Accident Overview
On an undisclosed date, a Beech U-21A and a Piper PA-31-350 collided nearly head-on at 7,000 feet above mean sea level over Independence, Missouri. The collision occurred in daylight visual meteorological conditions with 20 miles visibility. The U-21 was in level cruise, while the PA-31 was climbing eastbound to an undisclosed altitude en route to Saint Louis. Both aircraft were equipped with operating mode-C transponders.
Air Traffic Control Interaction
The controller in contact with the U-21 did not observe the conflict, and traffic advisories were not provided. The PA-31 was operating under visual flight rules; the U-21 was operating under instrument flight rules. After the collision, both aircraft crashed in an uncontrolled descent. There was no indication that either aircraft took evasive action.
System Deficiencies
The conflict alert subprogram of the ARTS III tracking system was not programmed to alert controllers to the impending collision. The two controllers did not observe any target in the vicinity of the data block representing the U-21.
Fatalities
All six occupants in both aircraft were killed.