Condition monitoring case study

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Engine condition monitoring case study

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Condition monitoring case study

  1. 1. Engine Condition Monitoring as a Route to Savings PGA – Portugália Airlines as a case study Gonçalo Matos dos Santos Marques A thesis in fulfilment of the requirements for the degree of Master of Aerospace Engineering Jury President: Prof. Fernando José Parracho Lau Advisor: Prof. Pedro da Graça Tavares Álvares Serrão External Examiner: Prof. António José Nobre Martins Aguiar November 2010
  2. 2. 1 Acknowledgements/Agradecimentos The language that will be used here in the acknowledgements will be Portuguese, for obvious reasons. Não menosprezando qualquer uma das pessoas que me apoiaram ao longo dos anos, gostaria de dedicar a realização deste trabalho, e portanto o concluir de uma fase importante da minha vida, à minha mãe Maria da Piedade Mendes, à minha avó Maria Angélica Pato e ao meu avô José Luís Pato, pela sua importância na minha construção como pessoa, no apoio e no carinho incondicionais. Agradeço também ao meu pai, Acílio Mendes pelo apoio, pelos conselhos e ensinamentos, que fizeram de mim uma melhor pessoa e um melhor cidadão do mundo. Obrigado a todos por possibilitarem a minha educação, tanto formal como pessoal. Agradeço também à restante família e especialmente aos meus irmãos João e Diana, pelas brincadeiras e sorrisos, que me alegraram nos momentos mais sombrios. Uma palavra especial de agradecimento para Susana Serra, pelo seu papel fundamental ao longo da realização deste trabalho e dos últimos anos do curso. As palavra amigas e de encorajamento que me deste para enfrentar os momentos difíceis, são apenas pequenos vislumbres da enorme pessoa que és, da pessoa que respeito e amo. Um agradecimento sentido também para muitos colegas e amigos, sem os quais a conclusão deste mestrado teria sido com certeza impossível, nomeadamente para os meus companheiros de estágio e amigos de aventuras João Ribeiro, Tânia Trindade e Pedro Martins, e também para os não menos importantes, Cátia Palmeiro, Pedro Pereira, João Lisboa, Henrique Escórcio, Rita Teixeira e Júlio Luta. Finalmente gostaria de agradecer ao professor Pedro Álvares Serrão, pelo apoio e conselho na realização do presente trabalho, e por me dar a possibilidade de realizar um estágio numa empresa de reconhecido valor no mundo da aviação. Uma palavra de agradecimento também para todos na PGA – Portugália Airlines, especialmente para o meu co-orientador Pedro Figueira, pelas ajudas e esclarecimentos, e Marta Boavida pela simpatia e companheirismo sempre disponíveis.
  3. 3. 2 Abstract The successive economical and financial world crises in the last decade are taking a toll in the sensitive aviation sector. The increased competition from new low-cost companies and the rising awareness towards the impact of the aviation industry in the environment, which will in a near future materialize in the EU Emissions Trading Scheme, are forcing established airline companies to compete by reducing costs through the optimization of their operations. The main objective of this master thesis is to evaluate the importance of well-fitted trend monitoring tools, particularly regarding engine condition and fuel consumption, to the optimization processes companies want to enforce. PGA – Portugália Airlines, a Portuguese Regional Airline, has provided the means to develop important tools and to conduct the present analysis. One objective is reviewing the flight profile for the Fokker 100 fleet, regarding engine life-limited mandatory parts. While not being able to improve the flight profile, the analysis provides good indicators to future improvements. A study is conducted to confirm the value of Engine Condition Monitoring as a useful optimization tool. Through an ECM tool, COMPASS, the idea is to study the different analyses that can be conducted in terms of ECM, and see what kind of conclusions could be withdrawn. Several real examples are given and the value of ECM is confirmed, due to its versatility. An additional tool was developed to actively monitor the fuel consumption across both PGA fleets, proving to be invaluable, linking maintenance to flight operations, and thus achieving optimization in both departments. Keywords: Flight Profile; Regional Airline; ECM – Engine Condition Monitoring; Turbofan; Fuel Consumption; Operational Optimization.
  4. 4. 3 Resumo As sucessivas crises económicas e financeiras da última década estão a ter um profundo impacto no frágil sector aeronáutico. A crescente competição de novas companhias low-cost e a crescente sensibilização para o impacto ambiental da indústria aeronáutica, estão a forçar empresas de aviação já estabelecidas a competir, reduzindo custos através da optimização das suas operações. O principal objectivo desta tese de mestrado é avaliar a importância da utilização de ferramentas de monitorização bem adaptadas para auxiliar os processos de optimização que as empresas desejam iniciar, sobretudo em termos da condição de motores e do consumo de combustível. A PGA – Portugália Airlines, providenciou os meios para desenvolver ferramentas importantes e para realizar o presente estudo. Um objectivo deste trabalho prende-se com a revisão dos perfis de voo da frota Fokker 100, relativamente a peças de motor de vida limitada. Embora não tenha melhorado o perfil de voo actual, a análise resulta em bons indicadores para futuras melhorias. Um estudo é realizado para confirmar o valor da Monitorização da Condição de Motores como uma útil ferramenta de optimização. Através da ferramenta computacional COMPASS, pretende-se mostrar as diferentes análises e conclusões que podem ser retiradas através da monitorização de motores. Vários exemplos reais de análises são apresentados e o valor da monitorização é confirmada, dada a sua versatilidade. Uma outra ferramenta computacional foi desenvolvida para monitorar activamente o consumo de combustível em ambas as frotas, provando ser valiosa, por estabelecer uma ligação entre os departamentos de manutenção e de operações de voo, optimizando a operação de ambos no processo. Palavras-chave: Perfis de Voo; Companhia Aérea Regional; Monitorização Condição Motor; Turborreactor Duplo Fluxo; Consumo de Combustível; Optimização Operacional.
  5. 5. 4 Contents Acknowledgements/Agradecimentos.......................................................................................................................1 Abstract..................................................................................................................................................................................2 Resumo...................................................................................................................................................................................3 Contents.................................................................................................................................................................................4 Index of Figures..................................................................................................................................................................5 Index of Tables....................................................................................................................................................................8 Acronyms Abbreviations and Terms......................................................................................................................10 1 – Objectives - Optimization as a Philosophy....................................................................................................12 2 – Portugália Airlines as a Case-Study..................................................................................................................14 3 – Flight Profile ..............................................................................................................................................................17 3.1 – Importance in Guaranteeing Airworthiness............................................................................17 3.2 – Determining Method..........................................................................................................................19 3.3 – Fleet Statistical Analysis...................................................................................................................21 3.4 – Results......................................................................................................................................................24 3.5 – Change in Thrust Mode.....................................................................................................................30 3.5.1 – Results..................................................................................................................................................30 3.5.2 – Consequences – Cost: Time and Fuel vs. Maintenance ....................................................32 4 – Engine Condition Monitoring..............................................................................................................................35 4.1 - Monitoring as a Route to Safety.....................................................................................................35 4.2 –Engine Monitoring Method and COMPASS................................................................................36 4.3 – Data Input...............................................................................................................................................41 4.4 – Results......................................................................................................................................................50 4.4.1 – Fleet Comparison with ECM........................................................................................................50 4.4.2 – ECM as a Problem Identification Tool – Drop in ITT Margin.........................................54 4.4.3 – ECM as a Pre-emptive Tool - Vibrations High Pressure Shaft.......................................57 4.4.4 – Overhaul or Midlife Influence in Engine Performance.....................................................60 5 – Fuel Monitoring........................................................................................................................................................64 5.1 - Monitoring as a Route to Savings..................................................................................................65 5.2 – A Fuel Monitoring Tool.....................................................................................................................67 5.3 – Acquired Results..................................................................................................................................69 5.3.1 – Comparison between fleets/routes .........................................................................................69 5.3.2 – Engine Offline Washing.................................................................................................................73 6 - Conclusions/Future Work ....................................................................................................................................82
  6. 6. 5 References..........................................................................................................................................................................84 Bibliography......................................................................................................................................................................84 Appendix I – ECM Trend Guideline Chart.............................................................................................................86 Appendix II – Embraer ERJ145 and AE3007 Specifications..........................................................................87 Appendix III – Fokker 100 and TAY650-15 Specifications............................................................................88 Appendix IV – IATA and ICAO Codes of Relevant Airports............................................................................89
