The flight instructor reported that, during the initial climb for the instructional flight with the student pilot/owner at the controls of the Luscombe 8A, the engine began to lose power.
The flight instructor assumed the controls and attempted a forced landing on a road in a residential area near Mount Dora, Florida.
During the forced landing, the left wing hit a tree, and the airplane then came to rest upright, which resulted in structural damage to the airframe.
During the post-accident examination, dark, granular sediment was found inside the fuel tank, and it was of sufficient quantity to interrupt fuel flow to the engine.
The airplane had been stored outside. It could not be determined how, or when, the granular contamination was introduced into the fuel tank.
An examination of the engine and fuel system revealed evidence of some leakage around the carburetor, and the cylinders around the exhaust valves showed signatures consistent with operation at high exhaust gas temperatures.
Examination of the fuel tank revealed that it contained automotive gasoline.
The student pilot believed that the use of auto gas was permitted, however, no supplemental type certificate (STC) for the use of auto gas existed, and the airplane was not placarded for auto gas use. The auto gas also might have contained ethanol, which was not permitted with or without an STC for auto gas use.
Probable cause: Excessive particulate contamination in the fuel tank, which resulted in the interruption of the fuel flow to the engine and a partial loss of power. The source of the contamination could not be determined based on the available information.
NTSB Identification: ERA15LA265
This July 2015 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.