Col Rob Fredell, Ph.D. Military Assistant to the Chief Scientist of the Air Force

1. A Paradigm Shift in Structural Life Prognosis …recapturing USAF aircraft availability, performance and supportability Col Rob Fredell, Ph.D.Military Assistant to the Chief Scientist of the Air Force Presented to AFOSR Workshop on Prognosis 19 February 2008 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

2. Overview • Aging aircraft in perspective • Carefree Structures • High-Velocity Maintenance • Prognosis Role as Integrator • Summary DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

3. Aging Aircraft in Perspective “I don’t want to have to write a letter…Your son or daughter is dead because the wing fell off on takeoff. We knew it was going to fall off, we just didn’t know when.” - General Ron Keys, COMACC, as quoted in USA Today, 8 May 2007 “The US Air Force has grounded its entire fleet of 676 F-15 fighter jets after a jet crashed on a training mission in Missouri last week.” - BBC on-line, 6 November 2007 "It's kinda like taking your…1970 Chevrolet and tearing it down, repairing anything you find wrong with it--extending the life of the car.” - Keith Gilstrap, Warner Robins ALC, as quoted in the Aim Points, 12 Feb 2008 “"We're trying to catch up with 20 years of neglect.” - Loren Thompson, the Lexington Institute, in the Dayton Daily News, 11 Feb 2008 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

4. Lack of investment in structures sustainment costing USAF… Finding, fixing cracks and corrosion: trending upward Maintenance Man Hours (MMH) ..while continued investment in propulsion paying big dividends Scheduled inspections Special inspections Airframe repair Landing gear Fuel systems Propulsion Maintenance Category DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

5. Prognosis lesson learned: make sure you look in the right place! Missouri Air National Guard Mishap2 Nov 2007 • Aircraft broke up in flight • Pilot ejected with injuries • Forward fuselage separated from acft Separation occurred here • Cause: Fatigue of “fatigue proof” upper cockpit longeron from mfg defect • 700+ aircraft grounded for detailed inspections • 162 aircraft remain grounded as of 11 Feb 08 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Source: www.af.mil

6. C-130 Structural Health Assessment • Center Wing Box fatigue, corrosion limiting life of E, H fleets • Many aircraft at or past upper limit for unrestricted use • Warner Robins ALC executing 3-phase program to renew H CWB • 3-year program to redesign wing splice fitting • Sole source purchase of conventional replacement CWBs and production data • Competitive purchase of 100s more replacement CWBs • Heavier Extended Service Life (ESL) wing for all new J models? • J models currently produced with similar wing as E, H replacements • More powerful engines, higher TOGW • Higher usage and severity factors mean similar cracking problems in ~20 years • ESL wing costs 1,000 lbs of added structure; reduces aircraft performance • Impact on availability • Reduced availability and increased support costs • Affects hundreds of aircraft supporting Air Mobility Command, AF Special Operations, US Coast Guard, US Navy, and many foreign partners DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

7. SecAF charge: break this cycle • SecAF goal: long-life structures and lower life cycle costs • Real solutions to fatigue cracking & corrosion, not just replacement • Reduction of inspection burden and improved fleet availability • Repeatable, consistent way to decide when to retire aircraft • “Care-free” structures concept offers opportunity • Truly optimized structures not min weight, but optimized for min life cycle cost • Cuts structural inspection of wing by 75 - 90% and recaptures weight lost to beef-ups • Retains current inspection and repair processes at lower life cycle costs • High Velocity Maintenance promises a “depot revolution” • Enhanced aircraft condition awareness prior to depot cycle • Better planning for more focused, shorter cycle times • No surprises…No wasted motion…No waiting • Effective State Awareness crucial to accomplishing all 3 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

8. Overview • Aging aircraft in perspective • Carefree Structures • High-Velocity Maintenance • Prognosis Role as Integrator • Summary DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

9. Hybrid “Care-Free Structures” Product of Dutch/German/US research • Follows on Fiber Metal Laminates (TU Delft NL, 1980s) • Key features: Durability, damage tolerance, long inspection intervals, ease of repair, corrosion- and impact-resistant structures • Excellent Service History: • 4 AC-130 flaps flown (early 1990s) • 40 C-17 aft cargo doors in service (1995-present) • Airbus A380 upper fuselage in service (2008) • Care-Free Concept not limited to FMLs • Put the Right Material in the Right Place! DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

