What happened
During the initial climb at 150 feet AGL, the pilot reported that the engine lost power. In an attempt to return to the airport, the pilot initiated a 180-degree turn; however, the aircraft crashed at approximately the 180-degree point of the maneuver.
The investigation
A post-crash examination of the engine showed no evidence of mechanical failure or malfunction. Investigators also found no evidence of fuel contamination. The operator noted that the aircraft was STC'd for autogas and had been fueled with a 50/50 mixture of AVGAS and autogas. Additionally, the operator reported advising the pilot just before departure that the engine was prone to carburetor ice and that weather conditions were favorable for such formation. The operator also observed that the pilot allowed the engine to idle for several minutes before starting the takeoff roll.
Findings
An examination of icing probability curves indicated that the reported weather conditions were favorable for serious icing at glide power settings. Furthermore, FAA Advisory Circular 91-33A indicates that FAA testing has shown carburetor ice can occur faster and at higher temperatures when using autogas compared to AVGAS.