Incident
The pilot reported that the engine lost power during the initial climb at 150 feet above ground level (AGL). He attempted to execute a 180-degree turn to return to the airport, but the airplane crashed at approximately the 180-degree point of the turn.
Examination
A post-crash examination of the engine revealed no evidence of mechanical failure or malfunction. Additionally, no evidence of fuel contamination was found.
Operational Factors
The operator reported that the aircraft had a supplemental type certificate (STC) for the use of autogas and was fueled with a 50/50 mixture of avgas and autogas. The operator noted that he had advised the pilot, just prior to departure, that the engine was prone to carburetor ice and that conditions were favorable for carburetor ice formation. The operator subsequently observed that the pilot allowed the engine to idle for several minutes before beginning the takeoff roll.
Weather Considerations
Examination of icing probability curves revealed that the reported weather conditions were favorable for serious icing at glide power settings. FAA Advisory Circular 91-33A notes that FAA testing has indicated that carburetor ice occurs faster and at higher temperatures with autogas than with avgas.