structural health management: a rotorcraft oem perspective · high-sensitivity vibe analysis...

Structural Health Management:

A Rotorcraft OEM Perspective

Mark Davis

Tech Fellow, Prognostics & Health Management

Sikorsky Aircraft Corporation (SAC)

10th International Workshop on Structural Health Monitoring

Palo Alto, CA

September 1, 2105

Export Control Warning This document contains no technical data controlled by the ITAR or EAR

Copyright Notice

This document, or an embodiment of it in any media, discloses information which is proprietary, is the property of Sikorsky Aircraft Corporation, is an unpublished work protected under applicable copyright laws, and is delivered on the express condition that it is not to be used, disclosed, or reproduced, in whole or in part (including reproduction as a derivative work), or used for manufacture for anyone other than sikorsky aircraft corporation without its written consent, and that no right is granted to disclose or so use any information contained therein. All rights reserved. Any act in violation of applicable law may result in civil and criminal penalties.

Copyright © 2015 An Unpublished work by Sikorsky Aircraft Corporation. All rights reserved (see cover page). This document contains no technical data controlled by the ITAR or EAR

© Unpublished Work, Sikorsky Aircraft (SAC) 2015. SAC Proprietary Information. All Rights Reserved. See restrictions on title page.

This page contains no technical data controlled by the ITAR or EAR.

OUTLINE

• Aircraft Health Management Vision

• HUMS/IVHMS Evolution and Current Capability

• SAC Experience with SHM

• SHM Assessment & Transition Challenges

• Mechanical Diagnostics Analogy

• Thoughts on a SHM Transition

• Concluding Remarks

2




SAC HEALTH MANAGEMENT VISION Eliminate Unscheduled Maintenance

Optimize Scheduled Maintenance

Focus Troubleshooting & Reduce False Removals

Maximize Detection Time Before Failure

Enhance Safety

3



This page contains no technical data controlled by the ITAR or EAR. 4

S-92®

CH-53E

S-61™

S-76C++™

CH-53K UH-60A,L,M

VXX

CH-148

SAFETY

MAINTENANCE & TROUBLE SHOOTING

CONDITION BASED MAINTENANCE

SAC HEALTH MANAGEMENT EVOLUTION




SAC HEALTH MANAGEMENT SYSTEM

S-92® Operators

HUMS Collected

Data Helicopter Flight Data Mgt.

Customer

MFD Ground Station

HUMS Toolbar

Sikorsky

Web Portal KDT

CI Box Plot

MDAT Matlab

Data Transfer

Multiple time a day

Value: new tools, maintenance credits, etc.

Drivetrain

Diagnostics

Rotor Track

& Balance

Exceedance

Display

Proactive Support

HUMS/Maintenance

Data & Field Events

New HUMS

Tools

Retirement

Time

Adjustment

S-92 Hub

Pro-Active

Support

5


S-92® HUMS Ten years of maturation and value

Downtime Avoidance

High-sensitivity vibe analysis

enabled early detection and

proactive response.

New Detection Capability

Isolated vibe-signature of previously

undetectable pivot bearing issue

and enabled software enhancement

Extended Time-on-Wing

Decision Support

Data mining and analysis to

understand field issues and

improve decision making

Over 250+ aircraft monitored

~750,000 Flight Hours

10GB+ data daily

Analysis & Tool Development

Web Portal

KDT Part Tracker



Leveraged S-92® Main Rotor Hub

life adjustment to gain additional

retirement time adjustment credits

SAC Ground

Based App


WHAT IS SHM?

Common Perspective: Structural Health Monitoring

Technologies required to detect, isolate, and characterize

structural damage (e.g., cracks, corrosion, FOD, battle

damage). Typically synonymous with monitoring of airframe

structural damage.

SAC Perspective: Structural Health Management

Holistic cradle-to-grave approach to ensure aircraft structural

integrity, safety, and reliability through optimized balance of

• design conservatism;

• monitoring of usage, loads, and structural damage;

• fleet management of flight critical components

• certification of SHM enabled condition-based maintenance (CBM).