  7. 7. 6 Index of Figures Figure 2.1 – Fokker 100 (CS-TPD) from PGA Portugália Airlines landing at Schiphol Airport ......................... 14 Figure 2.2 – Embraer 145 (CS-TPI) from PGA Portugália Airlines landing at Brussels Airport ......................... 15 Figure 2.3 – Rolls-Royce TAY 650-15 engine ..................................................................................................... 15 Figure 2.4 – Rolls-Royce Allison AE3007 engine................................................................................................ 16 Figure 3.1 – Plan B datum flight profile set, for low-pressure engine speed (N1) and high-pressure engine speed (N2), as defined in the RR TLM, Chapter 05-10-01............................................................................................. 18 Figure 3.2 – Flight profile assessment process...................................................................................................... 21 Figure 3.3 – Distribution of flights for each aircraft of the Fokker 100 fleet, for the year 2009........................... 22 Figure 3.4 – Distribution of flights in some routes throughout the Fokker 100 fleet, for the year 2009............... 23 Figure 3.5 a) – Datum flight profiles from Plan A to Plan D and analysis results for N2..................................... 24 Figure 3.5 b) – Datum flight profiles from Plan A to Plan D and analysis results for N2 (detail)........................ 24 Figure 3.6 b) – Datum flight profiles from Plan A to Plan D and analysis results for N2 .................................... 25 Figure 3.6 b) – Datum flight profiles from Plan A to Plan D and analysis results for N2 (detail)........................ 25 Figure 3.7 a) – Evolution of flight profile defining point N1 for Take-off, from 2005 to 2009............................ 27 Figure 3.7 b) – Evolution of flight profile defining point N2 for Take-off, from 2005 to 2009 ........................... 27 Figure 3.8 a) – Evolution of flight profile defining point N1 for Climb, from 2005 to 2009................................ 27 Figure 3.8 b) – Evolution of flight profile defining point N2 for Climb, from 2005 to 2009 ............................... 27 Figure 3.9 a) – Evolution of TGT corresponding to defining point N1 for Take-off, from 2005 to 2009 ............ 28 Figure 3.9 b) – Evolution of TGT corresponding to defining point N1 for Climb, from 2005 to 2009................ 28 Figure 3.10 a) – Evolution of TGT corresponding to defining point N1 for Take-off on TAY650-15 SN17392 engine, from 2005 to 2009 .................................................................................................................................... 29 Figure 3.10 b) – Evolution of TGT corresponding to defining point N1 for Climb on TAY650-15 SN17392 engine, from 2005 to 2009 .................................................................................................................................... 29 Figure 3.11 – Example of a Thrust Mode Select Panel (TMSP), not necessarily the one equipped on the Fokker 100 fleet ................................................................................................................................................................ 30 Figure 3.12 a) –Thrust mode impact in one specific flight, on defining point N1, according to FL..................... 31 Figure 3.12 b) –Thrust mode impact in one specific flight, on defining point N2, according to FL..................... 31 Figure 4.1 – ECM process for both Embraer 145 and Fokker 100 fleets.............................................................. 36 Figure 4.2 – COMPASS ECM software for the TAY650-15 and AE3007 engines, by Rolls-Royce................... 39 Figure 4.3 – Equipment Directory COMPASS tool.............................................................................................. 40 Figure 4.4 – Values for smoothed DFF parameter, from January to February 2010, in Embraer CS-TPI............ 44 Figure 4.5 – Values for smoothed DFF parameter, from January to February 2010, in Fokker CS-TPA............. 44 Figure 4.6 – Values for smoothed DTGT parameter, from January to February 2010, in Fokker CS-TPA ......... 45 Figure 4.7 – FF variation of values for a flight in CS-TPA, on the 26th February 2010 ....................................... 46 Figure 4.8 – FF variation of values for a flight in CS-TPA, on the 26th February 2010 (detail)........................... 47 Figure 4.9 – FF results with and without filtering, for CS-TPA flights, in January/February 2010...................... 49
  8. 8. 7 Figure 4.10 – FF approximate linear trends the Fokker 100 fleet, from January to August 2010......................... 50 Figure 4.11 – FF approximate linear trends the Embraer 145 fleet, from January to August 2010 ...................... 51 Figure 4.12 – Comparison of the scatter of DN2, DTGT/DITT and DFF parameters between Fokker 100 and Embraer 145, from January 2010 to July 2010 ..................................................................................................... 51 Figure 4.13 – DFF values and approximate linear trend, for both engines of the CS-TPJ Embraer aircraft and comparison with fleet average, from January to July 2010................................................................................... 52 Figure 4.14 – DN2 values and approximate 6th degree polynomial trend, for both engines of the CS-TPJ Embraer aircraft and comparison with fleet average, from January to July 2010................................................................ 53 Figure 4.15 – DITT values and approximate 6th degree polynomial trend, for both engines of the CS-TPJ Embraer aircraft and comparison with fleet average, from January to July 2010................................................. 53 Figure 4.16 – Margin parameters; interpretation guide to the engine limitation depending on SLOATL ............ 55 Figure 4.17 – Variation of smoothed SL N2 margin parameter, for the Embraer CS-TPJ, in August 2010......... 55 Figure 4.18 – Variation of smoothed SL ITT margin parameter, for the Embraer CS-TPJ, in August 2010........ 55 Figure 4.19 – Boroscope inspection to high pressure turbine blades in the SN311088 AE3007 engine .............. 56 Figure 4.20 – Boroscope inspection to high pressure turbine blades in the SN311088 AE3007 engine (detail).. 57 Figure 4.21 – HP shaft vibration values and approximate linear trend, during Takeoff in CS-TPM.................... 58 Figure 4.22 – HP shaft vibration values and approximate linear trend, during Cruise in CS-TPM...................... 58 Figure 4.23 – DFF variation with engine change in CS-TPE Fokker 100 aircraft, in 29/04/2010........................ 60 Figure 4.24 – DN2 variation with engine change in CS-TPE Fokker 100 aircraft, in 29/04/2010 ....................... 60 Figure 4.25 – DTGT variation with engine change in CS-TPE Fokker 100 aircraft, in 29/04/2010 .................... 61 Figure 4.26 – DN1 values before and after overhaul of engine SN17317; approximate logarithmic trend for post- overhaul engine operation, from February 2006 to August 2007.......................................................................... 63 Figure 4.27 – TGT values for critical N1 and approximate logarithmic trend, from 2006 to 2009 ...................... 63 Figure 5.1 – Evolution of kerosene prices, in US cents per US gallon, from June 1986 to June 2008 (analysis in August 2007) [7]................................................................................................................................................... 65 Figure 5.2 a) – Form1, form presented to users of the fuel monitoring tool, to introduce analysis criteria.......... 67 Figure 5.2 b) – Form1, example of correctly introduced analysis criteria ............................................................ 67 Figure 5.3 – Output of the fuel monitoring tool, corresponding to the criteria of Figure 5.2................................ 68 Figure 5.4 – Normal distributions of the DFC metric, in the LIS-OPO route, for the Fokker 100 fleet, from January to July 2010 ............................................................................................................................................. 69 Figure 5.5 – Normal distributions of the DFC metric, in the LIS-OPO route, for the Embraer 145 fleet, from January to July 2010 ............................................................................................................................................. 69 Figure 5.6 – Normal distributions of the DFC metric, in the OPO-BRU route, for the Embraer 145 fleet, from January to July 2010 ............................................................................................................................................. 71 Figure 5.7 – Passenger efficiency, i.e. fuel spent per passenger, for both fleets and several routes, with a 15-day period per average point, from January to July 2010............................................................................................ 72 Figure 5.8 – Time-based fuel efficiency for several routes for the Fokker 100 aircraft........................................ 73 Figure 5.9 – Example of an action of offline engine washing, not necessarily the exact equipment/method used in PGA’s washes ....................................................................................................................................................... 74 Figure 5.10 – Dust removal from pre-wash (on the left) to post-wash (on the right) from turbine blades ........... 75
  9. 9. 8 Figure 5.11 – Effect of engine wash on DTGT, for the TAY650-15 SN17277 and SN17276 engines ................ 77 Figure 5.12 – Effect of engine wash on smoothed DFF, for the TAY650-15 SN17277, SN17276 and SN17318 engines, in comparison with the non-washed SN17317 engine............................................................................ 78 Figure 5.13 – Variation of TFC with engine wash, for CS-TPA and CS-TPB Fokker 100 aircraft, in the LIS-OPO route, from January to July 2010........................................................................................................................... 78 Figure 5.14 – Variation of DFC with engine wash, for CS-TPA and CS-TPB Fokker 100 aircraft, in the ...... LIS- OPO route, from January to July 2010.................................................................................................................. 78
  10. 10. 9 Index of Tables Table 3.1 – Lives of some engine life-limited parts, depending on the current Flight Profile.............................. 18 Table 3.2 – Yearly results of N1 and N2 values, for each flight phase, from 2005 to 2009; flight profile limits and global results .................................................................................................................................................. 26 Table 3.3 – TGT values corresponding to the maximum values of N1 and N2 for Climb and Takeoff, from 2005 to 2009 .................................................................................................................................................................. 28 Table 3.4 – Obtained results and improvement in Flight Profile after change in Thrust Mode............................ 32 Table 4.1 – Entry and exit conditions used to define the representative take-off points (RTOP)......................... 37 Table 4.2 – Entry and exit conditions used to define the representative cruise points (RCP)............................... 38 Table 4.3 – Part of the trend guideline chart presented on APPENDIX I............................................................. 43 Table 4.4 – Compilation of FF results with and without filtering and respective improvement........................... 49 Table 5.1 – Typical operational profile and PGA example for the Embraer 145 aircraft; savings analysis.......... 66 Table 5.2 – Compilation of Normal Distributions results for the DFF, DN2 and DTGT parameters, before and after wash, and the correspond absolute and relative improvement...................................................................... 76
  11. 11. 10 Acronyms Abbreviations and Terms APU – Auxiliary Power Unit AI – Absolute Improvement BH – Block Hours CDU – Control-Display Unit CG – Centre of Gravity CMC – Central Maintenance Computer Critical Points – Moments when the N1 or N2 values are maximized for the take-off and climb flight phase, and are used for the determination of a flight profile. DFC – Distance-based Fuel Consumption DME – Direcção de Manutenção e Engenharia – Maintenance and Engineering Department ECM – Engine Condition Monitoring E&M – Engineering and Maintenance EASA – European Aviation Safety Agency ETA – Estimated Time on Arrival ETS – Emissions Trading System EU – European Union FAA – Federal Aviation Administration FC – Fuel Consumption FDR – Flight Data Recorder FH – Flight Hours FL – Flight Level FMS – Flight Management System FP – Flight Profile Gal – Gallon GPU – Ground Power Unit H/h – Hour HPT – High Pressure Turbine IATA – International Air Transport Association ICAO – International Civil Aviation Organization IPCC – International Panel for Climate Change ips – Inches per second ISA – International Standard Atmosphere ITT – Interstage Turbine Temperature kg – Kilogramme – Base unit of mass in SI l – Litre lb – Pound M – Mach Number MSL – Mean Sea Level MAXTOW – Maximum Take-Off Weight
