Accident Overview
On July 5, 2010, at 1745 central daylight time, a Robinson R-44 helicopter, registration N857PM, collided with a guy wire near Marion, Kentucky. The helicopter was operated by Forest Tech LLC under 14 CFR Part 137 as an aerial application flight. Visual meteorological conditions prevailed, and no flight plan was filed. The flight departed from a private strip at 1743. The helicopter came to rest in a field and was substantially damaged by post-crash fire.
Witness Account
A witness reported that the pilot was conducting an aerial spray operation in a corn field. The witness observed the helicopter take off and fly to the edge of the field to begin an aerial application run. The witness turned around and heard a loud “pop.” Turning back, he saw the helicopter collide with a power line guy wire and the ground before bursting into flames.
Pilot Information
The pilot, age 55, held a commercial pilot certificate for rotorcraft helicopter issued on March 6, 2009, and a second-class medical certificate issued on September 17, 2009, with the limitation requiring corrective lenses for distant and near vision. According to the pilot's logbook, he had logged 532.9 hours in type, 611.3 total flight hours, including 190.1 hours of aerial application, and 28 hours within the last 90 days.
Aircraft Information
The four-seat, skid-equipped helicopter, serial number 1034, was manufactured in 2001. It was powered by a Lycoming O-540, 250-horsepower engine. The last annual inspection was conducted on May 14, 2010, at a tachometer time of 1404.8 hours. The hour meter and tachometer were destroyed by the post-crash fire, preventing determination of current airframe hours.
Wreckage Examination
Examination of the crash site revealed that the helicopter impacted the top ground cable of a high voltage power line approximately 35 feet 6 inches above ground level. The top cable separated due to overload failure; the lower cable was contacted but did not break. The wreckage path extended about 75 feet on a heading of 275 degrees magnetic, with the main wreckage located about 100 feet beyond initial impact. The helicopter's longitudinal axis was oriented about 310 degrees magnetic. The cockpit, main cabin, and engine area were consumed by fire.
Both main rotor blades were damaged and exhibited cable scarring, separating from the mast outboard of the attachment points. The main rotor pitch change links were present, and the mast showed cable scarring. The tail boom and tail rotor assembly were not damaged. The tail rotor drive shaft separated at the forward attachment coupling, which was fire-damaged but not structurally damaged. Drive shaft continuity was established from the forward coupling to the tail rotor.
Engine Examination
The engine was fire-damaged but remained attached to the mounts. All external hoses, lines, and V-belts were fire-damaged, as were the magnetos. Partial disassembly revealed that the ignition harness and spark plugs were fire-damaged; the spark plugs had light gray combustion deposits. The engine could be rotated by hand, and compression and suction were obtained at all cylinders. Rocker arms and valves moved during crankshaft rotation, and valve train continuity was confirmed. The oil filter and screen were free of contaminants. The fuel and ignition systems could not be tested due to fire damage.
Postmortem Toxicology
An autopsy performed on July 6, 2010, determined the cause of death as multiple blunt force injuries. Toxicological testing detected no carbon monoxide, cyanide, or ethanol. Azacylonol was detected in urine but not in the heart. Diphenhydramine (0.032 ug/ml) was detected in blood but not in urine. Ibuprofen was detected in urine.