What happened
On the day of the incident, the C-141 Starlifter, registration 67-0006, departed from McGuire AFB. Prior to departure, a maintenance technician performed a radar check; although the aircraft had a documented history of eight previous weather radar malfunctions, the system was cleared for flight after appearing functional during the inspection.
During the flight, the crew discovered that the weather radar was actually non-functional. Because no severe weather was initially predicted for their route to RAF Mildenhall, the crew proceeded with the mission. During the flight, a SIGMET regarding moderate to severe clear air turbulence between FL240 and FL400 was issued by British forecasters, but this information did not reach the cockpit.
As the aircraft progressed toward its destination, the crew received updated weather reports indicating thunderstorm activity and significant wind gusts. While attempting to contact RAF Mildenhall for further updates, they were unable to establish communication with the base, though another station reported thunderstorm tops reaching FL260.
During the descent phase, the aircraft entered cloud cover. At FL150, the crew requested vectors to avoid the weather; however, because the primary radar was not working, air traffic control struggled to provide effective avoidance instructions. The aircraft subsequently encountered the leading edge of an intense thunderstorm cell line. The aircraft was subjected to extreme forces, including an estimated 100 mph downward vertical airshaft. This resulted in the structural failure of the right wing, followed by the loss of the upper vertical stabilizer and all four engines.
Findings
The investigation noted that the maintenance inspection failed to identify ongoing radar issues, leading to a lack of weather-avoidance capability. The aircraft encountered extreme atmospheric turbulence within a thunderstorm environment.