Witness Observations
Several witnesses observed the airplane before impact and reported hearing engine noise that oscillated between no power and high power. No further details about the flight path or visual appearance were provided.
Wreckage Examination
Examination of the wreckage revealed that the two main fuel tanks were ruptured and charred. The two auxiliary fuel tanks were not compromised and appeared to be absent of fuel. Only drops of fuel were found in the mechanical fuel pumps, fuel lines from the pumps to the mixture controls, and fuel lines from the mixture controls to the injection manifolds. Inspection of the airframe, engines, and propellers did not reveal any pre-impact mechanical malfunctions.
Fuel Records and Usage
Review of fueling records showed that all four tanks were completely filled approximately one month before the accident. The airplane was operated multiple times after that initial fueling, and fuel was added to the main fuel tanks on four separate occasions prior to the accident. However, fuel was never added to the auxiliary fuel tanks. Although both auxiliary fuel tanks appeared to contain no fuel at the accident site, the investigative team was unable to confirm the positions of the fuel selectors before impact.
Pilot Experience
The flight instructor had about 50 hours of flight experience in the make and model of the accident airplane. The pilot/owner had about 100 hours of flight experience in the accident airplane.