ERA12LA131 · Haney John F B SEASTAR XP

Before the experimental, amateur-built, amphibious biplane's first test flight, the pilot/owner/builder ran the engine for about 20 minutes. He then taxied to the runway and departed. He flew for about 25 minutes before returning to the airport. After landing, he then taxied back to the runway, departed, circled the field for an additional 20 minutes, then returned to perform a touch-and-go landing. After touching down, adding power, and beginning the initial climb, the engine lost partial power and the engine's rpm decreased to about 3,000 rpm. Because the airplane was past the departure end of the runway, the pilot performed a water landing on a nearby reservoir. During the landing, the left lower wing struck the water and separated from its mounting location. After the airplane slowed, the pilot noticed that the engine was still running; however, when he advanced the throttle, the rpm would initially increase and then immediately decrease to 2,000 rpm. Examination of the airplane and engine revealed no mechanical failure or malfunction that would have precluded normal operation. It was further noted that the engine was not equipped with a carburetor heat system or insulated fuel hoses, as recommended by the engine manufacturer. Due to the ambient air temperature at the time of the accident, it was improbable that vapor lock caused the partial loss of power. Review of a carburetor icing probability chart revealed that weather conditions were conducive for serious carburetor icing. Therefore, it is likely that had a carburetor heat system been installed and the pilot had applied carburetor heat before his initial power reduction, the formation of carburetor ice would have been prevented.

Verbatim NTSB analysis and probable cause from the NTSB dataset