A utility wire that a helicopter clipped before crashing in Breathitt County last July was unmarked and not shown on a navigation chart, according to the National Transportation Safety Board.
The pilot and state trooper on board the helicopter were seriously hurt. The two were on a U.S. Drug Enforcement Administration mission to spot illegal marijuana patches.
The helicopter was equipped with blades to cut wires, one near the bottom of the fuselage and the other near the top.
However, the helicopter hit the wire at the level of the main rotor head, above the top cutter, as it flew about 500 feet above the valley floor, according to the NTSB report.
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The pilot tried an emergency descent, but had limited control. The McDonnell Douglas 369E hit the ground and burned.
The wire, which once served a coal mine, stretched between two ridges in the Evanston community.
The mine had been closed for some time. As a result, no one had reported the utility wire to the Federal Aviation Administration to be included on an aeronautical chart, according to the NTSB report. The NTSB reported its findings on the probable cause of the accident last week.