"There are two configurations of planet gear within the current type design. In depth review of the design and service data showed that one configuration has higher operating stress levels that result in more frequent events of spalling, associated with rolling contact fatigue, while the other exhibits better reliability behaviour. By limiting the type design to the gear configuration with lower stress levels and better reliability and specifying a reduced life limit, combined with more effective oil debris monitoring procedures and other operational controls, an acceptable level of safety can be restored."
Redesigning an epicyclic is hardly a trivial exercise and there must have been a very good reason to do so. I don't know the engineering history of this does anyone know if it was in response to earlier failures or simply to increase time between inspections or allow higher loadings?
Also were all the previous MGB accidents (excluding the bevel gear systems) involving type A?