Incident Overview
During cruise flight at an altitude of 1,500 feet above ground level, the pilot attempted to lean the fuel mixture. Upon doing so, he discovered that the mixture control could not be moved back to the rich position; instead, the control would spring back to an idle position. With the aircraft committed to a reduced-power descent, the pilot executed an intentional emergency landing on the westbound lanes of Interstate 84.
Landing and Ground Roll
As the aircraft approached the highway, the pilot had to maneuver over an overpass and beneath power lines crossing the road. The touchdown was described as hard, and during the rollout, the aircraft departed the paved surface. It veered left across the median, at which point the wheels struck a six-inch lip at the edge of the pavement of the eastbound lanes. The impact caused the aircraft to nose over.
Postcrash Examination
Examination of the aircraft after the incident revealed that the wire-wound sheathing surrounding the mixture control push-pull cable had separated from the solid fitting end, which is held firmly at the back of the instrument panel. This disconnection allowed the mixture control cable and its surrounding sheath to flex, but prevented the cable from altering the position of the mixture control at the carburetor.