Winchester, VA, USA
N7832X
CESSNA 172B
After a delay while he waited for several other airplanes to land and take off, the pilot departed and was climbing to cruise altitude when the engine began to lose power. Shortly thereafter, the engine lost power completely. The pilot then attempted to restore engine power and did not activate the carburetor heat until after the power loss. He was able to briefly restart the engine, but it ultimately lost power again after a brief period of rough running. During the subsequent off-airport landing, the nose landing gear separated from the airplane and it nosed over, substantially damaging both wings and the vertical stabilizer. The engine was successfully test run following the accident, and no mechanical deficiencies were found that would have precluded normal operation. The temperature and dewpoint at the departure airport around the time of the accident were conducive to the formation of carburetor icing. It is likely that, during the delay while the pilot was waiting to depart, the carburetor began to accumulate ice, that the ice accumulation continued during the subsequent takeoff and climb, and that the engine slowly lost power throughout. Because the pilot did not activate the carburetor heat until after the engine had lost power completely, the carburetor heat was ineffective at restoring engine power.
On February 24, 2021, about 1400 eastern standard time, a Cessna 172B, N7832X, was substantially damaged when it was involved in an accident near Winchester, Virginia. The pilot incurred minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. According to the pilot, after his preflight inspection he started up the airplane and taxied to runway 14 at Winchester Regional Airport (OKV), Winchester, Virginia for departure. He performed a magneto check and noted no anomalies. After waiting for 3 other airplanes to land and another airplane to depart, he took off around 1330. Shortly after departing, the pilot felt as if the airplane wasn’t climbing as well as he thought it should. Being too far away from the departure airport, he located a field for a possible emergency landing. The pilot executed a mental emergency checklist as the airplane descended and the engine continued to lose rpm. Around 1,700 feet, the engine stopped running completely. The pilot attempted to troubleshoot by ensuring that the fuel selector was on both tanks, the magnetos were on, the mixture was rich, and he turned on the carburetor heat. He then primed the engine and attempted to restart it. The engine started but was running roughly. The pilot left the carburetor heat on and then turned back toward the departure airport. The airplane would not climb with the available power, and shortly thereafter, the engine again lost total power. The pilot then established a best glide speed and guided the airplane toward a field for a forced landing. During the landing, the nose landing gear separated, and the airplane nosed over. Following the accident, the pilot stated that he felt the loss of engine power was due to the formation of carburetor ice. Examination of photos taken of the airplane following the accident showed that the vertical stabilizer and both wings were substantially damaged. A Federal Aviation Administration inspector examined the airplane and engine after it was recovered from the accident site. The inspector found that the carburetor float bowl contained fuel and that the intake was impacted with dirt from the accident site. After cleaning out the dirt from the intake, the inspector performed a successful test run of the engine and noted no anomalies. At 1415, the weather conditions at OKV, about 9 miles east of the accident site, included a temperature of 17°C and a dew point 01°C. Review of the icing probability chart contained within Federal Aviation Administration Special Airworthiness Information Bulletin CE-09-35 revealed that the atmospheric conditions at the time of the accident were conducive to the formation of carburetor icing at glide and cruise engine power settings. According to FAA Advisory Circular 20-113, "To prevent accident 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 percent, "…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."
The pilot’s delayed use of carburetor heat, which resulted in carburetor icing and a subsequent total loss of engine power.
Source: NTSB Aviation Accident Database
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