Originally Posted by
turboshafts
With respect to the LN-OPG accident, I have read the report again to understand a bit more further the strategy of the ongoing investigation. It is written explicitly in the report, that gearboxes are interchanged between helicopters in the fleet. The same is said for the engines. After overhaul they could be mounted on any aircraft of the type (per my understanding).
The ability to replace major components (like gear boxes and engines) is a desirable design feature for a variety of customers. Modularity does not, by itself, lead to gear boxes or engines failing. (I am not sure what point you are trying to make with that observation). Your reference to that accident led me to the very thorough report AIBN did for that accident: it was interesting from a lot of angles. (Thank you!) Your question on "what if" regarding TBO differences (higher or lower) probably can't be answered definitively without being able to account for the health of the fleet overall, and how frequently this family of main gear boxes have to be removed
before the TBO due to various removal criteria.