Statistical Modeling of Aircraft Engine Fuel Burn
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Statistical Modeling of Aircraft Engine Fuel Burn by Yashovardhan Sushil Chati Bachelor of Technology, Indian Institute of Technology Bombay (2012) Master of Technology, Indian Institute of Technology Bombay (2012) Submitted to the Department of Aeronautics and Astronautics in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY February 2018 Massachusetts Institute of Technology 2018. All rights reserved. Signature redacted Author................................................. Department of Aeronautics and Astronautics 15 January 2018 Certifiedby.........................Signature redacted Hamsa lialakrishnan Associate Professor, Aeronautics and Astronautics Thesis Supervisor A ccepted by ........................................................ Hamsa Balakrishnan MASSACHUSETTS INSTITUTE OF TECHNOLOGY 3 Associate Professor, Aeronautics and Astronautics FE Chair, Graduate Program Committee FEB 2A 2018 LIBRARIES < This doctoral thesis has been examined by a committee comprising the following members: Signature redacted Prof. Hamsa Balakrishnan . Associate Professor of Aeronautics and Astronautics Thesis Supervisor Prof. Tamara Broderick ... Signature redacted Assistant Professor of Electrical Engineering and Computer Science Doctoral Committee Member Signature redacted Prof. Edward M. Greitzer. ... H. N. Slater Professor of Aeronautics and Astronautics Doctoral Committee Member Dr. Jayant Sabnis ............ Signature redacted Senior Lecturer of Aeronautics and Astronautics Doctoral Committee Member Signature redacted Prof. Moe Z. Win...................... 7............ Professor of Aeronautics and Astronautics Doctoral Committee Member Statistical Modeling of Aircraft Engine Fuel Burn by Yashovardhan Sushil Chati Submitted to the Department of Aeronautics and Astronautics on 15 January 2018, in partial fulfillment of the requirements for the degree of Doctor of Philosophy Abstract Fuel burn is a key driver of aircraft performance, and contributes to airline costs and aviation emissions. While the trajectory (ground track) of a flight can be observed using surveillance systems, its fuel consumption is generally not disseminated by the operating airline. Emissions inventories and benefits assessment tools therefore need models that can predict the fuel flow rate profile and fuel burn of a flight, given its trajectory data. Most existing fuel burn estimation tools rely on an architecture that is centered around the Base of Aircraft Data (BADA), an aircraft performance model developed by EUROCONTROL. Operational data (including trajectory data) are generally processed in order to generate the inputs needed by BADA, which then provides an estimate of the fuel flow rate and fuel burn. Although a versatile tool that covers a large number of aircraft types, BADA makes several assumptions that are not representative of real-world operations. Consequently, the reliance on BADA results in errors in the fuel burn estimates. Additionally, existing fuel burn modeling tools provide deterministic predictions, thereby not capturing the operational variability seen in practice. This thesis proposes an alternative model architecture that enables the development of data- driven, statistical models of fuel burn. The parameters of interest are the instantaneous fuel flow rate (that is, the mass of fuel consumed per unit time) and the fuel burn (cumulative mass of fuel consumed over a particular phase or the entire trajectory). The new model architecture uses supervised learning algorithms to directly map aircraft trajectory variables to the fuel flow rate, and subsequently, fuel burn. The models are trained and validated using operational data from flight recorders, and therefore reflect real-world operations. A physical understanding of aircraft and engine performance is leveraged for feature selec- tion. An important characteristic of statistical methods is that they provide both estimates of mean values, as well as predictive distributions reflecting the variability and uncertainty. Lo- cally expert models are developed for each aircraft type and for each of the flight phases. The Bayesian technique of Gaussian Process Regression (GPR) is found to be well-suited for mod- eling fuel burn. The resulting models are found to be significantly better than state-of-the-art aircraft performance models in predicting the fuel flow rate and fuel burn of a trajectory, giving up to a 63% improvement in total airborne fuel burn prediction over the BADA model. 