ORIGINAL: FLYBOY
The manual in my full scale twin says to let the engine cool for at least 3 minutes after landing before shutting it down to cool the turbos down. My mechanic says that I will replace the turbos more often letting them cool that way than I would if I just shut them off. I have yet to replace one doing it his way. He is good. He has spent his life dealing with these engines. Sometimes you have to go with the people that you know and trust and forget the manual.
That is interesting to hear. Id always been told it wasnt so much letting the engines 'cool' at idle for 3 minutes, but letting the turbo's slow down whilst oil is still being pumped to them. Shutting down with the turbos still spinning hard meant they then spin for a bit without oil being pumped to them which can or may cause damage. Thats why trucks and other vehicles with turbos have timers, so after turning of the ignition and getting out, the engine will still run for a few minutes. Admitably after an approach to land and then taxi to parking at your average airfield the engines will have been at or near idle for at least three minutes anyway. Im not disagreeing with your mechanic, just commenting on my experience flying turbo aircraft.