SE5A N685SE accident near Virginia Beach, Virginia

Probable cause

A partial loss of engine power due to an interruption of the normal fuel/air mixture to the engine.

NTSB analysis

The pilot was performing the first flight after assembly of the experimental airplane. The day before, the pilot started and taxied the airplane with no anomalies observed, and the preflight taxi and engine run-up on the morning of the accident flight also revealed no anomalies. The pilot advanced engine power slowly for takeoff and the engine ran "perfectly" as the airplane quickly accelerated and became airborne. When the airplane was about 200 to 300 feet above ground level and more than 3/4 of the way down the runway, he sensed that the engine was losing power. By the end of the runway, it became apparent that it was losing power. The pilot then started a gradual left turn and attempted to troubleshoot the loss of power but realized that the airplane was not going to make it back to the airport. The pilot performed a forced landing to a recently harvested cornfield, during which the airplane sustained substantial damage.

Examination of the airplane’s vintage engine did not reveal evidence of any preimpact malfunction or failure that would have precluded normal operation. The engine was not equipped with carburetor heat and review of a carburetor icing probability chart revealed that the atmospheric conditions at the time of the accident were conducive to the formation of carburetor ice. It is possible that while operating the airplane on the ground before takeoff (a period during which the engine would typically be operating at low power), carburetor ice started forming and continued until the engine began losing engine power during the initial climb. The fuel system was also of a vintage design and used an air pump to apply pressure to the fuel tank, enabling fuel to flow to the carburetor. According to the builder, a partial loss of power could have occurred if the fuel system was not properly vented, and the engine could have incurred fuel starvation as a result.

Either carburetor icing or inadequate fuel venting could have resulted in a partial loss of power; however, it could not be determined which scenario occurred and resulted in the accident. Given the potential for either scenario, and that no evidence that a mechanical failure contributed to the loss of engine power, it is likely that an interruption of the normal fuel/air mixture to the engine resulted in the loss of engine power.

Text from the NTSB. Open the NTSB docket for ERA18LA003 for the full record.