3 Finally, the Takeoff Weight (TOW) of an aircraft is recognized as an important variable for determining the fuel burn. The thesis therefore develops and evaluates a methodology to estimate the TOW of a flight, using trajectory data from its takeoff ground roll. The proposed statistical models are found to result in up to a 76% smaller error than the Aircraft Noise and Performance (ANP) database, which is used currently for TOW estimation. Thesis Supervisor: Hamsa Balakrishnan Title: Associate Professor, Aeronautics and Astronautics 4 Acknowledgments I dedicate my thesis to maharSi pANini, the (around) 6th century BCE Indian grammarian, who codified the entire Sanskrit Grammar in his revolutionary text aSTAdhyAyI. His ancient work of recognizing patterns in the ocean of Sanskrit language and distilling them into less than 4,000 aphorisms is simply incredible. I was fortunate to learn about aSTAdhyAyI during my time at MIT. As this thesis has used machine learning techniques to understand patterns in aircraft engine fuel burn from flight data, my thesis dedication to this ancient language scientist is befitting. It is said that there is nothing as pure as knowledge in this world. My doctoral research has indeed been a journey of learning, of venturing into uncharted waters with the aim of expand- ing the horizons of knowledge. Many people have been instrumental in supporting me in this journey of over 5 years and as I near my destination, I would like to acknowledge their help and support. I would, first and foremost, like to thank my advisor, Prof. Hamsa Balakrishnan without whose support, this thesis would not have seen the light of the day. She has been a very encour- aging mentor over the past many years and discussions with her opened new doors whenever I got stuck. She has been enormously responsible for my growth as a researcher. I am also thankful to the other members of my doctoral committee, Prof. Edward Greitzer, Prof. Moe Win, Prof. Tamara Broderick, and Dr. Jayant Sabnis for giving new ideas to work on and for teaching me to not lose sight of the big picture while being engrossed in the technical aspects of research. I also thank Dr. Tom Reynolds and Prof. Saurabh Amin for graciously accepting to be my thesis readers. I am extremely grateful to all the agencies who funded the research and my stay at MIT. This research has been supported in part by the National Science Foundation (NSF) and in part by the Federal Aviation Administration (FAA). I would also like to thank the Transportation Research Board (TRB) for awarding me a scholarship through the 2016-2017 Graduate Research Award Program on Public-Sector Aviation Issues. I am thankful to Monica Alcabin, Bob Arnott, Larry Goldstein, Brian Kim, and Saadat Syed for having reviewed my research under the auspices of the Graduate Research Award Program and to Mary Sandy and Sarah Pauls for managing the logistics of the program. The anonymous reviewers who reviewed my other conference submissions also deserve my sincere acknowledgments for having given new ideas to proceed forward. My colleagues in the International Center for Air Transportation have played a huge role in my successful journey towards a PhD. They always ensured that the atmosphere in the office was conducive to research. I am thankful to Harshad, Lishuai, Akshay, Tamas, Sathya, Luke, Mike Wittman, Hector, Jacob, Patrick, Karthik, Joao, and Jackie for the wonderful discussions and fun moments spent together. I am particularly thankful to Sandeep Badrinath for being an amazing collaborator on the FAA project, friend, and source of inspiration. I am indebted to the staff of the Department of Aeronautics and Astronautics for promptly providing me logistical help whenever needed. Thank you, Beth for being a wonderful graduate program administrator and my go-to person for clarification of rules and procedures. I am thankful to Quentin and Ping for taking care of all my financial matters. Having a roof over one's head is a fundamental need of every human being. I am therefore 5 grateful beyond words to the Tang Hall Graduate Residence for being my home for 5 years, and to its heads of house (Dawn and Larry Anderson), house manager (Michael Collins), and staff for providing me with all the amenities necessary for a comfortable living. I also got the golden opportunity to serve on the officer board of Tang Hall and in the process improve my organizational and leadership skills. I am going to terribly miss the exercise room in Tang Hall which has been vital in improving my fitness levels during my stay at MIT. Life at MIT would have been tough without the constant support of my roommates and friends. I will always cherish the wonderful moments I spent with them. Thought-provoking discussions with them have matured my thinking process, which has positively impacted my research too. I would like to place on record my appreciation for Vaibhav, Sanket, Sameer, Parnika, Naga, Tapovan, Divya, Krithika, Ashwin, Jaichander,