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RPI DSES-6070 HV7 Project Derk Philippona Fall 2008. Introduction: Description of the Problem Radar component failure data collected over a three year period on 241 Navy F/A-18 aircraft, taken from Blischke reference, were analyzed to provide a basis for making warranty decisions.
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RPI DSES-6070 HV7 Project Derk Philippona Fall 2008
Introduction: Description of the ProblemRadar component failure data collected over a three year period on 241 Navy F/A-18 aircraft, taken from Blischke reference, were analyzedto provide a basis for making warranty decisions
Methodologies: Summary Description • Data best fit failure distribution function identified with MINITAB • Expressions and plots for failure functions obtained with MAPLE • Constructed Monte Carlo model of data with EXCEL • Verified no benefit for age replacement policy with EXCEL model • Studied benefit of cold standby redundancy with MAPLE and EXCEL
Results: Analysis / DiscussionExponential and Weibull distributions fit data well
Results: Analysis / DiscussionReliability functions defined • F := 1-exp(-t/(223.653)); 1 - exp(-0.004471212101 t) • R := 1-F; exp(-0.004471212101 t) • f := diff (F, t); 0.004471212101 exp(-0.004471212101 t) • z := f/R; 0.004471212101 • MTTF := int (R, t = 0 .. infinity); 223.6530000
Results: Analysis / DiscussionAge replacement policy does not reduce total cost(as expected with constant failure rate)
Results: Analysis / DiscussionCold standby redundancy doubles MTTF • Rs := exp(-0.004471212101 t) + 0.004247651496 exp(-0.004471212101 t) t • evalf(subs(t = 223, Rs)); 0.7184390857 • evalf(subs(t = 223, R)); 0.3689551089 • MTTFs := int(Rs, t = 0 .. infinity); 436.1233500
Conclusions: • Exponential distribution function fits failure data well • Failure rate is approximately constant; 4.47 failures / 1000 flight hours • MTTF is 223.65 flight hours • An age replacement policy does not reduce total cost, as expected with • a constant failure rate • Modifying the radar system to add a cold standby exciter and switch • could approximately double MTTF