Primary finding
Probable cause
The loss of engine power due to carburetor icing.
Investigator assessment
Analysis narrative
The amateur-built airplane's engine lost power after takeoff, and the pilot performed an off-airport landing. The airplane struck trees during the landing. A postaccident examination revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. The temperature and dew point about the time of the accident were favorable for carburetor icing. Further, the Ford Model A engine that was installed on the airplane is noted for its susceptibility to the formation of carburetor ice. Additionally, the pilot reported his belief that the carburetor heat system of the airplane was ineffective at flight speeds and that the loss of power was due to the formation of carburetor ice.
Source record
Factual narrative
On May 9, 2012, about 1200 central daylight time, an amateur-built Stovall Pietenpol Aircamper, N728MK, collided with trees during a forced landing following a loss of engine power near Rose Hill, Kansas. The pilot was not injured. The airplane sustained substantial damage to both wings. The aircraft was registered to an individual and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 as personal flight. Visual meteorological conditions prevailed for the flight, which was not on a flight plan. The local flight was originating from Cook Airfield, Rose Hill, Kansas at the time of the accident. The pilot reported that the airplane's engine was run on the ground, at various power settings, for about 30 minutes. The airplane was then taxi tested for 45 minutes to 1 hour. On the first takeoff of the airplane, when it had reached an altitude about 400 feet above ground level, the engine power began to deteriorate. The engine power continued to decrease and an off-airport landing was made. The airplane struck trees during the landing. The temperature and dew point at the time of the accident were 20 degrees Celsius and 6 degrees Celsius. According to Federal Aviation Administration Special Airworthiness Information Bulletin CEN-09-35, these measurements indicated that the airplane was operating in a range susceptible to the formation of carburetor ice. The airplane was powered by a converted Ford Model A automobile engine. As installed on automobiles, the Model A engine was noted for its susceptibility to the formation of carburetor ice and heat tubes were installed to alleviate this problem. The pilot reported that he believed that the loss of power was due to the formation of carburetor ice. Although the airplane had provisions for carburetor heat that was effective during ground operations, the pilot believed the ram air introduced by flight conditions prevented the system from working effectively at flight speeds. A postaccident examination of the airframe and engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation.