Aging of U.S. Air Force Aircraft

FINAL REPORT

Committee on Aging of U.S. Air Force Aircraft

National Materials Advisory Board

Commission on Engineering and Technical Systems

National Research Council

Publication NMAB-488-2

NATIONAL ACADEMY PRESS
Washington, D.C.
1997



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Aging of U.S. Air Force Aircraft: Final Report Aging of U.S. Air Force Aircraft FINAL REPORT Committee on Aging of U.S. Air Force Aircraft National Materials Advisory Board Commission on Engineering and Technical Systems National Research Council Publication NMAB-488-2 NATIONAL ACADEMY PRESS Washington, D.C. 1997

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Aging of U.S. Air Force Aircraft: Final Report NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance. This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Bruce M. Alberts is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. William A. Wulf is interim president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Kenneth I. Shine is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy’s purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Bruce M. Alberts and Dr. William A. Wulf are chairman and vice chairman, respectively, of the National Research Council. This study by the National Materials Advisory Board was conducted under Contract No. F49620-96-C-0040 with the U.S. Air Force Office of Scientific Research. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the organizations or agencies that provided support for the project. International Standard Book Number 0-309-05935-6 Available in limited supply from: National Materials Advisory Board 2101 Constitution Avenue, N.W. HA-262 Washington, DC 20418 202-334-3505 Additional copies are available for sale from: National Academy Press 2101 Constitution Avenue, N.W. Box 285 Washington, DC 20055 800-624-6242 or 202-334-3313 (in the Washington metropolitan area) Copyright 1997 by the National Academy of Sciences. All rights reserved. Cover: F-15 air superior fighters. U.S. Air Force photograph. Printed in the United States of America.

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Aging of U.S. Air Force Aircraft: Final Report COMMITTEE ON AGING OF U.S. AIR FORCE AIRCRAFT CHARLES F. TIFFANY (chair), NAE, Boeing Military Airplanes (retired), Tucson, Arizona SATYA N. ATLURI, NAE, Georgia Institute of Technology, Atlanta CATHERINE A. BIGELOW, Federal Aviation Administration Technical Center, Atlantic City, New Jersey EARL W. BRIESCH, Dayton Aerospace Inc., Dayton, Ohio ROBERT J. BUCCI, Alcoa Technical Center, Alcoa Center, Pennsylvania WENDY R. CIESLAK, Sandia National Laboratories, Albuquerque, New Mexico EUGENE E. COVERT, NAE, Massachusetts Institute of Technology, Cambridge B. BORO DJORDJEVIC, Johns Hopkins University, Baltimore, Maryland CHARLES E. HARRIS, NASA Langley Research Center, Hampton, Virginia JAMES W. MAR, NAE, Massachusetts Institute of Technology (retired), Pacific Grove, California J. ARTHUR MARCEAU, Boeing Commercial Airplane Group, Seattle, Washington CHARLES SAFF, Boeing Information, Space, and Defense Systems Group, St. Louis, Missouri EDGAR A. STARKE, JR., University of Virginia, Charlottesville DONALD O. THOMPSON, NAE, Iowa State University, Ames National Materials Advisory Board Staff THOMAS E. MUNNS, Senior Program Officer AIDA C. NEEL, Senior Project Assistant BONNIE SCARBOROUGH, Research Associate National Materials Advisory Board Liaison JAN D. ACHENBACH, NAS/NAE, Northwestern University, Evanston, Illinois Air Force Science and Technology Board Liaison ALTON D. ROMIG, JR., Sandia National Laboratories, Albuquerque, New Mexico Air Force Technical Liaison JIM C.I. CHANG, Office of Scientific Research, Washington, D.C. WILLIAM R. ELLIOTT, Warner-Robins Air Logistics Center, Robins AFB, Georgia JOSEPH P. GALLAGHER, Wright Laboratories, Wright-Patterson AFB, Ohio JOHN W. LINCOLN, Aeronautical Systems Center, Wright-Patterson AFB, Ohio DONALD PAUL, Wright Laboratories, Flight Dynamics Directorate, Wright-Patterson AFB, Ohio VINCENT J. RUSSO, Wright Laboratories, Materials Directorate, Wright-Patterson AFB, Ohio O. LESTER SMITHERS, Aeronautical Systems Center, Wright-Patterson AFB, Ohio

