Incident Overview
The aircraft had been parked for approximately two months with a partial fuel load. Prior to departure, 40 gallons of auto fuel were added. Both wing tank sumps and the gascolator were drained, with only a minimal amount of water found.
Sequence of Events
Shortly after takeoff, the engine lost power. During an emergency landing in an open field, the nose gear dug in and the aircraft nosed over.
Post-Accident Examination
Examination revealed that the carburetor bowl was about half full of water. Water was also found in the line from the gascolator to the carburetor. Inspection of the fuel tanks showed wrinkles or ridges in the bottom of the rubber cells, sufficient to trap water and prevent it from flowing to the tank sumps for normal draining.
Additional Information
The fuel cells had been installed on December 15, 1978. The pilot was aware of the wrinkles in the fuel cells. Auto fuel was approved for use in this aircraft per a Supplemental Type Certificate (STC).