  12. 12. 11 N1 – Ratio between actual and maximum rotational speed of the low-pressure shaft N2 – Ratio between actual and maximum rotational speed of the high-pressure shaft OAT – Outside Air Temperature OEW – Operational Empty Weight Pax – The same as passengers PGA – Portugália Airlines RCP – Representative Cruise Point R&D – Research and Development RI – Relative Improvement RJ – Regional Jet, which for the purpose of this work, is assumed to be an aircraft capable of flying up to medium-haul routes, carrying no more than 100 passengers. RP – Representative Point RR – Rolls Royce RTOP – Representative Take-off Point s – Second, the base unit of time in SI SI – International System of Units – “Système International d’Unités” SL – Sea Level TAP Portugal – Major Portuguese Airline TFC – Time-based Fuel Consumption TGT – Turbine Gas Temperature, a temperature measured at the first stage of the low pressure turbine nozzle guide vanes TMSP – Thrust Mode Switch Panel TOC – Top of Climb TOD – Top of Descent TOW – Take-Off Weight TPA TPF – References to the tail numbers of the Fokker F28 Mk 100 aircraft that constitute one of PGA’s fleets, namely CS-TPA, CS-TPB, CS-TPC, CS-TPD, CS-TPE, CS-TPF TPG TPN – References to the tail numbers of the Embraer ERJ145 aircraft that constitute one of PGA’s fleets, namely CS-TPG, CS-TPH, CS-TPI, CS-TPJ, CS-TPK, CS-TPL, CS-TPM, CS-TPN TSFC – Thrust Specific Fuel Consumption TP – Turbo Props US – United States
  13. 13. 12 1 – Objectives - Optimization as a Philosophy It is a global world. In great part thanks to the aviation industry. And now, that global world commercial aviation has so proudly created has become an impossible dichotomy: it is both its livelihood and its worst adversary. The recent global crisis, the effort to decelerate global warming to avoid a global catastrophe, and rampage fierce global competition between airlines while the passenger increases only feebly are leaving their mark in the aviation industry, with bankruptcies being almost commonplace. All these factors, associated with the introduction in the last few years of a number of new low-cost, low-service airline companies, have forced established airlines to adapt and find new ways to compete, by focusing or widening their operation, through undesirable personnel downsizes, with mergers between some of the largest companies and company acquisitions, and naturally by trying to reduce costs in all departments and aspects of operation. The aeronautical industry is probably the one industry that has been suffering the most with the constant increase of international oil prices in the last decade. Fuel has always represented a significant part of the airline companies’ expenses, but now, more than ever, operators have started to take action and make investments in order to implement preventive and corrective measures, with the objective of reducing unnecessary fuel consumption. The environmental impact associated with the burn of fossil fuels is also becoming an increasing factor of concern to the aviation industry. According to the IPCC, in the last ten years, the number of passengers in commercial scheduled flights has increased about sixty percent, and even with oscillations due to economical crisis, the prediction is that it will continue to grow at an average rate of five percent per year for the next ten to fifteen years. Although aviation only contributes to the production of green house gases by two or three percent, there is a will to maintain these contributions to the minimum possible, and some airline companies are already taking some measures in that sense. Presently, the possibility of savings through reduction in fuel consumption is only focused on the cost of the fuel itself. However, in a near future operators will also have to support, proportional to the fuel consumption, the additional cost associated with the mandatory compensation for resulting carbon dioxide emissions, as a consequence of the implementation of the ETS in the EU. This perspective is giving companies one more reason to optimize their engines’ and operations’ efficiency, which should result in less fuel consumption and less pollutant emissions. Besides the investments in equipment and procedures which have the objective of reducing fuel consumption, there is an increasing bet in systems to monitor the aircraft’s fuel consumption. These systems allow airline companies to follow the evolution of fuel consumption and quantify the effects of the measures undertaken within projects of fuel consumption reduction. Additionally, in order to achieve significant improvement regarding fuel-costs, it is important to maintain a close monitoring on the degradation of each fleet, so that the consumption of each single flight can be optimized.
  14. 14. 13 The monitoring of aircraft and engines consists in a continuous compilation process of flight data, which is then analysed in different ways to assess the level of degradation and performance at that moment. Particularly for engines, the continuous following of an engine’s health can allow significant savings in several ways. Engine Condition Monitoring (ECM) is becoming used on a daily basis in many airline companies, for they have understood the potential savings that can be achieved, in fuel, parts and maintenance actions. ECM continuously assesses the health of an engine, and therefore the performance it will present in terms of fuel consumption. If this information could be complemented with a Fuel Monitoring tool that would compile and analyse all data regarding routes, flight time, aircraft weight, number of passengers, take-off weight (TOW), etc, the operator could establish a direct correlation between every engine maintenance action and fuel consumption, assessing their cost-effectiveness and allowing to define long term strategies to reduce costs. PGA – Portugália Airlines, a Portuguese Regional Airline is one of those companies that have grasped the importance of ECM and fuel monitoring as tools to optimize its operation and reduce costs all around. The present work is the result of one of the first steps towards ECM full implementation process. The initial objective was to review the flight profile for the Fokker 100 fleet, regarding engine life- limited mandatory parts, in order to assess if there could be an improvement in the fleet’s flight profile. Such an improvement would translate into increased lives for critical engine parts, which would reflect in significant changes for the company. That analysis has been performed and achieved good results, with the process and results being thoroughly presented in Chapter 3. Also in this analysis there was an assessment of engine condition, but in this case specifically concerning life-limited parts. It was concluded that a broader study should be conducted to confirm the value of ECM as a versatile optimization tool. An engine trend monitoring tool, COMPASS, which was supplied by the engines’ manufacturer Rolls-Royce, should be implemented at 100% although it was already used by PGA’s DEM (M&E). Furthermore, a pc-tool was to be developed to facilitate and automatize the process of introduction of adequate flight data into COMPASS. After uploading the necessary information, through COMPASS the objective was to study the possibilities of conducting different analysis in terms of ECM, and see what kind of conclusions could be withdrawn from such analysis. This process is described in Chapter 4 of this work, where ECM and COMPASS software are properly presented, several real examples of analysis where ECM can be invaluable are given and conclusions are withdrawn regarding the potential and capabilities of ECM implementation into PGA’s operations. Chapter 5 of this thesis will be about the introduction to a simple fuel monitoring tool created by the author, whose objective is to create a bridge between flight operations and maintenance practices, and furthermore, a direct link between maintenance practices and fuel consumption savings. The tool will be briefly explained and its capabilities presented, in order to show the different conclusions that can be withdrawn from the statistical analysis on fuel consumption, from different viewpoints and considering different variables. This tool will be used together with COMPASS to assess whether offline engine washing is cost-efficient for the PGA’s particular case.
  15. 15. 14 2 – Portugália Airlines as a Case-Study PGA Portugália Airlines is a Portuguese Regional Airline company based at Lisbon International Airport operating scheduled international and domestic routes from Lisbon and Oporto. While officially established on the 25th July 1988, it only began its operation two years later because of a delay on the liberalization of the Portuguese commercial aviation scenario. The first flight was from Lisbon to Oporto, followed by the immediate integration of other domestic destinations. In June 1992 PGA flew for the first time an international route, starting to operate European routes to Strasbourg, Cologne and Turin. As the destinations were becoming more varied and the demand was rising, PGA continuously increased its Fokker 100 fleet, which was completed in 1993, acquiring then from 1997 to 2000 eight Embraer ERJ-145 to satisfy the demand imposed by several new destinations in Spain. On June 2007 PGA was acquired by the Portuguese national carrier TAP Portugal, marking the beginning of a new era in the company. Though there is a strict business relationship between the two companies, PGA kept its own flight crews, maintenance personnel, human resources and engineering department, but in this new phase the company provides a service to TAP by covering TAP’s necessities in the short-haul domestic, Iberian and European scenarios PGA has imposed itself as a reference in the European market, marked by its innovative spirit and excellence in customer service. An effective management of its operations, an enthusiastic team and a commitment towards quality and safety have granted PGA international acknowledgement through numerous awards, namely “Best European Regional Airliner” for six years in a row. Figure 2.1 - Fokker 100 (CS-TPD) (source http://www.flickr.com) PGA currently possesses two fleets, the Fokker 100 (Figure 2.1) and the Embraer ERJ-145 (Figure 2.2), with cabin layouts of 97 and 49 passengers respectively. Although both aircraft models fly to most destinations according to demand, the Fokker 100 is more suited for the medium-haul routes to destinations in France, Italy, Switzerland, Holland and Belgium, while the Embraer 145 is more efficient covering Iberian destinations. Both
  16. 16. 15 models have been continuously updated in terms of navigation and safety systems, allowing both PGA fleets to keep up with the increasing demands from national and international regulators. Figure 2.2 - Embraer 145 (CS-TPI) (source http://www.flickr.com) In a new phase of its operation, and in a particularly difficult international economical scenario, Portugália Airlines is looking for ways of optimizing its operations, in order to reduce costs and maintain its valid contribution as an asset within the TAP group. Because maintenance costs and fuel costs constitute a very large part of the yearly total expenses, the validation of practices to reduce costs with engine parts, with maintenance inefficiency and with fuel consumption, was important for PGA and a challenge presented to the author, who accepted it through practical development of optimization tools and then wrote a compilation of the obtained results in the form of a master thesis. All the data analyzed in this thesis is collected from PGA’s FDR and CMC records, and so the realization of this thesis would be impossible without PGA’s support. Figure 2.3 - Rolls-Royce TAY 650-15 engine (source http://commons.wikimedia.org) Because the engines present in PGA’s fleets will be the focus of this work, they will be now briefly presented. The Tay 650-15 engine that powers the Fokker 100 fleet is an axial flow, by-pass engine with two compressor spools. The Rolls-Royce Tay is the combination of two highly successful engines. The high pressure system comes from the RB183-555 engine of the Fokker F28 and the low pressure system comes from the RB211-53E4 engine. The combination of reliability, low fuel burn and low noise makes the Tay engine family very popular in RJs. The biggest advantage of the 650 relatively to the other TAY models was the better performance at higher altitudes and a better climb rate. The Tay 650 on the Fokker 100 aircraft provides
  17. 17. 16 increased maximum thrust for take-off, climb and cruise, plus efficiency improvements through small increases in fan diameter and an advanced high-pressure turbine. Figure 2.4 - Rolls-Royce Allison AE3007 engine (source http://www.fly-corporate.com) The Allison AE3007 is the powerplant of choice for the Embraer 145 and has been a fuel efficiency leader since its introduction in 1995, making it the greenest and one of the quietest engines in its class. The engine produces 7.200 pounds of thrust at sea level and has been certified at an altitude of 51.000 feet. The AE3007 turbofan core is derived from the AE1107 turboprop engine and it was developed to provide a turbofan member of the AE common core family for the growing regional jet and medium/large business jet markets. Designed with excellent reliability, maintainability and performance in mind, the capability and versatility of the AE 3007 turbofan is demonstrated by its use in regional, corporate and military applications. Over the first seven years of operation on Embraer’s 37 to 50 seat Regional Jets the AE 3007A achieved over 10 million hours service experience, powering over 750 Embraer deliveries.
