On August 7, 2020, about 1145 mountain daylight time, a Cessna T210M airplane, N2245S, was substantially damaged when it was involved in an accident near Hanna, Utah. The private pilot and one passenger sustained serious injuries, and four passengers sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. Flight track data showed the airplane as it departed from Roosevelt Municipal Airport (74V), Roosevelt, Utah, and climbed northwest over mountainous terrain to an altitude of 12,896 ft mean sea level (msl) during the first 20 minutes of the 25-minute flight. The flight track then showed that the airplane’s altitude decreased as the airplane approached a large canyon. The pilot reported that the airplane lost partial engine power during a turn over mountainous terrain. The pilot did not describe what actions, if any, he took to address the partial loss of engine power. The pilot stated that he decided to fly down the canyon as the propeller continued to windmill. He initiated a forced landing to an open field, where the airplane made a hard landing. The field was near the shoreline of a lake at an elevation was 8,100 ft msl, and the accident site was south and down the canyon about 7 1/2 miles. The figure below shows the accident flight track; shortly after the airplane reached the canyon, the flight track data ended. Figure. Accident flight track and accident location. An onboard video of the flight was recorded by the front-seat passenger. Shortly after the engine was started, the fuel selector handle was positioned from the right tank to the left tank. The fuel tank quantity indicator showed about 19 gallons for the left tank and about 12 gallons for the right tank. About 20 minutes into the flight, when the airplane was over the lake, the sound the engine rpm increased momentarily and then began to fluctuate at a lower rpm. The sound of the engine then slowly decreased through to the end of the video recording. The pilot prepared the airplane for a forced landing by extending the landing gear and announcing his intentions to the passengers. As the airplane approached the shoreline, the stall warning horn was heard intermittently before the airplane banked to the left and impacted terrain. A screenshot of the instrument panel at that time showed that the rpm gauge indicated about 1,600 rpm, the manifold pressure gauge was at 19 inches of mercury, and the fuel flow gauge needle was off the scale. The throttle, propeller, and mixture levers were all in the fully forward position. The pilot had his private pilot checkride endorsement on May 27, 2016, and he had about 250 hours of total flight experience. His last biannual flight review was on June 16, 2020. At the time of the accident, the pilot’s third-class medical was overdue by about 6 months. Review of the airplane’s maintenance records revealed that, on June 12, 2020, the engine had accumulated 947 hours of operation since its overhaul. The airplane had a completed a top overhaul about 30 flight hours of operation before the accident. Engine data that were downloaded from an onboard instrument revealed that the fuel flow decreased from 20 to about 16 gallons per hour. The fuel flow remained at 16 gallons per hour for about 1 minute before rising to about 18 gallons per hour before dropping again to about zero. A few seconds later, the engine rpm increases momentarily to just above 2,500 rpm and then slowly decreased to about 1,900 rpm. Calculations based on the data revealed that about 8 1/2 gallons of fuel was consumed during the flight. The accident site examination revealed that the airplane’s forward fuselage and cabin area were crushed upward and that the engine was partially separated from the firewall. Both wings were buckled near the tips. Postaccident examination of the engine and airframe revealed no evidence of preimpact malfunctions or anomalies. A sound spectrum analysis of the onboard video was performed but was unable to determine if the engine speed decrease was due to a lack of cylinder combustion or if the engine continued operating but at a reduced speed.