WPR11FA350

The helicopter was contracted to overfly the rural cherry orchard in order to dry the cherries following rain showers. A witness reported that the helicopter was flying over the cherry orchard from south to north, and it had just completed a left turn when it collided with power lines that bordered the orchard. The helicopter impacted terrain, in a nose low attitude, about 45 feet south of the power lines. Power line wires were found wrapped 3 to 4 times around the main rotor mast and striation marks on the leading edge of the main rotor blades were indicative of a wire strike. Examination of the accident site revealed that four wires were strung between poles with the top three wires about 50 feet agl and the lower wire about 40 feet agl. Postaccident examination of the airframe and engine revealed no evidence of a preimpact mechanical malfunction or failure that would have precluded normal operation.

HISTORY OF FLIGHT On July 25, 2011, about 1438 Pacific daylight time, a Sikorsky S-55B Helicopter, N5663, sustained substantial damage after colliding with powerlines and impacting terrain near Chelan, Washington. The helicopter was registered to Golden Wings Aviation and operated under the provisions of Title 14 Code of Federal Regulations Part 91. The commercial pilot, who was the sole occupant of the helicopter sustained fatal injuries. Visual meteorological conditions prevailed and no flight plan was filed for the flight. The local flight originated from a staging area near the accident site about 10 minutes prior to the accident. A witness reported that the helicopter was flying over the cherry orchard from south to north, and just completed a left turn when it collided with the powerline. The witness reported the helicopter then descended out of view after the collision; however, seconds later, he observed a large cloud of black smoke near the area where the helicopter was maneuvering. The helicopter was contracted to overfly the rural cherry orchard in order to dry the cherries following a rain shower, and was engaged in cherry drying operations when the accident occurred. PERSONNEL INFORMATION The pilot, age 22, held a commercial pilot certificate with rotorcraft-helicopter and instrument ratings. Additionally, he held a flight instructor certificate, with a rotorcraft-helicopter rating. His most recent first-class airman medical certificate was issued May 5, 2011, with a restriction that he is required to wear corrective lenses. The pilot's logbook was not recovered for examination. The operator reported that the pilot’s total rotorcraft-helicopter flight time was 1,192 hours, with 50 hours in accident make and model. AIRCRAFT INFORMATION The accident helicopter, a Sikorsky S-55B, was manufactured in 1959 and powered by a Wright R-1300 radial engine rated at 800 HP. The helicopter was configured with a three blade main rotor system, and conventional tail rotor. The maximum gross takeoff weight for the restricted category helicopter was 7,200 pounds. The helicopter’s most recent inspection, an annual inspection, was completed June 1, 2011, at a total airframe time of 7,397 hours; the engine total time since overhaul at the inspection was 13 hours. METEOROLOGICAL INFORMATION At 1455, the reported weather conditions at Pangborn Memorial Airport, Wenatchee, WA, located about 35 miles south of the accident site, at an elevation of 1,229 feet, were winds from 300 degrees at 8 knots, clear skies, visibility 10 miles, temperature 23 degrees Celsius (C), dew point 14 degrees C, and altimeter setting 29.91 inches of mercury. WRECKAGE AND IMPACT INFORMATION Examination of the accident site revealed that the helicopter impacted terrain, in a nose low attitude, approximately 45 feet south of the powerlines. A postcrash fire ensued. The initial point of impact was a series of power delivery lines that ran northwest to southeast along the northernperimeter of the orchard. The wire span between the two nearest support poles was approximately 800 feet. Four wires were strung between the two poles, with each of the four wires consisting of a bundled complex of six individual wires. Three wires were situated coplanar to each other while the third was located vertically beneath. The height of the top three wires was approximately 50 feet, while the bottom wire was approximately 40 feet. The main wreckage was located in the confines of a burn area approximately 45 feet south of the powerlines. The cockpit, instrument panel, pedestal and cabin area sustained extensive impact and thermal related damage. The helicopter rotor system consisted, in part, of three blades; each blade was found attached to the helicopter rotor hub assembly. The powerline wires were wrapped 3-4 times around the main rotor swash plate and rotor mast. All dampeners were detached from the rotor blades; two of the pitch change (PC) links were completely detached from the main rotor hub, while the third PC link was bent. All fracture surfaces associated with the mast assembly appeared to be the result of overstress separation. Striation marks, indicative of a wire strike, were noted on the leading edge (full span) of blades A and C. Numerous strands of powerline wire were located in the general area of the main wreckage. The wires showed a tension-like failure mode. A postaccident examination of the airframe and engine revealed no evidence of a preimpact mechanical failure that would have precluded normal operations. MEDICAL AND PATHOLOGICAL INFORMATION The FAA's Civil Aerospace Medical Institute, Oklahoma City, Oklahoma, performed toxicological testing on the pilot. Fluid and tissue specimens tested negative for cyanide, ethanol, and tested drugs. SURVIVAL ASPECTS An autopsy was performed on the pilot on July 26, 2011, at Central Washington Hospital. The postmortem report attributed the pilot’s cause of death to asphyxia due to inhalation of products of combustion. ADDITIONAL INFORMATION A review of the pilot’s cellular telephone phone records revealed that his phone was active on the day of the accident; however, no outgoing text messages or telephone calls were documented between 1430 and the time of the accident.