I have a question about analyzing the data from an engine trend check in an S76A. And I figured somebody kicking around here probably could enlighten me!
We do in-flight power checks instead of the ground power check option. So it means a 30min power check every 50hrs with daily trend checks preformed in between.
You keep an average of the trend checks called the "rolling average" (last 20 +/- 5 checks), and there are 3 criteria used to determine if you have acceptable power or not.
I'm fine with 2 out of the 3 criteria.
1.) The "rolling average" (average of last 20 checks) can never be negative... OK
2.) The daily trend margin can never be less than 4% below the rolling average... OK
3.) And finally the one I'm confused with: The rolling average can not have deteriorated by more than the power margin established in the last 30min power check
SO...
say the last 30 min power check had a margin of +4
To what do you compare today's rolling average with to get the answer for the 3rd criteria?
The RFM is vague at best with the description. And the FSI manual words it a bit better
Where I've found the most help is a Customer Service Notice that Sikorsky put out in 1988... which mentions a "base line" (the 5th trend after the 30min check)
Is that what you are supposed to compare the rolling average to?
If so why isn't it in the RFM?
Thanks!