Operational Needs for a Paradigm Shift in Life Prognosis

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

Presented to AFOSR Workshop on Prognosis19 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.

http://images.google.com/imgres?imgurl=http://www.stargazr.us/Photo%2520Gallery/C-130%2520night%2520landing.jpg&imgrefurl=http://www.stargazr.us/photo.htm&h=514&w=800&sz=27&hl=en&start=16&tbnid=nXKICtoeS_qHnM:&tbnh=92&tbnw=143&prev=/images%3Fq%3Dc-130%26ndsp%3D20%26svnum%3D10%26hl%3Den%26lr%3D%26sa%3DN

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Overview

Aging aircraft in perspective

Carefree Structures

High-Velocity Maintenance

Prognosis Role as Integrator

Summary


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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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Top 10 Maintenance Drivers (MMH), Total AF

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

03 11 04 13 46 14 74 23 76 12

Mill

ions

WUC

MM

H

20012002200320042005

WUC WUC Description % of Total FY05 MMH Hrs

03 LOOK PH OF SCH INSP 14%11 AIRFRAME 12%04 SPECIAL INSPECTIONS 11%13 LANDING GEAR 8%46 FUEL SYSTEM 5%14 FLIGHT CONTROLS 5%74 FIE CONTROL 4%23 POWER PLANT 4%76 TAC ELEC WRFRE SYS 3%12 CKPT & FUSE COMPTS 3%

68%Total of Top 10 =

Finding, fixing cracks and corrosion: trending upward

Sche

dule

d in

spec

tions

Airf

ram

e re

pair

Spec

ial i

nspe

ctio

ns

Land

ing

gear

Fuel

syst

ems

Mai

nten

ance

Man

Hou

rs (M

MH

)

Prop

ulsi

on

Maintenance CategoryDISTRIBUTION 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

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Missouri Air National Guard Mishap2 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


Prognosis lesson learned: make sure you look in the right place!

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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

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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


Carefree Structures



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!


http://www.airbus.com/product/a380_backgrounder.asp

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Alcoa Hybrid Wing Panel Tests (2006) Ultra-Long Life Under Severe Conditions

0

25

50

75

100

125

150

175

0 2,500 5,000 7,500 10,000 12,500 15,000 17,500 20,000 Flights

Hal

f Cra

ck L

engt

h, 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


Artificial fla

w

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Damage Tolerance Approach Conventional Aluminum Structures

2ASIP 2006., Nov. 29, 2006

Current Practice: Inspect for Structural Safety

ResidualStrength Initial Insp.

= 1/2 life

LimitRepeat Inspections more frequent as multiple cracks occur

Ultimate

2nd Insp.= 1/4 life

1 lifeToday's Metallic

Life extension

repairs

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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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


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Now I think we’re prepared for the inspector to enter the wing through this spacious access hole….

Why is inspection so difficult?


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Safety through inspection

…rely on him to be perfect, every single time.Compliments of David CampbellOklahoma City ALC NDI Program Mgr


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- 1 -

Flight Cycles1X 2X 3X 4X 5X 6X

ResidualStrength

Limit LoadFail-safe req.

0

Life Extension

Inspect & Repair

"Care-free"Economic Life

1 DSG 2 DSG Current Practice: Damage Tolerance1 DSG Proposed Care-free 2 DSG

UltimateLoad

Damage TolerantEconomic Life

Onset of widespread fatigue damage

"Care-free"1st inspection

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


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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

PR

IOR

I TY


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Overview


Carefree Structures



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

• 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

Vel

ocity

(hrs

/day

)

PDMISO ISOHSC ISOMaintenance Cycle

“Current” State

C-130 PDM = $3.5M ea, 95/yr, 22K Hrs, 160 DaysF-15 PDM = ~$3.75M ea, 97/yrC-5 PDM = $16.3M ea, 18/yr

“To Be” State

Additional Availability


After Dement & Keene

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HVM Vision

No Surprises…No Wasted Motion…No Waiting

Increase aircraft availability using common sense tools to

Establish a synchronized, integrated, end-to-end process

Maintenance must not impact mission requirements.

AircraftAvailability

HVM

ECSSCAMGLSC

PLMLCSE

AAIP

HVM for PDM/ISO

WR-ALC C-130 Prototype

Optimizes the PDM process (the “how”)

Includes all supporting processes

Optimize the field/depot reqmts

(the “what, when and where)

RCMCBM+

MSG-3Expands HVM to be

“scalable and transportable”

Overar

ching

enter

prise

initia

tives

Std Work Supply Chain Ops Lifecycle Mgmt Sourcing Tech Development

IntegrityPrograms


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HVM Attributesfrom Warner Robins ALC

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

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 to 14% more aircraft on station

Enhanced State

Awareness


Find, then fix

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Information Enabled Planning & Execution

Spiral 3:Total Weapon System

State Awareness

Cap

abili

ty

Time

Enhanced State

Awareness

Spiral 1: Research

Supporting Key Technologies

Spiral 2:Vehicle Health Mgmt

Integrated Management System- Integrated Data from all systems- Plans/Schedules

Now

Airframe ConditionPredictive analysis- RCM, MSG-3- Dets assess condition

Airframe ConditionSHMS- On-board systems diagnostics- Corrosion sensors- 100% flight Loads dataAuto data transfer & analysis

Fully Integrated Management System- Automated Data Collection &

Distribution- Anticipatory Spares Ordering- Automated POM generation of $$

Airframe Condition- Fully Instrumented (IVHM)- Onboard Prognostics/Life Prediction

Enhanced State Awareness- Structural Integrity Prognosis

System- Active Autonomous Dialogue

with Depot

Integrated Supply Chain Management

Standard Work for ISO/PDM

Standard Work Documented for All Processes

Standard Work Documented for Integrated System

Single Maintenance Concept

Net-Centric Solution w/ Supply Base

ISO and PDM Integrated

Integrated Requirements and Funding Process

- Right maintenance accomplished when mission requirements allow

Total State Awareness determines when MX required

No surprises

Low cost per flying hr

HVM for Developmental AircraftCapability Spirals


Total State Awareness

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Overview


Carefree Structures



Summary


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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?


Desired state Damaged state FailureAfter K Jata, Sept 2007

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Prognosis as Integrator

Design

Analysis &

Development

Tests

Design Information

(Materials Allowables)

Full-Scale Testing

Force Management

Production, Industrialization, Safety, Maintenance, Inspection

Sensing for State Awareness

Prediction & Prognosis

Fault Detection &

Trending


Care-Free

Structures

Self-h

ealin

g

materia

ls

Failure Progressio

n

Failure Analysis

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Prognosis as Integrator

Prognosis Drivers:

Data Physics Cost Availability Capability Safety Tribal Customs


Prediction

CBM

+

High-Velocity Mx

Prognosis

Dia

gnos

tics

Care-Free Structures

Aircraft Structural Integrity Program in the age of

state awareness

ASIP-SA

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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.


Operational Needs for a Paradigm Shift in Life Prognosis

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