such as failure probability, failure rate, mean time to first failure, mean time between failures, availability and 1 University of Žilina in Žilina, Faculty of Operation and Economics of Transport and Communications; Univerzitná 1; Žilina; Slovakia. Tel: , andrej.ciger@fpedas.uniza.sk 2812

2 other factors. These variables have a stochastic character and defined distribution function or probability density[1], [2]. There is significant development in maintenance approaches over passed twenty years. This is based on increasing quantities of equipment, products and objects that require adequate maintenance. Devices are very complex and are controlled by strict legislative frame works. There also should be constantly ensured the safety and protection of the environment. From the early thirties can be the development of maintenance divided into three generations. The first generation is from mid-thirties up to beginning of World War II. The industry was not so developed and mechanized and also there was not significant focus on maintenance. The out of service time did not play a role. Devices were robust and relatively easy constructed. Their repair was simple performed. Maintenance required only basic operations such as routine inspection, cleaning and lubrication. The second generation lasted until the mid-seventies, but the most significant change in maintenance occurred around the period of World War II. War pressure and reducing the number of workers brought into production increasing usage of mechanization. Products were produced quickly with appropriate quality. It was no longer possible to deactivate the manufacturing facility for a long time from the production process and there was the idea of prevention of disorders used for the first time. However, this idea of the periodic over hauling was costly and not always necessary. The third generation continuously follows the previous and gradually evolving to this day. In this period there were efforts to remedy the deficiencies that occurred in maintenance before. One of the principal techniques are undesirable downtime. With the introduction of methods of "Just in Time" where small failure had significant effect on the entire system. With the increasing automation of production, it was necessary to ensure the quality of products, which account for the complex system of the higher amount of potential failures. It also may have significant defects of high environmental impact. Highlighted the issue of the elimination of costs and cost-effectiveness was one of priorities. Maintenance used constant monitoring of a much greater emphasis on reliability and maintainability. Work tasks are performed in the form of team work with an emphasis on cooperation and flexibility of the process itself [3]. 2 BASIC MAINTENANCE METHODS Maintenance of aircraft is very complex and difficult process in which many question must be solved. The most important is the question of safety. It is followed by question of reliability, economy and operational effectiveness. Maintenance procedures involve many tasks to perform airworthiness in compliance with Certificate of Airworthiness (CoA) and approved maintenance program. 2813

3 Fig.1: Maintenance methods tree (source: author) Methods which are not related to condition of component of system are often used for parts which have exact time to be used or number of cycles (rubber components). Methods which are related to condition of part uses methods of monitoring and their replace is done related to condition or when failure occurred [4]. Traditional method is very inflexible and its main task is to replace the components which have limited time in service. It is possible to overhaul the component and use it again. (engines, propellers) Progressive method uses reliability analysis of systems and components and allows to do tasks only when it is needed and useful. Hard block method uses aircraft blocks such as wings, engines, avionics to easily remove and replace it by new or overhauled component (block). Permanent maintenance is used when during significant large maintenance are done also smaller tasks. It helps to eliminate down time and saves money. It is easier to utilize work force of employees. Reliability-centered maintenance uses monitoring equipment and analysis to ensure safety and do needed tasks only when it is necessary [5]. 3 ANALYSIS OF FAILURES AT FLIGHT TRAINING AND EDUCATION CENTRE (LVVC) OF UNIVERSITY OF ZILINA ON ZLIN Z-40 TYPE. In addition to flight training LVVC also focuses on maintenance activities of air craft. This complex process requires meet legislation and technical requirements of the European Parliament and Council Regulation (EC) no.216/2008and Commission Regulation(EC) no.2042/2003 and the subject to the conditions that were maintenance organizations specified in the approval. LVVC holds Maintenance Organization Approval Certificate conducted under reference number SK.MF.006. in accordance with Section A, SubpartF of AnnexI (Part M) to Commission Regulation (EC) no.2042/2003. This certificate applies to the above signed legal frame work and has unlimited validity with ongoing fulfillment of all provisions of the Annex. It is defined for specific types of aircraft, engines, units other than complete engines or APU(Auxiliary PowerUnit) and special services. The certificate include A2 category aircraft (airplanes with MTOW of 5700 kgor less) with a restriction on the types ofzlinz-42m, MU, ZlinZ-142 ZlinZ-43, L-200 A, DMorava, PiperPA (Continental). Furthermore, it is within the scope of authorization defined maintenance of engines 2814

