PT6's are probably the most reliable turbine out there with a MTBF allowing Commercial IFR SE flight, please don't hijack. Don't know the frequency, but compressor washes and borescopes are mandatory. BTW there was a Beech 99 in AK that lost a blade. tore the engine off the mounts. The chances of a Grumman product losing a wing without fire or other ancillary cause is quite slim