Accident Overview
On July 18, 2014, at approximately 1541 central standard time, a Stinson 108-1 single-engine floatplane, registration N9034K, was substantially damaged during a forced landing after losing engine power near Bruno, Minnesota. The private pilot, the sole occupant, was not injured. The aircraft was registered to Mimus Aero LLC of Minneapolis, Minnesota, and operated by a private individual under Part 91 of the Federal Code of Regulations. No flight plan was filed, and visual meteorological conditions prevailed.
Flight History
The flight originated from Sky Harbor Airport (DYT) in Duluth, Minnesota, at about 1510, bound for Surfside Seaplane Base (BY4) in Lino Lakes, Minnesota. Approximately 30 minutes after departure, while at an altitude of 2,000 feet above ground level, the engine sputtered for about 10 seconds and then lost all power. The pilot initiated emergency restart procedures and identified an off-airport landing site during the subsequent descent.
Landing and Damage
The aircraft touched down on its floats in a grassy field. Post-accident inspection revealed bucking damage to the fuselage just aft of the right cabin door and additional buckling near the left aft float attachment point. Both float attachment struts were broken. Marks on the aft face of the propeller blades indicated contact with the walk wire between the floats. The aircraft came to rest in a slight right-wing-low attitude. Fuel flowed freely from the engine fuel sump. A total of 7 gallons were drained from the left fuel tank and 21 gallons from the right tank. The fuel appeared clean and uncontaminated, resembling 100LL aviation fuel. The fuel selector valve was positioned to the right tank and functioned normally within its detents.
Engine Examination
On-site examination revealed no obvious anomalies. The top spark plugs were removed, and the engine was rotated by hand with the propeller in the normal direction. All six cylinders exhibited good compression. Both magneto impulse couplings snapped normally during rotation. Spark plugs appeared in good condition.
After recovery, maintenance personnel started the engine using an external fuel supply. The engine ran for about 30 seconds before stopping. The fuel gascolator and carburetor intake screen were then removed and cleaned; no significant debris was found, though a small amount was present in the carburetor fuel bowl. Following further inspection, the engine was restarted and ran for approximately one minute before stopping again. A replacement carburetor was installed, after which the engine started and ran normally.
Findings
The National Transportation Safety Board investigated the accident. No probable cause was stated in the preliminary report. The aircraft was recovered for further examination.