CEN16LA193

The commercial pilot was conducting an aerial application flight about 25 ft above ground level when the airplane suddenly made an uncommanded descent and impacted a wheat field. The airplane came to rest inverted and sustained damage to both wings, wing struts, fuselage, and tail surfaces. Although the pilot noted some discrepancies with the airplane after it was rebuilt, examination of the wreckage, including the horizontal jackscrew assembly, did not reveal any evidence of preimpact mechanical malfunctions or failures that would have precluded normal operation.

On May 24, 2016, about 1010 central daylight time, a Piper PA-18-150, N4234Z, was substantially damaged when it impacted terrain near Cozad, Nebraska. The pilot sustained minor injuries. The airplane was registered to the pilot and was operated by Gothenburg Flying Service, Inc., under the provisions of Title 14 Code of Federal Regulations Part 137 as an agricultural application flight. Visual meteorological conditions (VMC) prevailed and no flight plan had not been filed. The local flight departed Fiese Airstrip (2NE5), Gothenburg, Nebraska, about 1000. The pilot said he had just finished purging the spray booms of air and rinsate and was flying 25 feet above the ground when the airplane suddenly made an uncommand descent. The right wing struck the flat wheat field and the airplane skidded to a stop, coming to rest inverted about 120 feet from the initial point of impact. There was substantial damage to both wings, wing struts, fuselage, and tail surfaces. The airplane had recently been rebuilt. The pilot/owner noted multiple discrepancies with the airplane following delivery. One discrepancy was that the jackscrew and drive pulley assembly for the horizontal stabilizer were not replaced as he had requested. He noted that the jackscrew assembly was worn and there was excessive slack in the drive cable. Pitch trim had to be constantly adjusted as a result. The builder had told the pilot that the assembly had been "tightened up." The pilot stated that this was not possible as the screw was made of steel and the housing was made of aluminum. The FAA conducted examinations of the airplane following the accident and noted play in the jackscrew assembly, but determined the slack was insufficient to cause the screw to slip. No other mechanical issues were found with the airplane.