CEN21LA381

The pilot reported that, shortly after takeoff, she noticed that the airplane was not climbing normally and heard the stall warning horn. The pilot then noticed the engine speed was rapidly decreasing from 2,500 to 1,500 rpm. The pilot established the airplane’s best glide speed and prepared for a forced landing to a corn field. She did not apply carburetor heat. After touchdown, the airplane nosed over, resulting in substantial damage to the fuselage, vertical stabilizer, and rudder. A postaccident examination of the engine revealed low compression on the No.1 cylinder, but, after staking the valves, compression increased with no leaking past the valves. Also, the airplane’s most recent annual inspection was completed 4 days before the accident with normal compressions noted. Thus, the low compression during the postaccident examination was likely a result of the accident and the airplane remaining in an inverted position in the field for about 4 days after the accident. When the temperature and dew point of the area surrounding the accident site were entered into a carburetor icing probability chart, the result was in the “moderate icing – cruise power” and “serious icing – glide power” category. When the pilot was asked how the carburetor heat was checked, she stated that she turned it on, saw a drop in engine rpm and immediately turned it off. Thus, the loss of engine power was likely due to carburetor icing that accumulated before and during the takeoff, and the pilot’s failure to apply carburetor heat when the engine speed began to decrease. The momentary application of carburetor heat before takeoff was likely not sufficient to reduce or eliminate the ice buildup.

On August 10, 2021, about 1000 eastern daylight time, a Cessna 150, N66748, sustained substantial damage when it was involved in an accident near Wadsworth Municipal Airport, Wadsworth, Ohio. The pilot and passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that, after she taxied to runway 21, she used the airplane’s checklist to perform an engine run-up, which included checking the magnetos and carburetor heat. Afterward, she taxied the airplane into position on the runway, held the brakes, and advanced the throttle to full power before releasing the brakes to initiate the takeoff. The pilot stated that, shortly after takeoff, she noticed that the airplane was not climbing normally and heard the stall warning horn. She then noticed the that the engine speed had rapidly decreased from 2,500 to 1,500 rpm and was continuing to decrease. The pilot stated that, due to the airplane’s low altitude, she had time only to establish the airplane’s best glide speed and prepare for forced landing to a corn field. After touchdown, the airplane nosed over, resulting in substantial damage to the fuselage, vertical stabilizer, and rudder. The airplane remained inverted in the field for about 4 days prior to recovery. Postaccident examination of the engine revealed low compression on the No.1 cylinder. Further examination with a borescope found a small amount of carbon and lead fouling on the piston and valves. The valve cover was removed, and all valves were observed moving without restriction. After staking the valves, compression increased from 12/80 to 60/80 with no leaking past the valves. (At the time of the engine’s most recent 100 hour and annual inspection, which was 4 days before the accident, the compression in the No.1 cylinder was 78/80.) All spark plugs were removed and tested; all produced a strong blue spark. When the temperature (20°C) and dew point (17°C) that were present in the area surrounding the accident site were entered into a carburetor icing probability chart, the result was in the “moderate icing – cruise power” and “serious icing – descent power” category, as shown in the figure below. The Cessna 150 pilot’s operating handbook stated, “carburetor ice, as evidenced by an unexplained drop in RPM, can be removed by application of full carburetor heat.” Figure . Carburetor icing probability chart (Source: AAIB).