  18. 18. 17 3 – Flight Profile 3.1 – Importance in Guaranteeing Airworthiness The type of record and the level of control applied over its life vary according to the part, depending on its importance to the engine’s performance, condition and ultimately to the aircraft’s airworthiness. For this purpose, parts are divided into Groups A – Critical Parts, B – Sensitive Parts and C – Unclassified Parts. Furthermore, Group B parts are divided into mandatory parts and non-mandatory parts. The definition of the engine’s flight profile is associated with Group A and mandatory Group B parts, therefore only these will be considered henceforth. The failure of a critical part in an engine can have serious consequences. These parts are together termed Group A parts: a mandatory (not to be exceeded) operating life is declared for each of them. Group A parts comprise those major rotating parts of an engine the failure of which could, if uncontained, affect the airworthiness of the aircraft. They are the only parts of the engine for which an Airworthiness Authority certified life is required and notification of the lives must be made to each aircraft operator. These parts are thus subjected to strict life limitations which must not be exceeded in service. These limitations are made as a result of experience collected by the manufacturer through cyclic ring testing, development engine testing, metallurgical investigation and other techniques, including sampling of service run parts. The service life achieved on a part may prove to be less than that permitted by the manufacturer for airworthiness consideration. For example, corrosion or wear may result in rejection of the part at an earlier life than the quoted limitation. Mandatory Group B parts are the ones which test and service experience have shown require special attention in service, in order to avoid failures which: May be serious in terms of engine disruption but are classed as considerably less significant than the possible consequences of a Group A part failure; Though not hazardous in their own right, may threaten the integrity of a Group A part. The lives of Group A and mandatory group B parts are expressed in terms of Flight Cycles. This is the most direct and accurate way of controlling the service life or parts. The life is calculated from the rate of fatigue life usage per datum flight. A flight cycle can be defined as a normal take-off to landing cycle or a “touch and go” situation. In Table 3.1 some examples of engine life-limited parts can be found, as well as each part life limitation cycle-wise, depending on which flight profile the fleet has. For these particular parts, an improvement from Plan B to Plan A would result in a life increase of 10%, therefore about 10% of cost reduction with limited- life parts. Taking into account the large number of parts (especially blades) and the elevated cost of each of those parts, it’s easy to understand the operator’s will to upgrade its flight profile.
  19. 19. 18 Part Description Group Plan A Plan B Plan C Plan D LP compressor rotor discs assembly A 23 000 21 000 20 000 20 000 HP compressor rotor disc stage 2 A 22 000 20 000 20 000 20 000 HP turbine shaft and seal assembly A 23 000 21 000 21 000 20 000 HP turbine rotor disc stage 1 A 23 000 21 000 18 000 14 250 LP compressor blade B 22 000 20 000 20 000 20 000 T able 3.1 - Lives of some engine life-limited parts, depending on the current Flight Profile A Flight Profile is a graphical representation of the actual service operations over an entire fleet and route structure and the operator is responsible for its determination. Flight profiles are classed from A to D, A being the best flight profile, associated with the largest life-limits and D the worst a fleet can present in terms of life-limits. At regular intervals, as agreed between the operator and his local airworthiness authority, usually annually, the operator must review the fleet representative flight profile data and send it to the manufacturer for analysis. If the operator thinks that his operation is no longer represented by the reference datum flight profile, the changed fleet representative flight profile data must be supplied to the manufacturer. This was the case of Portugália Airlines. Figure 3.1 - Plan B datum flight profile set for N1 and N2 In the last couple of years, PGA has increased its effort to stride forward when optimization is concerned, always trying to find new ways of reducing costs without compromising flight safety or passenger comfort. Maintenance is responsible for a very significant part of the company’s global annual expenses, in part because of the inevitability of replacing very expensive life-limited critical parts. The possibility of extending the use of those parts is therefore very appealing and worth looking into. In the last years measures have been taken to reduce engine wear, both in the Flight Operations department, where pilots have been given strict instructions to reduce power when possible, namely in take-off and climb and also in the Maintenance department, where trend-monitoring and frequent inspections and overhauls keep the engines in the best condition possible. The enforcing of these measures gave PGA the confidence to assess if they could improve its long-lasting Flight Profile “B” through a more detailed analysis from FDR data.
  20. 20. 19 The most common methods used to collect data on flight profiles are manual cockpit flight data recording or automatic cockpit flight data recording (using an FDR or DFDR), from which the latter is preferred in this particular case, because it’s more practical, more accurate and reduces the pilot’s workload. The operator must make sure that the recorded operational flight data contains all areas in which the datum flight profile could be more than the limit. An example of a flight profile reference datum is displayed in Figure 3.1 and although the whole flight is represented, in most cases the most extreme points are sufficient to attribute a fleet’s flight profile, through comparison with the reference data flight profiles. The minimum required parameters are: Maximum speed of each rotor (N1, N2) during the take-off phase Maximum speed of each rotor (N1, N2) during the climb phase. To find out if it agrees with a datum flight profile, the recorded peak rotor speeds must be averaged over a twelve month period. The average of the recorded peak rotor speed must be less than or equal to the corresponding value in the reference flight profile, as given in the RR Time Limits Manual, Chapter 05-00-02. In association with the maximum rotor speeds, other information should be sent for further analysis such as TGT, FF, flight conditions at the moment like Mach, TAT and altitude, not to mention the hour and date when the maximum values appeared. In terms of data representativeness, some cautions must be taken when choosing the data that will be processed to result in a flight profile classification, namely for the case study: For a fleet size of 6 aircraft, all aircraft should be sampled, as evenly as possible and the minimum total number of flights to be recorded per twelve month period is 60 flights. The data collected must be representative of the total operation. Samples are to be taken throughout the year, which contain the complete route structure and must include any extremes of the operation, which may affect engine speed. 3.2 – Determining Method In the previous sub-chapter, the definition of a flight profile was given, conditions were imposed and the objective was set. In this section it will be described how the analysis was exactly conducted, to determine the fleet’s current flight profile, while making an effort to provide the most accurate and representative results possible in relatively short time. The Flight Data Recorder, as previously stated, was the selected source of information from which the flight profile would be assessed. FDR data is easy and practical to obtain, making it possible to have records from every aircraft, throughout the year and in any conditions. Also, apart from any FDR or sensor malfunctions, FDR data is easy to work with and usually accurate and reliable. PGA has a relatively large FDR data archive, which is the result of continuous data downloads and archiving throughout the last years. To provide with an
  21. 21. 20 accurate and complete flight profile assessment, it was determined that analysing flight profile status and FDR records from 2005 onwards would suffice. Firstly, because the flight profile analysis is made in an annual basis, the recorded files were processed and analysed by years, namely 2005, 2006, 2007, 2008 and 2009. The year of 2010 wasn’t considered because this analysis was concluded in May 2010 and the data acquired until that point wasn’t representative enough of the year 2010, to include in an annual-based analysis. According to the requirements presented before, a 6- aircraft fleet should present at least 60 FC to correctly determine the fleet’s flight profile, however to achieve the most accurate result possible, more flights were analysed, as calculated below (approximate values): Total ൬ FC year ൰ ൌ 25 ൬ FC aircraft ൈ quarter ൰ ൈ 4ሺquarterሻ ൈ 6ሺaircraftሻ ൌ 600 ൬ FC year ൰ Equation 3.1 About 25 flights were considered per aircraft per quarter, which results in about 600 flights per year and about 3000 FC for total analysed flights. The records were divided in quarters to assure that all flight and operational conditions were covered, but after that, for a given quarter, the choosing process of the FCs was completely random and without any criteria, with the objective of not adulterating the result. The determination of the flight profile is represented in Figure 3.2 and commences with the FDR pre- selected analysis files, which have to be introduced into a software program that changes the .DLU files downloaded from the FDR into ASCII (.txt for example) files. This tool also selects which parameters are important for the upcoming analysis. In this case the following parameters are: Aircraft, Date/Time, Flight Phase, Pressure Altitude, Airspeed, Groundspeed, TAT and for each engine TGT, EPR, N1 and N2. The process continues by processing the .txt files with a program developed in Visual Basic for Applications language under Microsoft Access, which detects all the files to be processed in a user-selected folder. Only files of the same year should be processed together. Afterwards, some filtering has to be done in order to eliminate sensor reading errors and other data spikes and discrepancies. The maximum high-pressure and low-pressure rotor speeds (N1 and N2 respectively) are obtained, and the points where these maximum values take place become Critical Points, for they correspond to the moments when engine operation is the most extreme. All information associated with these Critical Points is recorded into a Microsoft Excel sheet for further processing.
