Incident Overview
A pilot reported that while conducting "practice" aerial application operations at an altitude of approximately 30 feet above ground, the engine gradually lost power. The pilot executed a left turn and subsequently landed in a bean field. The landing resulted in substantial damage to the right wing and left elevator.
Pilot Reports
In postaccident interviews, the pilot stated that just before the power loss, the aircraft was in wings-level flight with the mixture set to full rich and power at a cruise setting. The carburetor heat was off for the entire flight. The pilot described the power loss as gradual, with no visible oil spray on the windscreen. Following the accident, the pilot checked the oil level and found no anomalies.
Examination Findings
An airframe and powerplant mechanic conducted a postaccident examination. They drained 13 gallons of fuel from the single fuel tank. The float carburetor and gascolator were inspected and found to be unremarkable. The propeller could be rotated normally.
Weather and Carburetor Icing Considerations
An automated weather observing system located 13 nautical miles northeast of the accident site, near the time of the incident, reported a temperature of 81°F (27°C) and a dew point of 66°F (19°C). According to a carburetor-icing-probability chart, the engine was at risk of "moderate icing" at cruise power. The Federal Aviation Administration Pilot's Handbook of Aeronautical Knowledge (PHAK) notes that carburetor ice can form when temperatures are below 70°F (21°C) and relative humidity above 80%, but also at higher temperatures due to evaporative cooling. The PHAK states that ice buildup can cause engine cessation. The airplane manufacturer's owner manual advises selecting the minimum amount of carburetor heat to keep ice cleared when conditions are conducive to carburetor icing.
Probable Cause
The investigation suggested that the loss of engine power was likely due to carburetor ice, but the pilot, who was also the airplane owner, did not make the airframe or engine available for examination by the National Transportation Safety Board.