STINSON 108

Full Narrative

On August 21, 2019, about 1338 central daylight time, a float-equipped Stinson 108-3 airplane, N647C, was substantially damaged during a forced landing following a loss of engine power near Grand Rapids, Minnesota. The pilot had departed from Lily Lake located immediately north of the Grand Rapids/Itasca County Airport (GPZ) shortly before the accident. The pilot sustained minor injuries. The airplane was registered to a private individual and operated by the pilot as a Title 14 Code of Federal Regulations Part 91 personal flight. Visual meteorological conditions prevailed, and the flight was not operated on a flight plan. The local flight was originating at the time of the accident.
The pilot reported that he allowed the engine to warm-up for about 15 minutes before takeoff. He used the carburetor heat during the run-up and before takeoff. The subsequent takeoff was normal. Shortly after establishing climb power, he noticed a reduction in power; although, the engine was still running smoothly. He turned to a left downwind for landing on Lily Lake. "Several seconds" later, the engine "popped twice and quit completely." The propeller continued to windmill. The airplane did not have enough altitude to land at the lake and the pilot executed a forced landing to a grass area near the water treatment plant northeast of the airport.
A postaccident examination revealed that the airframe exhibited damage to the aft fuselage, left wing, left horizontal stabilizer, and right float. The right wing appeared intact with exception of minor deformation at the wing tip. The left-wing fuel tank was dislocated from the wing. The grass was blighted at the location the fuel tank came to rest consistent with a fuel exposure. The right-wing fuel tank appeared intact and about 20 gallons of fuel was recovered from that tank.
The engine remained securely attached to the engine mount. The examination did not reveal any anomalies with respect to the engine, engine accessories, or related airframe components. An engine test run was conducted. The engine started without difficulty on the first attempt and ran smoothly. Magneto and carburetor heat checks were normal. The engine oil pressure remained within normal operating limits during the run. No anomalies consistent with an inability to produce rated power were observed.
According to documentation issued by the Federal Aviation Administration, the possibility of carburetor icing at glide power existed at the time of the accident.