ERA23LA221 · Aeronca 7DC-CONV

The pilot and passenger departed and climbed the airplane to about 2,000 ft mean sea level. Due to traffic at the intended destination, the pilot chose to instead descend and follow a river toward another airport. Upon reaching his desired altitude over the river, the pilot leveled the airplane and applied engine power, but reported that there was “no thrust.” He adjusted the throttle, the mixture, applied carburetor heat, and cycled the magnetos without a change in engine speed. The engine continued to run at 1,000 rpm. The pilot completed a forced landing to the river, where the airplane touched down in shallow water, nosed over, and came to rest inverted. Examination of the airplane at the site revealed substantial damage but no preimpact anomalies that would prevent normal operation. After recovery, the engine and its accessories were dried, the impact-damaged propeller was replaced, and fuel was plumbed directly to the carburetor due to an impact-damaged fuel line. The engine started and ran smoothly and continuously at various power settings until the test run was discontinued. Review of weather information in the area of the accident site revealed conditions conducive to the development of carburetor icing at glide and cruise power. In both his interview and his written statement, the pilot stated that he applied carburetor heat only after detecting the loss of engine power. Based on the available information, it is likely that the engine developed carburetor icing during the pilot’s descent toward the river, which resulted in a partial loss of engine power.

Verbatim NTSB analysis and probable cause from the NTSB dataset