Weather Briefing and Flight Plan
At 1615, the pilot contacted a Flight Service Station (FSS) for a weather briefing and to file an instrument flight rules (IFR) flight plan. The briefer reported thunderstorm activity building in intensity, extending from Raton, New Mexico, to Garden City, Kansas, with scattered activity in the Oklahoma panhandle. The briefer added that the storms were moving east-southeast.
Departure and Communication
The pilot checked in with Albuquerque Center at 1750 during the departure climb to 21,000 feet. At 1755, Convective SIGMET 70C was issued for isolated severe thunderstorms located 10 miles north-northeast of Las Vegas, New Mexico. Per FAA Order 7110.65J, section 2-6-2, controllers are required to advise pilots of hazardous weather that may impact operations within 150 nautical miles of their sector. However, the center controller did not relay SIGMET 70C to the pilot.
Loss of Contact and Encounter
Radio contact with the aircraft was lost at 1823. The pilot reported that the airplane was in visual meteorological conditions (VMC) and approaching precipitation when it encountered hail. The hail broke out the pilot's windshield, resulting in depressurization of the aircraft.
Probable Cause
The probable cause, as stated in the official findings, is the pilot's inadvertent flight into hail, which shattered the pilot's windshield and resulted in his incapacitation due to hypoxia.