What happened
The pilot departed from his residence at a private lake in a float-equipped airplane with the intention of transporting passengers to another remote lake. Prior to this final flight, the pilot had performed several refueling operations. Initially, the aircraft was fueled using a 1,000-gallon metal tank located on the pilot's property; this process continued until the supply was exhausted, leaving one fuel tank full and the other nearly full. Later, the pilot purchased 15 gallons of additional fuel at a nearby airport and added 5 gallons to the aircraft's tanks. After completing two round-trip flights to the remote lake and spending a day fishing, the pilot returned to his residence and added another 10 gallons of fuel. Two empty five-gallon fuel cans were located at the pilot's dock.
On the flight in which the accident occurred, the pilot departed to pick up additional passengers from the remote lake but failed to reach the destination. The aircraft was discovered inverted in an area of tall trees with the flaps extended full down. There were no fatalities reported.
The investigation
A post-accident examination of the engine revealed no mechanical malfunctions. Investigators noted minor wrinkles along the bottom of each of the airplane's fuel bladders. The gascolator contained approximately one teaspoon of water and particulate contamination, while the header tank contained about an ounce of fuel and water. The fuel pump was found to be empty of fuel. Additionally, a fluid sample taken from the fuel filter housing—which was attached to the pilot's fuel tank hand pump—showed evidence of tan-colored particulate contamination.