AirNet Systems Flight USC146

The pilot reported that he had the airplane refueled before takeoff but that he did not check the fuel tanks for contaminants after fueling. The pilot performed an engine run-up before departure and reported no discrepancies. After departure, the airplane climbed to 8,500 feet mean sea level while proceeding toward the destination airport. After about 15 minutes in cruise flight, the pilot positioned the fuel selector to the left tank, and, about 15 minutes later, the engine lost power; however, the fuel flow increased to about 140 pounds per hour, and the fuel flow needle reached the maximum indication. The pilot's attempts to restore engine power were unsuccessful. The airplane was unable to maintain altitude, so the pilot used the on-board GPS receiver to locate the nearest airport; however, he realized that the airplane would be unable to reach the airport. He maneuvered the airplane for a forced landing on a road but again realized that he would be unable to reach that road. After descending below the clouds, he maneuvered the airplane for a landing on another road, and the airplane subsequently collided with an unmarked power line that crossed the road diagonally. The airplane contacted the ground and then came to rest upright.

Postaccident examination of the airplane revealed water contamination in both fuel tanks, the fuel strainer, and left header tank; however, no water was detected in the engine fuel system components; both of the fuel caps' seals were satisfactory. There were no reports of other airplanes fueled by the same truck having water contamination issues, and an examination of the truck used revealed that it was clean and in good repair. The source of the water could not be determined. The engine was removed from the airplane and placed in a test cell, and it was operated to near-full takeoff rpm with no discrepancies noted. Although no water was detected in the engine fuel system components, the excessive fuel flow reported by the pilot at the time of the total loss of engine power was consistent with water freezing at the manifold valve, which prevented the piston from allowing the fuel to flow to each cylinder.

Postaccident surveillance of the airline by its Federal Aviation Administration principal maintenance inspector revealed four instances in which other company pilots did not check the fuel tanks for contaminants after fueling, which was not in accordance with the operator's operations manual. After the accident, the company's director of operations issued flight operations bulletins reminding company pilots of the requirement to check the fuel tanks after fueling and the location of the fuel tank drains.

Verbatim NTSB analysis and probable cause from the NTSB dataset