What happened
On July 15, 2008, a Hughes 269B helicopter, registration N469E, was conducting a power line patrol near Salesville, Arkansas, when it struck a high voltage transmission line and impacted the terrain. The flight was being performed under Part 91 regulations without a flight plan. The pilot and a passenger, a vegetation control manager, were both fatally injured.
The flight began near West Plains, Missouri, and proceeded to Willow Springs, Missouri, to pick up the passenger. The crew was following Sho-Me Power Electric Cooperative high voltage transmission lines to identify vegetation encroachment. At the time of the accident, the helicopter was following line SM-609. As this line descended from a ridge into a valley, it crossed perpendicularly underneath an Entergy 161 kilovolt (KV) transmission line (Ent-161).
While the SM-609 line was approximately 51 feet above the ground, the Ent-161 line was estimated to be 154 feet above the ground. During the patrol, one of the helicopter's main rotor blades struck the middle strand of the Ent-161 line, which subsequently broke. The helicopter then impacted the ground, and the wreckage was destroyed by the impact and a post-impact fire.
The investigation
Investigators examined the wreckage and found that the main cabin, transmission, and engine had been consumed by fire. The tail boom had separated from the fuselage, and the rotor mast had fractured and separated from the transmission.
Detailed examination of the three main rotor blades revealed that one blade exhibited a pattern of abrasion consistent with striking a wire. The engine investigation showed no evidence of pre-impact mechanical failure that would have prevented the engine from producing power.
Data recovered from a Garmin GPSMap 269 unit tracked the flight from the pilot's home to Willow Springs and then along the various transmission lines. The final track points showed the aircraft descending in altitude and changing heading just before the impact.
An autopsy of the pilot determined the cause of death was multiple blunt force injuries. Toxicological testing for carbon monoxide, cyanide, and ethanol was negative; however, naproxen was detected in the urine.