Conference AERONET "Aviation Valley" , 13-14 2011
Risk assessment in aerospace systems
Jacek S. Stecki
PHM Technology/Monash University
Melbourne, Australia
Jacek S. Stecki
PHM Technology Pty Ltd
1
Conference AERONET "Aviation Valley" , 13-14 2011
Key issues – Risk drivers
Supportability:
–
Reduction of life-cycle cost
–
Safety – environmental, personnel
–
Reliability – hardware, functional
Reduced manning levels
Need to reduce the volume of scheduled maintenance
Secondary effects of failures
Inherent design problems
Need to reduce spare parts inventory
High performance requirements
Availability of specialised personnel
Insurance and classification
Criticality of the equipment to productivity/availability
Cost of lost production or lost availability as a result of equipment failure
Cost of fixing a problem in terms of repair and bringing the machine back to a serviceable
condition
Etc.
Jacek S. Stecki
PHM Technology Pty Ltd
2
Conference AERONET "Aviation Valley" , 13-14 2011
Integrated Logistics Support
Integrated logistics support (ILS) is an integrated approach to the management of
logistic disciplines in the military
The pupose of ILS is to ensure that the supportability of the system is
considered during its design and development in order:
To create systems that last longer and require less support
To reduce costs
To increase return on investments
To assure supportability throught the operational life of the system
The impact of ILS is measured in metrics:
Reliability - Availability - Maintainability (RAM)
Reliability - Availability - Maintainability - Testability (RAMT)
Reliability - Availability - Maintainability - System safety (RAMS).
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
Integrated Logistics
Support
Reliability, Maintainability
and Maintenance) Planning
Supply (Spare part) Support
acquire resources
Training and Training
Support
Manpower and Personnel
Technical Data / Publications
Integrated
Logistics
Design Interface
Facilities
Packaging, Handling,
Storage, and Transportation
Support and T est
Equipment/Equipment
Computer Resources
Support
UK Defence Standard (DEFSTAN) 00-600
Supportability of the System
Assuring continued operation and functioning of the systems
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
Performance-based Logistics
Performance-based Logistics (PBL) is an outcome-based, performanceoriented product support strategy
A product support provider (PSP) or product support integrator (PSI) is contracted
to meet performance metric (s) for a system or product
The purpose of PBL:
increased system availability, reliability
shorter maintenance cycles, and/or
reduced costs
Thus PBL fits well with ILS
---------------------------------–
–
In U.S. Department of Defense (DoD) acquisition programs, the PBL approach is mandated as a firstchoice strategy.
A PBL contract was awarded to Alstom for delivery of trains in France
Also called Performance-based-Contracts
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
Reliability - Availability – Maintainability (RAM)
The ability of an item to perform a required function under given conditions for
a given time interval
It is generally assumed that the item is in a state to perform this required
function at the beginning of the time interval
Generally, reliability performance is quantified using appropriate measures. In
some applications these measures include an expression of reliability
performance as a probability, which is also called reliability.
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
Risk reduction – CBM/PHM
Sensors
Diagnostic
FDI
Prognostics
Risk
Design
Failures
Identification
Criticality
Assessment
What is it?
Risk assessment using techniques like FMECA, HAZOP, RCM etc.
Diagnostics – is the process of determining the state of a component to perform
its function(s)
Prognostics – is predictive diagnostics which includes determining the remaining life or
time span of proper operation of a component
Health Management – is the capability to make appropriate decisions about maintenance
actions based on diagnostics/prognostics information, available resources and
operational demand.
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
PHM - Fusion of the technologies
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

Sensors
Artificial intelligence Neural nets,
fuzzy logic, genetic algorithms
Algorithms (vibration etc.)
