Nederland, CO, USA
N999DW
Bell 47G-3B-1
Prior to the flight in mountainous terrain, the pilot obtained a weather forecast that called for winds from the southwest at 30 mph, with gusts up to 40 mph. The flight departed and was in cruise flight at 9,000 feet (700 feet agl) with a 20-25 knot headwind and experiencing light turbulence, when the flight encountered "severe turbulence." The pilot stated that the helicopter went "up and down violently for a period of 2-3 seconds." The tailrotor drive shaft was severed by the main rotor blades, and the helicopter then experienced "a right yaw that full application of left pedal would not correct." The pilot stated that during the event the engine and rotor rpm increased past their upper limits. He was able to bring the engine and rotor rpm within limits and regained control of the helicopter. Subsequently, the pilot performed an autorotation to sloping terrain without further incident. According to a witness, who was fishing on a lake 4 miles from the accident site, he observed water spouts between 2 and 8 feet tall and high swirling winds near the time of the accident.
On June 8, 2002, at 1030 mountain daylight time, Bell 47G-3B-1 helicopter, N999DW, was substantially damaged when it encountered turbulence while in cruise flight near Nederland, Colorado. The helicopter was registered to and operated by the pilot. The private pilot, sole occupant of the helicopter, was not injured. Visual meteorological conditions prevailed, and a flight plan was not filed for the 14 Code of Federal Regulations Part 91 personal flight. The local flight originated from the pilot's private staging area in Nederland at 0900. According to the pilot, he obtained weather from a television station in Denver, Colorado. The weather forecast called for winds from the southwest at 30 mph, with gusts up to 40 mph. The flight departed, flew approximately 1.5 hours , and was in cruise flight at 9,000 feet (700 feet agl) with a 20-25 knot headwind experiencing light turbulence, when the flight encountered "severe turbulence." The pilot stated that the helicopter went "up and down violently for period of 2-3 seconds." The tailrotor driveshaft was severed by the main rotor, and the helicopter then experienced "a right yaw that full application of left pedal would not correct." The pilot stated that during the event the engine and rotor rpm increased past their upper limits. He was able to bring the engine and rotor rpm within limits and regained control of the helicopter. Subsequently, the pilot performed an autorotation to sloping terrain without further incident. The pilot examined the helicopter and reported that the tailrotor drive shaft was separated, the tailboom was damaged, and one main rotor blade was damaged. According to a witness, who was fishing on a lake 4 miles from the accident site, he observed water spouts between 2 and 8 feet tall and high swirling winds near the time of the accident. The witness further stated that "in 26 years of backpacking to high lakes I had never seen this happen."
the pilot's inadvertent in-flight encounter with severe turbulence, which resulted in main rotor-tailboom contact and the separation of the tailrotor drive shaft.
Source: NTSB Aviation Accident Database
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