What happened
While en route under instrument flight rules, an aircraft began to reverse its course without apparent reason. An air traffic controller noticed the deviation and contacted the pilot to inquire if he was experiencing difficulties. The pilot confirmed that he was flying through clouds and reported a failure of his artificial horizon. He admitted that he did not realize the aircraft had entered a turn.
The pilot subsequently reported failures of both the artificial horizon and the autopilot system, stating that he was attempting to fly using only the magnetic compass, turn-and-bank indicator, and airspeed indicator. The controller provided gyro-out procedures to assist him, but the pilot was unable to maintain a stable altitude or heading. Weather conditions throughout the area consisted of low ceilings and clouds extending above 18,000 feet.
The controller advised the pilot that the best weather in the vicinity was at Chattanooga, Tennessee, which had a ceiling of 1,300 feet scattered, 2,000 feet overcast, visibility of three miles with light rain and fog. Shortly after this advice, radio and radar contact were lost. Parts of the aircraft were later found in the Combhee River, with the right wing located approximately 1,000 feet from the water.
The investigation
Recovery teams retrieved the vacuum pump, engine, turn-and-bank indicator, and several other items from the river. Examination of these recovered components revealed no malfunction or failure that would explain the accident.