NTSB Identification: FTW96FA288.
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Accident occurred Tuesday, July 02, 1996 in HUFFMAN, TX
Probable Cause Approval Date: 04/29/1997
Aircraft: Air Tractor AT-400, registration: N501JS
Injuries: 1 Fatal.
NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
After completing aerial application, the pilot entered a right base turn to final approach for landing at a private dirt airstrip. During the turn, a witness observed the 'the left wing' go down and 'also the nose.' The airplane crashed in a left wing low (descending) attitude. The pilot/mechanic had performed maintenance on the aircraft and had certified on March 1, 1995, that the 'aircraft has been inspected in accordance with an annual inspection and was determined to be in an airworthy condition.' Postaccident examination revealed that the empennage flight controls exhibited severe corrosion. The left elevator bellcrank assembly elevator horn was found separated from the control rod elevator torque tube. The left stabilizer strut lower attachment was separated where the tube of the strut was welded to the 'U' shaped attachment bracket. Examination of the 'U' bracket only revealed corroded remnants of the forward bracket and no evidence of the edge welds that joined the bracket pieces together. Fracture surfaces on the elevator horn were consistent with overstress separation. Manufacturing specifications required a 0.080 inch steel sheet for the elevator horn. Over the majority of the horn and near the control rod attachment fracture, the thickness was as low as 0.059 inches.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: corroded flight control components, due to the operator's inadequate maintenance and inspection of the airplane; the pilot's failure to follow procedures and directives, by flying the airplane without proper maintenance and annual inspection; and subsequent failure of a corroded flight control component. Full narrative available
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