Accident Overview
On February 7, 2013, at approximately 1600 central standard time, an Air Tractor AT-502 airplane, registration N198LA, collided with terrain during a landing near Forrest City, Arkansas. The commercial-rated pilot sustained injuries, and the airplane was substantially damaged. The aircraft was registered to and operated by South Delta Aviation, LLC, of West Helena, Arkansas, under 14 Code of Federal Regulations Part 91 as a maintenance test flight. Visual meteorological conditions prevailed, and no flight plan was filed.
Pilot Report
The pilot reported departing with 150 gallons of water to calibrate the spray system. After completing a spray pass, he initiated a climbing left turn, at which point the airplane began vibrating and shaking. The pilot managed to return the airplane to straight and level flight, but it continued to rock from left to right. He observed that the left aileron was moving up and down, full travel from stop to stop.
The pilot found that when he reduced speed to 90 mph, he lost aileron control, and the airplane began a slow left turn while rocking back and forth. He then performed a long circle and selected a hay field adjacent to the airport for an emergency off-field landing.
Post-Accident Inspection
According to the responding Federal Aviation Administration (FAA) inspector, the airplane was substantially damaged during the accident. Inspection revealed that two bolts in the aileron push-pull rod were missing. The bolts and associated hardware were not located among the wreckage. The inspector also noted that the airplane had undergone extensive maintenance approximately five months before the accident. A review of the airplane's maintenance manual indicated that the nuts installed in the airplane control system are self-locking nuts.