Final Report: MU-2 suffered in-flight breakup during storm

 - August 27, 2007, 12:18 PM

Mitsubishi MU-2B-35, Argyle, Fla., Sept. 1, 2006 – The NTSB determined the probable cause of the MU-2 accident to be the pilot’s inadvertent flight into thunderstorm activity that resulted in the loss of control, design limits of the airplane being exceeded and subsequent in-flight breakup. A factor was the failure of ATC to use available radar information to warn the pilot he was about to encounter moderate, heavy and extreme precipitation along his route.

The pilot’s initial weather briefing called for no adverse conditions, but a sigmet was broadcast two hours later for thunderstorms southwest of the route. The airplane flew through an intense to extreme weather radar echo containing a thunderstorm, and on descent the pilot was told to contact Tyndall Approach. A witness heard a “loud bang,” and saw the airplane in a nose-down spiral, with parts separating during the descent.

The left wing separated inboard of the left engine and nacelle. Both the front and rear spars failed from “catastrophic static up-bending overstress.”

Although the controllers denied that there was any weather displayed ahead of the airplane, recorded radar and display data indicated that moderate to extreme precipitation was depicted on and near the route of flight. During the flight, the pilot received no real-time information about the weather ahead. The Mitsubishi MU-2 was equipped with a weather radar system.

The pilot was killed in the accident. The airplane was registered to Intercontinental Jet of Tulsa, Okla., and operated by Berg Steel Pipe of Panama City, Fla.