ERA25LA189

A total loss of engine power on approach due to carburetor ice.

During the second landing of an instructional flight to obtain currency in tailwheel airplane takeoffs and landings. The first takeoff and landing were uneventful. During the second approach, while abeam the numbers on the downwind leg of the pattern, the pilot receiving instruction reduced engine power, applied carburetor heat, and began a descent. While turning from base leg to final, the instructor told the pilot to increase engine power to not fly below the proper glidepath; the pilot advised that the engine was not responding to throttle input. The instructor took control of the airplane and lowered the nose to maintain airspeed. He then verified that the fuel, mixture, primer, switches, and carburetor heat controls were in the correct position. About 300 ft above ground level (agl), the instructor realized the airplane was too low to clear a road and guardrail just before the runway, so he chose to turn right to land in a field. During the landing, the airplane struck a wire fence, the right main landing gear collapsed, and the airplane came to rest on its right wing. Postaccident examination revealed no airplane or engine anomalies that would have affected normal operation except that the carburetor heat control and valve were found in the mid-range position. An icing probability chart indicated “Serious Icing – glide power” for the recorded temperature and dew point about the time of the accident. Engine manufacturer service instructions included a caution to not use a mid-range position for carburetor heat control on aircraft, like the accident airplane, that were not equipped with a carburetor air temperature gauge. The mid-range position of the carburetor heat control, along with the ambient temperature and dew point, could have resulted in carburetor ice after reducing engine power on approach, resulting in a total loss of engine power. However, the position of the carburetor heat control before the accident could not be confirmed due to impact damage to the airbox.

On April 26, 2025, about 1030 eastern daylight time, a Champion 7GCBC, N9117L, was substantially damaged when it was involved in an accident near Weyers Cave, Virginia. The flight instructor and commercial pilot receiving instruction were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. The flight instructor reported that the purpose of the flight was for the commercial pilot to obtain currency in tailwheel airplane takeoffs and landings. They departed with 16 gallons of fuel and remained in the airport traffic pattern at Shenandoah Valley Regional Airport (SHD), Weyers Cave, Virginia. The first takeoff and landing were uneventful. During the second approach, “abeam the numbers,” the pilot receiving instruction reduced engine power, applied carburetor heat, and began a descent. When the airplane was turning from base leg to final leg, about 600 ft agl, the instructor advised the pilot to increase engine power so they would not fly below the proper glidepath. At that time, the pilot advised that the engine was not responding to throttle input and the instructor took control of the airplane. The flight instructor lowered the nose to maintain airspeed. He then verified that the fuel, mixture, primer, switches, and carburetor heat controls were in the correct position. About 300 ft agl, the instructor noted that the airplane was too low to clear a road and guardrail just before the runway, so he chose to turn right to land in a field. During the landing, the airplane struck a wire fence, the right main landing gear collapsed, and the airplane came to rest on its right wing. Examination of the wreckage found substantial damage to the right wing and fuselage, and confirmed adequate fuel remaining onboard. The carburetor heat control was found in the mid-range position, but it was also noted that the airbox had sustained some impact damage. The engine was later examined, with a representative from the engine manufacturer, after the wreckage was recovered to a hangar. No anomalies were found with the engine other than the carburetor heat control and valve in the mid-range position. When the propeller was rotated by hand, crankshaft, camshaft, and valvetrain continuity was confirmed to the rear accessory section of the engine, and thumb compression was attained on all cylinders. Fuel remained in the carburetor bowl and gascolator, and it was absent of debris. A comparison of the recorded temperature and dew point about the time of the accident with the carburetor icing probability chart found in FAA Special Airworthiness Information Bulletin CE-09-35, Carburetor Icing Prevention, indicated a risk for “Serious Icing” at glide power. . Lycoming Service Instruction 1148C, Use of Carburetor Heat Control, included a warning: “CAUTION MUST BE EXERCISED WHEN OPERATING WITH PARTIAL HEAT ON AIRCRAFT THAT DO NOT HAVE A CARBURETOR AIR TREMPERATURE GAUGE. USE EITHER FULL HEAT OR NO HEAT IN AIRCRAFT THAT ARE NOT EQUIPPED WITH A CARBURETOR AIR TEMPERATURE GAUGE.” The accident airplane was not equipped with a carburetor air temperature gauge.