col rob fredell, ph.d. military assistant to the chief scientist of the air force presented to afosr...

Download Col Rob Fredell, Ph.D. Military Assistant to the Chief Scientist of the Air Force Presented to AFOSR Workshop on Prognosis 19 February 2008 A Paradigm

Post on 17-Dec-2015

212 views

Category:

Documents

0 download

Embed Size (px)

TRANSCRIPT

  • Slide 1
  • Col Rob Fredell, Ph.D. Military Assistant to the Chief Scientist of the Air Force Presented to AFOSR Workshop on Prognosis 19 February 2008 A Paradigm Shift in Structural Life Prognosis recapturing USAF aircraft availability, performance and supportability DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
  • Slide 2
  • 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.
  • Slide 3
  • 3 Aging Aircraft in Perspective I dont want to have to write a letterYour son or daughter is dead because the wing fell off on takeoff. We knew it was going to fall off, we just didnt 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 your1970 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.
  • Slide 4
  • 4 Finding, fixing cracks and corrosion: trending upward Scheduled inspections Airframe repair Special inspections Landing gear Fuel systems Maintenance Man Hours (MMH) Propulsion Maintenance Category DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Lack of investment in structures sustainment costing USAF..while continued investment in propulsion paying big dividends
  • Slide 5
  • 5 Missouri Air National Guard Mishap 2 Nov 2007 Aircraft broke up in flight Pilot ejected with injuries Forward fuselage separated from acft Separation occurred here Source: www.af.mil 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. Prognosis lesson learned: make sure you look in the right place!
  • Slide 6
  • 6 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 C-130 Structural Health Assessment DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
  • Slide 7
  • 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 surprisesNo wasted motionNo waiting Effective State Awareness crucial to accomplishing all 3 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
  • Slide 8
  • 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.
  • Slide 9
  • 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.
  • Slide 10
  • 10 Alcoa Hybrid Wing Panel Tests (2006) Ultra-Long Life Under Severe Conditions 0 25 50 75 100 125 150 175 02,5005,0007,50010,00012,50015,00017,50020,000 Flights Half Crack Length, a [mm] B777 wing @ Baseline Stress Bolt Ctr Line Airbus 380 wing @ Baseline Stress Transport Wing Fatigue Spectrum, saw cut with severed stringer Baseline: mean flt = 12 ksi, max = 27.6 ksi, ground = - 6 ksi; RH > 90% Skin side Stringer side Skin side Stringer side Desired natural fatigue Early Hybrid Concept @ + 25% Stress Al Sheets Extruded Al Stringer Fiber Metal Laminate Evolved Hybrid @ +25% Stress No external crack growth Bucci, et al, ASIP 2006 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Artificial flaw
  • Slide 11
  • 11 Damage Tolerance Approach Conventional 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.
  • Slide 12
  • 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.
  • Slide 13
  • 13 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! Safety through inspection? Difficult DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
  • Slide 14
  • 14 Now I think were prepared for the inspector to enter the wing through this spacious access hole. Why is inspection so difficult? DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
  • Slide 15
  • 15 Safety through inspection rely on him to be perfect, every single time. Compliments of David Campbell Oklahoma City ALC NDI Program Mgr DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
  • Slide 16
  • 16 Benefits of the Care-free design after Hinrichsen, Alcoa Longer inspection intervals Much longer a crit, easier to find Safety, economy and availability May make enhanced state awareness easier DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
  • Slide 17
  • 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 1 st article By 33 months First lifetime of fatigue testing while transitioning to production By 33 months Install and flight test 2 nd article By 48 months First production article in new and retrofit aircraft PRIORITY DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
  • Slide 18
  • 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.
  • Slide 19
  • 19 High-Velocity Maintenance ALC 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 1000 500 0 Mx Velocity (hrs/day) PDM ISO HSC ISO Maintenance Cycle Current State C-130 PDM =