49 Years ago today: On 29 June 1972 an Air Wisconsin Twin Otter collided with a North Central Airlines CV-580 near Appleton, WI, both aircraft crashed killing all 13 occupants.

Date:Thursday 29 June 1972
Time:10:37
Type:Silhouette image of generic DHC6 model; specific model in this crash may look slightly different
de Havilland Canada DHC-6 Twin Otter 100
Operator:Air Wisconsin
Registration:N4043B
MSN:13
First flight:1966
Total airframe hrs:15664
Engines:Pratt & Whitney Canada PT6A-20
Crew:Fatalities: 2 / Occupants: 2
Passengers:Fatalities: 6 / Occupants: 6
Total:Fatalities: 8 / Occupants: 8
Collision casualties:Fatalities: 5
Aircraft damage:Damaged beyond repair
Location:ca. 8 km S of Appleton, WI (   United States of America)
Phase:Approach (APR)
Nature:Domestic Scheduled Passenger
Departure airport:Sheboygan Memorial Airport, WI (SBM/KSBM), United States of America
Destination airport:Appleton-Outagamie County Airport, WI (ATW/KATW), United States of America
Flightnumber:671

Narrative:
North Central Flight 290, a Convair CV-580 departed Green Bay (GRB) at 10:30 for a flight to Oshkosh (OSH), Milwaukee (MKE) and Chicago. The aircraft climbed to 2,500 feet and proceeded on an approximate course to Oshkosh. At 10:35 the flight made its initial contact with Oshkosh tower stating, “…we’re about, seven northeast, two thousand five hundred, VFR.” The crew were cleared for a runway 27 landing at 10:36. At that same time, an Air Wisconsin Twin Otter turboprop plane was on its way from Sheboygan (SBM) to Appleton (ATW) at the same altitude. An in-flight collision occurred at 10:36:47 over Lake Winnebago, at an altitude of approximately 2,500 feet. Explosion and fire followed the and both aircraft fell into Lake Winnebago. The accident occurred in hazy sunlight below a scattered cloud layer.

Probable Cause:

PROBABLE CAUSE: “The failure of both flight crews to detect visually the other aircraft in sufficient time to initiate evasive action. the Board is 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.”