…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
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Overview
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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
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2.0
1.5
1.0
0.5
0.0
3.5
3.0
2.5
Top 10 Maintenance Drivers (MMH), Total AF
Finding, fixing cracks and WUC WUC Description corrosion: trending upward
03 LOOK PH OF SCH INSP
11 AIRFRAME
04 SPECIAL INSPECTIONS
13 LANDING GEAR
46 FUEL SYSTEM
14 FLIGHT CONTROLS
74 FIE CONTROL
23 POWER PLANT
Lack of investment in structures
12 CKPT & FUSE COMPTS sustainment costing USAF…
Total of Top 10 =
% of Total FY05
MMH Hrs
14%
12%
11%
8%
5%
5%
4%
4%
3%
3%
68%
..while continued investment in propulsion paying big dividends
2001
2002
2003
2004
2005
03 11 04 13 46
WUC
14 74
Maintenance Category
23 76
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4

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
• Cause: Fatigue of “fatigue proof” upper cockpit
• 700+ aircraft grounded for detailed inspections
• 162 aircraft remain grounded as of 11 Feb 08
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Source: www.af.mil
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Center Wing Box fatigue, corrosion limiting life of E, H fleets
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Many aircraft at or past upper limit for unrestricted use
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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?
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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
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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
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 SecAF goal: long-life structures and lower life cycle costs
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Real solutions to fatigue cracking & corrosion, not just replacement
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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
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Retains current inspection and repair processes at lower life cycle costs
 High Velocity Maintenance promises a “depot revolution”
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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
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Overview
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Aging aircraft in perspective
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High-Velocity Maintenance
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Prognosis Role as Integrator
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Summary
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Product of Dutch/German/US research
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Follows on Fiber Metal Laminates (TU Delft NL, 1980s)
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Key features: Durability, damage tolerance, long inspection intervals, ease of repair, corrosion- and impact-resistant structures
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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)
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Care-Free Concept not limited to FMLs
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Put the Right Material in the Right Place!
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175
Ultra-Long Life Under Severe Conditions
Transport Wing Fatigue Spectrum, saw cut with severed stringer
Baseline: mean flt = 12 ksi, s max = 27.6 ksi, s ground = - 6 ksi; RH > 90%
150
125
B777 wing
@ Baseline Stress
Airbus 380 wing
@ Baseline Stress
Bucci, et al, ASIP 2006
Bolt Ctr Line
Extruded Al Stringer
Fiber Metal
Laminate
Al Sheets
100
75
50
Early Hybrid Concept
@ + 25% Stress
Evolved Hybrid
@ +25% Stress
No external crack growth
Skin side
25
Skin side Stringer side
Desired “natural” fatigue
0
0 2,500 5,000 7,500 10,000 12,500 15,000 17,500 20,000 Flights
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Damage Tolerance Approach
Conventional Aluminum Structures
As damagetolerant aircraft age past original design life, inspection burden grows…
… and risk of inspection-induced damage increases
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ASIP 2006., Nov. 29, 2006 2

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Example: bolt hole eddy current inspection of a fuel tank structures
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Highly skilled technician
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Hand-held eddy current probe
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Example: bolt hole eddy current inspection of a fuel tank structures
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Highly skilled technician
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Hand-held eddy current probe, mirror, flashlight, technical data, and
NDI standards
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A good NDI technician is hard to find!
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 Now I think we’re prepared for the inspector to enter the wing through this spacious access hole….
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Compliments of David Campbell
Oklahoma City ALC NDI Program Mgr
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Benefits of the Care-free design after Hinrichsen, Alcoa
Residual
Strength
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Longer inspection intervals
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Much longer a crit , easier to find
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Safety, economy and availability
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May make enhanced state awareness easier
"Care-free"
Economic Life
Damage Tolerant
Economic Life
"Care-free"
1 st inspection
Ultimate
Load
Inspect & Repair
Limit Load
Fail-safe req.
Onset of widespread fatigue damage
Life Extension
Flight Cycles
0 1X
1 DSG
2X 3X 4X 5X
2 DSG Current Practice: Damage Tolerance
1 DSG Proposed Care-free 2 DSG
6X
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- 1 -

