NTSB Factual Report

On July 28, 2001, at about 1500 central daylight time, an Air Tractor AT-301, N4361S, piloted by a commercial pilot, was substantially damaged when it impacted a ditch and nosed over during takeoff from a road near Edmore, North Dakota. The 14 CFR Part 137 Aerial application flight was operating in visual meteorological conditions and was not on a flight plan. The pilot received minor injuries. The local flight was originating at the time of the accident.

Post accident examination of the wreckage revealed that the right outboard wheel half, right tire, and right tire inner tube had separated from the airframe. No other anomalies were found that could be associated with a pre-impact condition.

Three of the right wheel through bolts were recovered from the accident scene. Two of the recovered bolts had stripped threads and the third was fractured in the threaded portion of the bolt. The left wheel was examined and was found intact. Seven of the through bolts that hold the left wheel halves together were found to have been over-torqued. The torque readings were from 125 to 175 inch-pounds on these bolts. The specified torque as printed on the wheel is 90 inch-pounds. The remaining two bolts were found to be stripped. One of the through bolts was found to be a coarse thread bolt. The bolts specified for attaching the wheel halves are AN4 fine thread bolts.

NTSB Probable Cause

The incorrect installation of the wheel assembly bolts by maintenance personnel resulting in the stripped bolt threads and ultimate failure of the wheel, and directional control not possible by the pilot. A factor was the ditch