225 cleared to fly in UK & Norway

[Concentric]

Originally Posted by SASless

Concentric,

Are you agreeing with my statement that the definitive cause has not been fully identified and all EVERYONE (including AH Engineers) is discussing are symptoms, responses, and assumptions resulting from that lack of certainty about what kicks off that sequence of events?

SASless,

Generally speaking, I am in agreement that the definitive cause (or ‘root cause’ as I would prefer to call it) has not yet been satisfactorily explained or reported. The regulators lifting the restrictions before the AIBN has reported seems to me like ‘putting the cart before the horse’. Hopefully since the ‘cart’ has already appeared, the ‘horse’ will not be too far behind. Mee3 claims inside knowledge that the report is coming soon. I can’t tell if that comes from the horse’s mouth though, given the apparent direction of travel.

What the other 2 posters described were both consequences and each was generally correct as such but neither is the absolute root cause. They were not quite adjacent ‘dominos’ in the failure sequence either but the speed with which the whole design came apart illustrates the vulnerability of the 1960’s era architecture of this MGB.

Those consequences illustrate the criticality of ensuring all possible failure modes of the planet gear/bearing are considered in its design and in particular fatigue tolerance, which leads into riff_raff’s excellent post above. One thing I would add to that is that the mechanical properties of the stock material can be considerably different to those of the finished heat treated component.