  22. 22. Figure The result of the previous steps for any given year is two Excel Workbooks, one for the Take and another for the Climb phase, each of them with two worksheets, one with the Critical Points information when N1 was maximum and the other with the Critical Points data when N2 was maximum. The last step consists on making a simple average of the low each worksheet, in other words, an average per speed, per flight phase, per year. If more tha analysed, like in the present case, a final simple or weighed average phase to achieve one final flight profile. so they can analyse these results and attribute a flight profile classification from A to D. description of this final process will be presented in 3.3 – Fleet Statistical Analysis The concept of one flight profile being able to describe an entire fleet can be puzzling. a couple of numbers be sufficient to represent the condition of a fle in different moments in terms of their maintenance program, whose engines have just been overhauled or haven’t been refurbished for a while? In the flight operations department, with the multitude of destination is the flight profile a trustworthy representation of all the different routes? Is this over In this section, these questions will be answered, Figure 3.2 - Flight profile assessment process The result of the previous steps for any given year is two Excel Workbooks, one for the Take b phase, each of them with two worksheets, one with the Critical Points information when N1 was maximum and the other with the Critical Points data when N2 was maximum. The last step consists on making a simple average of the low-pressure rotor speed N1 and high-pressure rotor speed N2 each worksheet, in other words, an average per speed, per flight phase, per year. If more tha , a final simple or weighed average should be done for each parameter and fli phase to achieve one final flight profile. Finally the results and data should be sent to the engine’s manufacturer, so they can analyse these results and attribute a flight profile classification from A to D. process will be presented in section 3.4. Fleet Statistical Analysis The concept of one flight profile being able to describe an entire fleet can be puzzling. a couple of numbers be sufficient to represent the condition of a fleet, whose planes have different ages, in different moments in terms of their maintenance program, whose engines have just been overhauled or haven’t In the flight operations department, with the multitude of destination is the flight profile a trustworthy representation of all the different routes? Is this over-simplifying the problem? will be answered, by pointing out what requirements the fleet must fill, 21 The result of the previous steps for any given year is two Excel Workbooks, one for the Take-off phase b phase, each of them with two worksheets, one with the Critical Points information when N1 was maximum and the other with the Critical Points data when N2 was maximum. The last step pressure rotor speed N2 in each worksheet, in other words, an average per speed, per flight phase, per year. If more than one year is should be done for each parameter and flight Finally the results and data should be sent to the engine’s manufacturer, so they can analyse these results and attribute a flight profile classification from A to D. A more detailed The concept of one flight profile being able to describe an entire fleet can be puzzling. How can literally et, whose planes have different ages, can be in different moments in terms of their maintenance program, whose engines have just been overhauled or haven’t In the flight operations department, with the multitude of destinations PGA flies to, simplifying the problem? what requirements the fleet must fill, by
  23. 23. explaining the concept from a statistical PGA’s Fokker 100 fleet. There are various explanations for the valid questions related with the aircraft’s age. PGA’s Fokker 100 fleet has several characteristics that help validating the use of a single flight profile per fleet: The aircraft all have roughly the same age, the maximum discrepancy being which in theory would result in similar when the maintenance program is concerned There is an effort to equally utilize all aircraft, as can be seen in Figure 3.3, so they also have similar behaviour in terms of flight If scheduled inspections are strictly carried out and engine trend persistently enforced, the engines shoul immediately detected, investiga Some fleets from other airline companies won’t be able to present t probably have more difficulty in justifying the single flight profile for that fleet. Figure 3.3 - Distribution throughout the Fokker 100 In terms of flight operations, flight profile. Different destinations result in different climates, runway lengths and altitudes, altitudes and noise-related directives. Also longer routes mean more fuel and thus more weight, which forces the engine rotor speeds to increase, degrading the associated flight profile. The same weight increase happens in busier routes. Flight profile assessment these variations, while unavoidable, statistically speaking will be averaged and in consequence down although this aspect must be accounted for in the final stages of the pro this particular case, it’s easy to see that PGA’s fleet won’t be too affected in terms of flight of its regional operation status. PGA’s longest route is only about 800 NM, most destinations ar 16,9% 17,1% 16,4% Flight Distribution in Fokker 100 Fleet e concept from a statistical perspective to ultimately justify the use of a single flight profile for There are various explanations for the valid questions raised above and one of the most importa PGA’s Fokker 100 fleet has several characteristics that help validating the use of a The aircraft all have roughly the same age, the maximum discrepancy being in theory would result in similar behaviour and even a relative closeness between aircraft aintenance program is concerned There is an effort to equally utilize all aircraft, as can be seen in Figure 3.3, so they also have in terms of flight-cycle maintenance f scheduled inspections are strictly carried out and engine trend-monitoring is actively and persistently enforced, the engines should all be in very good condition, with small deviations being immediately detected, investigated and when possible corrected Some fleets from other airline companies won’t be able to present these argument probably have more difficulty in justifying the single flight profile for that fleet. Distribution throughout the Fokker 100 fleet for the year 2009 tions, different routes imply numerous differences that will affect the calculated flight profile. Different destinations result in different climates, runway lengths and altitudes, related directives. Also longer routes mean more fuel and thus more weight, which forces the engine rotor speeds to increase, degrading the associated flight profile. The same weight increase happens in Flight profile assessment must obviously consider all routes, despite their length or occupancy and these variations, while unavoidable, statistically speaking will be averaged and in consequence down although this aspect must be accounted for in the final stages of the process. Although these differences exist, in this particular case, it’s easy to see that PGA’s fleet won’t be too affected in terms of flight PGA’s longest route is only about 800 NM, most destinations ar 16,5% 16,2% 16,8% 16,4% Flight Distribution in Fokker 100 Fleet TPA TPB TPC TPD TPE TPF 22 stify the use of a single flight profile for above and one of the most important is PGA’s Fokker 100 fleet has several characteristics that help validating the use of a The aircraft all have roughly the same age, the maximum discrepancy being around two years, behaviour and even a relative closeness between aircraft There is an effort to equally utilize all aircraft, as can be seen in Figure 3.3, so they also have monitoring is actively and , with small deviations being arguments and therefore, will the year 2009 imply numerous differences that will affect the calculated flight profile. Different destinations result in different climates, runway lengths and altitudes, obstacle clearing related directives. Also longer routes mean more fuel and thus more weight, which forces the engine rotor speeds to increase, degrading the associated flight profile. The same weight increase happens in must obviously consider all routes, despite their length or occupancy and these variations, while unavoidable, statistically speaking will be averaged and in consequence down-rated, cess. Although these differences exist, in this particular case, it’s easy to see that PGA’s fleet won’t be too affected in terms of flight-operations, because PGA’s longest route is only about 800 NM, most destinations are in mild
  24. 24. Western Europe and most destination runways are almost at sea differences. Furthermore, long runways allow PGA’s relatively small aircraft to take engine power, which improves operational flight profile. Also in this area the concept makes sense and can be applied as long as the existing variations in flight operations are not forgotten and are included in the final safety margin After understanding that statistically which present relatively mild climates, we mustn’t forget that with statistical averages comes an error or deviation, and that the worst-case deviation is the one specific aircraft does almost exclusively all year, especially in the summer, from Lisbon to these tropical locations, Madeira and Casablanca with high humidity, very high temperatures aircraft engines, resulting in worse flight profile results than the rest of the fleet. In this situation, the lif critical parts of these engines, while part of the fleet, aren’t expected to last as long as the rest, so the fleet’s flight profile doesn’t represent these engines profile is to expose all engines to all operating conditions. routes (thus not exposing the engine to differing route operating conditions), an individual operational flight profile monitoring must be made for the group of engines operat fleet. PGA has taken this into account and, also for maintenance reasons, tries to assign each plane to cover all routes in order to average engine and aircraft behaviour. This effort can be visualised the most frequent flown routes are displayed because of their importance from a statistical perspective, but the rest of the routes also follow the same distribution model Figure 3.4 - Distribution of flights in some routes through t 0,0 5,0 10,0 15,0 20,0 25,0 LIS-OPO LIS-MAD Flights(%) Flight Distribution per Route Western Europe and most destination runways are almost at sea-level, which reduces some of the referred differences. Furthermore, long runways allow PGA’s relatively small aircraft to take-off with perational flight profile. Also in this area the single concept makes sense and can be applied as long as the existing variations in flight operations are not forgotten margin. that statistically almost all of PGA flights are made for European destinations, which present relatively mild climates, we mustn’t forget that with statistical averages comes an error or case deviation is the one we should worry about. As an example, let us imagine that one specific aircraft does almost exclusively four routes: LIS-FNC, LIS-PXO, LIS-CMN summer, from Lisbon to these tropical locations, Madeira and Casablanca very high temperatures and over large