Incident
A mid-air collision occurred over Lake Winnebago approximately five miles southeast of Appleton Airport. The accident happened during the descent phase of a Twin Otter, which had been on an uneventful flight from Sheboygan. At the same time, a North Central Airlines Convair CV-580, registered N90858, was en route from Green Bay to Oshkosh. Both aircraft were operating under visual flight rules (VFR) in uncontrolled airspace. The collision took place at an altitude of 2,500 feet in relatively good weather conditions.
Aircraft
The Convair CV-580, operated by North Central Airlines, was carrying two passengers and three crew members. The Twin Otter's occupant count was not specified, but the combined total of occupants on both aircraft was 13. Following the collision, both aircraft crashed into Lake Winnebago. Debris was found floating on the water, and both airplanes were totally destroyed.
Aftermath
All 13 occupants on board the two aircraft were killed. The accident resulted in the complete destruction of both the Twin Otter and the Convair CV-580. Search and recovery efforts located debris floating on the surface of Lake Winnebago.
Probable Cause
The official investigation determined the probable cause to be the failure of both flight crews to detect visually the other aircraft in sufficient time to initiate evasive action. The Board was unable to determine why each crew failed to see and avoid the other aircraft; however, the Board believes that the ability of both crews to detect the other aircraft in time to avoid a collision was reduced because of the atmospheric conditions and human visual limitations.