Repairable Aerospace Systems

[JeremyJohnson]

What is the best analysis method for looking at the reliability of an aircraft engine, which has unscheduled removals (some failures and some unnecessary removals, ie. no faults are found), and scheduled overhauls? Additionally what should be used as suspensions? Current operational engines or ones that have made it from one overhaul cycle to the next (assuming overhauls restore the system to "as good as new").

[David]

Hi Jeremy,

"Best" is a relative term. But for repairable systems there are a few options. First, you could use RGA (http://rga.reliasoft.com) to analyze the repairable systems data. Information regarding repairable systems can be found at http://www.weibull.com/RelGrowthWeb/Repairable_Systems.htm. A few articles which present methods to analyze repairable systems can be viewed at:

http://www.reliasoft.com/newsletter/v5i1/repairable.htm
http://www.weibull.com/hotwire/issue64/hottopics64.htm
http://www.weibull.com/hotwire/issue64/relbasics64.htm

Another option is to use recurrent event data analysis which can be found in Weibull++ 7 (http://weibull.reliasoft.com). Details on parametric recurrent event data analysis can be found at http://www.weibull.com/LifeDataWeb/parametric_recurrence_data_analysis.htm. Additional information on this can be found at http://www.weibull.com/hotwire/issue59/relbasics59.htm.

Finally, you could create a reliability block diagram (RBD) and conduct a system analysis. This is a much more detailed analysis than the previous methods mentioned and requires a great deal more information regarding the sytem and the parts that make-up the system. This type of analysis can be conducted using BlockSim (http://blocksim.reliasoft.com).

In general, there are multiple options available. It comes down to how much information (data) do you have and what specifically are you trying to determine.

I hope this helps.