10/31/2005 A V I A T I O N E N G I N E E R I N G D I R E C T O R A T E 1

24 Oct 2005

DOD MAINTENANCE

SYMPOSIUM

Dr. Bill Lewis A V I A T I O N E N G I N E E R I N G D I R E C T O R A T E

CBMMain Rotor Swashplate Bearing

Fault Detection

Spalling/Corrosion

Broken Cage

CBM

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DOD MAINTENANCE SYMPOSIUM

METHODOLOGY

TRANSITION TO A CBM ENVIRONMENT

CULTURE CHANGE

AMRDEC- COMITTED TO DEVELOPING THE METHODOLOGY TO SUPPORT THE CBM PROCESS

TIME BASED

TBO’S

REAL TIME CONDITIONED BASED

CI’S (DIAGNOSTICS) CI’S (PROGNOSTIC’S)

TODAY

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CBM STEPS

DOD MAINTENANCE

SYMPOSIUM

• IDENTIFY PARTS• FAILURE MODES• DATA REQUIREMENT• ANALYSIS METHODS• COLLECT DATA• CONDITION INDICATORS• CORRELATE USAGE• PROGNOSTICS• CI THRESHOLDS• MAINTENANCE ACTIONS• DOCUMENT

INITIAL STEPSCI’S THAT LEAD US TO

PROGNOSTICS “THE PROMISED LAND”

FOR THE FUTURE

“MORE THAN 1 CI”

• CI’S• FIELD• COLLECT MORE DATA• REFINE CI’S• FIELD• BECOMES “CYCLE OF CI”

CBM REVOLVES AROUND CI’S

ON

E CI

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• The primary focus of AED with respect to CBM is the acquisition and analysis of “HUMS (vib) data” to diagnose the condition of components.

• Exactly what is “HUMS data”?– Significant signal processing/know-how is required to get trend able

and actionable data from an accelerometer

Signal ProcessingCI = 4

Vibration

Time(Sec) Time

(Months)

CI

DOD MAINTENANCE

SYMPOSIUMCBM PERSPECTIVE

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1. Flight hours, not Calendar Time2. Correlation of maintenance events with vib data3. Help with units/CCAD-AIB for teardown4. Seeded faults to help set thresholds

-Fault progression from “yellow” to “red”

CI (Vibration)

3. & 4.What is yellow?

Calendar Time

1. Nine months, how many flight hours?2. Maintenance?

DOD MAINTENANCE

SYMPOSIUMHOW DO WE START?

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83-23874 &83-23900

Fleet

Jan 2003 Jan 2004Jan 2002 Jan 2005

Condition Indicator History

Outliers

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Oil Cooler Fan Bearing Race

Faults CI = Sum of Vibration = 8

Faulty Oil Cooler

(Abnormal)

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CI = Sum of Vibration = 3

New Oil Cooler

(Normal)

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AWRs* Enabled CBM Processes On More Than 100 Aircraft* Air Worthiness Release

SYSTEM ITEM ACTION / BENEFIT

AH-64M/R Swashplate Eliminates 50 Hr Bearing Inspection (Between 1750 and 2250 Hrs)

Eliminates Maintenance Operational Check (approx 1 hr)MMH Saved per Inspection 7.4 Hrs. Downtime Saved per Aircraft 5.9 Hrs

AH-64APU Clutch Eliminates Vibration Checks at Installation and Phase. Extends APU Mount

Inspection From 250 to 500 Hrs. MMH Saved per Inspection 28 Hrs. Downtime Saved per Aircraft 9 hours

AH-64 Aft Hanger Bearing

Safety Improvement With Continuous Diagnostic Monitoring. Extends TBO From 2500 to 2750.

AH-64 Fwd Hanger Bearing

Safety Improvement With Continuous Diagnostic Monitoring. Extends TBO From 2500 to 2750.

UH-60 Oil Cooler Axial Fan Bearing

Eliminates 120 Hour Inspection With Continuous Diagnostic Monitoring.Extends TBO From 2500 Hrs to 3000 Hrs.