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Aging of U.S. Air Force Aircraft: Final Report NATIONAL MATERIALS ADVISORY BOARD ROBERT A. LAUDISE (chair), NAS/NAE, Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey G.J. ABBASCHIAN, University of Florida, Gainesville JAN D. ACHENBACH, NAS/NAE, Northwestern University, Evanston, Illinois MICHAEL I. BASKES, Sandia/Livermore National Laboratories, Livermore, California JESSE L. BEAUCHAMP, NAS, California Institute of Technology, Pasadena EDWARD C. DOWLING, Cyprus Amax Minerals Company, Englewood, Colorado FRANCIS DISALVO, NAS, Cornell University, Ithaca, New York ANTHONY G. EVANS, NAE, Harvard University, Cambridge, Massachusetts JOHN A.S. GREEN, The Aluminum Association, Washington, D.C. JOHN H. HOPPS, Morehouse College, Atlanta, Georgia MICHAEL JAFFE, Hoechst Celanese Corporation, Summit, New Jersey SYLVIA M. JOHNSON, SRI International, Menlo Park, California LIONEL C. KIMERLING, Massachusetts Institute of Technology, Cambridge HARRY A. LIPSITT, Wright State University, Dayton, Ohio RICHARD S. MULLER, NAE, University of California, Berkeley ELSA REICHMANIS, NAE, Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey KENNETH L. REIFSNIDER, Virginia Polytechnic Institute and State University, Blacksburg EDGAR A. STARKE, JR., University of Virginia, Charlottesville KATHLEEN C. TAYLOR, NAE, General Motors Corporation, Warren, Michigan JAMES WAGNER, Johns Hopkins University, Baltimore, Maryland JOSEPH WIRTH, Raychem Corporation, Menlo Park, California BILL G.W. YEE, Pratt and Whitney, West Palm Beach, Florida ROBERT E. SCHAFRIK, Director

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Aging of U.S. Air Force Aircraft: Final Report Preface The U.S. Air Force requested the National Research Council to identify research and development (R&D) needs and opportunities to support the continued operation of their aging aircraft. Specifically, this study focuses on aging aircraft structures and materials and has the major objectives of developing an overall strategy that addresses the Air Force aging aircraft needs recommending and prioritizing specific technology opportunities in the areas of fatigue, corrosion fatigue, and stress corrosion cracking corrosion prevention and mitigation nondestructive inspection maintenance and repair failure analysis and life prediction methodologies The approach that the committee took to accomplish this study was to conduct working sessions to identify current aging aircraft problems and technology needs; review ongoing and planned aging aircraft R&D efforts by the Air Force; and review related research at other government agencies, within industry, and in the academic research community. The committee conducted a total of six meetings, prepared an interim report (NMAB-488-1), which was released in March 1997, and prepared this final report. In addition, numerous data-gathering discussions were held between individual committee members and various individuals from within the Air Force's research, engineering, logistics, and operational organizations. The purpose of the first meeting held at the Wright Aeronautical Laboratories, Wright-Patterson AFB, Ohio, was to review current and planned laboratory programs that are part of the Air Force aging aircraft program. The purpose of the second meeting, held at the San Antonio Air Logistics Center, Kelly AFB, Texas, was to identify the common problems associated with maintaining and operating aging systems and to review the applied R&D efforts under way at the Air Force air logistic centers (ALCs). Representatives from the five ALCs (i.e., Warner-Robins, Oklahoma City, San Antonio, Ogden, and Sacramento) participated in the meeting. At the third committee meeting, held in Washington, D.C., the committee reviewed ongoing and recently completed basic research programs at the Air Force Office of Scientific Research and developed the preliminary findings for the interim report. The fourth meeting was held in Irvine, California, at which time the committee reviewed related research being conducted by the National Aeronautics and Space Administration and the Federal Aviation Administration, finalized the interim report, and began developing recommendations for an overall aging aircraft strategy and identifying future research opportunities. At the fifth meeting, which was held in Washington, D.C., the committee reviewed related research being conducted by the Navy and received briefings on the F-15 aircraft structural history and on the aging of advanced composite structures. In addition, the committee continued their discussions on recommended strategy, research opportunities, and an approach for the prioritization of these opportunities. The sixth and final committee meeting was held in Washington, D.C., for the purpose of finalizing the prioritization of research opportunities and reviewing the initial draft of this final report. The interim report that was released in March 1997 was prepared at the request of the Air Force research community and included the committee's preliminary technical assessment of the Air Force current aging aircraft R&D program. The report provided a description of the Air Force's aging aircraft problem from the force management perspective, a preliminary assessment of the force management process and its needs, a discussion of the key technical issues and apparent R&D needs, and a preliminary assessment of the current aging aircraft R&D program along with suggested areas of improvement and changes in emphasis. As was pointed out in the preface to the committee's interim report, it became apparent very early in this study that the overall strategy to address the Air Force's aging aircraft needs must encompass much more than R&D needs and opportunities. There are a number of overarching engineering and management issues that also need to be addressed. These include issues involving the force management process, the continued enforcement of the Air Force's Aircraft Structural Integrity Program and its supporting structures and materials specifications, the need to update the durability and damage tolerance assessments of the aging aircraft, the need for increased emphasis on identifying and applying existing technologies to the Air Force's aging aircraft problems, the need for stable funding for technology transition at the Air Force's ALCs, and the technical skills needed to support the aging aircraft program. This final report presents an overall strategy that the committee believes addresses these issues as well as the near-term and long-term research and development needs and opportunities. Charles F. Tiffany, Chair Committee on Aging of U.S. Air Force Aircraft

