My two Bobs worth
Lets not get into that old chestnut of twin versus single. How about considering that PT6 turbines, like all engines, have an overhaul at TBO regardless of what hours that may be. Now have a think about how long they have been in service. The PT6 can be overhauled a number of times. It may well be that some of these failures might have occured in engines that have been reworked 3 or 4 times and that work may not have been done in the PWC factory approved work shop. I am not pointing anywhere in particular but there are overhauls and there are overhauls. What we may possibly be seeing is the result of overhauls not quite up to scratch on an engine that has in excess of 10,000 hours since new. Just a thought!!!!!!
Groggy