Primary finding
Probable cause
The failure of the pilots of both airplanes to see and avoid each other. Contributing to the accident was the improper planning/decision of the pilot of the Cessna 210 to depart the traffic pattern on the downwind leg rather than on the upwind leg as recommended in the AIM, and the improper planning/decision of the pilot of the Beech 23 to enter a 2-mile downwind.