Aircraft Availability

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Aircraft Availability

• EMIS 7370
• Amber Trahan

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Introduction

• Improving aircraft availability is integral to
  the customers ability to successfully complete
  missions while lowering costs.
• Downtime Contributors
• Failed components
• Scheduled maintenance
• Availability can be improved by
• Eliminating unnecessary maintenance tasks
• Improving maintenance task time
• Increase component reliability

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Approach

• Analyze failure records for two aircraft
  components.
• Determine if components are performing as
  expected.
• If not
• Determine leading cause of failures
• Decided on possible solution
• Calculate Cost-Benefit for proposed solution
• Calculate possible aircraft availability
  improvement

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Aircraft Availability
Inherent Availability (Ai) determined from
failure rates and corrective maintenance times
only.
Goal Decrease margin between Inherent
Availability and Operating Availability.
Operational Availability (Ao) determined from
time between maintenance actions, scheduled and
corrective maintenance times and all associated
logistics and administrative delays.
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Mean Time Between Failure

• Field MTBF

• Predicted MTBF

• Failure data collected from field
• failures
• Flight hours
• Corrective actions
• MTBF flight hours divided by number of failures

• Based on guidelines in MIL-HDBK-217
• Weighted average over multiple temperatures
• -40C (2)
• -20C (5)
• 25C (80)
• 40C (6)
• 55C (5)
• 71C (2)

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Cost-Benefit Analysis

• Tool used in business to make economic decisions.
• Compares the cost of accomplishing a project to
  the benefit gained once that project is complete.
  
• Can be used to help choose between multiple
  options for a project.

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Component A
Month Field MTBF Predicted MTBF
Jan '08 1829 1800
Feb '08 789 1800
March '08 4253 1800
April '08 2406 1800
May '08 2534 1800
June '08 1030 1800
July '08 1656 1800
Aug '08 1238 1800
Sept '08 2355 1800
Oct '08 2684 1800
Nov '08 1765 1800
Dec '08 4679 1800
Jan '09 2297 1800
Feb '09 1935 1800
March '09 1811 1800
April '09 4876 1800
May '09 1708 1800
June '09 1688 1800
July'09 1321 1800
Aug '09 2455 1800
Sept '09 1199 1800
Oct '09 2466 1800
Nov '09 1793 1800
Dec '09 2650 1800
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Component A
Mean 2226
Standard Deviation 1060
Minimum 789
Maximum 4876
Range 4087
H0 µ 1800 H1 µ lt 1800     -t0.05,23
-2.807
Since t gt -t0.05,23 the MTBF of Component A is
indicated to be at least 1,800 flight hours.
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Component B
Month Field MTBF Predicted MTBF
Jan '08 914 1250
Feb '08 564 1250
March '08 1418 1250
April '08 962 1250
May '08 845 1250
June '08 859 1250
July '08 993 1250
Aug '08 707 1250
Sept '08 942 1250
Oct '08 1342 1250
Nov '08 1059 1250
Dec '08 780 1250
Jan '09 656 1250
Feb '09 967 1250
March '09 905 1250
April '09 1625 1250
May '09 732 1250
June '09 1013 1250
July'09 1057 1250
Aug '09 818 1250
Sept '09 2397 1250
Oct '09 822 1250
Nov '09 769 1250
Dec '09 662 1250
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Component B
Mean 992
Standard Deviation 387.43
Minimum 564
Maximum 1625
Range 1061
H0 µ 1250 H1 µ lt 1250     t0.05,23 2.807
Since t lt -t0.05,23 the MTBF of Component B is
indicated to be less than 1,250 flight hours.
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Component B
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Proposed Solution

• Switch backlighting from bulbs to LEDs
• LEDs have a higher reliability
• Less failures less downtime

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Cost-Benefit Analysis
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Availability Savings
Task Frequency Applicable Failures/Flight Hours 0.000185 1/FH
Downtime Task Frequency MTTR 0.0000925 hr/FH
Downtime Savings Old Downtime New Downtime 0.000378 hr/FH
Availability Savings (Downtime Savings Utilization) Hours per Year 0.13
The availability savings after implanting the LED
solution is indicated to be 0.13. This is a
significant predicted increase in aircraft
availability.
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Summary

• Component A achieving predicted MTBF
• Component B not achieving predicted MTBF
• Determined most frequent cause of failure was
  lamp failures
• Proposed switching to LED backlighting
• Decrease lamp failures by 80
• Cost-Benefit Analysis showed return 6 years after
  implementation
• Aircraft availability savings estimated to be
  0.13

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Conclusion

• Analyzing failure data for a component on the
  aircraft and implementing a cost effective
  solution can bring the operating availability of
  an aircraft closer to the inherent availability.
• Availability savings allows the customer to
  discern which improvements to implement, saving
  them time and money.

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