Originally Posted by
SASless
How many hours did the two gearboxes have that failed?
How much of a margin would be appropriate to guarantee safety?
G-REDL's MGB had accumulated 4467 hrs since new and the planet gears had accumulated 3623 hrs since new. Together they had accumulated 2354 hrs since last overhaul.
LN-OJF's MGB had accumulated 1080 hrs before it was installed in that aircraft and 1340 hrs total since new at the time of the accident.
Setting a safety margin based on such a small sample of data and considering differences in maximum loading between L2 and H225 variants would be extremely difficult, in my opinion, not to mention differences in flight profiles. Maybe HUMS data could give a little insight into the latter variations.