STRUCTURAL HEALTH MANAGEMENT

8

Structural Health Management

Lo

ad

s, U

sag

e,

En

vir

on

me

nta

l

Op

era

tio

na

l H

isto

ry

No

n-d

es

tru

cti

ve

Eva

lua

tio

n a

nd

Vis

ua

l

Insp

ecti

on

s

In-S

itu

Da

mag

e D

ete

cti

on

an

d D

am

ag

e G

row

th

Mo

nit

ori

ng

Pre

dic

tive T

ech

no

log

ies:

Da

ma

ge

gro

wth

/ R

UL

Ma

inte

na

nc

e A

cti

on

s:

Ins

pe

ct,

Re

pa

ir, R

ep

lac

e

Design

Conservatism

Fatigue

Testing

Structural

Analysis

Flight Load

Survey Testing




ROTORCRAFT SHM CHALLENGES

9

Variability and Complexity of Physics of both Probabilistic & Random Failure Modes Rotor Hub

DamperPitch

ControlRod

Shaft ExtenderBlade Pin

Flap/Lag/Pitch/Thrust Bearing

(inside hub arm)aka elastomeric/MDOF bearing

Rotor Blade

Spindle, Nut, Tie-Rod

Rotor Blade

Cuff Assy

Bifilar Absorber

Pitch Horn

Swashplate(below cowling,attaches to lower PCR end)

Droop Stop

Scissors Assy

Variability of Operational Usage & Loads

Variability of Operational & Maintenance Environments

• Fatigue

• Corrosion

• FOD

• Battle

Typical Failure Modes


HOLISTIC SHM APPROACH




USAGE/LOADS MONITORING

Virtual Structural Usage/Loads Monitoring



Example Key Physical Sensors


SAMPLE S-92® A/C BENEFITS LLP Retirement Extension (Serial #)

• FAA approved S-92® main rotor (MR) hub life extension based on MR rpm GAG

• Average benefit of 50% one-time CRT extension calculated from first 20 fleet hubs

Data Driven

Inspection

Ro

tor

Sp

ee

d (

rpm

)

50 sec @ 58% RPM

4 min @

39% RPM

2 min @ 50% RPM

Avoid Range

Time

Focused

Troubleshooting

0

20

40

60

80

100

120

140

160

180

0-105 0-110

Rotor RPM Ground Air Ground Cycle

Oc

cu

ra

nc

es

Design

A/C 11

A/C 12

A/C 13

A/C 14

A/C 15

Fleet Avg

Rotor Cycles

0

20

40

60

80

100

120

140

160

180

0-105 0-110

Rotor RPM Ground Air Ground Cycle

Oc

cu

ra

nc

es

Design

A/C 11

A/C 12

A/C 13

A/C 14

A/C 15

Fleet Avg

Rotor Cycles

Component

Retirement

Adjustment

S-92 MR

Hub

Fleet Mean ~ 0.6

STD ~ 0.5

~260 Hours

Left Accessory GBX Bearings

Operator

Alerted

Health AlertsAccessory Gearbox

Accelerometer

Location

Abrasion

Strips replacedInspected No

Fault Found –

Rebalanced

Dis-bonded

Pivot Bearing

Ta

il R

oto

r V

ibra

tio

n (

ips)

Calendar Time

Maintenance Triggers

1/1/20091/1/20081/1/20071/1/2006

3500

3000

2500

2000

1500

1000

500

0

Removal Date

Flig

ht H

ours

at

Rem

oval

Bearing Faulty or worn

Indeterminate

Interference

Scheduled

Vibrations

Code

Scatterplot of Hours on Oil Cooler Blower at Removal Date

Lost Opportunities

Assignable Cause

TBO

Extension

1/1/20091/1/20081/1/20071/1/2006

3500

3000

2500

2000

1500

1000

500

0

Removal Date

Flig

ht H

ours

at

Rem

oval

Bearing Faulty or worn

Indeterminate

Interference

Scheduled

Vibrations

Code

Scatterplot of Hours on Oil Cooler Blower at Removal Date

Lost Opportunities

Assignable Cause

TBO

Extension

TBO Extensions

Clear Outlier

Fleet

Analysis

Level 1 Limit 0.37 G




Anomaly Detection

New Condition

Indicators

Fleet Spectrum Update (Part #) • Virtual Monitoring of Loads (VML) used to calculate TR torque from 500kFH HUMS data

• Load statistics used to revise usage spectrum 3.25X retirement time

• Same approach can be used for serial # credit

TR

Po

we

r (H

P)

