BFO85FA049

The helo was in level cruise flt at 1500 ft and 115 KTS when the no. 2 eng chip light illuminated, accompanied by lowering oil pressure. The plt reduced pwr and started a rt turn to return to base when half way thru the turn a loud bang occurred followed by complete power loss of both engines and eng cmpt fire. A successful autorotation ensued, and the fire was extinguished with the acft system after lndg. Later examination revealed that the no. 3 bearing had failed. Ultimately releasing the pwr turbine assy from the eng. The turbine disc welded to the tailpipe center body, failing the disc. Fragments struck the no. 1 engine which resulted in its uncommanded shut down. Both engines had a lengthy history of chip alarms. Lycoming had recently approved a 100 hr. Extension to the recommended hot section interval after a review of maint. Records. Three scavenge chip alarms occurred drg the 50 hrs prior to the failure.