20130510024819A

The aircraft a power line and the ground during an aerial application flight. Weather had included low clouds, poor visibility, and periods of heavy rain and thunderstorms with a cold front moving through. The pilot and crew had been unable to work during that time. Frontal passage occurred shortly before the flight, with cloudy skies continuing but visibility improving. Weather at kowb, 330 degrees and 22 NM, at 2256Z (1756 CDT) was 230/04 vis 10, sct 015 bkn 100 21/18 29.86. The pilot loaded the chemicals to complete the current field. The crop he was treating was wheat, about 2-1/2 ft high. It was green. He circled around it 3 times looking for obstructions, houses and people and to develop a plan to spray the field. He completed two spray passes and during the third spray pass, he heard a ?pop? Sound and saw ??the lines? As they contacted the windscreen. The helicopter then yawed slowly to the right and pitched slightly nose-down at which point control was lost. The helicopter continued to rotate clockwise and veered to the right, then impacted the ground slightly nose-down with a slight left roll angle. The helicopter pivoted clockwise around the nose about 180 degrees. It then rocked back on its tail, breaking off the tail boom just behind the attach point. The stub of the tail boom impacted the ground, then the aircraft rolled left, coming to rest on its left side. The pilot reported there was no pre-impact mechanical failure or malfunction with the helicopter or its systems.

Damage to the aircraft included a severed tail boom, main rotor mast separation just below the static stops, displacement of the main transmission and breakage of the transmission mounts, crushing of the lower nose area, and breakage of windscreens, lower nose windows, and overhead windows. The main rotor group was adjacent to the main wreckage, about ten feet away. One main rotor blade was attached to the main rotor hub and was broken at the outboard tip, consistent with a ground strike. The other main rotor blade was broken with a section about four feet in length attached to the main rotor hub. The outboard portion, approximately twelve feet in length, was located about 1,000 feet to the northwest. There were ground scars consistent with the rotor striking the ground. Control continuity was established from the cyclic control to the swashplate, and from the anti-torque pedals to the point where the tailboom separated. The collective lever was broken and displaced about 90O to the left; therefore collective control continuity could not be established.

The lower fuselage separated laterally along a line connecting the aft edge of the lower nose windows. The instrument panel broke loose from the floor, displacing to the left. The right forward door post separated from the lower nose area, with the separation running from the aft outboard corner of the lower nose window to a point about four inches below the lower right corner of the windscreen. The left skid separated from the aft crosstube and broke into two pieces. The belly-mounted chemical tank separated from the aircraft and from the left spray boom. There was no spillage of chemical; neither was any fuel spilled. The pilot?s lap belt and shoulder harness restrained him during the crash sequence. He sustained a minor scrape to his left calf, for which he refused medical treatment. He wore a gentex flight helmet. He received two blows to the head, from which the helmet provided adequate protection. The helmet had two marks of significant abrasion, with some dark residual marks and scratches on the helmet. Remnants of three-strand copper wire were wrapped around the tail rotor shaft, and around the main rotor head. The wire was tarnished and green in color. Also, remnants of wire were embedded in the horizontal and vertical stabilizers, with several feet of wire trailing behind the vertical stabilizer.