Cumulative TR Power Spectrum






SAC SHM TECH DEVELOPMENT PROGRAMS

13

SIMS IRDT COST-A IHSMS ASTRO RDDT

Tech Assessment

Challenge Problem

Characterization

Metal sub-components

& PSE

Damage detection

sensing validation

Load sensing

evaluation

Prognostic system

architecture

VML extension

Metal PSE

Damage detection

sensing

Damage growth

modeling

Damage tolerant design

framework

Limited composites

VML application

Focus on H-60

Metals only

Damage, corrosion, &

impact detection and

quantification

VML application

Addresses structures,

drives, & rotors

On-board/off-board

system integration

Very focused on

composites

Local damage

propagation modeling

Integration of models

with sensor feedback

Coupon testing for

correlation with models

Focus on CH-53K

composite aircraft

Local / zonal damage

monitoring

Usage & loads

monitoring

Measure load changes

on select primary

structures due to

damage

Reduce over-

maintenance of

composite airframes –

focus on “big damage”

Estimate damage from

fewer sensors

Quantify effect of

damage on load

distribution and DT

Multi-site Damage

Energy Harvester

Load Sensor

Harvester Circuit, Microprocessor, and RF Transmitter

RF Antenna

SIMS Structural Integrity Monitoring System

IRDT Integrated Rotorcraft Damage Tolerance

COST-A Capability-Based Operations Sustainment

Technologies – Aviation

RDDT Rotorcraft Durability and Damage Tolerance

IHSMS Integrated Hybrid Structural Management System

ASTRO Autonomous Sustainment Technologies for Rotorcraft

Operations

2006-9 2008-10 2010-14 2010-13 2012-17 2013-17


TECHNOLOGY READINESS DEFINITIONS

• System Completed

• Flt / Mission Qual

• System/Subsystem

Development

• Tech Demo

• Tech Development

• Research to Prove

Feasibility

• Basic Research

In Service ……………………………………..

Qualification / Certification ………………….

System Demo ~ Flight Test ….……………….

Sys/Subsys Demo ~ Relevant Lab Environ …

Component~ Relevant Environ …….……….

Component/~ Lab Environ ………….………

Analytical /Exp Proof-of-Concept………….

Technology Concept …………………………

Basic Principles ………………………………

TRL 9

----

TRL 8

----

TRL 7

----

TRL 6

----

TRL 5

----

TRL 4

----

TRL 3

----

TRL 2

----

TRL 1

• Bulk of work in SHM community TRL 3 to 6

• Ok for R&D and at-aircraft monitoring

• TRL-7 required for embedded systems

• TRL-8 required for CBM credits






Stiffened Bay Panels

Sub-Component RR(Doubler Joint)

Laser

Scribe

Doubler Joint Angle Lap Joint

Sub-Component (TRL 3-5)

• Representative

Features

• Lab transducers, DAQ,

and processors

Beam/Frame Joint Frame Splice Cabin Top-Deck Sub-Assembly

• Full-Scale test articles

• Representative SHM

hardware/software

• Software partially

integrated with

OBS/GBS HUMS/IVHMS

50-100 tests* 20-30 tests*

1-5 tests*

SAC SHM TRL PROGRESSION

1 test*

* Rough number of tests that can be conducted for cost of one sub-assembly test

Full-Scale Primary Structural Elements (PSEs) & Sub-Assemblies (TRL 5-6)




This research was partially funded by the Government under Agreement No. W911W6-10-2-0006. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes

notwithstanding any copyright notation thereon. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies,

either expressed or implied, of the Aviation Applied Technology Directorate or the U.S. Government.

CAPABILITY-BASED OPERATION SUSTAINMENT

TECHNOLOGY – AVIATION (COST-A)

Objectives

• Mature and integrate embedded diagnostics and prognostics to decrease O&S

costs by reducing maintenance and transitioning to Condition-Based Maintenance

• Demonstrate an integrated set of prognostic technologies across six focus areas:

Propulsion, Drive, Structural, Rotor, Electrical, and Vehicle Management Systems

16

System/Sub-System-Level Reasoners Vehicle Management System (VMS)

No. 1 and No. 2 Pumps + Back-up

UH-60M VMS Components

•Multiclass SVM•Evolutionary Prog.•Particle Filter•Advanced Fusion

Health, RUL, +Conf.Vehicle

State Data

Hydraulic (Sub-) System

System Reasoning and Prognostics

Subsystem/ Component PHM

Stabilator EMA

VMS Sensor Validation & Diagnostics

Empirical System Models

Frequency Analysis

Fusion

Performance Models

Dynamic Signal Analysis

Hydraulic Pumps, Valves, Servos

VMS Sensor and Vehicle

State Data

Automatic Flight Control System

Model

System

Damage Estimator

Measured Input

Measured System Output

Output Residual + Degradation ID

-

+

+

+

Fault Effects & Variation Uncertainty

High Fidelity Dynamic Models

Current Asymmetry Analysis

0 0.01 0.02 0.03 0.04 0.05-6

-4

-2

0

2

4

6

time [sec]

curr

ent [

Am

ps]

On-Aircraft Systems Integration

Integrated Software

Aircraft Data


© Unpublished Work, Sikorsky Aircraft (SAC) 2015. SAC Proprietary Information. All Rights Reserved. See restrictions on title page. This page contains no technical data controlled by the ITAR or EAR.

