Piper J5A N40985 accident near Atlantic Ocean, AO

Probable cause

A loss of engine power for reasons that could not be determined because the aircraft sank after ditching and was not recovered.

NTSB analysis

The pilot filled the airplane’s fuel tanks before departing on the over-ocean aerial observation flight. About 5.8 hours into the flight, while the pilot was returning to the departure airport, the engine began losing power. The pilot attempted to restore engine power using carburetor heat and the engine primer but was unsuccessful, so he ditched the airplane in the ocean about 21 miles from the destination airport. The airplane subsequently sank and was not recovered; therefore, no postaccident examination of the engine or airframe could be conducted. Although no information was available regarding the dew point conditions near the accident site, according to a Federal Aviation Administration carburetor icing probability chart, the temperature and dew point at the destination airport were conducive to the formation of carburetor ice at cruise/glide power settings. Postaccident fuel consumption calculations based on information published by the engine manufacturer showed that the airplane had a potential fuel endurance of between 3.8 and 7.1 hours depending on power setting, with an average endurance of 4.8 hours. The pilot estimated that the airplane contained about 5 gallons of fuel when the engine lost power. Because the airplane sank, the investigation was not able to conclusively determine the reason for the loss of engine power.

Text from the NTSB. Open the NTSB docket for ERA12LA410 for the full record.