USAF Aircraft Structural Integrity Program (ASIP) San Antonio, Texas 28 – 30 November 2006 DamageDamage ToleranceTolerance FactsFacts andand FictionFiction Dr. Ulf G. Goranson (Retired) Boeing Commercial Airplane Company Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 1 12/13/2006 Damage Tolerance – Facts and Fiction Overview Elements of Damage Tolerance Structural Maintenance Considerations Continuing Airworthiness Challenges Summary Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 2 12/13/2006 Royal Institute of Technology - Stockholm Department of Aeronautics 1958 - 1965 Aeronautical Research Laboratory 1962 -1967 Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 3 12/13/2006 SAAB 37-Viggen - First Flight 1965 Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 4 12/13/2006 Boeing Commercial Airplane Company 1967 - 2001 Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 5 12/13/2006 Boeing B-2707 Supersonic Transport Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 6 12/13/2006 Boeing Family of Commercial Aircraft Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 7 12/13/2006 Inger and Ulf 50 year Celebration Cruise Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 8 12/13/2006 Damage Tolerance – Facts and Fiction Overview Elements of Damage Tolerance Structural Maintenance Considerations Continuing Airworthiness Challenges Summary Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 9 12/13/2006 Design Principles Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 10 12/13/2006 Boeing BW-12 Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 11 12/13/2006 Boeing BW-12 Replica Boeing 50th Anniversary 1966 Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 12 12/13/2006 Boeing Model 40 “…let no new improvement in flying and flying equipment pass us by” W.E. Boeing - 1929 Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 13 12/13/2006 777 Static Test Wing Tip Deflection: - 18 feet & 2.50g - 24 feet & 3.75g Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 15 12/13/2006 Design Principles Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 16 12/13/2006 Boeing Clipper 314 Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 17 12/13/2006 Boeing 377 - Stratocruiser Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 18 12/13/2006 De Havilland Comet Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 19 12/13/2006 Design Principles Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 20 12/13/2006 Fail-Safe Jet Transports Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 21 12/13/2006 Boeing 707 Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 22 12/13/2006 Wing Fail Safety Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 23 12/13/2006 Fail-Safe Test Verification Pressurized test section • Example of blade skin cuts made at critical locations Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 24 12/13/2006 Fuselage Crack Arrest Test Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 25 12/13/2006 Hull Losses and/or Fatal Accidents Per Million Departures Worldwide commercial jet fleet — 1959 through 2005 All other causes Maintenance = 14% Structures = 4% • Structures • Systems •Propulsion Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 26 12/13/2006 Structural Safety System Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 27 12/13/2006 Design Principles Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 28 12/13/2006 FAA Regulation Comparisons Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 29 12/13/2006 Boeing 757 and 767 Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 30 12/13/2006 Basic Concepts Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 31 12/13/2006 Damage Tolerance Constituents Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 32 12/13/2006 Damage Tolerance – Facts and Fiction Overview Elements of Damage Tolerance Structural Maintenance Considerations Continuing Airworthiness Challenges Summary Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 33 12/13/2006 Elements of Damage Tolerance Vision Allowable damage Damage Damage growth detection Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 34 12/13/2006 Elements of Damage Tolerance Research Community Focus Allowable damage Damage Damage growth detection Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 35 12/13/2006 Elements of Damage Tolerance Lecture Focus Allowable damage Damage Damage growth detection Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 36 12/13/2006 Interaction of Damage Tolerance Elements Requires safe-life design Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 37 12/13/2006 Damage Tolerant Structure Damage detection Ultimate load Ultimate and restoration capability required after damage detection Structural strength Regulatory fail-safe requirement NDI Visual detection detection period period Damage Operating loads size Max. Allowable damage Visual Damage detection NDI thresholds Service time Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 38 12/13/2006 Classification of Structures Category 3 : Inspections match Structural Characteristics Safety Structural Technique of Structural category analysis classification ensuring safety requirements examples 1 Design for loss of Wing spoiler segment Other • Continued component or safe (safe separation or structure Secondary safe flight structure separation safe loss of function) 2 Adequate residual Damage strength with extensive •Residual Wing fuel leaks Damage obvious or damage obvious during strength Structurally tolerant malfunction walkaround or indicated significant design evident by malfunction items or •Residual principal 3 All primary structure strength structural Damage Inspection program not included in •Crack elements detection by matched to structural categories growth (primary planned characteristics • Inspection structure) inspection 24or program Landing gear structure Safe-life 4 Conservative fatigue • Fatigue (conservative fatigue design life Safe life life) Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 39 12/13/2006 Structural Technology Standards Durability Methods and Allowables Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 40 12/13/2006 Technology Standards Development Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 41 12/13/2006 Fatigue Check Procedure Structural Capability Analysis Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 42 12/13/2006 Fatigue Damage Model log fa fa Alternating stress f f = constant max m 105 Alternating stress DFR 1 P 105 fmo Cyclic life log n Mean stress fm ⎛ ⎞ 1 f − f P ⎜ mo m ⎟ ⎛105 ⎞ f = ⎜ ⎟ ⋅ ⎜ ⎟ a ⎛f ⎞ ⎜ φN ⎟ ⎜2 ⎜ mo ⎟ −1⎟ ⎝ ⎠ ⎝ ⎝ DFR⎠ ⎠ 5 DFR= fatigue rating (fmax at N=10 and R = 0 with 95% reliability and 95% confidence) fmo = focal mean stress P = slope φ = load sequence factor Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 43 12/13/2006 Required Fatigue Rating Solution Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 44 12/13/2006 Relative Operating Stress Levels Wing & Fuselage Capability Examples Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 45 12/13/2006 Durability Design Guide Example Spar Chord Discontinuity Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 46 12/13/2006 Analytical Detail Fatigue Ratings DFR = DFR BASE x ABCDEU Hole-filling factor (A) Standard rivet 1.10 Fluid-tight rivet 1.14 Relative stress Alloy factor (B) 2024 1.0 Reference 7075 10.8 Cycles (N) Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 47 12/13/2006 Fatigue Check Procedure Requirement Analysis Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 48 12/13/2006 Design Service Objectives Fleet use Relative Range number of Short G Medium G Long G flights Crack free (< 1% cracking) 1.0 Economic repair (< 5% cracking) 1.5 Fatigue-check missions Design service goals Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 49 12/13/2006 Fatigue Check Examples Fatigue check summary Flight profile damage data Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 50 12/13/2006 Fatigue Design Requirement Contours • Required fatigue rating to meet short, medium, and long flight design service goals Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 51 12/13/2006 Structural Durability Validation Sources for Detail Fatigue Ratings Most Preferred • Fleet Experience • Full-Scale Airplane Test • Part Airplane Test • Component Test Modified Using • Fleet Full-Scale Part Airplane Or Component Test } Small-Scale Laboratory Specimen + • Small-Scale Laboratory Specimen Copyright © 2006 Boeing. All rights reserved. DM2220.462 h Test Versus Service Pros and Cons Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 53 12/13/2006 Service Bulletin Modifications - Labor-Hours Corrosion and Fatigue Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 54 12/13/2006 Design Service Objectives 767 Jet Transports Database from 586 active 767s Copyright © 2006 Boeing. All rights reserved. Filename.ppt | 55 12/13/2006 Service-Demonstrated Fatigue Lives Service - demonstrated characteristic life 1999 commercial fleet data Service - β Number of Highest Demonstrated demonstrated 0.95 Model airplanes flights life delivered 103 flights 103 flights