4 B2 types M137A, AZ andm337a, AK. LVVC is charged with the maintenance of propellersv-500a, V-503A, 410AandV-506, as well as carrying out destructive tests form capillary method. Fig.2: Types of aircraft included in approval (source: author) LVVC holds a certificate of the Continuing Airworthiness Management Organization (CAMO) established under the reference SK.MG.025. This certificate is valid in accordance with Annex I (Part M), Section A, Subpart G of Regulation(EC) no. 2042/2003 and entitles the organization to manage the continuing airworthiness of aircraft(z-42 M, MU, Z-142, Z-43 and L-200 Morava) and make recommendations, or a certificate of airworthiness in according to M.A.710 Annex I to Regulation (EC)[6]. University of Zilina owns special PA T Piper Seneca V, OM-UTC - Aerolab 1 (Figure no.3), which is used for flight validation in a range of GND - FL100 intended for scientific and research purposes. One of the specific objectives of the activities ofspecial aviation technology is flight verification of aviation navigation aids and increasing its safety. That special aircraft equipment is laboratory device that is able to monitor the airspace in the Slovak Republic with a vertical range between the ground and FL100 (i.e meters AGL). The monitoring device shall be capable of operating in difficult weather conditions, as well as instrumentally has to be equipped for precision approach equipment including certification for CAT I. respectively. II with regard to the possibility to perform a reliable measurement of light icing conditions. Equipment onboard is able to perform IFR flights. Fig.3: PA T PiperSeneca V Aerolab 1, OM-UTC (source: author) In spite of required maintenance there is neccesary to perform availability and special meintenance also of equipment aboard of laboratory. The following analysis includes data from years There were no fatal accidents and data represents only light incidents or failures. Tab. 1. Total number of failures which occurred during flight training (source: LVVC) Type Z-42 Z-142 Z Total

5 Next table takes into account the number of take-offs and number of flight hours Tab. 2. Total number of flight hours and total number of take-offs on each type (source: LVVC) Type Z-42 Z-142 Z Hours Take-offs Hours Take-offs Hours Take-offs Hours Take-offs Hours Take-offs Total Hours Take-offs In next section there will be presented statistically significant correlation between total number of failures and total number of flight hours or total number of failures and total number of take-offs. For this calculation we used MS Excel s function CORRELL. Tab. 3. Correlationcoeficients (source: LVVC) Year Totalnumber of faulires Totalnumber of flighthours Totalnumber of take-offs Correlationcoeficient 0, , Table 3 shows that correlation 0.87 and 0.86 is very high and almost linear. It means that total number of failures is both correlated on total number of flight hours and also total number of takeoffs. Next table shows that Zlin Z-142 is most used but it has also the highest mean time between failures and the least failure rate. It proofs that maintenance is done very precisely and on high level. Tab. 4. Mean time between failure and failure rate in period of (source: LVVC) Typ Z-42 Z-142 Z ,60 401,33 393, ,67 252,00 574, ,00 119,67 97, ,50 350, ,60-216,00 Average MTBF (h) 146,29 313,58 288,00 Failureintensity (h -1 ) 0,0068 0,0032 0,

6 CONCLUSION Flight training is a complex system and requires a high precision operations during the flight and also during maintenance of aircraft. Article describes the basic description of maintenance and generally defines its basic methods. The most sophisticated is reliability-centered maintenance and it is actively used in the operation of aircraft of Flight training and education center of University of Zilina. Based on the analyses it is clear that the maintenance is performed properly and operations do not bring significant hazard. It was also shown that there is a relatively linear relationship between the occurrence of faults and the number of hours flown or the number of take-offs. The main maintenance safety priority has to be still full filled and all operational and maintenance tasks should be performed with high priority and precision. Application of modern maintenance systems in General Aviation Abstract The following article further describes the issues of maintenance and basic terms such as maintenance, fatigue, reliability and others that are closely related to it. The following section follows the chronological development of maintenance and different approaches to it, which are based on social and political events evolved over time to what it is today. Next part of the article will focus on the maintenance of aviation equipment and aviation special equipment, which continuously develops and requires technological, but financial demands. University of Zilina has at disposal such special equipment, which is very difficult to operate and fulfill all requirements. The author describes the various methods used for the maintenance of aeronautical products and the last part will describe performed failure analysis of aircraft in a flight training performed by Flight training and education center of the University of Zilina This paper is published as one of the scientific outputs of the project: CENTRE OF EXCELLENCE FOR AIR TRANSPORT, ITMS: BIBLIOGRAPHY 1. Business dictionary. [online]. Available at: 2. KAHÁNEK, V Únavová životnostletadlových konstrukcí. 1. issue. Bratislava: Alfa, p MOUBRAY, J Reliability-centered maintenance. 2. issue. New York: Industrial Press Inc p. ISBN S KRÁL, M.: Provozaúdržbaletecké techniky II. 1. issue. VA AZ p. 5. The aircraft maintenance basic philosophies. [online]. Available at: 6. Interview with Mr. Stanislav Kyselica (head of F-Organization) and Mr. Roman Topoľčány (Compliance manager) 7. Failure analysis at University of Žilina - the aircraft operator [Analýza porúchna Žilinskej univerzite prevádzkovateľalietadlove techniky] / Martin Bugaj, Branislav Kandera. In: READ Research and education in aircraft design [elektronický zdroj] : October 17-19th Brno, University of Technology, Czech Republic. - ISSN [Brno: University of Technology], CD-ROM, [9] s. 2817

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