stretches of ocean, puts additional stress on the aircraft engines, resulting in worse flight profile results than the rest of the fleet. In this situation, the lif , while part of the fleet, aren’t expected to last as long as the rest, so the fleet’s ese engines properly. This is why one of the requirements for a all operating conditions. If the operator uses dedicated aircraft on individual routes (thus not exposing the engine to differing route operating conditions), an individual operational flight profile monitoring must be made for the group of engines operating a common route as though it were a single PGA has taken this into account and, also for maintenance reasons, tries to assign each plane to cover all routes in order to average engine and aircraft behaviour. This effort can be visualised in Figur the most frequent flown routes are displayed because of their importance from a statistical perspective, but the rest of the routes also follow the same distribution model. Distribution of flights in some routes through the Fokker 100 fleet for MAD LIS-BCN OPO-LGW LIS-LYS OPO-LUX OPO-AMS OPO-FCO Routes Flight Distribution per Route 23 level, which reduces some of the referred off without requiring full single flight profile per fleet concept makes sense and can be applied as long as the existing variations in flight operations are not forgotten are made for European destinations, which present relatively mild climates, we mustn’t forget that with statistical averages comes an error or As an example, let us imagine that CMN and LIS-CAS. Flying summer, from Lisbon to these tropical locations, Madeira and Casablanca respectively, puts additional stress on the aircraft engines, resulting in worse flight profile results than the rest of the fleet. In this situation, the life-limited , while part of the fleet, aren’t expected to last as long as the rest, so the fleet’s properly. This is why one of the requirements for a single flight If the operator uses dedicated aircraft on individual routes (thus not exposing the engine to differing route operating conditions), an individual operational flight ing a common route as though it were a single PGA has taken this into account and, also for maintenance reasons, tries to assign each plane to cover all in Figure 3.4, where only the most frequent flown routes are displayed because of their importance from a statistical perspective, but the fleet for the year 2009 FCO TPA TPB TPC TPD TPE TPF
  25. 25. 24 In conclusion, the fleet’s age, the up-close and consistent monitoring of engine behaviour, the compliance of mandatory inspections and other maintenance tasks, associated with pilot standardized procedures, flight operations optimization and even the airline’s own regional status, justify the use of only one Flight Profile to accurately describe PGA’s Fokker 100 fleet, when critical engine parts are concerned. 3.4 – Results The process itself to obtain the fleet’s flight profile, although simple, was a bit time-consuming, which was expected given the number of flights involved, spread throughout five years. However the normal annual flight profile analysis should be relatively simple and quick to complete, depending on the used sample. As described before and illustrated in Figure 3.1, flight profile reference data is given for all the duration of an example flight, however in a first analysis only the points where the rotor speeds reach maximum values are of interest to compare with these reference profiles and attribute a flight profile to the fleet, because these are the operational Critical Points. Only if these Critical Points prove to be insufficient to provide a clear flight profile result, should other points from other moments of the flight be considered. Figure 3.5 a) and b) - Datum flight profiles from Plan A to Plan D and analysis results for N1 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 N1(%) Minutes N1 Flight Profile Data A B C D AVG 75 77 79 81 83 85 87 89 91 93 0 5 10 15 20 25 30 N1(%) Minutes N1 Flight Profile Data Detail A B C D AVG
  26. 26. 25 As explained in section 3.1, flight profile A is the most demanding, in the sense that the maximum rotor speeds should be the lowest, which means that engine operation must be very smooth. To easily grasp the differences between profiles at every flight stage, in Figure 3.5 and 3.6 the reference flight profiles are graphically displayed. PGA’s obtained Critical Points for the conducted analysis are also represented in the Graphs, to give an idea of the fleet’s situation and to make predictions about the manufacturer’s future flight profile attribution. Analysing these graphical representations, particularly in Figure 3.5 b), where the differences between reference profiles at high rotation speeds can be easily seen, it becomes clear the growing level of demand in terms of engine health and operational profile from D all the way to A, represented by the increasing limitation in the maximum speeds of the low-pressure rotor. It is also noticeable how the C and D reference profiles are almost identical except during take-off, which is the most demanding and critical phase of the flight engine-wise and where it was therefore expectable that a difference between the reference profiles would exist. ` The yellow dots in Figures 3.5 and 3.6 represent the N1 and N2 respective Critical Points which characterize PGA’s Fokker 100 fleet for the considered period of time, in terms of flight profile. The obtained 50 60 70 80 90 100 110 0 10 20 30 40 50 60 70 N2(%) Minutes N2 Flight Profile Data A B C D AVG 90 92 94 96 98 100 102 0 5 10 15 20 25 30 N2(%) Minutes N2 Flight Profile Data Detail A B C D AVG AVG Figure 3.6 a) and b) - Datum flight profiles from Plan A to Plan D and analysis results for N2
  27. 27. 26 results are systematized in Table 3.2, where the 5-year analysis is divided by years, as it was already referred in section 3.2., and then by parameters and flight phase. Flight Phase Parameter Limits 2005 2006 2007 2008 2009 Average Take-off N1 A < 84,5 83,99 83,91 84,00 83,45 82,96 83,66 A A A A A A N2 94,9 < B < 96,4 95,96 95,85 96,07 95,47 95,52 95,77 B B B B B B Climb N1 A < 89,0 87,97 88,81 88,85 88,13 88,42 88,44 A A A A A A N2 94,6 < C < 96,6 95,36 95,45 95,49 95,18 95,37 95,37 C C C C C C Table 3.2 - Yearly results of N1 and N2 values; flight profile limits and global results A simple average was used in this case, although a weight average was also considered, but because the difference between the results obtained by each approach was very small, the weight average was discarded. With further observation of Figure 3.6 b), there’s a strange situation that draws the observer’s attention. Around the 25 minute mark, when the aircraft’s engines reach the maximum values of high-pressure rotor speed, it comes to attention that the blue line, which represents reference flight profile B, is lower than the red line, which represents reference flight profile A, which means that in that important instant, reference flight profile B is actually more demanding (requires lower maximum values of rotor speed to be applied) than reference flight profile A. When calculating average values from the 5-year data of the N2 parameter for the climb flight phase (see Table 3.2), the result is 95.37%, which is 0.77% over the reference profile A and 1.23% below reference profile C. The fact that the profile B isn’t half-way between profiles A and B as usual, forces PGA’s Critical Point for N2 climb phase to an apparently unfair flight profile C. Although understanding that this kind of analysis isn’t scientifically correct, but just to give an idea of the damage the inexistence of a reference profile B in the referred point, considering that a numerical scale would exist from 1 to 4, which would correspond to the existing classification, from D to A (in other words, if D ൌ 1, C ൌ 2, B ൌ 3 and A ൌ 4), the “average” final result with and without reference profile B would be: FP ൌ ୅ା୆ା୅ା୆ ସ ൌ ସାଷାସାଷ ସ ൌ ଵସ ସ ൌ 3,5 ൌ A and FP ൌ ୅ା୆ା୅ାେ ସ ൌ ସାଷାସାଶ ସ ൌ ଵଷ ସ ൌ 3,25 ൌ B. Equation 3.2 Despite the lack of scientific value of this analysis, and more in a qualitative basis, assuming that 3.5 would round to 4 then PGA’s flight profile would have an A classification, which would represent huge savings for the company. Moreover, because the take-off phase is more demanding for the high-pressure rotor system than the climb phase, an increased importance should be put in the results of the most demanding phase, and the good behaviour demonstrated at take-off should be taken into account. Further discussion about this situation
  28. 28. 27 will be presented at the end of this section, when the final flight profile attribution by the manufacturer will be analysed. Turning the focus to the historical evolution of the studied parameters from 2005 to 2009, in order to better visualize the results presented in Table 3.2, graphical representations of the results were obtained and are displayed in Figures 3.7 a) through d), where the evolutions of flight profile defining points N1 and N2 for Take- off and N1 and N2 for Climb throughout the last five years can be more easily analysed. Figure 3.7 a) and b) - Evolution of flight profile defining point N1 and N2 for take-off Figure 3.8 a) and b) - Evolution of flight profile defining point N1 and N2 for climb Observing the graphical representations displayed in Figure 3.7 a) and b) and Figure 3.8 a) and b), it is clear that the maximum high and low pressure rotor speeds didn’t suffer great variations in the last five years, varying in about 1% at the most. Furthermore, the registered variations were never sufficient to make any of the determined Critical Points change their position relatively to the reference flight profiles, a trend that can be easily confirmed by checking Table 3.2. Despite the relatively small variations and the immutability of the flight profile classification, two aspects should be pointed out. Firstly, if we take into consideration for instance that in the take-off phase between reference profiles A and B, both for N1 and N2, there are differences of less than 2%, it becomes evident that a variation of even 1% or 0.5% can result in a big difference. An improvement of about 2.1% can represent upgrading a C profile to an A profile and in consequence saving 15% or even 28% in the example parts shown in table 3.1. This possibility of great savings with apparent little improvement is the main reason airline companies take measures to reduce 82,50 83,00 83,50 84,00 84,50 2005 2006 2007 2008 2009 N1(%) Year Take-off N1 94,80 95,30 95,80 96,30 96,80 2005 2006 2007 2008 2009 N2(%) Year Take-off N2 87,50 88,00 88,50 89,00 89,50 2005 2006 2007 2008 2009 N1(%) Year Climb N1 94,20 94,70 95,20 95,70 96,20 2005 2006 2007 2008 2009 N2(%) Year Climb N2
