Investigation of Electromagnetic Field Threat to Fuel Tank Wiring of a Transport Aircraft
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Investigation of Electromagnetic Field Threat to Fuel Tank Wiring of a Transport Aircraft Jay 1. Ely, Truong X. Nguyen, Kenneth L. Dudley, Stephen A. Scearce, and Fred B. Beck Langley Research Center, Hampton, Virginia Manohar D. Deshpande NYMA, Inc., Hampton, Virginia C. R. Cockrell Langley Research Center, Hampton, Virginia National Aeronautics and Space Administration Langley Research Center Hampton, Virginia 23681-2199 March 2000 The use of trademarks or names of manufacturers in this report is for accurate reporting and does not constitute an official endorsement, either expressed or implied, of such products or manufacturers by the National Aeronautics and Space Administration. Available from: NASA Center for Aerospace Information (CASI) National Technical Information Service (NTIS) 7 1 2 1 Standard Drive 5285 Port Royal Road Hanover, MD 21076- 1320 Springfield, VA 22161 -21 71 (30 1 ) 62 1-0390 (703) 605-6000 Acknowledgements NSWC Contributors: Michael 0. Hatfield, Robert E. Richardson, and Arturo Lopez. Mr. Hatfield provided consultation and technical expertise regarding the selection of a retired aircraft, and in performing the aircraft measurements. His knowledge of reverberation measurement methodology, instrumentation and theory were highly valued in developing a efficient and effective means of collecting aircraft data. Dr. Richardson provided consultation, and performed time-domain comparison measurements to supplement the aircraft CWT reverberation data reported in Section 4.4.2.1. He also performed the isolated fuel probe tests reported in Section 4.4.4. Mr. Lopez provided the UVTRONB ionization detection devices, along with associated circuitry, and advice. LTI Contributors: Franklin A. Fisher, Edward J. Rupke, J. Anderson Plumer, Keith Crouch. Mr. Fisher was a valuable resource in the areas of electrical sparks and factors governing the ignition of aircraft fuel. As part of this investigation, Mr. Fisher provided a report outlining a traditional understanding of electrical breakdown, heating, and fuel combustion, and supplements the knowledge with available information regarding aircraft fuel-vapor ignition by RF sources. Mr. Rupke, Mr. Plumer, and Mr. Crouch provided valuable consultation regarding aircraft wiring inspections, detection of electrical discharge, and fuel combustion processes. Douglas J. Hughes: IIT Research Institute, JSC Support Group. Mr. Hughes provided manufacturers data regarding PED emissions, that served as a basis for additional analysis reported herein. Also, Mr. Hughes provided supplemental data regarding RF sources below 30 MHz frequency, external to TWA-800 at the time of the accident. Thomas G. Campbell: Head, Electromagnetics Research Branch (ERB), Airborne Systems Competency, for developing the relationship with the NTSB and initiating the reimbursable task agreements which enabled the LaRC investigations. Reuben A. Williams: Responsible for managing the High Intensity Radiated Fields Laboratory (ERB) in support of numerous experiments as part of this activity. In addition, Mr. Williams provided significant contributions at critical stages of this project, which enabled the overall success of the LaRC effort. Examples of this support include developing an effective and timely contract with AAR for EM testing on a center wing fuel tank, procuring the necessary sensors for laboratory FQIS testing; and for the overall resource allocations for all LaRC tasks. Max Williams, Lockheed-Martin Corporation: Fabrication and design of numerous laboratory setups and test fixtures. The experimental test goals of this effort could not have been achieved without the assistance of Mr. Williams. Sandra Koppen, Lockheed - Martin, Corporation: Test control software was required for laboratory and remote operations with little preparation time, and a high degree of reliability. Ms. Koppen was responsible for all data acquisition and control software used in experimental testing, as well as assistance reviewing the final draft. Bob Glover, Lockheed-Martin Corporation: Assisted with the seemingly impossible task setting up a contractual mechanism for enabling AAR Roswell to be funded in the short period of time required to support the test schedule. Remote test operations could not have occurred without his support. Elden Ross, Self-employed: Assisted LaRC engineers with information sources and timely updates to relevant aircraft accident and incident reports and articles. Performed an in-depth ASRS and PED incident data analysis as a supplementary tool related to the effort. Acknowledgements continued AAR Roswell: Provided retired aircraft access and mechanical support. The value of the measurement data is directly