NYC07LA178 · Beech B60

The airplane was in visual conditions, on an instrument flight rules flight plan, at flight level 270 (FL270), and in contact with air traffic control (ATC). The pilot reported that he observed a 10-mile wide opening between a large thunderstorm cell, and a smaller cumulonimbus (CB) build-up that was developing just to the southwest of the large cell. As the airplane approached the gap between the two cells, the pilot noticed that the CB was developing faster than he had anticipated, with tops that had grown from about FL270, to about FL290. The airplane's onboard weather radar was depicting only light precipitation, while the large thunderstorm cell northwest of the airplane was depicting extreme precipitation. As the airplane entered the northeast side of the CB, it encountered light to moderate turbulence, which was followed by an extreme downdraft. The pilot initially lost control of the airplane, then recovered at an altitude of about 14,500 feet, and the airplane sustained substantial damage. A reconstruction of the "WARP NEXRAD" weather data displayed to the ATC controller during the time leading up to the airplane's loss of control, revealed that the airplane had entered an area of extreme (VIP 6) echoes. Review of ATC communications revealed that the pilot had been in contact with the ATC controller for about 5 minutes before the airplane's encounter with the adverse weather, and the controller did not provide any weather advisories to the pilot.

Verbatim NTSB analysis and probable cause from the NTSB dataset