1. Risk assessment in aerospace systems PHM Technology/Monash University
Jacek S. Stecki
PHM Technology/Monash University
Melbourne, Australia

2. 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.
[2 min]
This slide is intended to be a lead in to Session 2 - Introduction to theory of designing and selecting machinery systems 2

3. 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).
[2 min]
This slide is intended to be a lead in to Session 2 - Introduction to theory of designing and selecting machinery systems 3

4. Integrated Logistics Support
[2 min]
This slide is intended to be a lead in to Session 2 - Introduction to theory of designing and selecting machinery systems
Assuring continued operation and functioning of the systems 4

5. Performance-based Logistics
Performance-based Logistics (PBL) is an outcome-based, performance-oriented 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 first-choice strategy.
A PBL contract was awarded to Alstom for delivery of trains in France
Also called Performance-based-Contracts
[2 min]
Renting a motors – performance -based example 5

6. 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.
[2 min]
This slide is intended to be a lead in to Session 2 - Introduction to theory of designing and selecting machinery systems 6

7. Risk reduction – CBM/PHM
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.

8. PHM - Fusion of the technologies
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)

9. Goals of PHM 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

10. PHM Paradigm (Joint Strike Fighter F35)

11. Joint Strike Fighter F35 PHM Setup

12. Aerospace Tools to deal with risks 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

13. CBM/PHM - what are we dealing with?
Algorithms
Failure modes
Failure modes
Failure modes
Functional Analysis
Production Losses
Training
Training
Training
Training
FMECA
FMECA
FMECA
FMECA
FMECA
FMECA
Detection
Sensors
Prognostics
Standards
BIT
Risk Minimization
$$$$$$$!
Reliability
Reliability
Reliability
Diagnosis
Diagnosis
Diagnosis
Training
Training
Training
Simulation
Fault Tree
Condition monitoring
Sensor fusion
Sensor fusion
Sensor fusion
Maintenance
Downtime
Faults
Hazards
Safety
Testing
Fall-back Analysis
ROI
Education
Education
Artificial intelligence
Maintainability
Availability

14. 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

15. Risk reduction or is it? 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

16. 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

17. Risk Assessment FMECA Failure Modes FMECA Effects FMECA
Possible Failures
FMECA
Effects
What effect does
the failure have ?
FMECA
Criticality Analysis
Criticality Analysis of failure
FMECA

18. Modeling Failure

19. Modelling of failure

20. Fault propagation - dependability
All faults are enumerated.
Transient and steady-state responses to faults are identified

21. PHM Cycle
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.
PHM requires two main cycles of development, design and operation

22. Interaction between MAD and CBM/PHM Layers at Design Stage
MAD – Maintenance aware Design

23. 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?

24. MADe software

25. RR250 Engine Lubrication System

26. Jet Engine Lubrication System Model

27. Model of pump

28. Define Component Structure

29. Define Component Functions

30. Define Physical Failures

31. Propagate Functional Failures >> Dependency

32. Assess Criticality

33. Produce FMEA/FMECA Report

34. Assess hardware Reliability

35. Fault Tree

36. Define Sensors Locations

37. Select sensors and generate diagnostic rules

38. CAD concurrent with MADe

39. 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

40. 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

41. Thank You!