http://http://www.aaib.gov.uk/public...ma__g_redw.cfm
Page 6 onwards....
and perhaps when they say this in July you'd think you would have an answer by now:-
The investigation will continue to review the results from the fatigue tests, with other data and evidence, to establish the mechanism that caused the initiation and propagation of the fatigue cracks in the bevel gear vertical shaft. It will also review the manufacturing process, dimensional inspections and quality system.