What happened
The pilot was operating an aircraft that had recently undergone a complete engine overhaul and the replacement of the right fuel tank bladder. Approximately 1 hour and 50 minutes into the flight, the engine stopped running without any prior warning. The pilot subsequently performed a forced landing in a corn field, during which the aircraft nosed over and sustained damage.
The investigation
Post-accident inspections of the aircraft revealed a wrinkled right bladder fuel tank and a visible fuel stain located aft of the left fuel cap. Very little fuel was found remaining on board at the time of the investigation. When four gallons of fuel were added to the left tank, the engine ran successfully.
The investigation also focused on the aircraft's modifications under Supplemental Type Certificate (STC) SA4121SW. It was discovered that there were no maintenance entries in the aircraft logbook documenting compliance with all conditions required by the STC. Specifically, Cessna Service Bulletin (SB) SEB88-1 was applicable to this STC. This bulletin instructs technicians to add a strip of foam seal around the wing strut under the upper strut cuff to prevent airflow from disrupting proper fuel venting via vortex generation. The service bulletin also notes that excessive gaps between the wing strut and the strut cuff can lead to fuel bladder tank wrinkling, unsnapping, and inaccurate fuel quantity indications.