Mitsubishi MU-2B-36, Pittsfield, Mass., March 25, 2004–The NTSB determined the cause of the accident was “the pilot’s loss of aircraft control for undetermined reasons, which resulted in an inadvertent stall/spin and subsequent impact with the ground.”
The last transmission from the 6,500-hour ATP pilot was his acknowledgment of New York Center’s instruction to contact Boston Center. The Royal Air Freight MU-2, en route from Hagerstown, Md., to Bangor, Maine, continued level at 17,100 feet, at a groundspeed of 255 knots, for approximately two minutes. It then climbed 300 feet and descended abruptly, losing 10,700 feet in 46 seconds, at 255 knots. The airplane climbed from 6,700 feet to 7,600 feet, stayed there for four seconds and descended until the last radar contact 17 seconds later, at an altitude of 2,400 feet.
Several witnesses described the airplane as being in a “flat spin” with the engines running before impact. Several areas of light to moderate echoes in the vicinity had maximum echo tops from 14,000 to 25,000 feet, with tops near 17,000 feet over the accident site. The airplane flew through an area of lower echoes for approximately five minutes before the accident.
An airmet for icing conditions from the freezing level to 22,000 feet was current, and four pireps indicated light-to-moderate rime to mixed icing in the clouds from the freezing level to 16,000 feet. Crews of two other aircraft reported cloud tops from 16,000 to 17,000 feet.
Investigators found no pre-impact mechanical anomalies. The propeller de-ice, engine intake heat, windshield anti-ice and wing de-ice were all in the “off” position. Pseudoephedrine and diphenhydramine were detected in the body of the pilot, who was killed. The airplane was substantially damaged.