Communication capabilities
Interchange of maintenance data
Integration of data
Security of data
User friendly interface
Autonomy to be provided by
software agents (Jack platform
from AOS)
Jacek S. Stecki
Prognosis
Layer
Prognostics and
Health
Management
PHM
Maintenance
aware Design
PHM Technology Pty Ltd
Sensors
Layer
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Conference AERONET "Aviation Valley" , 13-14 2011
Goals of PHM

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

Enhance Mission Reliability and Equipment Safety
Reduce Maintenance Manpower, Spares, and Repair Costs
Eliminate Scheduled Inspections
Maximize Lead Time For Maintenance and Parts
Procurement
Automatically Isolate Faults
Provide Real Time Notification of an Upcoming Maintenance Event at all
Levels of the Logistics Chain
Catch Potentially Catastrophic Failures Before They Occur
Detect Incipient Faults and Monitor Until Just Prior to Failure
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
PHM Paradigm (Joint Strike Fighter F35)
Reliableand
Robust
PHMParadigm
Open
Architecture
Prognostic
capability
Sensor
based
Model-based
Prognostics
Virtual Sensing
Proactive
Maintenance
awareDesign
Model-based
Prognostics
DataFusion
Co-current with
Design
Autonomous
Intelligent
Sensors
Optimization
LifeCycle
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
Joint Strike Fighter F35 PHM Setup
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
Aerospace
Risks
Severe operating environment
Stringent statutory safety standards
Safety critical systems
Expensive Maintenance
Long innovation lead time
High technology
Conservative attitudes
High reliability requirements
Single shot operations
Very high cost of failure
Tools to deal with risks
Computer based design methods
Reliability and Hazard Analysis
Failure analysis (FMECA/FTA)
PHM (Prognostics and Health
Management)
Condition Monitoring - CBM
Testing
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
CBM/PHM - what are we dealing with?
Failure modes
Training
Detection
BIT
Training
Fault Tree
Jacek S. Stecki
Simulation
Condition monitoring
Fall-back Analysis
ROI
Standards
Sensor fusion
Testing
Education
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
Reasons for failure of Risk Assessment
Dependencies of failures not identified – spreadsheet vs model based
Inadequate Identification of Risks - functional failures (failure modes) vs physical
failures
Incomplete database of failures (deficient FMECA)
Taxonomy – confusion what is the cause, mechanism of failure, fault, symptom
and/or failure mode
Sensor fusion not based on failures dependencies (fall-back – testability)
Diagnostic rules not based on dependencies
Reliability of Hardware not the same as Functional Reliability
Different models for Criticality and Reliability Assessment
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
Risk reduction or is it?
Sensors
Diagnostic
FDI
Prognostics
Risk
Design
Failures
Identification
Criticality
Assessment
Risk is still there if failures are missed
We cannot design a diagnostic system without knowledge of failures
We do not really know what we should monitor
Sensors cover only identified failures
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
Barriers
The Advanced Technology Program (ATP), of the National Institute of Standards and
Technology (NIST), held a workshop on Condition-Based Maintenance (CBM) as part of it's
November 17-18, 1998 Fall Meeting in Atlanta.
Discussions with companies identified 3 technical barriers to CBM's widespread
implementation:
The inability to accurately and reliably predict the remaining useful life of a machine (
prognostics)
The inability to continually monitor a machine (sensing)
The inability of maintenance systems to learn and identify impending failures and
recommend what action should be taken (reasoning).
These barriers could potentially be addressed through innovations in three technical areas:
Prognostication capabilities
Cost effective sensor and monitoring systems
Reasoning or expert systems
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
Risk Assessment FMECA
Failure Modes
Possible Failures
FMECA
Effects
What effect does
the failure have ?
FMECA
Criticality Analysis
Criticality Analysis
FMECA
of failure
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
Modeling Failure
Highrange
ponent
Com
FunctionDefinition
Control
eters
param
e.g.
pressure
Noise
e.g.. friction
Measured
variable
e.g.. force
applyforce
,
Effect 1downstream
agedsupport
e.g.. dam
Upper
it
lim
acceptable
operatingrange
FailureModes
andEffects
it
Lower lim
Effect 2downstream
e.g. failedtolift
Lowrange
Physical
ponent
Com
e.g. actuator
ponent
Com
Representation
e.g. drawing
Energy
ponent
Com
odel
m
Energy
FailureModes
andEffects
ear
W
Friction
FailureModes
andEffects
odel
FMEAm
Load
Velocity
etc.
ponent
Com
odel
m
odel
Tribological m
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
Modelling of failure
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
Fault propagation - dependability
All faults are enumerated.
Transient and steady-state responses to faults are identified
Fault
Fault
Fault
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
PHM Cycle
PHM requires two main cycles of development, design and operation
The Design Cycle is required in
order to generate the knowledge
base from which the PHM
system can obtain its decisions.
