Incident Overview
On a routine flight from Atlanta, Air South Flight 168 departed at 21:07. At 21:13, the crew reported reaching their assigned cruising altitude of 7,000 feet. The aircraft, a Beech, had been cruising for approximately eleven minutes when it gradually entered a nose-down attitude due to a change in longitudinal trim.
Pilot Response
Approximately six seconds after the trim change began, the pilots noticed the deviation and initiated recovery actions. However, the horizontal stabilizer continued to move to a full nose-down position. The pilots were required to apply excessive pulling force on the control column to attempt recovery from the resulting high-speed dive.
Aircraft Behavior
The necessary stick forces to control such an out-of-trim condition can exceed the physical capability of a single pilot, and in some cases, even two pilots. The Beech continued to descend until both wings failed at high speed, just before the airplane struck the ground in a near-vertical attitude.
Investigation Findings
The probable cause, as determined by the official investigation, was an unwanted change in longitudinal trim that resulted in a nose-down high-speed flight condition beyond the pilots' physical capability to overcome. The initiating element of the accident sequence could not be specifically determined. However, the design of the aircraft's flight control system was conducive to malfunctions that, if undetected by the crew, could lead to a loss of control.