Primary finding
Probable cause
The loss of engine power due to carburetor ice due to the pilot’s delayed application of carburetor heat.
Investigator assessment
Analysis narrative
The pilot was enroute to a private grass airstrip to practice touch-and-go landings. A witness observed the airplane approach the airstrip about 300 ft. The airplane was in a shallow left turn and the engine was running rough. He said that the engine lost and regained rpms about four times before it stopped running. The airplane appeared to be flying slowly. Seconds later, the witness heard the airplane make a sudden and audible contact with the ground, and he went immediately to the accident site. The airplane was lying upright in a vegetated field with the forward part of the fuselage and wings substantially damaged. The pilot told the witness that all he could remember was that the engine was running rough and that he was trying to correct the problem. The pilot said that he thought that he had carburetor ice, so he applied carburetor heat, but the engine roughness got worse. Examination of the airframe, flight controls, fuel system, and the engine, did not reveal any pre-impact anomalies that would have precluded normal operations. The airplane was being operated in weather conditions conducive to serious carburetor icing at glide power. Based on the pilot’s and the witness’s recollection of the event and the weather conditions, the loss of engine power was most likely the result of carburetor icing due to the pilot’s delayed application of carburetor heat.
Source record
Factual narrative
On June 3, 2023, about 1635 central daylight time, a Temco GC-1B airplane, N3830K, was substantially damaged when it was involved in an accident near Bristow, Oklahoma. The pilot sustained serious injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot stated that he was enroute to a friend’s private grass strip airport (OK69) to practice touch-and-go landings. A witness observed the airplane approach OK69 from the north about 300 ft above ground level. The airplane was in a shallow left turn, and the engine was running rough. He said that the engine lost and regained rpms about four times before it stopped running. The airplane appeared to be flying slowly. The witness lost visual contact with the airplane behind some trees. Seconds later, he heard the airplane make sudden and audible contact with the ground and he immediately called the police department and went to the accident site. According to the witness, the pilot was sitting up and unbuckled in the left seat and was unclear as to where he was or how he got there. The pilot asked questions as to what had occurred; he kept telling the witness that all he could remember was that the engine was running rough and that he was trying to correct the problem. He thought that the engine had carburetor ice, so he applied carburetor heat, but the engine roughness got worse The airplane wreckage was found lying level in a vegetated area. The front portion of the cockpit and the wings were crushed aft. The examination of the airframe, flight controls, fuel system, and engine did not reveal any pre-impact anomalies that would have precluded normal operations. The Federal Aviation Administration’s Special Airworthiness Information Bulletin CE-09-35 includes a carburetor icing probability chart. Using the nearest reported temperature of 26° C, and a dew point of 17° C, the chart indicated that the airplane was operating in weather conditions conducive to serious carburetor icing at glide power.