This research was partially funded by the Government under Agreement No. W911W6-10-2-0006. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright

notation thereon. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the Aviation Applied Technology

Directorate or the U.S. Government.

COST-A FULL-SCALE TESTING

Point 1: 270k Cycles




0 Load Block 40

Zonal PZT Damage Index Est Damage from Visual

28 Load Block 40

1

0

3.5

0

Inc

hes

296.3k 276.3k 286.3k

Zonal Direct Path Image Progression (20x30 inch area)

Top Deck Fatigue Test Article Local Eddy Current CI

17




SHM MONITORING READINESS

18

• Individual SHM monitoring and diagnostic technologies have

matured greatly over last 10 years. Leading technologies

have achieved TRL-6+.

•Both local and zonal crack detection methods are ready for

prime time under right circumstances.

•Significant transition challenges remain:

– Lack of agreed upon reliability methods and certification

requirements

–Expense of validation and POD substantiation

–Expense of integrating into legacy aircraft and/or need for

new ground support equipment

–Scalability to total aircraft monitoring

–System productionization




MECHANICAL DIAGNOSTICS ANALOGY

• Similarities between SHM and Mechanical Diagnostics

‒ Vibration is indirect, remote indication of gearbox faults

‒ Cost of drive system seeded fault tests are prohibitive

‒ Aircraft seeded fault tests typically not allowed

• Approach for developing condition indicators (CIs)

‒ Identify CIs via physical understanding, modeling, rig test or fleet analysis

‒ Substantiate feature performance via small-scale tests

‒ Substantiate fault progression and feature performance via full-scale tests

‒ Conduct controlled introduction to service

19

Component Tests Full-Scale System Tests Controlled Introduction to Fleet Service




VIBRATION-BASED SHM EXAMPLES

20

Gearbox Support Crack Monitoring Tail Pylon Gearbox

Support Structure Fleet Comparison of Vibration CI

Aircraft Tail No.

Vibration HI Trend

Found Visually

Repaired

Time

Planetary Main Gearbox Carrier Plate (CP Crack Monitoring

Candidate Accel Locations

on Housing

Vibration HI Trend

GAG Cycle Number0 100 200 300 400 500 600 700 800 900 1000

Total Crack Length, inches1.3 2.5 3.0 3.5 4.1 4.5 6.8 7.1 7.6

GAG Cycle Number0 100 200 300 400 500 600 700 800 900 1000

GAG Cycle Number0 100 200 300 400 500 600 700 800 900 1000



small

crack

medium

crack

large

crack

Seeded Fault Test

Planet Assembly Carrier Plate Main Gearbox

COTS Crack Gages CP Crack Morphology




WHAT CAN SHM COMMUNITY DO TO BE READY

TO EXPLOIT NEXT TRANSITION OPPORTUNITY? SHM Technology providers

‒ Leverage HUMS lessons learned

‒ Address technology challenges

► Develop trendable SHM CIs and robust load/temp compensation algorithms

► Develop methods for monitoring health of fail-safe SHM networks

► Develop viable approach for substantiating POD and CI performance

► Develop turnkey solutions that provides actionable info

‒ Develop list of applications for which technologies are truly transition ready

Aircraft OEMs

‒ Provide clear guidance on viable architectures and CONOPS

‒ Develop application specific approach(es) for certification

‒ Support SAE and regulatory agency efforts to develop unified guidance

HUMS OEMs

‒ Develop robust SHM interface(s) that can support multiple technologies

Regulatory Agencies and Airworthiness Authorities

‒ Support SAE efforts to develop unified guidance

‒ Solicit SHM community input into airworthiness guidelines

21




CONCLUDING REMARKS

22

• HUMS lessons learned and infrastructure are a solid foundation for SHM

• Most likely transition opportunity is fleet issue requiring frequent inspections

during long design/dev/qual/retrofit deployment cycle

• SHM community must be positioned to respond quickly to next opportunity

• Once confidence is gained by OEM & airworthiness community, SHM will

be powerful tool for reducing operator burden while resolving fleet issues

• Close collaboration between tech developers and OEMs on specific

applications is required




CHANGING THE O&S PARADIGM

23

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