Systems Availability Modeling & Analysis

1. Systems Availability Modeling & Analysis Systems Availability Modeling & Analysis Rev 04.30.13

2. System Availability Modeling and Analysis Availability Metrics, Concepts and Relationships System Availability Models System Availability Model Development Summary

3. Availability Analysis provides a mathematical basis for evaluating system design and development decisions based on system level performance measures in order to influence the air vehicle design concurrently with support system design.

4. Availability Metrics, Concepts and Relationships

5. System Operational Parameters Operational Effectiveness • Readiness or Availability • Mission Success Ownership Cost • Logistic Support Cost • Operating Cost

6. System Performance Measures Availability: A measure of the degree to which an item is in an operable state at the start of a mission when the mission is called for at a random time. Expressed as inherent, achieved, or operational. Readiness: The probability that military forces, units, weapons systems, equipment and personnel will be capable of undertaking the mission and function for which they are designed or organized, at any random point in time. Sustainablity The capability of military forces, units, equipments and personnel to maintain a specified level of mission activities for specified times.

7. Availability (Operational Readiness) “The Probability that at any point in time the system is either operating satisfactorily or ready to be placed in operation on demand when used under stated conditions.”

8. Operational Readiness (OR) Definition Operational Readiness (OR) is defined by the Navy to be a condition status indicating an operational unit aircraft to be safely flyable and capable of performing one or more (but not necessarily all) of the primary missions of the unit to which assigned.

9. Availability Definition Easy to understand Difficult to compute Uptime and downtime are difficult to define Steady state value

10. Availability, Reliability, Maintainability 1 MTBF Operational State Failed State 1 MTTR

11. Inherent (Intrinsic) Availability Probability that a system or equipment shall operate satisfactorily at any given time when used under stated conditions, without consideration for any schedule or preventive maintenance, in an ideal support environment. Refers primarily to the built-in capability of the system or equipment – function of repair times and failure frequency No defect may or may not be included depending upon ground rules.

12. Operational Concept Support Concept Maintenance Concept The System View • Availability • Sortie Generation Rates • Basing Product • Reliability • Maintainability • Supportability • Testability • Organization • Requirements • Schedule Maintenance • Unscheduled Maintenance • Spares • Technical Publications • Training • Support Equipment

13. Availability Analysis Flow Diagram • Mission Reliability • MTBF • MTBM Reliability Analysis Availability Analysis Maintainability Analysis Cost EffectivenessAnalysis • MTTR • MDT (A) • MDT (L) Supportability Analysis Life Cycle CostAnalysis

14. Requirements ReliabilityMaintainabilitySupportability Effectivenessand Availability Design Life Cycle Cost Reliability, Maintainability & Supportability Systems Operation Performance

15. ConfigurationComplexityStress AccessConfigurationComplexityAvailability Reliability Design AccessConfigurationComplexity AccessConfigurationComplexity Maintainability Reliability & Maintainability Relationships

16. System Design Evaluation Categories System/Segment (Type A)Functional Baseline Operational Effectiveness Evaluation Operational Suitability Evaluation • Requirements • MOEs/MOSs • Critical Issues • Test Objectives • Thresholds • Deficiency andFailure Tracking “To what degree does this system satisfactorily support mission accomplishment when used by representative personnel in the expected or potential environment for operational employment of the system considering organization, doctrine, tactics, survivability, vulnerability, and threat?” “To what degree can this system satisfactorily be deployed considering availability, compatibility, transportability, interoperability, reliability, wartime usage rates, maintainability, safety, human factors, manpower supportability, documentation and training requirements?” Functional Effectiveness Evaluation ScheduleEvaluation “How and to what degree will this system satisfactorily contribute to the required mission(s) in the predicted operational environment?” (a combined, system-level assessment) CostEvaluation

17. RM&S Integration into System Engineering Process TechnicalDisciplines Pre-FSD FSD • Logistics Concept Planning and Development • Life Cycle Cost Goals • Supportability Specifications • Operations Analysis • Life Cycle Cost • Survivability/Vulnerability • Safety • Reliability/Parts Standardization • Maintainability • Human Factors • Maintenance Concept/Plan • Spares Provisioning • Support Equipment • Training equipment • Training • Technical Publications • Packaging, Handling, Storage & Transportation • Facilities • Manpower Requirements & Personnel • Logistics Support Resource Funding • Energy Management • Computer Resources • ILS Test & Evaluation • ILS Planning • ILS Management System SupportSystem Transition toProduction • Update ILS Plans • Quantification of Support Requirements • Integration of Support Studies and Analyses • Design Support Trade Off Studies • Evaluation of Support System Effectiveness TrainingSystem System Engineering, LSA, Integrated Logistics Support Operations • Identification & Resolution of Support Problems • Analyses for Operational/Support Concept ChangesEvaluation of System Mods Impacts on Support

