Incident Summary
A Citation aircraft, while on approach into Billings, suffered an upset and crashed. The aircraft was sequenced behind a Boeing 757, and both airplanes were cleared for visual approaches. Approximately 1.5 miles from the runway, the Citation was observed to roll rapidly to an inverted position and then descend almost vertically into the ground.
Sequence of Events
According to air traffic control transcripts and the airplane's cockpit voice recorder, the crew of the Citation had maintained visual awareness of the position of the Boeing 757 throughout the approach. At the time of the upset, the vertical separation between the two airplanes was between 600 and 1,000 feet, and the horizontal separation was decreasing below 2.6 miles. One of the Citation captain's last comments was, "almost ran over a seven fifty seven." Winds reported were 5 knots. All eight occupants aboard the Citation were killed.
Probable Cause
The official probable cause, as stated by the investigating authority, was the pilot-in-command's failure to follow established vortex avoidance procedures, as published in the airman's information manual, to provide his own wake turbulence separation.