Transcript Document

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
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Overview
 Aging aircraft in perspective
 Carefree Structures
 High-Velocity Maintenance
 Prognosis Role as Integrator
 Summary
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2
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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Millions
Top 10 Maintenance Drivers (MMH), Total AF
3.5
Finding, fixing cracks and
corrosion: trending upward
Maintenance Man Hours (MMH)
3.0
03
11
04
13
46
2001
2002
2003
2004
2005
Propulsion
Fuel systems
0.0
..while continued investment in
propulsion paying big dividends
Landing gear
0.5
Special inspections
1.0
Airframe repair
2.0
1.5
03
11
04
13
46
14
74
23
76
12
% of Total FY05
MMH Hrs
LOOK PH OF SCH INSP
14%
AIRFRAME
12%
SPECIAL INSPECTIONS
11%
LANDING GEAR
8%
FUEL SYSTEM
5%
FLIGHT CONTROLS
5%
FIE CONTROL
4%
POWER PLANT
4%
TAC ELEC WRFRE SYS
3%
CKPT & FUSE COMPTS
3%
Total of Top 10 =
68%
WUC Description
Lack of investment in structures
sustainment costing USAF…
Scheduled inspections
MMH
2.5
WUC
14
74
WUC Category
Maintenance
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
Prognosis lesson learned: make sure you
• Cause: Fatigue of “fatigue
proof” upper cockpit
longeron
mfgplace!
defect
look
in thefrom
right
• 700+ aircraft grounded for
detailed inspections
• 162 aircraft remain
grounded as of 11 Feb 08
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Source: www.af.mil
5
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
6
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
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Overview
 Aging aircraft in perspective
 Carefree Structures
 High-Velocity Maintenance
 Prognosis Role as Integrator
 Summary
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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!
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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
B777 wing
@ Baseline Stress
Airbus 380 wing
@ Baseline Stress
Bucci, et al, ASIP 2006
Half Crack Length, a [mm]
150
Bolt Ctr Line
Extruded Al Stringer
Fiber Metal
Laminate
125
Al Sheets
100
Early Hybrid Concept
@ + 25% Stress
75
Evolved Hybrid
@ +25% Stress
No external crack growth
50
25
Skin side
Stringer side
Skin 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
Current Practice: Inspect for Structural Safety
repairs
Residual
Strength Initial Insp.
2nd Insp. Repeat Inspections more frequent
= 1/4 life as multiple cracks occur
= 1/2 life
1 life
Life extension
Today's Metallic
Ultimate
Limit
As damage-tolerant aircraft age past original design life, inspection burden grows…
… and risk of inspection-induced damage increases
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Safety through inspection?
 Example: bolt hole eddy
current inspection of a
fuel tank structures
 Highly skilled technician
 Hand-held eddy current
probe
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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!
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Why is inspection so difficult?
 Now I think we’re
prepared for the
inspector to enter
the wing through
this spacious
access hole….
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Safety through inspection
…rely on him to be perfect, every single time.
Compliments of David Campbell
Oklahoma City ALC NDI Program Mgr
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Benefits of the Care-free design
after Hinrichsen, Alcoa
 Longer inspection intervals
 Much longer acrit, easier to find
 Safety, economy and availability
 May make enhanced state awareness easier
Residual
Strength
"Care-free"
Economic Life
"Care-free"
1st inspection
Damage Tolerant
Economic Life
Ultimate
Load
Onset of widespread
fatigue damage
Inspect & Repair
Limit Load
Fail-safe req.
Life Extension
0
1X
1 DSG
2X
3X
4X
5X
6X
Flight Cycles
2 DSG Current Practice: Damage Tolerance
1 DSG Proposed Care-free 2 DSG
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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
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Overview
 Aging aircraft in perspective
 Carefree Structures
 High-Velocity Maintenance
 Prognosis Role as Integrator
 Summary
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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
Mx Velocity (hrs/day)
• Airlines: 500-800 man-hours/day
• Depot: 145-220 hours/day
C-130 PDM = $3.5M ea, 95/yr, 22K Hrs, 160 Days
 Field and Depot not synchronized
F-15 PDM = ~$3.75M ea, 97/yr
• Function as two independent systems
C-5 PDM = $16.3M ea, 18/yr
• Little communication
“To Be”  Aircraft condition not well known at induction
1000
State
• Result: Long lead times
• High opportunity costs = larger than needed fleets
Additional Availability
“Current” State
After Dement & Keene
0
ISO
HSC
ISO
PDM
ISO
Maintenance Cycle
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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
AAIP
LCSE
PLM
GLSC
CAM
ECSS
Std Work
HVM
MSG-3
Expands HVM to be
RCM
“scalable and transportable”
CBM+
HVM for PDM/ISO
WR-ALC C-130 Prototype
Optimizes the PDM process (the “how”)
Includes all supporting processes
Supply Chain Ops
Lifecycle Mgmt
Sourcing
Integrity
Programs
Tech Development
No Surprises…No Wasted Motion…No Waiting
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HVM Attributes
from Warner Robins ALC
Current State
Future State
 Limited Knowledge of A/C Condition
 Known Aircraft/End Item Condition
•
 5+ Year PDM cycle (C-130)
•
•
Two Mx systems; creates knowledge barriers
Damage accumulates, so “must fix now” mentality
•
 Mechanic-Centric Focus (Surgeon)
 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
Use lead time ahead of induction
Order Parts, Training, Infrastructure, Equipment, Data, etc.
•
•




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 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
Spiral 2:
Vehicle Health Mgmt
Supporting Key Technologies
Capability
Enhanced
State
Awareness
Airframe Condition
Predictive analysis
- RCM, MSG-3
- Dets assess condition
Enhanced State Awareness
- Structural Integrity Prognosis
System
- Active Autonomous
Dialogue with Depot
Now
Standard Work for ISO/PDM
Airframe Condition
SHMS
- On-board systems diagnostics
- Corrosion sensors
- 100% flight Loads data
Auto data transfer & analysis
Integrated Supply Chain
Management
Spiral 3:
Total Weapon System
State Awareness
Total State Awareness
Airframe Condition
- Fully Instrumented (IVHM)
- Onboard Prognostics/Life Prediction
- Right maintenance
accomplished
when mission
requirements allow
Net-Centric Solution w/ Supply
Base
Total State Awareness
determines when MX
required
Standard Work Documented for All
Processes
No surprises
Single Maintenance Concept
Low cost per flying hr
Fully Integrated Management System
- Automated Data Collection &
Distribution
- Anticipatory Spares Ordering
- Automated POM generation of $$
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
 Aging aircraft in perspective
 Carefree Structures
 High-Velocity Maintenance
 Prognosis Role as Integrator
 Summary
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Prognosis Role in Community Integration
 How can material and structural state awareness be achieved?
Desired state
Damaged state
Failure
After K Jata, Sept 2007
 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?
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Prognosis as Integrator
Prediction &
Prognosis
Sensing for State
Awareness
Force
Management
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Prognosis as Integrator
Prognosis Drivers:
 Data
 Physics
 Cost
 Availability
 Capability
 Safety
 Tribal Customs
Prognosis
ASIP-SA
Aircraft Structural
Integrity Program
in the age of
state awareness
Care-Free Structures
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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.
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