The Operation Cycle describes
the steps taken within the PHM
system from detection of faults
through to conveying instructions
or actions.
Jacek S. Stecki
PHM Technology Pty Ltd
21
Conference AERONET "Aviation Valley" , 13-14 2011
Interaction between MAD and CBM/PHM Layers at Design Stage
System
specification
Contraints
Functional
diagram
FAST
Techniques
PHM
Layer
Diagnostics
Optimization
PHM Layer
Prognostics
Life cycle
Sensors
System Concept
Sensor set
FMECA/HAZOP
Techniques
Risk
Layer
MAD
Layer
Faults
Functions
Implementation
MAD – Maintenance aware Design
Manufacturing
Design process
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
Criteria for RCM Processes
SAE JA1011 “Evaluation Criteria for RCM Processes” defines seven questions
for RCM:
What are the functions…of the asset…(functions)?
In what ways can it fail…(functional failures)?
What causes each functional failure (failure modes)?
What happens when each failure occurs (failure effects)?
In what way does each failure matter (failure consequences)?
What should be done…(proactive tasks and intervals)?
What should be done if a suitable proactive task cannot be found?
Jacek S. Stecki
PHM Technology Pty Ltd
23
Conference AERONET "Aviation Valley" , 13-14 2011
MADe software
Testability
BIT design &
evaluation
Coverage of
ambiguity
Auto design of
diagnostic rules
Failure coverage
assessment
Auto Sensor selection
Use defined
sensors
Sensor selection/coverage
Failures criticality
Failure data
base
Auto report
generation
Auto functional
analysis
Failures
dependability
Auto qualitative
simulation
Functional failure
diagrams
Systems
FMEA/FMECA
Database
Failure diagrams
Component
Failure diagrams
Parts
Causes
Failure
Mechanisms
Faults
Failure taxonomy
Jacek S. Stecki
Failure modes
Failure database
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
RR250 Engine Lubrication System
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
Jet Engine Lubrication System Model
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
Model of pump
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
Define Component Structure
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
Define Component Functions
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
Define Physical Failures
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
Propagate Functional Failures >> Dependency
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
Assess Criticality
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
Produce FMEA/FMECA Report
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
Assess hardware Reliability
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
Fault Tree
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
Define Sensors Locations
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
Select sensors and generate diagnostic rules
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
CAD concurrent with MADe
Jacek S. Stecki
PHM Technology Pty Ltd
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Conference AERONET "Aviation Valley" , 13-14 2011
PHM Design Cycle Deliverables
At the end of the risk assessment process, the user has knowledge of:
How the system can fail (failure modes)
How critical each failure is
What are the causes of functional failures
What are the interactions between functional failures
What physical failures are linked to functional failure
Where to place sensors – i.e sensor fusing
How to monitor physical failures
How to diagnose functional failure
What is the expected reliability of the sensing system
What is the expected functional and hardware reliability of the system
Jacek S. Stecki
PHM Technology Pty Ltd
39
Conference AERONET "Aviation Valley" , 13-14 2011
Concluding Remarks
Despite expectations the acceptance and effectiveness CBM is in question. To be
effective:
CBM/PHM programs must be designed and executed with the knowledge of the
risks to which a system is exposed, i.e. the knowledge how the system fails
Model-based failure analysis, defining failures dependencies and improving
completeness of risk identifications, should be adopted in preference to spreadsheet
and “spreadsheet” like FMECA methodology
Model-based failure analysis should be adopted to enhance knowledge retention,
knowledge transfer and to facilitate integration of risk assessment through supply
chains
Taxonomies of functions, failure concepts, components should be adopted to
improve readability/portability of risk assessment results
Diagnostic rules and Sensors sets should be selected on the basis of dependencies
between failure modes (symptoms >>> syndrome)
Clear hierarchy of failure concepts (cause> failure mechanism> fault> failure mode)
should be enforced in risk assessment process
Physical failures (cause/failure mechanism/fault) and their symptoms should form
basis for BIT design
Jacek S. Stecki
PHM Technology Pty Ltd
40
Conference AERONET "Aviation Valley" , 13-14 2011
Thank You!
Jacek S. Stecki
PHM Technology Pty Ltd
41