  29. 29. 28 engine wear and request the update of their flight profile status frequently. Because a small difference can make a huge difference, this means that the representativeness of the considered data and the accuracy of the conducted analysis are essential to provide correct results. Secondly, although the variations in rotor speed are relatively small, observing graphical representations of Figure 3.7 and Figure 3.8, it is clearly visible that every parameter shows a trend to decrease the rotation speed, thus showing a slight improvement in engine condition, or at least it is approximately stabilized – Climb N2 is an example. It should be noted that the natural evolution of the rotor’s speed is to increase, corresponding to the natural degradation of the engine throughout its parts’ lives. The fact that the graphical representations show the opposite trend is explained by the good practices enforced by the company, such as directives for the pilots to use low power whenever possible, the effort of the maintenance team to maintain engine health by regular inspections and immediate part substitution when any faulted part is lowering the engine’s performance, etc. Many of these directives have been more fiercely enforced since late 2007 and the results can be seen graphically by the drop registered in both rotor speeds for both flight phases from 2007 to 2008. In 2009 rotor speeds stabilized or increased slightly, while still maintaining the same policies, which is somewhat puzzling. Naturally, the more the engine improves, the less margin for improvement exists, and so it’s comprehensible that the rate of improvement would diminish, and on the other hand, knowing that engine speed is highly dependent on the weather and particularly on the TAT, the fact that 2009 was one of the warmest years in history helps explaining this behaviour. TGT 2005 2006 2007 2008 2009 Average Take-off N1 701,0 694,4 696,3 690,6 691,7 694,8 N2 700,6 693,5 694,9 689,2 690,8 693,8 Climb N1 702,0 701,7 701,1 699,9 702,0 701,3 N2 704,3 704,6 704,3 702,3 706,1 704,3 Table 3.3 - TGT values corresponding to the maximum values of N1 and N2 Figure 3.9 a) and b) - Evolution of TGT corresponding to defining point N1 for Take-off and Climb Shaft rotation speed is one of the most important parameters to take into account when studying an engine’s condition, which is why flight profile is classified according to its values. Other important type of data is the engine’s TGT, a parameter very sensitive to variations in the engine’s operation, as a raise in TGT is 686,0 691,0 696,0 701,0 706,0 2005 2006 2007 2008 2009 TGT(ºC) Year TGT Take-off N1 695,0 697,0 699,0 701,0 703,0 705,0 2005 2006 2007 2008 2009 TGT(ºC) Year TGT Climb N1
  30. 30. 29 usually the first sign that something isn’t working as it should inside the engine or that its performance is for some reason degrading. It makes then perfect sense to study these two parameters together and analyse their trends as one. Just like with rotor speed evolution, similar tendencies of improvement until 2008 and stagnation or increase in 2009, generally in the engine wear rate, can be observed in Figure 3.9 a) and b) where TGT for both flight phases is graphically represented. Also noticeable is the almost 10 degree global decrease in TGT at take-off, which is a good symptom of engine health and a sign that the measures being taken to improve engine condition are being successful. Table 3.3 compiles all the evolutions of the TGT parameter for the 2005-2009 period. The engine’s sensitivity to variations of the outside temperature, in terms of fuel flow, TGT, shaft speeds and performance in general, makes the analysis at hand more difficult to conduct if a statistical method wasn’t used. Throughout the year, many climate characteristics such as humidity and winds at high altitudes continuously change, sometimes in unpredictable ways, directly affecting flight conditions and therefore engine performance. The effect of humidity on engine performance is a much discussed subject, because the amount of water in the intake air can affect the air’s temperature and density. Although some investigators believe it does affect engine performance [3][4], it is commonly agreed that the impact will be reduced when comparing to other variables. One of the characteristics that notoriously affect the process of flight profile determination is the temperature, in a more predictable way: when temperature increases, so does TGT, rotor speeds and fuel flow. An example for a specific TAY650-15 engine is displayed in Figure 3.10 a) and b), where graphical representations can be found, which show the TGT variation depending on the time of the year. Figure 3.10 a) and b) - Evolution of TGT corresponding to defining point N1 for Take-off on a specific TAY650-15 engine Inspecting the graphics in Figure 3.10 a) and b), in the horizontal axis the letter corresponds to the aircraft where the engine was installed in that moment (from CS-TPA to CS-TPF), which is followed by the date when the FDR data was downloaded, in the DD/MM/YY format, each download corresponding to about twenty 650,0 660,0 670,0 680,0 690,0 700,0 710,0 720,0 730,0 740,0 B310105 B260205 B040805 D160606 D170906 D131206 D010307 D140507 D240707 D111007 D140208 D200608 D130808 D141008 D080309 D240409 D110809 D211009 TGT(ºC) Aircraft + Date TGT N1 Take-off 670,0 680,0 690,0 700,0 710,0 720,0 730,0 740,0 B310105 B260205 B040805 D160606 D170906 D131206 D010307 D140507 D240707 D111007 D140208 D200608 D130808 D141008 D080309 D240409 D110809 D211009 TGT(ºC) Aicraft+Date TGT N1 Climb
  31. 31. 30 consecutive flights. The main reason for the “saw-shaped” display is the temperature and eventually humidity variation as the year progresses, with low values of TGT during the cold and dry winter months and higher values during hotter late-spring or summer-months. From 2007 onwards each stage of the oscillations is clear, with medium points corresponding to the spring or autumn and in 2005 and 2006, due to lack of stored data, only three points are presented, but the tendency is naturally the same. Through observation of the linear trend lines representing the global TGT evolution, it is also possible to see that overall the TGT increases in the five years of operation, which is a consequence of the natural degradation of the engine’s condition, with average variations of almost 20ºC, which can lead to diminished performance and even structural problems, once again proving the importance of up-close monitoring of engine health. 3.5 – Change in Thrust Mode 3.5.1 – Results The importance of an accurate determination of a fleet’s flight profile, with all the associated difficulties already described, justifies the analysis of a large sample of data, hence the usual utilization of FDR data, which can be easily collected from each single flight. However, flight profile assessment can also be conducted based on the cockpit manual flight data recording with an added workload to the pilot. The power output of an engine is influenced by many factors such as outside conditions, the engine’s bleed status which is controlled by the ECS, the anti-ice status and the Thrust Mode. The engine’s thrust is controlled by the Thrust Management Computer for reference EPR computation. The Thrust Mode Select Panel (TMSP), an example of which is represented in Figure 3.11, allows for selecting the Reference Thrust: TO/GA – Selects TO (takeoff) Mode on the ground or GA (go-around) Mode in flight; CLB – Selects CLB (Climb) Mode; CRZ – Selects (cruise) Mode; CON – Selects CON (max continuous/economical) Mode. Figure 3.11 - Example of a Thrust Mode Select Panel (TMSP) After takeoff, Thrust Mode will naturally change from TO to CLB, and stay that way until TOC is reached, where it will change to CRZ, which isn’t as demanding to the engine as the Climb Thrust Mode. A question was then raised: could the CRZ (cruise) Thrust Mode be applied while in climb flight phase? That would theoretical decrease engine wear and consumption but would it be possible operation-wise? It would be
  32. 32. 31 very interesting to have an idea about the savings that could be accomplished both in fuel and in maintenance while making a balance between savings and eventual added costs or problems and also limitations to its implementation. To measure the impact of changing the Thrust Mode, a directive would have to be approved, namely safety-wise, then transmitted to all the flight crews and finally systematically collected and then processed. A measure of this type, implemented in a whole fleet for a period of time, only to assess the possibility of an eventual gain, is too expensive and generates many changes to the flight crews’ routine, which could even compromise flight safety. A crew was then asked to manually record the engines’ rotor speeds in two flights in the same routes and similar conditions (consecutive days, with the same departure hour, same aircraft and roughly the same weight), one with the usual CLB Thrust Mode and other with the CRZ Thrust Mode. In Figure 3.12 a) and b), one can find the difference in N1 and N2 respectively, between the two Thrust Modes as the aircraft climbs, for both engines. Figure 3.12 a) and b) - Thrust mode impact in one specific flight, on defining point N1 and N2 Observing the graphical representations of Figure 3.12 a) and b), it becomes clear that the change of Thrust Mode results in a very significant difference in terms of both high and low pressure rotor speeds. 80 82 84 86 88 90 92 100 120 140 160 180 200 220 240 260 280 300 320 340 N1(%) Flight Level Thrust Mode Influence on N1 Eng1CLB Eng1CRZ Eng2CLB Eng2CRZ 92 93 94 95 96 97 98 99 100 100 120 140 160 180 200 220 240 260 280 300 320 340 N2(%) Flight Level Thrust Mode Influence on N2 Eng1CLB Eng1CRZ Eng2CLB Eng2CRZ
  33. 33. 32 Although the trends for the two thrust modes are similar for each motor, there is a clear offset between CLB and CRZ, representing a well defined reduction for the complete climb phase. The improvement is always larger than 1% and for some flight moments or flight levels the reduction sizes to about 4%. However, as already pointed out in section 3.2, for the calculation of a flight profile only the maximum speed values of the climb phase are required and so the maximum values of the line charts were collected and systematized in Table 3.4. In a separate note, there is a significant difference between engines which should be further investigated. Flight Phase Rotor Speed Limits Average Current Profile Engine CLB CRZ Improv. CLB/CRZ Equiv. Improv. New Profile Climb N1 ‫ܣ‬ ൏ 89 88,44 A 1 91,3 88,8 2,74 86,02 A 2 91,6 88,7 3,17 85,64 N2 94,6 ൏ ‫ܥ‬ ൏ 96,6 95,37 C 1 97,7 95,6 2,15 93,32 A 2 95,9 93,9 2,09 93,38 Table 3.4 – Obtained results and improvement in Flight Profile after change in Thrust Mode In the previous table, columns CLB and CRZ have the maximum speed values for each engine/rotor combination with the “Climb” and “Cruise” Thrust Modes respectively. The following column displays the speed reduction when changing Thrust Mode, in percentile. If we would assume that the whole fleet would have the behaviour of this engine, and thus have the improvement values displayed in this column, then the equivalent improvement of the fleet would be the same. Applying that improvement to the average of the fleet presented in Sub-section 3.4.1, which is displayed in the “Average” column in Table 3.4, would result in the values shown in the second to last column, “Equiv. Improv.”, which corresponds to Equivalent Average Improvement. When comparing these new results with the limits which are the criteria to attribute flight profiles, in column “Limits”, it is easy to realize that for the high-pressure shaft speed, the current flight profile of C would transition to an A, with huge consequences. Also in terms of the low-pressure rotor speed, the distance for the A reference profile would increase substantially, giving more confidence in the current A profile. Before taking conclusions about how beneficial such a change could be in terms of life-limited engine part costs, all other aspects of the airline’s operations which would be involved with such a change have to be taken into account and consequences have to be predicted. This will be the discussion of the next Sub-section. 3.5.2 – Consequences – Cost: Time and Fuel vs. Maintenance The objective of this Sub-section is to point out some of the potential problems that could arise if the Thrust Mode in the climb phase was changed from CLB to CRZ, which would assumedly result in an upgrade of the fleet’s flight profile. Firstly, the consequences of the flight profile upgrade will be addressed, followed by a discussion over the change in the Thrust Mode. As stated before in a case like this, when an operator believes that his operation is no longer represented by the reference datum flight profile, the new changed fleet representative flight profile data must be supplied to