10. Extruded Al Stringer Early Hybrid Concept @ + 25% Stress Fiber Metal Laminate Skin side Al Sheets Stringer side Desired “natural” fatigue Alcoa Hybrid Wing Panel Tests (2006)Ultra-Long Life Under Severe Conditions Transport Wing Fatigue Spectrum, saw cut with severed stringer Baseline: mean flt = 12 ksi, smax = 27.6 ksi, sground = - 6 ksi; RH > 90% 175 Airbus 380 wing @ Baseline Stress B777 wing @ Baseline Stress Bucci, et al, ASIP 2006 150 Bolt Ctr Line 125 100 Half Crack Length, a [mm] 75 Evolved Hybrid @ +25% Stress No external crack growth Stringer side 50 25 Skin side Artificial flaw 0 0 2,500 5,000 7,500 10,000 12,500 15,000 17,500 20,000 Flights DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

11. Damage Tolerance ApproachConventional Aluminum Structures As damage-tolerant aircraft age past original design life, inspection burden grows… … and risk of inspection-induced damage increases DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

12. Safety through inspection? • Example: bolt hole eddy current inspection of a fuel tank structures • Highly skilled technician • Hand-held eddy current probe DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

13. Safety through inspection? Difficult • Example: bolt hole eddy current inspection of a fuel tank structures • Highly skilled technician • Hand-held eddy current probe, mirror, flashlight, technical data, and NDI standards • A good NDI technician is hard to find! DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

14. Why is inspection so difficult? • Now I think we’re prepared for the inspector to enter the wing through this spacious access hole…. DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

15. Safety through inspection …rely on him to be perfect, everysingletime. Compliments of David Campbell Oklahoma City ALC NDI Program Mgr DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

16. Benefits of the Care-free designafter Hinrichsen, Alcoa • Longer inspection intervals • Much longer acrit, easier to find • Safety, economy and availability • May make enhanced state awareness easier DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

17. Opportunity: Care-Free Tech Demo?AF-managed OEM effort • Program: Develop care-free form-fit replacement problem wing structure • Extend life while improving availability • Eliminate fatigue and corrosion, reduce inspections, cut cost • Fly proof of concept with enhanced state awareness / IVSHM system? • Key Performance Parameters • Triple fatigue life of current wing • Eliminate PDM and all wing structural inspections in double current lifetime • Visual inspections for life (no critical flaw size small enough to require NDI) • Weight neutral with SOA structures • Attempt to prove maturity of prognostics in a demanding aircraft environment? • Notional Schedule: • By 18 months – Design, develop test plan, build 1st article • By 33 months – First lifetime of fatigue testing while transitioning to production • By 33 months – Install and flight test 2nd article • By 48 months – First production article in new and retrofit aircraft PRIORITY DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

18. Overview • Aging aircraft in perspective • Carefree Structures • High-Velocity Maintenance • Prognosis Role as Integrator • Summary DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

19. High-Velocity MaintenanceALC initiative to increase aircraft availability Reduce impact of sched maintenance on fleet availability Raise Efficiency of Depot Maintenance Processes Low man-hour “burn rate” compared to industry Airlines: 500-800 man-hours/day Depot: 145-220 hours/day Field and Depot not synchronized Function as two independent systems Little communication Aircraft condition not well known at induction Result: Long lead times High opportunity costs = larger than needed fleets • C-130 PDM = $3.5M ea, 95/yr, 22K Hrs, 160 Days • F-15 PDM = ~$3.75M ea, 97/yr • C-5 PDM = $16.3M ea, 18/yr “To Be” State Additional Availability ISO HSC ISO PDM ISO 1000 Mx Velocity (hrs/day) 500 “Current” State After Dement & Keene 0 Maintenance Cycle DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

