Beechcraft V35 N47WT

The pilot and two passengers were about 380 nautical miles (nm) into a planned 550nm, instrument flight rules (IFR) flight; the pilot was in communication with air traffic control. After flying at an altitude of about 7,000 ft mean sea level (msl) for a majority of the flight, the pilot requested to fly at 9,000 ft msl, as well as minor course deviations. The deviation requests were likely for weather avoidance although the pilot gave no explanation, and the controllers did not request the reason for the pilot’s requests. The controller assigned a heading to the north, informing the pilot that the turn north would be temporary and to expect a turn back to the original course; the pilot acknowledged the clearance and turned north. Weather data indicated that, as the airplane was climbing through 9,400 ft msl, it likely encountered light to moderate rain showers and updrafts. The controller then cleared the pilot to resume his previously assigned route; however, the pilot continued on his northerly heading and remained at 9,500 ft msl. The controller made several requests to the pilot to descend as he remained above 9,000 ft msl. The airplane then turned to the northeast, flying further into a significant area of developing convective weather with rain showers and updrafts. After another request by the controller, the pilot responded, “Uh descending to nine thousand for four seven whiskey.” There were no further communications from the pilot. A performance study based on ADS-B data indicated that, about 1 minute after the last transmission, while on a track of about 070° and at a groundspeed of 180 kts (calibrated airspeed 152 kts), the airplane entered a tightening right turn and began to descend. Initially, the descent rate did not exceed 3,000 ft per minute (fpm) but then rapidly increased to over 10,000 fpm while continuing in the right turn. Dispersal of the airplane wreckage was indicative of an inflight breakup. Examination of the airplane and engine revealed no evidence of a pre-accident anomaly that would have prevented normal operation. The area of moderate precipitation encountered by the flight was not displayed on the controller’s standard terminal automation replacement system (STARS) display. A postaccident review of the weather information available to the controller on the STARS display showed that the display was underreporting the weather intensity. Due to this underreporting, the weather intensity depiction on the controller’s display showed no available weather near the accident airplane at the time of the accident and limited the controller’s ability to accurately warn the pilot of hazardous weather along the route of flight. Further investigation indicated that the primary reason the storm was not displayed to the controller was that the developing storm was initially too small to survive the spatial smoothing processing of the facility’s radar system. Based on the airplane’s flight track data, it likely encountered strong updrafts while in growing areas of precipitation and instrument meteorological conditions, which ultimately resulted in the pilot’s spatial disorientation, loss of airplane control, and an in-flight breakup as aerodynamic forces on the airplane exceeded the structural integrity of the airframe. Contributing to the accident was the anomalous and intermittent display of weather intensity on the controller’s STARS display, which prevented his ability to accurately warn the pilot of hazardous weather.

Quoted verbatim from the NTSB record.