The aircraft descended and impacted terrain at 2018 Pacific time while in an airport traffic pattern. The private pilot and his passenger were killed, and the airplane was substantially damaged. Visual conditions prevailed. According to a witness, immediately after the accident airplane entered the downwind portion of the traffic pattern, the airplane entered a left turn. After the airplane completed about 180 degrees of turn, it appeared to be traveling more slowly than normal. The left wing then dipped and the airplane entered a descending spiral, impacting terrain.