20. HVM Vision Increase aircraft availability using common sense tools to Establish a synchronized, integrated, end-to-end process Maintenance must not impact mission requirements. Aircraft Availability Overarching enterprise initiatives AAIP MSG-3 HVM Optimize the field/depot reqmts (the “what, when and where) RCM LCSE Expands HVM to be “scalable and transportable” PLM CBM+ GLSC HVM for PDM/ISO WR-ALC C-130 Prototype Integrity CAM Programs Optimizes the PDM process (the “how”) Includes all supporting processes ECSS Std Work Supply Chain Ops Lifecycle Mgmt Sourcing Tech Development D&SWS No Surprises…No Wasted Motion…No Waiting DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

21. Enhanced State Awareness HVM Attributesfrom Warner Robins ALC Future State • Known Aircraft/End Item Condition • Use lead time ahead of induction • Order Parts, Training, Infrastructure, Equipment, Data, etc. • Mechanic-Centric Focus (Surgeon) • Parts, tools, data, equipment pre-positioned at point of use • Maximum use of kitting • Expand Standard Work & Processes • Single Maintenance Concept • Integrated Planning, Decision-making, & Data Collection • Equivalent to14% more aircraft on station Current State • Limited Knowledge of A/C Condition • Two Mx systems; creates knowledge barriers • 5+ Year PDM cycle (C-130) • Damage accumulates, so “must fix now” mentality • Job Shop Environment • Mechanic must fetch own tools; parts; set up • Inadequate plans – reqmts, parts, materiel, equipment • Lacks information – complete BOM, planned work, support • Stove-piped processes and execution • Lack of synchronicity leads to non-compliant work arounds Find, then fix DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

22. Total State Awareness Enhanced State Awareness Now HVM for Developmental AircraftCapability Spirals Spiral 3: Total Weapon System State Awareness Spiral 1: Research Supporting Key Technologies Spiral 2: Vehicle Health Mgmt - Right maintenance accomplished when mission requirements allow Total State Awareness determines when MX required No surprises Low cost per flying hr Airframe Condition - Fully Instrumented (IVHM) - Onboard Prognostics/Life Prediction Information Enabled Planning & Execution Net-Centric Solution w/ Supply Base Standard Work Documented for All Processes Airframe Condition SHMS - On-board systems diagnostics - Corrosion sensors - 100% flight Loads data Auto data transfer & analysis Single Maintenance Concept Airframe Condition Predictive analysis - RCM, MSG-3 - Dets assess condition Fully Integrated Management System • Automated Data Collection & Distribution • Anticipatory Spares Ordering • Automated POM generation of $$ Capability Integrated Supply Chain Management Standard Work Documented for Integrated System Enhanced State Awareness - Structural Integrity Prognosis System • Active Autonomous Dialogue with Depot ISO and PDM Integrated Standard Work for ISO/PDM Integrated Management System - Integrated Data from all systems - Plans/Schedules Integrated Requirements and Funding Process Time DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

23. Overview • Aging aircraft in perspective • Carefree Structures • High-Velocity Maintenance • Prognosis Role as Integrator • Summary DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

24. Desired state Damaged state Failure Prognosis Role in Community Integration • How can material and structural state awareness be achieved? • What is the role of an informed maintenance community in developing the prognosis concept? • Can total vehicle state awareness be achieved at an affordable cost? • Can leadership be convinced that prognosis is a better solution? After K Jata, Sept 2007 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

25. Design Information (Materials Allowables) Care-Free Structures Design Analysis & Development Tests Failure Progression Production, Industrialization, Safety, Maintenance, Inspection Sensing for State Awareness Prediction & Prognosis Fault Detection & Trending Failure Analysis Self-healing materials Full-Scale Testing Prognosis as Integrator Force Management DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

26. Prognosis ASIP-SA CBM+ High-Velocity Mx Aircraft Structural Integrity Program in the age of state awareness Diagnostics Prediction Care-Free Structures Prognosis as Integrator Prognosis Drivers: • Data • Physics • Cost • Availability • Capability • Safety • Tribal Customs DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

27. Summary • High-Velocity Maintenance Carefree structures concepts maturing • Prognosis community must integrate the “cultures” of the various “tribes” crucial to achieving USAF relevance • Possible collaboration on proposed Tech Demo will drive R&D to solve most difficult aging aircraft problems • Early transition to Tech Demo wing would challenge integrators to focus on the art of the possible. DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.