  34. 34. 33 the manufacturer. Any operator changing from one Life Profile Operation to another must notify the manufacturer of this change and the residual lives of all the Group A and Group B mandatory parts must be calculated again, and entered in the engine maintenance records. The formula is as follows: RL ൌ FPLL ൈ ൬1 െ CSN IPLL ൰ Equation 3.3 With RL = Residual Life; FPLL = Final Plan Life Limit; IPPL = Initial Plan Life Limit; CSN = Cycles Since New. When the flight profile is improved, in this case from “B” to “A”, the residual life of the critical parts will increase, providing a better flight cycle per part cost ratio, which was the intended effect. This easy calculation and the consequent information update of the airline’s databases is the only real task that would have to be performed to have the new flight profile, obviously besides maintaining all the practices and policies that granted the airline this flight profile in the first place. As the flight profile improves, so should the level of maintenance, with frequent inspections and trend-monitoring to continuously assess engine condition, processes that also come with its costs. However, because this improvement was achieved mainly based on low-power and reduced climb rate policies, this means that the flights will be a bit longer, which can affect passenger satisfaction, mean more fuel consumption and an increase in time-related costs. The climb phase has a huge impact on fuel consumption when considering short and medium range flights since it represents from 20% to 40% of the trip time, registering fuel flows 40% greater than on cruise phase. Climbing with reduced thrust will increase fuel consumption because it would extend time spent at lower altitudes where the fuel flow is higher. Therefore, reducing thrust during climb will not save fuel. On the other hand, using thrust settings higher than CLB to make the climb faster would as already seen severely penalize engine life. So in terms of overall fuel consumption, changing the Thrust Mode wouldn’t be beneficial. In terms of flight safety there are also some limitations and concerns that should be taken into account. In order to ensure that air traffic controllers can accurately predict flight profiles to maintain standard vertical separation between aircraft, pilots of aircraft commencing a climb or descent in accordance with an ATC Clearance should inform the air traffic controller if they anticipate that their rate of climb or descent during the level change will be less than 500 ft per minute, or if at any time during such a climb or descent their vertical speed is, in fact, less than 500 ft per minute, as referred in point 2.4.1 of UK’s AIP General Rules and Procedures [2], a limit internationally accepted. This means that the reduced thrust could be used, and if the aircraft’s ROC would be less than 500ft/min, the ATC had to be informed and ATC indications strictly followed. Also from an operational point of view, about 30% of PGA’s flights cover distances under 200 NM, in other words a significant part of the flights take 30-45 minutes in total, with sometimes only about 15-20 minutes in cruise at the selected flight level. This means that changing the Thrust Mode, thus flattening the
  35. 35. 34 climbing profile, prolongs the climb flight phase, reaching TOC later and therefore further shortening the cruise phase, which can be impossible or impractical in short-haul flights like LIS-OPO. Passenger satisfaction is always a top principle to any airline company, especially to PGA which has always made passenger satisfaction and comfort top priorities, having earned numerous awards and international recognition for it. Therefore any change in the company’s operational profile will have an effect in the costumers’ opinion that must be taken into consideration. An eventual change in Thrust Mode would influence their satisfaction in two ways. The lower rate of climb implies more time climbing and a longer flight in general, so this increase in flight duration would have to be measured to have an idea if it would make passengers less satisfied. An increase of just a couple of minutes shouldn’t damage PGA’s reputation in terms of passenger satisfaction, because it’s not very significant an increase from 47 min to 49 min for example on a LIS-OPO flight. On the other hand, lower thrust and lower rate of climb result in a more silent and smoother flight, with slower pressure variations, which together produce a more enjoyable and comfortable flight. Balancing both effects, it is predicted that a change in Thrust Mode would have an impact by slightly increasing passenger comfort and satisfaction, depending on the increase of flight time relatively to its original duration. A change in the Thrust Mode during climb and the consequent flight profile improvement is being considered because of the savings in flight-cycle dependent maintenance costs. However there are other costs that can be influenced by the increase in the climb flight time, one of them is fuel cost which would increase like it was already explained before in this Sub-section, and also time-related costs would also be affected and therefore it’s important to assess if the change in Thrust Mode would pay-off after the overall costs balancing was completed. Maintenance time-related costs should be the first to be analysed, although this would probably prove to be a difficult exercise: rust and wear inspections would be slightly affected, the 5000-hour, 10000-hour, etc checks would in theory be more frequent, approximately in the same amount as the average increase of flight time. Regarding the flight/cabin-crew costs, they would remain unaffected because PGA’s flight and cabin crew personnel are paid not by the hour but on a per-flight-basis or have a monthly fixed salary, thus unrelated with the flight’s duration. Finally there are some costs that depend on the aircraft’s flight hours, such as insurance, aircraft rental, interest and other company related costs. These would also need to be accounted for to assess the penalty associated with this change in the operational profile. The results presented in Table 3.5, although without statistical value, cannot be overlooked given their definite behaviour and the gain margins involved. The potential savings in maintenance costs justifies in a first stage the undertaking of a serious and thorough study about an eventual earlier change in Thrust Mode during climb, estimating gains and losses in all the departments affected by this change and assessing overall benefits from this measure. If it was predicted that such a measure would be advantageous, in a second stage it should be enforced in an experimental period, applying this change to several aircraft and different routes for a sufficient period of time while continuously collecting the FDR data as usual, comparing the results with the ones obtained in the same period in the previous year and assessing if an improvement was achieved. If so in a third stage this change would then be applied to all aircraft and all routes, or at least the routes in which it had proved to be beneficial.
  36. 36. 35 4 – Engine Condition Monitoring 4.1 - Monitoring as a Route to Safety Everyone agrees that there is no price for a human life, nor does it exist for a company’s reputation, and no eventual savings can justify the destruction of either one. For these reasons, ever since the beginning of commercial aviation, passenger and crew safety has always been the number one priority. Because an engine failure during a commercial flight is very likely to have a devastating effect, failures just can’t be tolerated, which is why most of the maintenance practices are conducted with the objective of guaranteeing safety. In the aeronautical industry a specific maintenance method is usually enforced, which consists of changing an engine or major modules in need of inspection and repair with a new or refurbished engine or modules. This method is commonplace in aviation for it allows the aircraft to remain in service as much as possible, without compromising flight safety. In the primordial years of aviation history, manufacturers and operators began to operate engines to failure, which means that the engine was left on wing until something failed, usually with catastrophic results. Since then, companies operating gas-turbine engines have tried to minimize its high maintenance costs by avoiding potential engine failure through preventative maintenance actions at fixed intervals. This practice ensured safety for the most part, but still wasn’t completely safe and wasn’t economically efficient, sometimes with little actual gain in engine health or performance. In recent years however, an Engine Condition Monitoring (ECM) approach has been adopted by many engine manufacturers and operators, in which intelligent real-time data analysis systems are employed to assess the condition of engine components. The objective is then to make maintenance needs be determined according to the engine’s operating condition, rather than maintenance being performed at fixed periods of time. ECM involves both “manual” practices such as MCD, oil consumption and vibration monitoring, and computer methods based on performance analysis and mechanical parameter monitoring using an adequate software tool. These monitoring systems for engine health typically process data from engine-mounted sensors, whose recent evolution in robustness and versatility have made the implementation of ECM possible. ECM may be used for three different approaches, one pre-emptive, one reactive and one more analytical and educational. Through the condition monitoring, early warning of potentially hazardous engine conditions may result in the identification of the precursors to component failure in advance of the actual failure. This is a prognostic approach to condition monitoring, and is useful for types of faults that may be prevented if identified soon enough. An example of this type of approach will be presented in Sub-Section 4.4.3. Faults for which there are no such precursors like a “bird strike" require a diagnostic approach. Those monitoring systems automatically identify engine faults that have occurred, and may recommend restorative maintenance actions appropriate to the type of fault. The analysis to the monitoring of an unplanned event resulting in some mechanical damage will be discussed in Sub-Section 4.4.2. Finally, ECM can be used as a post-event tool, not to repair eventual damage, but to understand the nature of the event or why it happened, and what was the cost or

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