Accident Overview
The pilot-owner was operating an airplane that had recently undergone a complete engine overhaul and 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 executed a forced landing in a corn field, during which the airplane nosed over and sustained damage.
Investigation Findings
Post-accident inspection of the airplane revealed a wrinkled right bladder fuel tank and a fuel stain aft of the left fuel cap. Very little fuel was found onboard. When four gallons of fuel were added to the left tank, the engine ran successfully, indicating that fuel starvation was a likely cause of the power loss.
Maintenance and Modifications
The airplane had been modified under Supplemental Type Certificate (STC) SA4121SW. However, there was no maintenance entry in the airplane's logbook documenting compliance with all conditions of the STC. Cessna Service Bulletin (SB) SEB88-1, which was applicable to the STC, contained instructions to add a strip of foam seal around the wing strut under the upper strut cuff. The SB noted that this sealing prevents airflow inside the cuff and disruption of proper fuel venting due to vortex generation forward of the vent tube. The SB also stated that excessive gaps between the wing strut and strut cuff could cause fuel bladder tank wrinkling, unsnapping, and inaccurate fuel quantity indications.
Although the investigation did not explicitly determine a probable cause, the evidence points to fuel system issues related to the STC modification and lack of compliance with the service bulletin, leading to fuel starvation and the subsequent forced landing.