On January 23, 2021, about 1455 eastern standard time, a Cessna U206G, Canadian registration C-GWAS, was substantially damaged when it was involved in an accident in Denton, North Carolina. The pilot and copilot were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 aerial observation flight. According to the pilot, she and the copilot had been flying mapping flights for the United States Geological Survey. The pilot stated they would fly about 250 ft above ground level in a grid pattern while mapping. She further stated that they had enough fuel on board for an approximate 6-hour flight. They departed Montgomery County Airport (43A), Star, North Carolina, about 1300 and planned on returning to the same airport. About 2 hours into the flight, the engine “rolled back” and started to lose power. The airplane immediately began to lose altitude and the pilot maneuvered the airplane for a forced landing. During landing, the airplane bounced, and the nose landing gear fractured and bent under the fuselage. The airplane slid into trees and both pilots egressed through the door. Postaccident examination of the airplane by a Federal Aviation Administration (FAA) inspector revealed that the firewall was creased, and the aft right engine mount structure was cracked. Further examination of the airplane revealed that the airplane was modified in accordance with a Supplemental Type Certificate (STC), which permitted the installation of additional fuel tanks in the wings outboard of the main fuel tanks. The additional tanks were connected directly to the main tanks by fuel and vent lines, for a total fuel capacity of 127 gallons. Internal examination of all fuel tanks revealed no anomalies. Fuel line continuity and selector valve operation was checked by blowing compressed air through the lines. All three propeller blades were bent aft mid-blade. The top spark plugs were removed and showed normal wear. The propeller was rotated by hand and thumb compression was established on all cylinders. The magneto impulse couplings could be heard engaging during rotation. The spark plugs were reinstalled, and a portable fuel can was connected to the upper left wing fuel line for preparation of a test run of the engine. The airplane fuel system was used from the wing attachment point to the engine, however; when the nose gear separated during the impact sequence, both fuel lines were separated from the fuel strainer. The strainer was removed, and the fuel lines were connected with a plastic hose for the engine run. The fuel strainer screen was clear of debris. The fuel selector was placed on the left fuel tank position, the boost pump was turned on until fuel pressure was established, and the starter was engaged. After two revolutions of the propeller, the engine started and ran nominally. The throttle was advanced to different power setting and the engine responded accordingly. No anomalies were noted with the engine and fuel system.