Condition Based Maintenance

Summary: The presentation provides an overview of Condition Based Maintenance research performed in the NASA Glenn Tribology and Mechanical Components Branch in support of the Subsonic Rotary Wing Project.

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National Aeronautics and Space Administration

www.nasa.gov

Fundamental Aeronautics Program

Dr. Paula DempseyTribology & Mechanical Components BranchNASA Glenn

Subsonic Rotary Wing Project

CBM

2011 Technical ConferenceMarch 15-17, 2011Cleveland, OH

What is CBM?

Condition Based Maintenance: Application & integration of processes, technologies &

knowledge via a systems approach to improve aircraft reliability and maintenance effectiveness*

» Reduce maintenance tasks» Increase aircraft availability » Improve flight safety » Reduce costs

*US Army ADS-79 HNDBK2

CBM Functions

Propulsion System Health• Health monitoring of dynamic mechanical components • Monitored by vibration signature analysis methods (condition indicators-

CI) and oil conditionStructural Health• Fatigue life management/component lifing based on actual usage &

regime recognitionExceedance Monitoring• Aircraft operational/parametric data (torque, speed, temperature)Engine Health• Power assurance check/Power ManagementRotor Smoothing• Automated track & balance of rotors to decrease vibrationsFleet Maintenance• Logging maintenance actions/CBM data 3

Propulsion System Health– Improved detection techniques– Improved diagnostic algorithms

• Multi-sensor data fusion• Performance metrics• Damage magnitude assessment

– Validated methods – rotorcraft field verification • Test methods representative of fielded faults

– Future prognostic algorithms• Damage life prediction models – predict remaining useful life

Structural Health & Exceedance Monitoring– Correlate aircraft operational parameters to component life.

Research enabled through Partnerships with the FAA and US Army– FAA funded Space Act Agreements– Access to > 2000 Army HUMS equipped helicopters

SRW CBM Focus - Propulsion

Gear Fault Detection Effectiveness

Objective:•Evaluate gear tooth pitting fatigue fault detection effectiveness

•Evaluate repeatability of gear tooth fault detection methods

•Evaluate CI threshold values

Approach:•Test gears: face gears with tapered involute pinions

•Vibration and oil debris monitoring during gear endurance testing

• Evaluate three common vibration CIs (RMS, FM4, NA4)

Propulsion System Health

Data point0 10000 20000 30000

NA4 (g's) - Healthy

0369

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Data point0 1000 2000 3000 4000

NA4 (g's) - Faulty

01020304050

NA40 20 40 60 80

Probability density function

0.00.10.20.30.4

False alarm rate0.0 0.2 0.4 0.6 0.8 1.0

Hit rate

0.00.20.40.60.81.0

Healthy

Faulty

NA4=35 4620

40

CI: NA4, Macro-Pitting, Single/Few Teeth

Propulsion System Health

Gear Fault Detection Effectiveness

Planetary Fault DetectionObjective:Demonstrate diagnostics to detect gear and bearing planetary system faults in main-rotor gearboxApproachDevelop algorithms from seeded fault tests on the OH-58 main-rotor transmission (AATD/Bell OSST)

0 45 90 135180225270315360 45 90 135180225270315360 45 90 135180225270315360-5

0

5a) Hunting tooth average of raw data.

Acc

eler

atio

n (V

)

34 35 1 2 3 -2

0

2b) Windowed data,

planet 1 carrier cycle 1.

Acc

eler

atio

n (V

)

Tooth number28 29 30 31 32

-2

0

2

Tooth number22 23 24 25 26

-2

0

2

Tooth number

1 2 3 4 5 6 7 8 9 1011121314151617181920212223242526272829303132333435 1 -2

0

2

Planet gear tooth number

Acc

eler

atio

n (V

) e) Completed planet 1 tooth vector.

Planet 1 first pass Planet 1 second pass Planet 1 third pass

c) Windowed data, planet 1 carrier cycle 2.

d) Windowed data, planet 1 carrier cycle 3.

Carrier rotation, deg

Propulsion System Health

Acc

eler

atio

n, g

's

-15-10

-505

1015

Acc

eler

atio

n, g

's

-15-10

-505

1015

Acc

eler

atio

n, g

's

-10

-5

0

5

10

Planet gear tooth number1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35

Acc

eler

atio

n, g

's

-10

-5

0

5

10

Accelerometer numberA1 A2 A3 A4 A5 A6 A7 A8

M8A

0

500

1000

1500

20001500020000 Healthy

Faulty

Fault

Propulsion System HealthPlanetary Fault Detection

99

Time Domain

Frequency Domain

time steps

undamaged

damagedSu

n G

ear D

ispl

acem

ent

Objective:Develop analysis method to simulate dynamic response of gear or bearing surfaces with damage

Approach:•Defect geometries defined by actual measurements

•Forces between components calculated via contact mechanics

•Deformations and vibration responses calculated via finite element

Propulsion System Health

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Objective:• Demonstrate (CI) responds to

failure progression & correlates to remaining useful life

Approach:• UH60 tail gearbox output shaft

thrust bearings • Removed from helicopters

installed in test stand• Periodic inspections to

measure spall growth• CI data mapped to the damage

state did not perform well for magnitude assessment

• Oil debris sensor monitored debris generation & indicated progression & remaining life.

Propulsion System Health

FAA Space Act Agreement Validation & Demonstration of HUMS for Maintenance Credits,

modified inspection & removal criteria,via FAA AC-29-2C, Section MG-15

Objectives:• Develop CI validation methods in the lab that represent fielded faults• Identify limitations of seeded fault data sets. • Case Study: Component with naturally occurring faults in the field and

test stand.Spiral bevel gears in the Apache nose gearbox (NGB)Spiral bevel gears tested in the Spiral Bevel Gear Fatigue Test Rig

Approach• Rig gears designed/tested with loads/speed scaled to NGB• Field units studied for failure modes & operational environment • Field/Rig data studied for CI performance• Usage data studied to determine if failure can be correlated to usage

Collaborative Team Effort: FAA, US Army, NASA, Boeing

s

Pinion Magnetic Tach

Oil Debris Sensor

MSPU IAC Model 1087

MDSS

Torque Meter

Chip Detector

Gear Optical Tach

s

Spiral Bevel Gear Fatigue Rig

FAA Space Act Agreement

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FAA Space Act Agreement

Assess CI performance from field & lab

0

25

50

75

100

125

150

1 10 100 1000 10000 100000

Torq

ue (%

)

Hours

Correlate usage to failures

SRW Phase II SBIR

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OH-58 main rotor transmission

NASA GRC 500-hp transmission test facility

Ridgetopwireless sensors

Embedded Data Acquisition Tools for Rotorcraft HUMS (Ridgetop)

Objective:Develop MEMS wireless sensor for fault detection in rotorcraft transmission applications

Approach:• Develop MEMS vibration-monitoring

accelerometer, microcontroller conditioner, wireless transmitter, and receiving unit for data collection.

• Mount directly on helicopter transmission component of interest to measure abnormalities and faults.

SRW Phase I SBIR

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Optical oil-debris sensor for rotorcraft health monitoring (Translume)

Objective:Develop an oil debris sensor to monitor rotorcraft power train oil.

Approach:• Develop sensor to simultaneously

detect both metallic and non-metallic debris

• Optimize sensor to detect, count and size particles

• Conduct a feasibility demonstration on a laboratory scale

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