SEA05LA089 · Aeronca 0-58B

The airplane lost engine power and collided with terrain during the forced landing. According to the pilot, after purchasing the airplane and being briefed on the fuel system, he departed on the first leg of the transcontinental flight. The fuel system was comprised of a 10 gallon overhead center tank which fed directly into a 2 gallon header tank. Also incorporated into the system was a 10 gallon right wing tank whose fuel line teed into the center tank's line. A shutoff valve was incorporated in the "T" which would allow both tanks to feed the header tank simultaneously. Procedures called to use half of the fuel in the center tank before opening a shutoff valve. On the first leg of the flight the pilot flew 45 minutes before opening the shutoff valve. After landing approximately 35 minutes later he instructed the fueling attendant to fill both the center and wing tanks so he could judge the consumption of fuel from each tank. After fueling was completed the attendant advised the pilot that he had put 8.5 gallons of fuel in the center tank, and that the wing tank was full. The pilot commented that this wasn't right, but voiced no further concerns and departed on the next leg of the flight, a distance of about 90 nautical miles. About one hour into the flight the pilot opened the wing tank shut off valve, and when he was about an hour and 30 or 40 minutes into the flight while descending he encountered a "surge" in the engine. The pilot added carburetor heat with no success, and when the engine quit completely he elected to land in a wheat field. After touching down and impacting a plow rut the airplane nosed over and came to rest on its back in an inverted position, resulting in substantial damage to the airplane's vertical stabilizer. The pilot stated that he felt the reason for the engine failure was due to fuel exhaustion as a result of fuel being vented from the wing tank, which resulted in fuel from the center tank being sucked into and replacing the fuel in the wing tank. Further examination by the FAA failed to reveal any fuel present at the accident site. It was also noted that the installation of the wing tank was a modification of the airplane, which required a Supplemental Type Certificate (STC). A search by the FAA failed to reveal an STC for this aircraft relative to the right wing tank installation. The inspector also supervised an engine test run with no anomalies noted. The reason for the reported loss of engine power could not be determined.

Verbatim NTSB analysis and probable cause from the NTSB dataset