ERA12LA126 · Classic Aircraft Corp WACO YMF5

The pilot reported that, at the beginning of the day, each of the main fuel tanks was about 7/8ths full. He completed two aerial sightseeing flights and was making a third flight. The airplane was about 2 nautical miles from the airport, which was located on an island, when, following a left turn climbing maneuver, the engine began to surge. The pilot elected to perform a forced landing in the ocean. Despite the fact that the engine stopped surging and began producing “almost takeoff power” when the airplane was about 500 feet above ground level, the pilot opted to continue with the ditching. Upon impact with the water, the bi-wing airplane nosed over and sustained substantial damage to both left wings. After the airplane was recovered from the water, about 4 gallons of fuel and 16 gallons of sea water were drained from the 36-gallon capacity left fuel tank; there was no fuel in the 36-gallon right fuel tank. Neither fuel tank had been breached. During a postaccident examination of the airframe and engine, no preaccident mechanical malfunctions or failures were found that would have precluded normal engine operation. Given the low fuel quantity, it is likely that, during the left turn climbing maneuver, the fuel tank inlet was unported, and air was introduced into the system, which caused the engine surge. Once the climbing turn was stopped, normal fuel flow began and engine operation resumed.

It was noted that the wires attached to the cork floats of each of the two fuel quantity sight gauges were bent and that this was causing the gauges to register a fuel quantity of 7/8ths, irrespective of the actual fuel quantity. It could not be determined if the wires were bent before the accident or as a result of the impact. If the wires were bent before the accident, then the pilot should have recognized that the indicated fuel quantity was not changing during the first and second flights of the day and should have taken further action to verify the actual fuel quantity aboard the airplane before initiating the accident flight. If the wires were bent as a result of the impact, then the fuel gauges would have been working properly, and the pilot should have noted the low fuel quantity and refueled the airplane before initiating the accident flight.

Verbatim NTSB analysis and probable cause from the NTSB dataset