SEP 1 0 2003 AERO

160 Pages·2013·6.4 MB·English

Sustainment of Commercial Aircraft Gas Turbine Engines:
An Organizational and Cognitive Engineering Approach
by
Shaun Shiao Sing Goh
B.S., Mechanical Engineering
Cornell University, 2002
Submitted to the Department of Aeronautics and Astronautics
in Partial Fulfillment of the Requirements for the Degree of
Master of Science in Aeronautics and Astronautics
at the
Massachusetts Institute of Technology MASSACHUSETTS INSTITUTE
OF TECHNOLOGY
June 2003
SEP 1 0 2003
_-LIBRAR IES
@ 2003 Shaun S. Goh. All rights reserved.
The author hereby grants to MIT permission to reproduce and to distribute publicly
paper and electronic copies of this thesis document in whole or in part.
Signature of A utnor ......... r .......................................................................
Department of Aeronautics and Astronautics
May 23, 2003
C ertified by .......... . .............................
Charles P. Coleman
Boeing Assistant Professor of Aeronautics and Astronautics
Thesis Supervisor
Accepted by ........... ........ . .. .......... .....
Edward M. Greitzer
H.N. Slater Professor of Aeronautics and Astronautics
Chair, Committee on Graduate Students
AERO
-1
Sustainment of Commercial Aircraft Gas Turbine Engines:
An Organizational and Cognitive Engineering Approach
by
Shaun Shiao Sing Goh
Submitted to the Department of Aeronautics and Astronautics
on May 23, 2003 in Partial Fulfillment of the
Requirements for the Degree of Master of Science in
Aeronautics and Astronautics
ABSTRACT
Sustainment of commercial aircraft gas turbine engines in the form of maintenance,
repair and overhaul (MRO) is a primary activity in the life-cycle of a modem commercial
aircraft system. About forty percent of a typical air carrier's maintenance costs are due to
engine MRO. As such, the MRO industry is constantly looking for opportunities to
reduce costs and make sustaining aircraft over long lifetimes an affordable proposition
for air carriers. Current MRO decision support tools focus on engine condition
monitoring and fault diagnostic systems, and most of the existing literature has focused
on developing algorithms for these systems. However, few researchers have suggested
how to design a broader set of computer-based decision support tools to meet various
other cognitive needs of the engine MRO community. Besides engine condition
monitoring and fault diagnostics, other cognitive needs can be found in areas such as
fault prognostics, maintenance planning, workscope generation and configuration
management.
This thesis presents a novel cognitive engineering approach to creating a framework that
more fully captures the decision support needs of commercial aircraft gas turbine engine
maintenance, repair and overhaul (MRO) organizations. Using field studies of various
airlines, engine MRO providers and engine manufacturers across North America, Asia-
Pacific and Europe, the analyses presented offers a thorough understanding of these
cognitive needs and the decision-making process in engine MRO. A set of preliminary
recommendations are proposed for a design framework of new decision support tools for
engine sustainment and how such tools can be implemented in future engine MRO
operations.
Thesis Supervisor: Charles Coleman
Title: Boeing Assistant Professor of Aeronautics and Astronautics

Sustainment of Commercial Aircraft Gas Turbine Engines: 5
An Organizational and Cognitive Engineering Approach Shaun S. Goh
Acknowledgements
I would first like to thank God for watching over me all these years and always answering
my prayers. I could not have made it this far in life without God's graces and blessings.
I would like to thank my thesis advisor, Professor Charles Coleman, for believing enough
in me to offer me the opportunity to embark on this research project. I may not have
attended MIT had it not been for him. He has been a wonderful advisor and colleague
and our meetings had always been thought-provoking and exciting. It has been a great
pleasure to work with him. My sincere appreciation goes to Sally Chapman who has
always been most helpful with the administrative aspects of my research work and a
pleasure to chat with.
