Primary finding
Probable cause
A total loss of engine power as a result of carburetor ice that formed while the engine was operating at a low power setting for an extended period of time before departure.
Investigator assessment
Analysis narrative
The pilot reported that after engine start, taxi, and run-up, he remained on the ground about 10 minutes at idle power waiting for a rise in oil temperature and reduction in oil pressure since it was the first flight of the day, and the engine was cold. Shortly after departure while turning onto the crosswind leg of the traffic pattern, the engine lost power and the pilot executed a forced landing to a gravel road. During landing, the airplane impacted a drainage ditch, which resulted in substantial damage to both wings. A review of meteorological information revealed that the airplane was operating in an environment conducive to serious carburetor icing at a glide power setting. During a postaccident examination, no preimpact mechanical malfunctions or failures were discovered that would have precluded normal operation. With no anomalies noted from the postaccident examination and the weather conditions present at the time of the accident, it is likely that carburetor ice formed during the extended ground run at idle power while the pilot waited for the oil temperature to rise.
Source record
Factual narrative
On June 3, 2023, about 0900 central daylight time, a Piper PA-25-235 airplane, N8843L, was substantially damaged when it was involved in an accident near Carrington, North Dakota. The pilot was uninjured. The airplane was operated as a Title 14 Code of Federal Regulations Part 137 aerial application flight. According to the pilot, after engine start, he taxied to the end of the runway to perform an engine run-up and allow the oil temperature to rise. During the run-up, the pilot checked the magnetos and turned on the carburetor heat. During the carburetor heat check, he noted an expected drop in rpm and then turned off the carburetor heat. He stated that he remained on the ground about 10 minutes at idle power waiting for a rise in oil temperature and reduction in oil pressure since it was the first flight of the day and the engine was cold. The pilot stated that shortly after departure while turning onto the crosswind leg of the traffic pattern, the engine lost power, and he executed a forced landing to a gravel road. During landing, the airplane impacted a drainage ditch, which resulted in substantial damage to both wings. During a postaccident examination, no preimpact mechanical malfunctions or failures were discovered that would have precluded normal operation. The temperature (75°F) and dewpoint (62°F) about the time of the accident were plotted on a carburetor icing probability chart, which showed that the airplane was operating in an environment conducive for serious carburetor icing at a glide power setting. (See figure.) Figure. Carburetor Icing Probability Chart. Reference: FAA Special Airworthiness Information Bulletin CE-09-35