18. TotalTime InactiveTime ActiveTime DownTime UpTime Corrective Maintenance Time MaintenanceTime Not OperatingTime Preventive Maintenance Time ModificationTime AlertTime DelayTime Supply DelayTime ReactionTime Time to RestoreFunctionsDuring Missions Administrative Delay Time MissionTime System Time Relationships

19. Aircraft Time Breakdown Availability Analysis Period of Interest Total Off Time Total System Operating Time Total Up Time Total Down Time Administrative/ Logistics Delay Time Active Maintenance Time Standby Time Operating Time P C TCM TPM

20. Aircraft Availability Relationship InitiateScenario Fly MissionProfile Yes Trouble Shoot @2-Digit WUC Level No Yes No Service andTurnaround Aircraft No ReadyAircraftAvailable? SubstituteAvailable? SpareAvailable? Repair OnAircraft? In-FlightGripe? Yes Defect? Repair andReturn to ReadyPool Yes No Yes Perform RepairMTL/EMT/MM No Replace Unitand Check Out Yes Remove Item No Repair Item Wait for Spare

21. Major Availability Analysis Process Elements Reliability Analysis Techniques (typical) • Failure Modes and Effects Analysis • Failure Modes and Effects Criticality Analysis • Reliability Block Diagrams • Failure Rate Estimation Maintainability Analysis Techniques (typical) • Maintenance Task Time Analysis • Engineering scale models

22. Major Availability Analysis Process Elements Supportability Elements (typical) • Logistics Support Analysis • Spares Provisioning Levels

23. Major Factor Influencing Availability System Reliability Design Characteristics • MTBF: a reliability function which assumes that operation occurs after early failure (infant mortality) and prior to war-out, i.e., a constant failure rate exists. • MTBMA: Mean Time Between Maintenance Actions - a reliability function which accounts for all causes of maintenance activity, whether a failure occurred or not.

24. Major Factor Influencing Availability System Maintainability Design Characteristics • Mean Time To Repair (MTTR): a maintenance function, includes corrective maintenance time (CMT) and preventive maintenance time (PMT) Support System Design Characteristics • Mean Logistics Down Time (MLDT): a maintenance related logistics function which involves spares provisioning and logistics delay time (LDT) administrative delay time (ADT)

25. Major Factor Influencing Availability System Maintainability Design Characteristics • MTTR: a maintenance function, includes corrective maintenance time (CMT) and preventive maintenance time (PMT) Support System Design Characteristics • Mean Logistics Down Time: a maintenance related logistics function which involves spares provisioning and logistics delay time (LDT) administrative delay time (ADT)

26. System availability Models

27. Types of Availability Inherent Availability (Ai): • designed in availability • does nor consider administrative and logistic downtime

28. R&M Trade-offs (typical) Maintainability (MTTR in hours) 120 100 80 60 40 20 A=0.984 A=0.995 Maximum A=0.999 2000 4000 6000 8000 10000 Reliability (MTBF in hours)

29. E1 l, m Inherent Availability Single Element with constant failure rate l and constant repair (restore) rate m - Instantaneous Inherent Availability- Steady State Inherent AvailabilityWhere

30. Inherent Availability Series Reliability Configuration with two Elements- Steady State Inherent Availability - Series Reliability Configuration with n Elements - Steady State Inherent Availability E1 E2 l, m l, m E1 E2 ... ... En l1, m1 l2, m2 ... ... ln, mn

31. E1 l, m E2 l, m Inherent Instantaneous Availability Two Element active parallel reliability configuration - Instantaneous Inherent Availability

32. Inherent Instantaneous Availability WhereSteady State Inherent Availability

33. E1 E2 En Inherent Steady State Availability Active Parallel Reliability Configuration with n Elements l1, m1 l2, m2 ... ... ln, mn

34. E1 E2 Inherent Steady State Availability Standby Configuration with Two Elements - Inherent Steady State Availability l, m l, m

35. Operational Availability Probability that a system or equipment shall operate satisfactorily at any given time (When used under stated conditions?) Measure of total capacity – function of repair times, failure frequency, preventive and scheduled maintenance, supply downtime, administrative down time, support equipment downtime, …

36. Aircraft Operational Availability (AO) Definition Aircraft operation availability AO is defined to be the probability that the aircraft is in an operable and committable state at a random point in time when used in a typical maintenance and supply environment. The downtime expected under wartime conditions (allowing for long term deferral of some maintenance) is determined from estimates of the rates of “essential: unscheduled maintenance actions (UMA’s) and “essential” removals.

37. Types of Availability Operational Availability (A0) • expected in-service availability • includes impact of logistics. • exactly which logistics elements are included must be defined in advance.