My appreciation also goes to the various airlines, OEMs and engine MRO shops that I
had visited for this research. I had very interesting interviews with the many engineers,
mechanics, pilots and senior management executives. Your feedback and comments
have been invaluable to this thesis.
To the many students I have met and made friends with along the way at MIT, especially
the wonderful people of Ashdown House, TCC and SSS, thanks for helping me feel so
much more at home while here at MIT. You have all made MIT an especially memorable
adventure for me.
Most of all, I would like to offer my utmost thanks to my family. To my Mum, my Dad,
my brother and my grandmothers: thank you for providing your endless love, support and
encouragement throughout my academic career. Though many miles from home, your
thoughts and prayers have kept me going when work was tough, and you have always
been there for me.
Sustainment of Commercial Aircraft Gas Turbine Engines: 6
An Organizational and Cognitive Engineering Approach Shaun S. Goh
Sustainment of Commercial Aircraft Gas Turbine Engines: 7
An Organizational and Cognitive Engineering Approach Shaun S. Goh
Table of Contents
A b stract........................................................................................................................... 3
Acknowledgements....................................................................................................... 5
Table of Contents......................................................................................................... 7
L ist o f F igures ..................................................................................................................... 9
List of Tables .................................................................................................................... 10
List of Acronyms and Abbreviations............................................................................. 11
CHAPTER 1: INTRODUCTION ................................................................................. 13
CHAPTER 2: M ETHODOLOGY ................................................................................. 19
2.1 Open Literature Review................................................................................. 19
2.2 Industry Field Studies ................................................................................... 19
2.3 Analysis M ethods.......................................................................................... 21
CHAPTER 3: BACKGROUND ................................................................................... 23
3.1 The Airline Industry...................................................................................... 23
3.2 The Commercial Aviation MRO Industry ................................................... 27
CHAPTER 4: AIRCRAFT and ENGINE MAINTENANCE, REPAIR and
OVERHAUL .......................................................................................... 33
4.1 Aircraft M RO................................................................................................. 33
4.1.1. Airline M aintenance Organization.................................................. 33
4.1.2. Aircraft M RO Processes ................................................................. 35
4.2 Engine M RO ................................................................................................ 42
4.2.1 Aircraft Gas Turbine Engines .......................................................... 42
4.2.2 Engine Faults and Failure M odes ................................................... 44
4.2.3 Engine MR O Processes.................................................................... 46
4.2.4 Engine MR O Shop.......................................................................... 53
4.2.5 Decision Support Tools for Engine M RO ....................................... 55
CHAPTER 5: ENGINE DIAGNOSTICS, PROGNOSTICS and CONDITION
M ONITORING...................................................................................... 59
5.1 Current State of Engine Diagnostics, Prognostics and Condition Monitoring. 59
5.2 M ethods and Algorithms............................................................................... 62
5.2.1 Condition M onitoring and Trend Analysis ...................................... 62
5.2.2 Emerging Technology...................................................................... 63
Sustainment of Commercial Aircraft Gas Turbine Engines: 8
An Organizational and Cognitive Engineering Approach Shaun S. Goh
CHAPTER 6: COGNITIVE ENGINEERING APPROACH ...................................... 65
6.1 Introduction to Cognitive Engineering .......................................................... 65
6.2 Cognitive Work Analysis...............................................................................69
CHAPTER 7: ANALYSIS .......................................................................................... 75
7.1 Engine MRO System ..................................................................................... 75
7.1.1 Engine MRO System Stakeholders.................................................. 75
7.1.2 Interactions and Processes ............................................................... 79
7.2 Cognitive Work Analysis............................................................................... 85
7.2.1 Work Domain Analysis.................................................................... 86
7.2.2 Control Task Analysis....................................................................... 106
7.2.3 Strategies A nalysis............................................................................ 125
