Cessna 206 N8255Q accident near Chalkyitsik, Alaska

Probable cause

A loss of engine power due to water-contaminated fuel as a result of the pilot’s inadequate preflight inspection. Contributing to the accident was the operator’s failure to ensure replacement filters were available for use during refueling operations.

NTSB analysis

The pilot landed on a remote gravel bar to fuel the accident airplane and to retrieve fuel for another airplane. The fuel used to refuel the airplane was from a fuel stash that had been set up by the operator about two months before the accident. The fuel was stored in a metal 55-gallon drum and the fuel used by the pilot had been transferred into two 15-gallon plastic drums before her arrival at the gravel bar.

The pilot allowed two hunters, who were waiting for another flight, to refuel the airplane. The hunters were unaware of company refueling procedures and the pilot did not discuss the possibility of water in the fuel with the hunters. No filters were used during the transfer of fuel into the airplane’s fuel tanks. No examination of the fuel drums was performed before refueling, and the pilot did not sump the airplane’s fuel tank before departure. The airplane was on the ground for about 12 minutes. The hunters reported that, just after takeoff, they heard the engine “sputtering” and they turned back toward the airplane. They saw it abruptly bank hard to the right before the right wing contacted the water. The airplane cartwheeled into the river, spinning about 270° before becoming partially submerged.

During the removal of the remaining fuel drums from the gravel bar, a company pilot examined one of the 15-gallon drums that contained about 8 gallons of fuel. He noticed that the fuel contained about 8 ounces of water. This drum was with the same stockpile of fuel that the accident pilot used. The operator had previously had numerous conversations with the accident pilot about the danger of water contamination in the fuel. The operator stated he stressed the importance of visually inspecting the fuel, using filters, and sumping the airplane’s fuel tank after refueling.

Examination of the intact portions of the fuel system revealed a mixture of fuel and clean water in the unmetered fuel line that ran to the metering valve, in the fuel line from the metering valve to the fuel manifold, and in the fuel flow manifold. Dirty water was observed in both the left and right header tanks. According to the operator, at the beginning of the season there was a fuel filter on the pump and a filtering funnel at the fuel stash location. The funnel was designed to filter out water, dirt, and debris. After the fuel filter became plugged, they removed it from the pump and never replaced it. The funnel was also lost and not replaced.

The measured codeine and morphine concentrations in the pilot’s urine were low and could represent drug use or poppy seed consumption. Neither codeine nor morphine were detected in the pilot’s blood, making it unlikely that opioid effects contributed to the accident. The pilot’s hydroxychloroquine use is unlikely to have contributed to the accident given what is known about the accident circumstances and the typical effects of hydroxychloroquine. Thus, it is unlikely that drug use contributed to the accident.

Text from the NTSB. Open the NTSB docket for ANC24FA102 for the full record.