GTSIO-520's
Fab engine if looked after, reckon TBO should be in throttle/RPM changes. assuming a 1 hour flight the engines were good for 8,000 changes. 1/ Take off. 2/cruise and descent 3/ approach 4/ landing. We had three 404's doing 800 hour/year each for 5 years, never even had to pull a cyinder that in 24,000 engine hours!