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Aging of U.S. Air Force Aircraft: Final Report Contents EXECUTIVE SUMMARY   1 PART I PROBLEM DEFINITION AND STATUS OF THE AGING FORCE   9 1   INTRODUCTION   11     Background,   11     Study Objectives,   11 2   AGING AIRCRAFT PROBLEM   13     Managing the Force Structure,   13     Future Force Projections,   16     Assessment of the Force Structural Management Process,   19 3   CURRENT STRUCTURAL STATUS OF THE AGING FORCE   22     Air Force-Supported Aircraft,   22     Contractor Logistics-Supported Aircraft,   24 4   TECHNICAL ISSUES AND OPERATIONAL NEEDS   27     Corrosion,   27     Stress Corrosion Cracking,   28     Fatigue Cracking,   29     Nondestructive Evaluation,   32     Structural Maintenance and Repairs,   33 PART II RECOMMENDED STRATEGY AND OPPORTUNITIES FOR NEAR-TERM AND LONG-TERM RESEARCH   35 5   ENGINEERING AND MANAGEMENT TASKS   39     Update of Durability and Damage Tolerance Assessments,   39     Update of Force Structural Maintenance Plans and Individual Aircraft Tracking Programs,   41     Stress Corrosion Cracking Assessments,   42     Improved Corrosion Control Programs,   43     Economic Service Life Estimation,   45     Continued Enforcement of the Aircraft Structural Integrity Program,   46     Technical Oversight and Retention of Technical Capabilities,   47     Technology Transition into Aging Aircraft,   48 6   RESEARCH RECOMMENDATIONS: FATIGUE   49     Low-Cycle Fatigue,   49     High-Cycle Fatigue,   51     Corrosion/Environmental Effects,   54 7   RESEARCH RECOMMENDATIONS: CORROSION AND STRESS CORROSION CRACKING   57     Corrosion Prevention and Control,   57     Stress Corrosion Cracking,   60