AF-managed OEM effort
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Program: Develop care-free form-fit replacement problem wing structure
 Extend life while improving availability
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Eliminate fatigue and corrosion, reduce inspections, cut cost
Fly proof of concept with enhanced state awareness / IVSHM system?
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Key Performance Parameters
 Triple fatigue life of current wing
 Eliminate PDM and all wing structural inspections in double current lifetime
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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?
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Notional Schedule:
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By 18 months – Design, develop test plan, build 1 st article
By 33 months
– First lifetime of fatigue testing while transitioning to production
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By 33 months – Install and flight test 2 nd article
By 48 months – First production article in new and retrofit aircraft
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Overview
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Aging aircraft in perspective
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Carefree Structures
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Prognosis Role as Integrator
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Summary
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ALC initiative to increase aircraft availability
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Reduce impact of sched maintenance on fleet availability
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
1000
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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
“To Be”
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State
Aircraft condition not well known at induction
• Result: Long lead times
• High opportunity costs = larger than needed fleets
Additional Availability
ISO
“Current” State
0 After Dement & Keene
HSC ISO PDM
Maintenance Cycle
ISO
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Increase aircraft availability using common sense tools to
Establish a synchronized, integrated, end-to-end process
Maintenance must not impact mission requirements.
Aircraft
Availability
GLSC
CAM
ECSS
LCSE
PLM
AAIP
HVM
MSG-3
Expands HVM to be
“scalable and transportable”
RCM
CBM+
HVM for PDM/ISO
WR-ALC C-130 Prototype
Optimizes the PDM process (the “how”)
Includes all supporting processes
Std Work Supply Chain Ops Lifecycle Mgmt Sourcing Tech Development
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from Warner Robins ALC
Current State
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Limited Knowledge of A/C Condition
• Two Mx systems; creates knowledge barriers
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5+ Year PDM cycle (C-130)
• Damage accumulates, so “must fix now” mentality
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Job Shop Environment
• Mechanic must fetch own tools; parts; set up
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Inadequate plans – reqmts, parts, materiel, equipment
• Lacks information – complete BOM, planned work, support
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Stove-piped processes and execution
• Lack of synchronicity leads to non-compliant work arounds
Future State
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Known Aircraft/End Item Condition
• Use lead time ahead of induction
• Order Parts, Training, Infrastructure, Equipment, Data, etc.
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Mechanic-Centric Focus (Surgeon)
• Parts, tools, data, equipment pre-positioned at point of use
• Maximum use of kitting
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Expand Standard Work & Processes
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Single Maintenance Concept
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Integrated Planning, Decision-making, & Data Collection
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Equivalent to 14% more aircraft on station
Enhanced
State
Awareness
Find, then fix
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HVM for Developmental Aircraft
Capability Spirals
Spiral 1:
Research
Supporting Key Technologies
Enhanced
State
Awareness
Spiral 2:
Vehicle Health Mgmt
Spiral 3:
Total Weapon System
State Awareness
Airframe Condition
- Fully Instrumented (IVHM)
- Onboard Prognostics/Life Prediction
Net-Centric Solution w/ Supply
Base
Standard Work Documented for All
Processes
Total State Awareness
- Right maintenance accomplished when mission requirements allow
Total State Awareness determines when MX required
Airframe Condition
Predictive analysis
- RCM, MSG-3
- Dets assess condition
Airframe Condition
SHMS
- On-board systems diagnostics
- Corrosion sensors
- 100% flight Loads data
Auto data transfer & analysis
Integrated Supply Chain
Management
Single Maintenance Concept
Fully Integrated Management System
Automated Data Collection &
Distribution
Anticipatory Spares Ordering
Automated POM generation of $$
No surprises
Low cost per flying hr
Now
Enhanced State Awareness
- Structural Integrity Prognosis
System
Active Autonomous
Dialogue with Depot
Standard Work for ISO/PDM
Standard Work Documented for
Integrated System
ISO and PDM Integrated
Integrated Management System
- Integrated Data from all systems
- Plans/Schedules
Integrated Requirements and Funding Process
Time
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Overview
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Aging aircraft in perspective
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Carefree Structures
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High-Velocity Maintenance
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Summary
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Prognosis Role in Community Integration
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How can material and structural state awareness be achieved?
Desired state Damaged state Failure
After K Jata, Sept 2007
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What is the role of an informed maintenance community in developing the prognosis concept?
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Can total vehicle state awareness be achieved at an affordable cost?

Can leadership be convinced that prognosis is a better solution?
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Prognosis as Integrator
Prediction &
Prognosis
Sensing for State
Awareness
Force
Management
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Prognosis Drivers:
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Data
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Physics
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Cost
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Availability
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Capability
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Safety
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Tribal Customs
Prognosis as Integrator
Prognosis
ASIP-SA
Aircraft Structural
Integrity Program in the age of state awareness
Care-Free Structures
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Summary
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High-Velocity Maintenance Carefree structures concepts maturing
 Prognosis community must integrate the “cultures” of the various “tribes” crucial to achieving USAF relevance
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Possible collaboration on proposed Tech Demo will drive R&D to solve most difficult aging aircraft problems
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Early transition to Tech Demo wing would challenge integrators to focus on the art of the possible.
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