Cranfield University

Cranfield University G. James Sweers Methodology for the design assurance of aircraft lightning protection systems continued airworthiness. School of Engineering Aerospace Engineering Group PhD Thesis Academic Year 2009-2010 Supervisor: Professor J.P. Fielding September 2010 This thesis is submitted in partial fulfillment of the requirements for the Degree of Doctor of Philosophy. © Cranfield University, 2008. All rights reserved. No Part of this publication may be reproduced without the written permission of the copyright holder. Abstract This thesis describes a new approach to lightning protection components design by incorporating the use of multiple data sources, aircraft environmental threats models and component characteristics to determine if the component design meets the continued airworthiness requirements. This innovative aircraft lightning protection component design methodology examines critical component characteristics and evaluates these characteristics for long term survivability given known environmental design data. Use of in-service data, test data, material sciences and detailed component construction produces predictive results and provides inputs for the design community. A simple case of non-active lightning protection components was used to validate this methodology, concluding that certain design degradation mitigations are necessary to improve the continued airworthiness performance. Following this validation, the methodology was exercised by several case studies using actual design data from a large transport aircraft. The case studies provide for understanding how the methodology can be applied and showed that value was produced in creating design optimizations for the protection components. The case studies also proved that the methodology could be applied to different lightning protection designs spanning from structural design protection components to systems infrastructure transport elements and wiring. For this work, analysis sheets were designed to provide the necessary design assessments to apply the methodology. Finally, the thesis concludes that application of this design methodology worked well for evaluation and optimization of lightning protection components and may work well for other aircraft system components. Future work associated with this study suggests that the methodology could more effectively deployed by use of an integrated computing system with the ability to share data efficiently between key design groups including electrical wiring design, electrical earthing engineering, electrical standards engineering, structural protection engineering and maintenance engineering departments. i Acknowledgements This body of work was supported by my family, friends, colleagues and most of all Cranfield University. Along the way, the following were inspirational and supportive to which I owe personal gratitude: Professor Fielding for supervising my quest for new knowledge, seeing the value in the exploration and discovery, and for you excellent advice, guidance and even administrative sponsorship in times when I needed ‘a little something more’ behind what I was trying to achieve. And of course, for your ability to draw out concepts, shape ideas, and pull from the abstract to the concrete. Cathy Centanino – A patient spouse who never threw any darkness on the one thing that has taken so much of my time from you and our son Dylan Centanino-Sweers. Doing a PhD thesis is like having an unanticipated family member who other family members do not get to know, visit for 5 years, and demand time away from normal and important life events. Dr. Mark Tuttle - A fellow Michigan Technological University grad that has helped me without any hesitation, gain access to the library at the University of Washington through a visiting researchers account sponsorship. Your graciousness in allowing me a place and library stacks to get started will be passed to those that I may have the good fortune to help in the future. Ann Galbraith - who provided me legal and personal counsel in navigating my way through sponsorship issues and assisted me in developing a successful plan. David M. Sweers who encouraged me to pursue this PhD and for whom my efforts honor him as someone who sees the accomplishments of his children as personal pride. His never ending encouragement and advice will be forever remembered and passed on to those I have the honor of helping along the way. The Boeing Company for the financial support and technical opportunity to add value to my personal expertise and for the mutually beneficial research that this thesis provides to Boeing and the industry for which this project would not have otherwise been achievable. ii Table of Contents Abstract .......................................................................................................................... i Acknowledgements ....................................................................................................... ii Table of Contents .......................................................................................................... iii Table of Figures ............................................................................................................. vi Table of Tables ............................................................................................................ viii Chapter 1 Introduction and Objectives ......................................................................... 1 1.1 General Description of Issues .................................................................................. 1 1.2 Research Focus and Background ............................................................................. 2 1.3 Research Objective .................................................................................................. 3 1.4 Research Method .................................................................................................... 5 1.5 Conclusion of the Problem Statement .................................................................... 6 Chapter 2 Lightning Characteristics and Impacts on Aircraft ....................................... 7 2.1 Regulations and Guiding Documents ...................................................................... 7 2.2 What is Lightning? ................................................................................................. 13 2.3 How do Aircraft get Struck by Lightning? ............................................................. 15 2.4 How often and under what Conditions is an Aircraft Struck by Lightning? .......... 17 2.5 Where Does Lightning Strike? ............................................................................... 21 2.6 What Happens when an Aircraft is Struck by Lightning? ...................................... 25 2.7 Does Lightning Cause Aircraft to Crash? ............................................................... 26 2.8 How is an Aircraft Protected from Lightning?....................................................... 28 2.9 Conclusion of “What is Lightning?” ....................................................................... 39 Chapter 3 Lightning/HIRF Protection Continued Airworthiness Design Methodology40 3.1 Reason for a New Methodology ........................................................................... 40 3.2 Value of Proposed Methodology .......................................................................... 40 3.3 The Current Design Methodology for Lightning Protection Development .......... 41 3.4 Proposed Methodology ......................................................................................... 49 3.5 Benefits of a Revised Model .................................................................................. 59 3.6 Implementation ..................................................................................................... 60 3.7 Assessment Sheets ................................................................................................ 60 3.8 Conclusion of the Methodology Development ..................................................... 61 Chapter 4 Validation of the L/HIRF Continued Airworthiness Design Methodology . 62 4.1 Abstract of the Validation Exercise ....................................................................... 62 4.2 Segment Diverter Strip Design Technology .......................................................... 63 4.3 Validating an Installation ....................................................................................... 64 4.4 An Example of a Completed Assessment Sheet .................................................... 65 iii 4.5 The Assessment Sheet Validation using Lightning Protection Supplier Data ....... 66 4.6 Conclusion of Validation ....................................................................................... 72 Chapter 5 - Introduction Case Studies (Non-Proprietary) .......................................... 73 5.1 Case Studies – Aircraft Lightning Protection Design Analysis of an Aircraft ......... 73 5.2 Including “Continued Airworthiness” Within the Aircraft Design Process ........... 73 5.3 Case Studies Description ....................................................................................... 81 5.4 Design Approach using “As Installed” Threats ...................................................... 96 5.5 Path Through to Certification ................................................................................ 98 5.6 Possible Routes through Design Process .............................................................

Load more