N373CStinson 108-2 · 1947

On August 3, 2009, about 1315 mountain daylight time, a Stinson 108-2, N373C, sustained substantial damage after making a forced landing due to a total loss of engine power about 2 miles east of the Salt Lake City International Airport (SLC), Salt Lake City, Utah. The commercial pilot was not injured, and the sole passenger sustained minor injuries. Visual meteorological conditions prevailed for the cross-country flight, which was operated in accordance with Title 14 Code of Federal Regulations (CFR) Part 91, and a flight plan was not filed. The flight departed the Rock Springs-Sweetwater County Airport (RKS), Rock Springs, Wyoming, about 1130, and was destined for the Bolinder Field-Tooele Valley Airport (TVY), Tooele, Utah.

The pilot reported that while in cruise flight at 10,500 feet mean sea level (msl) "…the engine suffered a catastrophic failure." The pilot stated that he set up a glide for SLC, but seeing he was not going to make it he elected to land in an field east of the airport. The airplane sustained substantial damage to the fuselage in the area where both main landing gear were attached.

A Federal Aviation Administration (FAA) airworthiness inspector, who responded to the accident site, reported damage to the accessory section of the Franklin 6A4-165 engine. A subsequent post-accident examination of the engine by a second inspector revealed that the crankshaft gear had failed, which resulted in the damage to the accessory section of the engine. The inspector further reported that all accessory gears exhibited mechanical damage. Over 50 percent of the crankshaft gear could not be found, and that the crankshaft gear appeared to have failed at both dowel pins slots.

The engine was a Franklin 6A4-165B-3 that was manufactured in 1947 and was the original engine installed by the Stinson factory at the time of the airframe manufacture. The engine had accumulated 2,520 hours time in service and was overhauled 147 hours prior to the accident.