Air Tractor Inc AT 502 N301LA accident near Kilbourne, Louisiana

Probable cause

The failure of the operator to comply with the terminating action of the airworthiness directive, which resulted in the subsequent failure and separation of the vertical stabilizer due to fatigue.

NTSB analysis

**This report was modified on March 23, 2026. Please see the docket for this accident to view the original report.**

The commercial pilot was conducting his second spray load application of the day to a field located about 1/4 mile north of the accident site. A farmer stated that the pilot's last passes were to finish spraying a tight area of the field that had trees at the end. A witness near the accident site saw the airplane turn at low altitude and then rapidly descend until ground impact. The airplane was destroyed by impact forces and a postimpact fire.

Postaccident examination of the wreckage and ground scars revealed that the airplane impacted terrain in a steep, nose-down attitude. Examination of the engine revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operation.

The pilot had hypertension and left ventricular hypertrophy (LVH). However, it is unlikely that the pilot's underlying hypertension and LVH contributed to the accident.

In December of 2025, the vertical stabilizer of the airplane was located in a wooded area northeast of the location where the main wreckage came to rest. Metallurgical examination of the vertical stabilizer revealed fractured surfaces on both fitting lobes with extensive post-fracture smearing damage. Thumbnail shaped areas contained macro features consistent with fatigue cracking which emanated from the forward face of the attach plate.

A service letter and airworthiness directive required periodic examination of the vertical fin front spar fitting for cracks with the installation of the steel doubler as a “terminating action.” There was no evidence that the steel doubler had been installed. Maintenance records for the accident airplane were not made available, and investigators were unable to determine if the periodic examination for cracks was accomplished.

It is most likely that the vertical stabilizer separated during the aerial application flight due to the progressive fatigue cracking within the front spar fitting. This separation resulted in a loss of airplane control and subsequent impact with terrain.

Text from the NTSB. Open the NTSB docket for CEN16LA154 for the full record.