ERA23LA221

The pilot’s failure to apply carburetor heat before initiating a descent in conditions conducive to the development of carburetor icing, which resulted in a partial loss of engine power due to carburetor ice.

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.

On May 5, 2023, about 0745 eastern daylight time, an Aeronca 7DC-CONV, N3058E, was substantially damaged when it was involved in an accident in Fort Mill, South Carolina. The private pilot and pilot-rated passenger were not injured. The airplane was operated a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot was interviewed by a Federal Aviation Administration (FAA) aviation safety inspector and provided a written statement. The pilot described a “normal” preflight inspection, engine start, run-up, taxi, departure, and climb to about 2,000 ft mean sea level, where he established a heading toward his planned destination. Because of radio and airplane traffic at the destination airport, he amended his destination, and decided to descend and follow a river toward another airport. The pilot reported that after descending about 1,000 ft, he leveled the airplane, “…applied power and there was no thrust.” He adjusted the throttle, the mixture, “pulled the carb heat,” and cycled the magnetos without a change in engine speed. The engine continued to run at 1,000 rpm. The pilot originally selected an open area of fields and golf courses for the forced landing, but decided to land in the river when he determined that the airplane would not reach the open area. The airplane touched down in shallow water, nosed over, and came to rest inverted. The pilot and his passenger each egressed the airplane without injury. Examination of the airplane at the site revealed damage to the rudder, wing attachment points and their associated attachment bolts. During recovery of the airplane, control continuity was established from the flight controls to all flight control surfaces. The airplane was recovered to the operator’s facility and prepared for an engine test run. The impact-damaged propeller was removed, and a propeller of the same make and model was installed. The spark plugs were removed, and water was drained from the cylinders. The plugs were dried, cleared of debris, and reinstalled. The magneto timing was confirmed, and the magnetos were removed, dried, and reinstalled in their as-found positions. The fuel line that ran between the fuel selector valve and the firewall beneath the instrument panel was fractured due to overstress, so a fuel container was plumbed into the carburetor for the test run. A fresh battery was installed in the airplane, and the starter was excited using battery power. The engine started with fuel plumbed through the primer port of the carburetor, idled and accelerated smoothly, and ran continuously until the engine was stopped using the mixture control in the cockpit. While the engine ran, a magneto check and a carburetor heat control check were performed satisfactorily at 1,700 rpm. The engine was then restarted with fuel supplied through the main fuel supply port, and the tests were repeated satisfactorily. The engine was then accelerated into the “green arc” before it was stopped again using the mixture control. According to the carburetor icing probability chart contained in FAA Special Airworthiness Information Bulletin (SAIB) CE-09-35, Carburetor Icing Prevention, the atmospheric conditions reported by the pilot at the point of departure and those recorded at a station about 10 miles west of the accident site were 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.