UH-60Engine Output Drive Shaft

Eliminates AVA Installation Requirement for 120 Hr Inspection. Replace With Continuous Diagnostic Monitoring. MMH Saved per Inspection 3.3 Hrs. Downtime Saved per Aircraft 1.8 Hrs

Aviation Engineering Directorate Published AWRs* 16 Jun 05

DOD MAINTENANCE

SYMPOSIUM

10/31/2005 A V I A T I O N E N G I N E E R I N G D I R E C T O R A T E 10

Prognostics for Mechanical ComponentsUH-60 Intermediate Gearbox

• Developed Estimates of Remaining Useful Life (Prognostics)

• Proved the Value of Seeded Fault and Bench Test Data

Georgia Tech Applied Research Corporation

10/31/2005 A V I A T I O N E N G I N E E R I N G D I R E C T O R A T E 11Algorithms for Estimating Remaining Useful Life

Estimated Remaining Life

35 hours

3 Tests Yielded High

Confidence Level

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Intermediate Gearbox Prognostics Summary

Demonstrated Capabilities:• Prognostic Algorithms Developed From Seeded Fault and Bench Test Data

• Prognostic Process Involved: – Fault Classification and Characterization

– Estimation of Remaining Useful Life (Prognostics)

– Validation of the Algorithms By Run to Failure and Teardown Analysis

• Calculated Probabilities of Component Health and Existence of a Fault

Benefits to the Warfighter:• Improved Maintenance Planning

• Proactive Supply Actions Based on Component Health

• Improved Operational Availability

DOD MAINTENANCE

SYMPOSIUM

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DOD MAINTENANCE

SYMPOSIUMHOW DO YOU DEVELOPE A CI?

Vibration MonitoringUsed For Time Change/Condition Change Assemblies with Rolling Element BearingsIdentifies Abnormal Vibration Signatures Due To Component Degradation

Regime RecognitionUsed For Fatigue Life Limited Critical ComponentsRetirement Life Based On ACTUAL Rather Than ASSUMED Usage SpectrumAllows Non-Fatigue Failures To Be Correlated With Usage

Performance MonitoringUsed For Time Change/Condition Change Assemblies Like Pumps, Gearboxes, And EnginesExamples Include Oil Analysis, Chip Detectors, Temperature, Torque,Pressure, Flow, Etc.

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DOD MAINTENANCE

SYMPOSIUMCONDITION INDICATORS

ENGINEERING ANALYSIS

SEEDED FAULT TESTINGPARTS

ALGORITHMS

TEST PLANS

TESTING

POST TEST

THE TBO’S OF TODAY BECOME THE CI’s OF TOMORROW

HOW MUCH IS ENOUGH TO SATISFY SAFETY

HOW MUCH IS THE MAX TO KEEP IT ON THE AIRCRAFT

CI’S

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1. History of part retirement for fatigue

2. Purpose

• Increase the Useful Life of a Part• Extend Fatigue Life (Calculate Actual Fatigue

Damage)• Plan for part removal to reduce unplanned

maintenance

The Basics

Regime Recognition

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Background on fatigue

Safe-life Fatigue Methodology

• Safe-life – the structure is able to withstand the repeated loadings that are encountered without detectable cracks

• Safe-life approach has been in use in the helicopter industry for more than 40 years to substantiate the retirement life of fatigue-loaded dynamic components

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Fatigue Methodology

• Takes into account:– Part strength as demonstrated in test– Loads as determined from flight surveys– Usage

• Total process gives desired reliability• Changing one aspect of process will

impact reliability

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Service Life

• Safe-life period• Crack initiation• Crack growth• Part failure

Safe Life

Crack Growth

Crack Initiation

Army approach is to stop use of the part before detectable crack initiation

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Safe-life Fatigue Overview

Flight Loads

UsageSpectrum

FatigueStrength

DamageAccumulation Model

CalculatedFatigue Life

RetirementLife

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Simplified, Sample Usage Spectrum

Condition Percent TimeTake Off 3Hover 15Climb 6Forward Flight 55Turns 10Pull-ups 3Decent 6Landing 2

100

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Regime Recognition:Definition

0

10

20

30

40

50

60

70

80

Ban

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Turn

GA

G C

ycle

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Fwd

Leve

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ight

Take

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Clim

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Side

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Flig

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Rev

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DesignActual

Regime Recognition Software reads the aircraft parametric data during each flight and determines the “Flight Regime” at any time during a flight.

The “Flight Regimes” are regimes which were used by the OEM to design the aircraft and have known loads associated with them.

