What happened
On the evening of the accident, a Cessna 170B and a Cessna 210J collided in flight approximately 5 miles southeast of Tenino, Washington. The collision occurred at an altitude of 3,000 feet mean sea level.
The pilot of the Cessna 170B, who was the sole occupant, had recently descended from 7,500 feet and was leveling off at 3,000 feet on a magnetic heading of 322 degrees. The aircraft was equipped with a transponder operating on code 1200 and providing Mode C altitude information. During the impact, the engine was separated from the CessNA 170B, but the pilot maintained control of the aircraft and performed a forced landing in an open field. The pilot was not injured.
The pilot of the Cessna 210J, also the sole occupant, was not transmitting a transponder code. Radar data indicated a target on a collision course with the first aircraft. Prior to the impact, radar tracked both aircraft as their lateral separation steadily decreased from 3.5 nautical miles to approximately 3,300 feet in the final seconds before the collision.
The investigation
Investigators analyzed scratch marks and paint transfer signatures found on both aircraft to reconstruct the event. Based on an estimated speed of 150 knots for the overtaking Cessna 210J and a GPS-recorded speed of 113 knots for the Cessna 170B, the closure speed was calculated at 41 knots with a collision angle of 8 degrees. The investigation also determined convergence angles of 22 degrees for the Cessna 210J and 150 degrees for the Cessna 170B.
Findings
- The Cessna 210J pilot had an unobstructed forward field of vision.
- Given the convergence angle, the pilot of the Cessna 210J should have been able to detect the Cessna 170B through standard visual scanning procedures used in VFR operations.