HISTORY OF FLIGHTOn June 26, 2022, about 1945 mountain daylight time, a Piper PA-20-135, N1231C, was substantially damaged when it was involved in an accident near Challis, Idaho. The pilot and passenger were fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. On day of the accident flight, a witness observed the accident airplane land at the Lower Loon Creek airport (C53), Challis, Idaho. She spoke briefly with the pilot and passenger, who indicated that they were camping at the Johnson Creek Airport (3U2) but were going to spend the day at Lower Loon. Later that evening, she observed the accident airplane taxi, take off, and then fly into the box canyon. Shortly thereafter, she observed a dust cloud. A friend of the pilot reported that he and the accident pilot were camping at 3U2. Earlier in the day, they had flown to C53 and, due to the density altitude, they waited to depart C53 for the return flight to 3U2, until later that evening. He further added that, at the time of departure, the density altitude was indicating about 6,200 ft msl. He observed the accident airplane depart to the north, climb, and then turn back toward the runway about 1930. He last observed the accident airplane on a southbound heading. Shortly after departing from C53, he observed smoke, which he believed to be a small ground fire. After landing and refueling at McCall Municipal Airport (MYL), McCall, Idaho, he continued his flight to 3U2 where he expected to meet with the accident pilot and passenger. They had not arrived, and he reported N1231C as missing. AIRCRAFT INFORMATIONDue to a 2,040-ft increase in elevation between the departure airport (4,200 ft msl) and the accident site (6,240 ft msl), the airplane’s climb rate, assuming it was within the center of gravity envelope and the pilot was operating within the airplane owner’s handbook instructions, would have decreased from about 477 feet per minute (fpm) to about 360 fpm. METEOROLOGICAL INFORMATIONThe calculated density altitude for the accident time and location was about 8,980 ft msl and a pressure altitude of 5,974 ft msl. AIRPORT INFORMATIONDue to a 2,040-ft increase in elevation between the departure airport (4,200 ft msl) and the accident site (6,240 ft msl), the airplane’s climb rate, assuming it was within the center of gravity envelope and the pilot was operating within the airplane owner’s handbook instructions, would have decreased from about 477 feet per minute (fpm) to about 360 fpm. WRECKAGE AND IMPACT INFORMATIONFirst responders located the airplane wreckage by air, about 1 ½ miles north of C53. The airplane impacted steep, rising mountainous terrain at an elevation of about 6,240 ft msl on an approximate southerly heading. The main wreckage came to rest upright about 30 ft below the initial impact point and was mostly consumed by fire. All major structural components of the airplane were observed at the accident site. Figure 1: Overview of the accident site location. Postaccident examination of the recovered airframe and engine did not reveal evidence of any mechanical anomalies that would have precluded normal operation. Flight control continuity was established from the cockpit to all primary flight controls. Numerous separations were noted within the flight control system with signatures consistent with overload separation or due to the recovery process.