Accident Overview
On the day of the accident, a general aviation airplane was en route from Green Bay to Oshkosh, flying at an altitude of 2,500 feet in relatively good weather conditions. It collided with an Air Wisconsin De Havilland DHC-6 Twin Otter 200, registered N4043B. The Twin Otter was traveling from Sheboygan to Appleton with six passengers and two pilots on board, and was descending toward Appleton Airport.
Collision Details
Both airplanes were operating under Visual Flight Rules (VFR) in uncontrolled airspace at the time of the collision. Following the impact, both aircraft crashed into Lake Winnebago, approximately five miles southeast of Appleton Airport. Debris was found floating on the water. Both airplanes were totally destroyed, and all 13 occupants—comprising the occupants of both aircraft—were killed.
Investigation Findings
The official investigation determined the probable cause of the accident: the failure of both flight crews to visually detect the other aircraft in sufficient time to initiate evasive action. The investigation 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 atmospheric conditions and human visual limitations.