This chart represents Regime Recognition:Flight time is divided into identifiable “Regimes”.

10/31/2005 A V I A T I O N E N G I N E E R I N G D I R E C T O R A T E 22

Parameter Name Minimum Sample Rate (Hz)

Parameter Name Minimum Sample Rate (Hz)

Indicated Airspeed or Calibrated Airspeed

Analog 4 Total Fuel Weight Analog 1

Vertical Speed (ROC) Analog 4 Tow Tension Analog 2Pitch Attitude Analog 4 Tow Angle Analog 2Roll Attitude Analog 4 External cargo weight or Analog or 1Pitch Rate Analog 4 Hook Release Open DiscreteRoll Rate Analog 4 Weight on Wheels or Discrete 1Heading Attitude Analog 4 MR Brake Applied Discrete 1Yaw Rate Analog 4 Wheel Brake Applied Discrete 1Nz (Load Factor ) Analog 10 RAST Landing in Progress Discrete 1Ny Analog 4 Rotor Fold Discrete 1Nx Analog 4 Pylon Fold Discrete 1MR Speed Analog 4 Sonar Deployed Discrete 1Engine Torque, each engine Analog 4 Air Refueling in Progress Discrete 1Ng, each engine Analog 4 APU On Discrete 1MR Torque Analog 4 Total Gross Weight Analog 1Pressure Altitude Analog 4 CG Analog 1Radar Altitude Analog 4 Accelerometers for drivetrain

monitoringTBD

Longitudinal Cyclic Stick Position

Analog 10 Accelerometers for gearbox monitoring

TBD

Lateral Cyclic Stick Position Analog 10 Accelerometers for engine monitoring

TBD

Collective Stick Position Analog 10 Accelerometers for rotor balancing

TBD

Pedal Position Analog 10 Main Rotor azimuth TBDLongitudinal Ground Speed Analog 4 Tail rotor azimuth TBDLateral Ground Speed Analog 4 Strain gages DC – 2000 hzOutside Air Temperature Analog 4

Sample of Parameters used for Regime Recognition

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Purpose of Regime Recognition

With the knowledge of how the parts are used, and the Root Cause for replacement, we can apply our engineering and testing activities such that we extend the useful life these parts.

Detailed hardware inspections (Score Card) will be used to determine why parts are removed before they reach their Design Life. (Root Cause for part replacement)

Correlate the Flight Usage Data, including the operational environment (i.e. desert, tropical, artic) with the Root Cause for the part replacements.

$0

$50

$100

$150

$200

$250

$300

0% 50% 100% 150% 200% 250% 300%% Design Life

Cos

t per

Yea

r -M

illio

ns

Usage Life

Design Life

Typical Actual Life ( 1/4 Design)

Improved Life (1/3 Design)

Δ=$20M

Δ=$50M

Step 1 Extend Actual to Design Life

Increase the Useful Life of a Part

Step 2Extend Fatigue Life

This “Design Life” chart shows that parts fall short of design expectations.

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% T o ta l D e s ig n D a m a g e b y R e g im e

0 %

1 0 %

2 0 %

3 0 %

4 0 %

5 0 %

6 0 %

Ban

ked

Turn

GA

G C

ycle

s

Fwd

Leve

lFl

ight

Take

-Off,

Clim

b, D

esce

nt

Pullo

ut

Side

& R

ear

Flig

ht

Con

trol

Rev

ersa

l

Hov

er

Aut

orot

atio

n

Land

ing

& T

axi

%To

tal D

esig

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amag

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D e s ig nA c tu a l

Given the amount of Time in a Regime and the Load in the part we can determine fatigue life remaining in that part.

Regime Recognition: Step 2Calculate Actual Fatigue Damage

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Planning for Part Removal

Based upon upcoming usage (e.g., deployment) will be able to plan for what will be the fatigue damage impact to each part on the aircraft

-What parts will need to be replaced?-How can we best schedule maintenance?

Regime Recognition will allow these sort of questions to be answered in a dependable way.

For example: tail rotor blade has 600 hours life left, being deployed to OEF/OIF for 1 year –will TR blade need to be replaced during deployment? Will it last longer than the deployment period? Should we change it out now and leave it for a stateside unit to use?

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Regime Recognition

Questions?