Accident Overview
On September 17, 2020, at 1254 eastern daylight time, a Stinson 108-2 airplane, registration N336C, was substantially damaged when it was involved in an accident near Newport, Pennsylvania. The flight instructor sustained minor injuries, and the pilot was not injured. The airplane was operating as a Title 14 Code of Federal Regulations Part 91 instructional flight.
According to the flight instructor, he and the pilot fueled the airplane, departed, and flew for about 1.5 hours. While cruising at 3,500 ft, the engine “started to sputter.” The instructor checked the magnetos, adjusted the mixture, switched fuel tanks, and pumped the primer and throttle. When he pumped the primer, the engine would “run for about 5 seconds then quit,” and the propeller continued to windmill. Unable to restore power, he elected to execute a forced landing to a field. During the landing rollout, the airplane impacted a berm.
Post-Accident Examination
Examination by a Federal Aviation Administration (FAA) inspector revealed that the airplane was intact and came to rest upright. The main landing gear collapsed, and the firewall and forward fuselage were impact damaged. One propeller was bent aft and exhibited chordwise scratching. Fuel was present in both wing tanks and appeared absent of water and debris. The cockpit mixture control was selected to full rich (IN).
The engine and its accessories were examined under FAA supervision at the accident site and later at a hangar. Spark plugs were removed and visually examined with no anomalies noted. Both magnetos were present, securely installed, and connected. Magneto-to-engine timing was within specifications, and both magnetos produced spark at all towers when the engine was rotated by hand. Rotation of the crankshaft produced compression on all cylinders, and normal valvetrain movement was observed. Fuel was present throughout the fuel system and was absent of water and debris, including in the gascolator and carburetor float bowl. Air blown through the fuel cap vent tubes to the carburetor fuel supply hose showed the vents and fuel lines were free of obstruction. The carburetor screen was unobstructed.
The carburetor mixture control cable was found disconnected at the carburetor. The carburetor mixture lever on the carburetor was found in the idle cutoff position. The attaching hardware that would have connected the mixture control cable connector fitting to the carburetor mixture arm was not located.