Aircraft: Waco YMF5. Injuries: None. Location: Marathon, Fla. Aircraft damage: Substantial.
What reportedly happened: According to the pilot, at the beginning of the day the main fuel tanks of the airplane were 7/8ths full. The pilot spent the day conducting sightseeing flights departing from an island airport.
The accident happened on the third flight of the day. The airplane was about two nautical miles from the airport when, following a left turn climbing maneuver, the engine began to surge. The pilot elected to perform a ditching 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 the water, the pilot opted to continue with the ditching. Upon impact with the water, the airplane nosed over.
After the airplane was recovered from the water, about four gallons of fuel and 16 gallons of sea water were drained from the 36-gallon capacity left fuel tank. The right 36-gallon fuel tank was empty. Neither fuel tank had been breached.
During the post-accident examination of the airframe and engine, no pre-accident mechanical malfunctions or failures were found that would have precluded normal engine operation.
Investigators determined that 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.
Probable cause: The pilot did not ensure that there was sufficient fuel aboard the airplane before initiating the flight, which resulted in temporary fuel starvation and an interruption in engine power during maneuvering. Contributing to the accident was the pilot’s decision to continue with the ditching after engine power was restored.
NTSB Identification: ERA12LA126
This December 2011 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.