THE PILOT REPORTED THAT THE AIRCRAFT WAS ON A RECONNAISSANCE FLIGHT TO SURVEY A PROPOSED POWERLINE PROJECT. HE REPORTED THAT DURING THE FLIGHT, THE ENGINE FLAMED OUT AND AN AUTOROTATION WAS INITIATED. HE MANEUVERED THE HELICOPTER TO LAND IN A CLEARANCE, BUT STRUCK THE TOP OF A TREE ABOUT 35 FT AGL. THE HELICOPTER THEN TRAVELED 90 FT HORIZONTALLY AND IMPACTED ON SOFT, SLOPING MUSKEG. AN EXAMINATION OF THE AIRCRAFT AND ENGINE REVEALED NO PREIMPACT FAILURES. THE ENGINE PERFORMED NORMALLY DURING AN OPERATIONAL CHECK. ACCORDING TO THE PILOT AND PASSENGERS, THE HELICOPTER HAD BEEN FLOWN THROUGH AT LEAST ONE AREA OF WET SNOWSHOWERS. HOWEVER, THE INTENSITY OF THE SHOWERS WAS NOT DETERMINED. THE HELICOPTER WAS EQUIPPED WITH AUTO-IGNITION, AN ANTI-ICE SYSTEM, AND A MODIFICATION TO THE ENGINE INLET SCREEN AND INSPECTION DOOR TO REDUCE FOD AND SNOW INGESTION.