19990401002899A

Papillion helicopters acft (1969 Bell 206B helicopter) was on a training flight when the engine failed on take-off, the acft crashed into trees while attempting to auto-rotate, one POB suffered fatal injuries and the other sustained serious injuries, the acft was destroyed, other circumstances are unknown. (.4)shortly after takeoff and transition to forward flight, the helicopter's engine stopped. During the ensuing autorotative landing glide, a main rotor blade struck a tree about 30 feet above ground level and the helicopter fell to the ground. This was the first flight of the day and the helicopter had been stored outside overnight in conditions of cold temperatures and light snowfall without engine air inlet covers installed. Prior to the flight the engine was difficult to start. There were five aborted starts before the engine was successfully started. During the first three start attempts, fuel was introduced, ignition occurred, the engine acceleration hung at 30 percent, and the starts were aborted. After the third start attempt a mechanic noted that the engine inlets were approximately half blocked by snow and cleared the snow from the inlets using a towel. He did not check the plenum chamber aft of the particle separator and forward of the engine inlet for snow. In the wreckage, the plenum chamber inspection window was found to be opaque. After the accident, another company mechanic who had dealt with the same starting difficulty on another helicopter of the same type parked under the same circumstances without inlet covers, reported finding several cups of snow. The engine manufacturer reported that tests of the engine had shown that ingestion of as little as 6 ounces of snow/slush could flame out the engine. The operator's procedure requiring that the last flight crew at the end of the day install the inlet covers on aircraft stored outside had not been followed. (-23)on April 1, 1999, at approximately 1136 local time, BHT-206B, N992UC departed the papillon Grand Canyon heliport in a southwest direction on a training flight with a new hire pilot, and company flight instructor on board. Shortly after take-off, and during the climb phase, the aircraft experienced an engine failure at which time an autorotation was initiated while co ntinuing on a southbound heading. During the autorotational descent, the aircraft rotor blade struck, and chopped off approximately 16 feet of the top of a ponderosa pine tree which was approxiamtely nine inches in diameter. Due to the sudden impact, the aircraft dropped vertically in a nose first altitude where it impacted the ground and was subsequently destroyed. The instructor pilot who was seated within the left seat sustained serious injuries, and the trainee seated within the right seat was fatally injuried.