System Availability Modeling

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System Availability Modeling AnalysisCase
Studies

• Systems Availability Modeling Analysis

Rev 04.30.13
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System Availability Modeling and Analysis Case
Studies

• Aircraft A Availability Modeling and Analysis
  Case Study
• Aircraft B Availability Modeling and Analysis
  Case Study
• Blue Frame Aircraft Case Study

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Aircraft A Availability Modeling and Analysis
Case study
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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

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Aircraft B Availability Modeling and
AnalysisCase Study
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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

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Maintenance Events Drivers
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Availability/Readiness (A/R) Model Example
Analysis Results
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Availability/Readiness (A/R) Model Example
Analysis Results
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Availability/Readiness (A/R) Model Example
Analysis Results
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Availability/Readiness (A/R) Model Example
Analysis Results
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Availability/Readiness (A/R) Model Example
Analysis Results
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UnclassifiedAvailability/Readiness (A/R) Model
Example Analysis Results
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Availability/Readiness (A/R) Model Example
Analysis Results
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Availability/Readiness (A/R) Model Example
Analysis Results
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Availability/Readiness (A/R) Model Example
Analysis Results
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Blue Flame Aircraft Case Study
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Blue Flame Availability Analysis

1. Previous availability support system analysis
   applications (heritage)
2. Review of Blue Flame Requirements and
   system/subsystem characteristics
3. Determination of radar component of Blue Flame
   availability
4. Development of Blue Flame radar availability
   model
5. Calculation of Blue Flame radar baseline
   availability estimates

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Blue Flame Analysis Working Definitions
Operational Availability (Ao)- the degree to
which an item (the radar set) is in an operable
and committable state at the start of a mission
when the mission is called for at a random time.

• System Reliability Design Characteristics
• Mean-Time-Between-Failure (MTBF)-a reliability
  function which assumes that operation occurs
  after early failure (infant mortality) and prior
  to wear-out, I.e., a constant failure rate
  exists.
• Mean-Time-Between-Maintenance-Actions (MTBMA)-a
  reliability function which accounts for all
  causes of maintenance activity, whether a failure
  occurred or not.
• System Maintainability Design Characteristics
• Mean-Time-To-Repair (MTTR)-a maintenance
  function, can include 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) and
  administrative delay time (ADT)

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Blue Flame Operational Availability

• Inherent Availability (Ai)
• Ai
• Achieved Availability (Aa)
• Aa
• Operational Availability (Ao)

MTBF
MTBF MTTR(CMT)
MTBF
MTBF MTTR
MTBF
Ao
MTBF MTTR MLDT
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Blue Flame Fleet Requirements

• Fleet Requirements
• Operational Availability -- 95
• Sortie Rate --12/PAA/Mo
  (Peacetime)
• Mission Reliability --93 (High
  Mission)
• 
  --96 (Low Mission)
• Fleet Operational Data
• 3.5 flying hrs/high mission --50 of missions
• 1.5 flying hrs/low mission --50 of missions
• 500 aircraft -- one
  radar set per aircraft
• 10 bases -- 50
  aircraft per base
• 1.5 to 1 ratio of operating hours to flying hours
• Radar set has 80 duty cycle relative to aircraft
  operating hours
• Average of 30 flying hours per aircraft per month
• 20 year field use period for each radar system

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Blue Flame Radar Support Characteristics

• Maintenance/Logistics Concept
• Organizational --Remove/Replace LRUs on
  aircraft (10 sites)
• Intermediate -- Remove/Replace SRUs at
  shop (10 sites)
• Depot -- Repair SRUs
  (1CONUS site)
• Sparing Concept --Intermediate (LRU SRU)
• --Depot
  (SRU Piece Parts only)
• Built-in Test Capability
• --Fault
  isolation to faulty LRU _at_90
• --Fault
  isolation to faulty SRU _at_90
• --Fault
  detection _at_ 2
• Support Equipment
• -Organizational -- None
• -Intermediate -- Simple PSGE
• -Depot --ATE
• All LRUs and SRUs are repairable

