Air Tractor AT502 accident near Eagle Lake, Texas, May 11, 2019

The NTSB's narrative final · quoted from the NTSB record

The non-instrument-rated commercial pilot departed from the operator's airstrip and was planning to conduct a visual flight rules (VFR) aerial application flight in an airplane that was not equipped for instrument flight rules (IFR) flight. Shortly after departure in visual meteorological conditions, the pilot contacted the operator and reported that he observed fog that was "rolling in."  The pilot reported that he was flying above the fog layer.  The pilot stated that he was going divert to a local airport, instead of returning to the operator's airstrip, and terminate the flight. No further communication was received from the pilot. Data obtained from two onboard units that contained airplane track data showed that, during the last several minutes of the flight, the airplane entered two spiraling turns. The second spiraling turn included a rapid descent from the airplane's altitude in the direction of the accident site. The airplane wreckage was discovered in a grass field about 7.5 miles southwest from the diversion airport. Two witnesses who were near the accident site heard the accident airplane flying overhead and reported that they did not hear any sounds associated with an airplane problem before the sound of the airplane's impact. An examination of the airframe and engine revealed no mechanical anomalies. The investigation was unable to determine, with the available evidence, whether the pilot had received an official weather briefing or accessed weather information before the flight. Multiple weather sources indicated low ceilings and the presence of fog, which were conducive to low IFR conditions, before and at the time of the accident for the area near the accident site. The witnesses who heard the accident airplane reported a low level of fog about the time of the accident and an area of clear visibility between the ground and fog. Fog differs from clouds in that the base of fog is at the Earth's surface, while clouds are above the Earth's surface. Given the weather data, airplane track data, and witness statements, the airplane likely flew into an area of fog just before the accident for underdetermined reasons. The IMC present at the time was conducive to the development of spatial disorientation, and the airplane's flight track was consistent with the known effects of spatial disorientation.

The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.