38. Types of Availability Estimates Point Estimate – single, average or “mean value” of availability characteristic Interval Estimate – confidence that availability is within a specified range of values (with a certain probability) Instantaneous Estimate – availability measure value at a particular point in time Special Cases of field system reliability/availability estimates: • Apparent Availability – availability of a system calculated considering detected failures only • Real Availability – availability of a system considering all system failures

39. System Availability Model Development

40. Model Development Overview • Analysis Objectives • Analysis Planning • Development Approach • Development Considerations • Inputs and Outputs • Data Requirements • Algorithm Development • Implementation Examples

41. Typical Availability Model Applications Overall Requirements assessment ECP Evaluation Trade Studies on R&M Wide Range of Sensitivity Analysis Manpower Requirements Derivation LRU Spares/Not Mission Capable due to Spares (NMCS) Evaluation Flying Hour Program Evaluation Sequential vs Parallel Maintenance Options Support System Evaluation ….

42. General Modeling Options Analytical Representations • Mathematical formulas and symbolic models • May use computers to process the formulas Computer Simulations • Imitation of the physical phenomena(movement, war, performance overtime) using computer generated activities and results • human decision making represented by pre-programmed and/or probabilistic decision rules Assemblage of Gaming People and Tools • Human-based “game playing” to achieve insights (e.g. war games) Field Experiments • Replications of a physical situation under controlled and limited scale environments to estimate total system level performance

43. When Simulation Models Make Sense(An Analyst’s Checklist) • When mathematical models do not exist, or analytical methods of solving them have not yet been developed • When analytical methods are available, but mathematical solution methods are too complex to use • When analytical solutions exist and are possible, but are beyond the mathematical capabilities of available personnel • When it is desired to observe a simulated history of the process over a period of time in addition to estimating relevant parameters • When it may be the only possibility because of difficulty in conducting experiments and observing phenomena in their actual environment • When time compression may be required for systems or processes over long time frames

44. When simulation models make sense • When mathematical models do not exist, or analytical methods of solving them have not yet been developed • When analytical methods are available, but mathematical solution methods are too complex to use • When analytical solutions exist and are possible, but are beyond the mathematical capabilities of available personnel • When it is desired to observed a simulated history of the process over a period of time in addition to estimating relevant parameters • When it may be the only possibility because of difficulty in conducting experiments and observing phenomena in their actual environment

45. Advantages of Simulation • Permits controlled experimentation with: • consideration of many factors • manipulation of many individual units • ability to consider alternative polices • little or no disturbance of the actual system • Effective training tool • Provides operational insight • May dispel operational myths • May increase effectiveness of management decision making • May be the only way to solve problem

46. Disadvantages of Simulation • Costly (very costly?) • Uses scarce and expensive resources • Requires fast, high capacity computers (use of PC’s?) • Takes a long time to develop • May hide critical assumptions • May require expensive field studies • Very much dependent on availability of data and is validity

47. Thoughts To Remember • The overall objective of availability modeling and analysis is to provide support to the system design, development, and deployment process in order to influence system design by considering all aspects of its reliability, maintainability, and support system characteristics • The objective remains unaffected by the choice of using one model solution technique (e.g. simulation) over the other. • The choice of one method over another will be influenced primarily by outside factors (e.g. cost, schedule, availability of data, personnel and facility capabilities).

48. Availability Analysis Objectives • Specification Requirements Evaluation • Requirement Integration - Conflicts? Attainable? • Verify and Demonstrate Compliance • Verify Demonstrate Adequacy of Logistics Support • Support System Design Influence • Evaluate Impacts of Changes to Operation and Maintenance Concepts • Analyze & Evaluate Operational Suitability • Support Functional Trade-off Analyses on Alternative Designs • System Design Assessment • Examine the Total Picture at the System Level • Address Impacts of All Variables at once • Evaluate Impacts of Flight/Scenario/Usage Rate Changes • Management Visibility • Provide Useful Predictions for All Levels of Management • Assist Management in Identification and Resolution of Reliability, Maintainability, and Supportability Issues

49. RMS Analysis Objectives by Program Phase • Concept Definition • Support Contractual Requirements Analysis • Examine Operations, Maintenance, and Support Concepts • Support Design Concept Trade-off Studies • Identify Cost, Schedule, Risk, and Support Drivers • Demonstration/Validation • Refine Concept Definitions • Support Requirements Allocation Process • Provide Capability to Influence Design • Estimate Fielded System performance Levels • Full-Scale Engineering Development • Support Detailed Trade-off Studies • Establish Support System Requirements Baseline • Assess/Validate Operations, Maintenance, Support Concepts • Production and Deployment • Asses Fielded System Performance Levels • Refine Support Concepts/Levels • Identify System Improvement Requirements

50. RMS Analysis Planning Considerations Evaluate A/R/S Analysis Reqs. • Where does data come from? • Experiment? • Field tests? • Previous experience? • Simulation? • Other resources? • What will data be used for? • How will data be collected and managed? • What tests/simulations need to be executed, and when? • How will results be dev. and rec? • How does everything fit together to meet the system test & eval. objectives? Develop Test / Analysis Plans • Critical Issues • Objectives • MOEs & MOSs • Success Criteria • Schedule • Test Design • Analysis Plan • Data Collection & Management Plan • Test Execution Plan • Documentation Plan • Test and Evaluation Master Plan