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Blue Flame RM Requirements

• Aircraft MTBM
  4.0 hrs.
• Aircraft MMH/FH (unscheduled)
  3.0 hrs.
• Aircraft MMH/FH (scheduled)
  0.5 hrs.
• Radar MTBM
  20.0 hrs.
• Radar MMH/FH
  0.5 hrs.
• Radar Failure Rate Allocation
• Antenna/Receiver LRU 16,667
  failures/10x6 hrs
• Transmitter LRU
  20,000 failures/10x6 hrs
• Processor LRU
  10,000 failures/10x6 hrs
• Displays/Controls LRU 2,500
  failures/10x6 hrs
• Power Supply LRU 883
  failures/10x6 hrs
• Radar MTTRs Scheduled Maintenance
• Organizational level MTTR
  0.5 hrs
• Intermediate level MTTR
  2.5 hrs
• Depot level MTTR
  6.0 hrs
• XMTR Magnetron replacement Every 1000
  flying hrs,
• 1 person,4.0 hrs.

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Miscellaneous Blue Flame Characteristics

• Spares turnaround time (TAT)
• Intermediate level --75
  days
• Depot level --
  45 days
• Constant failure rate assumed
• Re-test OK(RTOK) rate
• Intermediate level -- 20
• Depot level --
  8
• Learning curve on maintenance -- 90
• One set PGSE per base
• Depot ATE availability --
  80
• Ave. administrative delay time -- 0.75
  hrs./repair
• Ave. logistics delay time --
  6.6 hrs./repair
• 90 probability of
  spare in 2.0 hrs.
  
• 10 probability of
  no spare in 48 hrs.

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Blue Flame Aircraft system Elements

• WBS Level 0 Blue Flame Aircraft
• WBS Level 1-Major Systems
• Airframe
• Flight Controls
• Navigation
• Propulsion
• Radar
• WBS Level 2-Subsystems (Radar)
• Antenna/Receiver
• Transmitter
• Processor
• Display/Controls
• Power Supply
  

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Blue Flame Tradeoff Analyses

• Design Tradeoffs
• Baseline -- single transmitter
• Alternate -- redundant transmitters (2)
  operating redundancy
• Support Tradeoffs
• Baseline -- 90 spares assurance
• Alternate -- 80 spares assurance

The big question before the house is Where do we
start?
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Blue Flame Aircraft Radar Availability Case
Study
Review the Blue Flame Case Study excel
spreadsheet and check/verify the availability
numbers corresponding to a single transmitter on
the next page and show the results of your
analysis.
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Radar Trade Result Summary

• Radar Availability at stated Spares Level
• Design Option 90 Spares 80 Spares
• Single Transmitter 65 55

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Blue Flame Aircraft Radar Availability Solution
The formula for operational availability, Ao,
is Therefore we need to obtain only the
values of the following terms to evaluate
Ao MTBMA MTTR(CMT) MTTR(PMT) MTTR(LDT) MTTR(
ADT)
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Blue Flame Aircraft Radar Availability Solution
90 Spares From the given data for a single
transmitter, we get Total Radar Maintenance
Action MTBMA 20 hours MTTR(CMT) 0.5 hours
(Organizational Level) MTTR(PMT) 4 hours (Radar
Transmitter Magnetron R/R time) MLDT(ADT) 0.75
hours MLDT(LDT) 0.92 0.148 6.6
hours Since the probability of spare in 2 hours
90 and the probability of spare in 48 hours
10 Plugging these numbers into the formula for
Ao gives us Therefore Ao 0.628 62.8
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Blue Flame Aircraft Radar Availability Solution
80 Spares All the data is the same as for 90
spares, except for MLDT(LDT) 0.82 0.248
11.2 hours Since the probability of spare in 2
hours 80 and the probability of spare in 48
hours 20 Table for comparison of
values 90 Spares 80 Spares Given Value
65 55 Calculated Value 62.8
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