Accident Details
On June 23, 2023, at about 0950 eastern daylight time, an Aeronca 11AC (registration N9543E) was substantially damaged when it was involved in an accident at Hinton-Alderson Airport (WV77), Pence Springs, West Virginia. The commercial pilot and student pilot were not injured. The flight was conducted as a Title 14 Code of Federal Regulations Part 91 personal flight.
According to the pilot, while in the airport traffic pattern at about 1,000 ft above ground level, he reduced engine power and the airplane began “sinking.” He attempted to arrest the descent by adding full power, but the engine did not respond. He noticed that the engine rpm was at 1,500 and there was no forward thrust. He attempted to troubleshoot, applied carburetor heat, and lowered the nose to maintain glide speed but was unable to restore power. The airplane descended into the trees, with the left wing impacting the trees first, then impacting terrain before coming to rest upright.
Examination
A postaccident examination revealed substantial damage to the wings. The left wing was fractured and displaced aft near its midspan. Further examination of the engine and components showed the propeller was undamaged and exhibited no signatures consistent with rotation at impact. Engine continuity was confirmed, and a compression check of the engine’s cylinders along with a spark plug exam showed no anomalies. Fuel sampled from the airframe was free of water or debris. The carburetor heat tubing was not completely attached to the carburetor intake box and did not display evidence of impact damage.
Weather Conditions
At 0950, the weather reported at Greenbrier Valley Airport (LWB), Lewisburg, West Virginia, about 18 miles northeast east of the accident site, included a temperature of 18°C and a dew point of 16°C. Visible moisture was present in the area with overcast conditions at 800 ft. The calculated relative humidity at this temperature and dewpoint was 62%. Review of the icing probability chart contained in Federal Aviation Administration (FAA) Special Airworthiness Information Bulletin CE-09-35 revealed that the weather conditions at the time of the accident were "conducive to serious icing at glide [idle] power."
According to FAA Advisory Circular 20-113, "To prevent accidents due to induction system icing, the pilot should regularly use [carburetor] heat under conditions known to be conducive to atmospheric icing and be alert at all times for indications of icing in the fuel system." The circular recommended that when operating in conditions where the relative humidity is greater than 50%, "…apply carburetor heat briefly immediately before takeoff, particularly with float type carburetors, to remove any ice which may have been accumulated during taxi and runup." It also stated, "Remain alert for indications of induction system icing during takeoff and climb-out, especially when the relative humidity is above 50 percent, or when visible moisture is present in the atmosphere."