Amateur-built LANCAIR IV accident near Kooskia, Idaho, August 11, 2019

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

The pilot departed on a visual flight rules cross-country flight. A review of radar data revealed that the airplane began to climb from its previously established cruise altitude of around 10,800 ft mean sea level (msl) to 13,500 ft msl. During the climb, the groundspeed decayed from about 215 knots to 79 knots and continued to decay as the airplane subsequently entered a rapid, left-turning descent that continued until ground contact. The airplane was largely consumed by a postcrash fire, but examination revealed no evidence of any mechanical malfunctions or anomalies that would have precluded normal operation. The pilot was not in communication with air traffic control during the flight. Around the time the airplane began to climb, it entered an area of light-to-heavy precipitation and likely reduced visbility. A model atmospheric sounding for the area of the accident site revealed a potential for icing above 14,000 ft msl and the likely presence of updrafts and downdrafts. Witnesses near the accident site reported heavy rain and lightning around the time of the accident. Whether or to what extent the pilot obtained preflight weather information could not be determined, and there was no record of the pilot receiving a weather briefing for the flight from an access-controlled source. Although the pilot was instrument rated and his logbook indicated that he had completed 28 instrument approaches within the 10 months before the accident, he did not record any actual or simulated instrument flight experience during that time, and his instrument proficiency could not be determined. The airplane’s loss of airspeed throughout the climb and its subsequent rapid descent without an associated increase in airspeed suggest that the airplane entered an aerodynamic stall/spin that continued until impact.

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.