Once one goes if they don’t know why it is prudent to check all.
Once one goes if they don’t know why it is prudent to check all.
I am sure that since the helicopter was in the Islands that maybe it was disassembled to get it there? Could that have been the issue?
Inspection interval was 300 hours? This one failed 114 hours after the last inspection? As I understand it, inspection intervals are set such that a latent defect had two chances to be detected before a failure occurs. In this case, it sounds like 50-hour inspections are called or. I don’t know how hard this area is to inspect, but if it’s an easy visual to see “is the bolt/nut really there?” maybe frequent inspections aren’t so bad.
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The inspection’s incudes a torque check.
Typical fasteners materials are a286 steel and Titanium alloys both of these tend to have good fatigue and stress corrosion cracking properties. We do kit have any data of failure mode in these items so an initial drive to increase inspection is a good idea until further details emerge.
As for one failure !? Who knows it may be similar to Alisha air failure where time of flight was nit the crack growth factor but number of airframe cycles. Who knows yet where this investigation finds
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Honestly, from looking at the NTSB pictures, it looks like ALL the nuts never let go of the bolts. The picture at the top of this article even shows that it was the top-left bolt itself had fractured.
If it’s corrosion or over-torqued bolts, then I don’t think that torque checking the bolts or a visual inspection would find this kind of problem. They should at least do metallurgy on that top-left bolt for what kind of corrosion is on it before concluding that it was simply “loose”.
I’m guessing that the “inspection” was pencil whipped.