Originally Posted by
Blacksheep
As no airworthiness issues are identified in the civil environment, the problem seems to lie within the BBMF alone. If it were otherwise it would (or should be) a matter that needs to be shared with all operators of either Spitfire and Hurricane aircraft or Merlin engines, as well as other non-EASA "Permit to Fly" types that have Merlin engines installed. As the grounding affects different aircraft types and different marks of the Merlin engine, I suspect oil or fuel system contamination or something similar as a most likely scenario.
Stitching together the few facts on here and stirring in a little more speculation like everyone else is...
This thread sort of suggests that the RAF (BBMF) may have selected a supplier to manufacture new shafts/gears and may have installed the same standard in all their Merlins. If this was the case, civil owned Merlins may not have used the same supplier and, therefore, not be affected.