CHAPTER 8: CONCLUSIONS and RECOMMENDATIONS.................................... 147
8.1 Summary of Research Findings ...................................................................... 147
8.2 Recommendations for Future Research.......................................................... 149
8.3 C onclusions..................................................................................................... 150
B ib liography ................................................................................................................... 15 1
Appendix A: Decomposition Levels for Engine Modules.............................................. 155
Sustainment of Commercial Aircraft Gas Turbine Engines: 9
An Organizational and Cognitive Engineering Approach Shaun S. Goh
List of Figures
Figure 1: Typical Aircraft Cost Structure (Belobaba, 2002) ........................................ 26
Figure 2: Commercial Aviation MRO System .............................................................. 27
Figure 3: Commercial Aviation MRO Market in 2002 (Jackman, 2002)..................... 31
Figure 4: Airline Organizational Structure ................................................................... 33
Figure 5: Schematic of a Turbofan Engine................................................................... 43
Figure 6: Engine Overhaul Process (Adapted from Mohammed et al, 1996) ......... 53
Figure 7: Various layers of a complex sociotechnical system (Vicente, 1999)............ 66
Figure 8: Abstraction-Decomposition Space (Vicente, 1999)...................................... 70
Figure 9: Decision Ladder (Vicente, 1999) ................................................................... 72
Figure 10: Stakeholders of the Engine MRO Enterprise ............................................... 76
Figure 11: Front-line Maintenance Operations............................................................. 79
Figure 12: Airline Decision Process for a Failed Engine .............................................. 81
Figure 13: Decision Support Tools in the Engine MRO System.................................. 82
Figure 14: Integration of Decision Support Tools into the MRO Process.................... 83
Figure 15: 3-Tiered MRO Hierarchy ............................................................................ 84
Figure 16: Airline CEO's Abstraction-Decompostion Space ........................................ 87
Figure 17: Engine MRO manager's abstraction-decomposition space ......................... 90
Figure 18: Engine MRO shop manager's abstraction-decomposition space................. 94
Figure 19:Abstraction Hierarchy for an Aircraft Engine System (adapted from Namidian
et al, 2 0 02 ) ................................................................................................................ 9 5
Figure 20: Means-ends mappings between adjacent levels of the engine abstraction
hierarchy (adapted from Dinadis & Vicente, 1999).................................................. 97
Figure 21: Engine condition monitoring variables ......................................................... 100
Figure 22: Mapping of a troubleshooting trajectory onto the engine abstraction-
decom postion space ................................................................................................ 10 1
Figure 23: Normal in-flight engine monitoring .............................................................. 107
Figure 24: Decision Ladder for In-flight Engine Fault Management ............................. 109
Figure 25: Normal Ground-based Condition Monitoring ............................................... 113
Figure 26: Ground-based Engine Fault Management..................................................... 115
Figure 27: Current vs. Future DPCM systems................................................................ 118
Figure 28: Engine M RO M anagem ent............................................................................ 119
Figure 29: Engine MRO Shop Decision Ladder............................................................. 122
Figure 30: C ondition M onitoring.................................................................................... 126
Figure 31: Pattern R ecognition ....................................................................................... 128
Figure 32: Pattern-matching using a decision table ........................................................ 129
Figure 33: Pattern-matching using physics-based engine models .................................. 131
Figure 34: Prognostics for a Failed Engine System........................................................ 133
Figure 35: Engine Fault Prognostics............................................................................... 135
Figure 36: W orkscope G eneration.................................................................................. 137
Figure 37: Short-term Engine Maintenance Management.............................................. 141
Figure 38: Long-term Engine Maintenance Management .............................................. 143
Sustainment of Commercial Aircraft Gas Turbine Engines: 10
An Organizational and Cognitive Engineering Approach Shaun S. Goh
List of Tables
Table 1: Aviation M aintenance Facts ............................................................................ 15
Table 2: Worldwide Commercial Jet Fleet Forecast (Jackman, 2002)......................... 24
Table 3: MRO Forecast for 2002-2012 (Jackman, 2002)............................................ 32
Table 4: Some Examples of Existing Decision Support Tools for Engine MRO......... 56
Table 5: Engine MRO as a Complex Sociotechnical System........................................ 67