Midair Collision Between Cessna 170B and Cessna 210J Near Tenino, Washington (N3510D)

Incident Overview and Location At 2038:10, a Cessna 170B and a Cessna 210J collided in flight approximately 5 miles southeast of Tenino, Washington. The impact occurred at 3,000 feet mean sea level, which was about 2,700 feet above ground level. ## Aircraft Status and Pilot Actions The Cessna 170B was operated by a private pilot who was the sole occupant. The aircraft was equipped with a transponder, squawking code 1200 and emitting Mode C altitude information. At the time of the collision, the Cessna 170B had just descended from 7,500 feet mean sea level and was leveling off at 3,000 feet on a magnetic heading of 322 degrees. The pilot of the Cessna 210J, also the sole occupant, was not emitting a transponder code, meaning no altitude or other identifying information was available for that aircraft. ## Radar Data and Collision Dynamics Radar data indicated that at 2036:11, the aircraft were approximately 3.5 nautical miles apart. The Cessna 210J was oriented on a heading of north, while the Cessna 170B was on a magnetic heading of 309 degrees. By 2036:34, their lateral separation had diminished by 0.75 miles, placing them 2.75 miles apart. At 2036:58, the lateral separation was reduced by another 0.5 miles to 2.25 miles, and at 2037:22, it was further reduced to 1.25 miles. At 2037:46, 24 seconds prior to the collision, radar data indicated the aircraft were separated by a lateral distance of approximately 3,300 feet. ## Post-Collision Analysis Based on scratch marks and paint transfer signatures observed on both aircraft, as well as an estimated speed of the overtaking Cessna 210J being 150 knots and the GPS readout speed of the Cessna 170B of 113 knots, calculations revealed a closure speed of 41 knots and a collision angle of 8 degrees. A calculated convergence angle of 22 degrees was determined for the Cessna 210J and 150 degrees for the Cessna 170B. It was concluded that based on the Cessna 210J's convergence angle and the pilot's unobstructed forward field of vision, the Cessna 210J pilot should have been able to detect the presence of the Cessna 170B using normal visual scanning procedures consistent with visual flight rule (VFR) operations.