related to the fact that aircraft fuel tank measurements were performed. This would not have been possible otherwise. Elite Structural Services: Several 12-hour days were required for remote operations to collect the required fuel tank data. The efficiency and professionalism of the Elite Structural Services team was crucial to these aircraft measurement tasks. Tony Clark: (NASA Marshall Space Flight Center): Mr. Clark provided unique references regarding dielectric breakdown in alternating fields. This information was related to previous programs (some decades old), supported by previous MSFC researchers. Much of this information could not be found in other references. Stephen A. Borg: Mr. Borg, of the LaRC Aerodynamic Measurements Branch, was a resource for providing and operating the Thermal Imaging System in the laboratory testing. In addition to his other assigned duties, his expertise and willingness to support the test schedule was greatly appreciated. Brian H. Bailie: Mr. Bailie was instrumental in assembling the original cover page, contents section, and converting the Appendix D to electronic form. He was also a valuable resource for assembling interim presentations during the effort. Contents i Abstract ................................................................... vii ii Executive Summary .......................................................... vii iii Symbols and Abbreviations .................................................... ix 1 Introduction ................................................................. 1 1.1 Background Information .................................................... 1 1.2 Areas and Limits of the Investigation.......................................... 2 1.3 Approach ................................................................ 2 1.3.1 Quantifying the Source [A(f)] ........................................... 3 1.3.2 Estimating the Path Factor [B(f)], Phased Approach ......................... 4 1.3.3 Estimating the Event Power [C(f)] ....................................... 4 1.3.4 Appendices ......................................................... 5 1.4 Participating Agencies ...................................................... 5 1.5 References for Section 1 ................................................... 5 2 FQIS and Aircraft Description .................................................. 5 2.1 The Capacitive Fuel Probe .................................................. 8 2.2 Connectors and Cables ..................................................... 9 2.3 References for Section 2 ................................................... 12 3 Determination of Threat from RF Sources External to Aircraft ........................ 13 3.1 Introduction............................................................. 13 3.2 Symbols for Section 3 ..................................................... 14 3.3 Initial Analysis ........................................................... 15 3.3.1 Estimation of Maximum Available Energy ................................ 15 3.3.2 TWA Electromagnetic Environment versus Standard HIRF Environments........ 16 3.4 Analytical Modeling ...................................................... 18 3.4.1 Development of the Method of Moments.................................. 20 3.4.2 Input Impedance of FQIS Wire ......................................... 23 3.4.3 Energy Delivered to CWT by FQIS Wire ................................. 23 3.5 Numerical and Experimental Validation of the ModalIMoM Code .................. 25 3.6 Numerical Estimation of EM Threat to the CWT of a B-747- I00 Due to FQIS Wiring . 32 3.6.1 Choice of Frequency Sampling ......................................... 32 3.6.2 Choice of Number of Cavity Modes ..................................... 33 3.6.3 Choice of Number of Aperture Modes ................................... 33 3.6.4 FQIS Wire Length Selection ........................................... 33 3.6.5 CPU Time Requirement .............................................. 38 3.7 Conclusions for External Analysis ........................................... 39 3.8 References for Section 3 ................................................... 39 4 Determination of Threat from Portable RF Sources Internal to Aircraft ................. 41 4.1 Introduction............................................................. 41 4.1.1 Baseline Measurement on Actual Aircraft ................................ 41 4.1.2 Acquisition of FQIS Components, Installation in Laboratory .................. 43 4.1.3 Duplication of Field Measurements in Laboratory. Comparisons ...............44 4.1.4 Detailed Measurements in Laboratory .................................... 44 4.1.5 Detailed Outline of Section 4 ...........................................45 4.2 Symbols for Section 4 .....................................................47