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Aging of U.S. Air Force Aircraft: Final Report 8   RESEARCH RECOMMENDATIONS: NONDESTRUCTIVE EVALUATION AND MAINTENANCE TECHNOLOGY   63     Nondestructive Evaluation,   63     Maintenance and Repair,   68 9   PRIORITIZED RESEARCH RECOMMENDATIONS   73     Critical Priorities,   73     Near-Term Research,   73     Long-Term Research,   74 10   FUTURE STRUCTURAL ISSUES: COMPOSITE PRIMARY STRUCTURES   76     Applications and Service Experience,   76     Recommendations for Long-Term Research,   77 REFERENCES   79 APPENDICES     A   SYNOPSES OF AIR FORCE AGING AIRCRAFT STRUCTURAL HISTORIES   87 B   BIOGRAPHICAL SKETCHES OF COMMITTEE MEMBERS   111

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Aging of U.S. Air Force Aircraft: Final Report Tables and Figures TABLES ES-1   Priority-1 Near-Term and Long-Term-Research Recommendations   5 ES-2   Priority-2 Near-Term and Long-Term Research Recommendations   6 ES-3   Priority-3 Near-Term and Long-Term Research Recommendations   7 2-1   Tasks of the Air Force Aircraft Structural Integrity Program   15 3-1   Data on Force Status for Air Force-Supported Aircraft   23 3-2   Air Force Commercial-Derivative Aircraft Using Contractor Logistics Support   24 3-3   Comparison between Utilization of Air Force CLS Aircraft and Commercial Equivalents   25 5-1   Prioritization of DADTA Update Needs for Air Force-Supported Aircraft   40 8-1   Critical NDE Inspection Needs for Aging Aircraft   65 9-1   Prioritized Near-Term Research Recommendations   74 9-2   Prioritized Long-Term Research Recommendations   75 FIGURES 2-1   Force structure projection for the ACC fighter, bomber, and attack aircraft   17 2-2   Force structure projection for the ACC airlift and rescue aircraft   17 2-3   Force structure projection for other ACC aircraft   18 2-4   Force structure projection for AMC aircraft   18 2-5   Force structure projection for AFSOC aircraft   19 2-6   Force structure projection for AETC aircraft   20 II-1   Recommended overall strategy to address Air Force aging aircraft challenges   36 II-2   Basic elements of the recommended near-term and long-term R&D programs   37 5-1   Overall approach to durability and damage tolerance assessments   40 5-2   Organization of commercial aircraft industry aging aircraft working groups   44 A-1   C-5 flying hour distribution   90 A-2   General locations for B-52G/H structural improvements   92 A-3   B-52H current use rate   93 A-4   F-15 buffet-induced problems   96 A-5   F-16 structural arrangement   97 A-6   F-16 structural modification areas   98 A-7   A-10 structural arrangement   99 A-8   Boeing 707 wing tear-down locations   102 A-9   F-111 D6ac steel components   105 A-10   Original lower wing skin design for the T-38 aircraft   109

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Aging of U.S. Air Force Aircraft: Final Report Acronyms AATSG aging aircraft technical steering group AAWG Airworthiness Assurance Working Group ACC Air Combat Command ACI analytical condition inspection AETC Air Education and Training Command AFMPP Air Force modernization planning process AFR Air Force regulation AFSOC Air Force Special Operations Command ALC air logistics center AMC Air Mobility Command ASIP Aircraft Structural Integrity Program CACRC Commercial Aircraft Composite Repair Committee CLS contractor logistics support CPC corrosion-preventive compound CPCP corrosion prevention and control program DADTA durability and damage tolerance assessment EIF equivalent initial flaw FAA Federal Aviation Administration FAR Federal Air Regulation FSMP force structural maintenance plan IATP individual aircraft tracking program JPATS Joint Primary Aircraft Training System JSF Joint Strike Fighter LESS loads/environment spectra study LIF lead-in fighter NASA National Aeronautics and Space Administration NDE nondestructive evaluation NDI nondestructive inspection PDM programmed depot maintenance POD probability of detection R&D research and development

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Aging of U.S. Air Force Aircraft: Final Report SAB Scientific Advisory Board SCC stress corrosion cracking TIE Technology and Industrial Support Engineering (ALC) TPIPT technology planning integrated product team VOC volatile organic compound WFD widespread fatigue damage