What happened
The flight was operating in visual meteorological conditions at the surface, where the temperature was recorded at 32 degrees Fahrenheit. However, atmospheric reports indicated that temperatures were higher at the 4,000-foot altitude level. The pilot initially reported a complete loss of forward visibility caused by ice accumulation on the windshield. In response to these deteriorating conditions, the pilot diverted toward Cedar City Airport (CID), which is staffed with Radar Approach Control (RAPCON).
The aircraft climbed to an altitude of 4,000 feet MSL. During this climb, the pilot noted that the aircraft was beginning to lose accumulated ice but subsequently reported encountering worsening icing conditions. Air traffic control at CID vectored the aircraft toward the airport runway. While descending toward the field, the pilot reported that one engine had quit. The pilot stated that the aircraft could no longer maintain altitude and then reported going down. The aircraft entered a spin and crashed into an open farm field.
The investigation
A physical examination of the wreckage revealed critical details regarding the aircraft's configuration and equipment status. The aircraft was not equipped for flight in icing conditions. Although the carburetor heat control was found in the full-on position, the pitot heat control was discovered in the off position. No propeller, windshield, or airframe deicing equipment was installed on the aircraft.
However, a windshield electrical anti-ice system had been installed and was confirmed to be on at the time of the accident. The investigation also noted that the aircraft had undergone a modification to permit the use of automotive gasoline (auto gas). According to FAA Advisory Circular 91-33A, this specific modification increases the potential for carburetor icing.
Findings
The pilot's weather briefing was limited by the pilot but was partial in nature. It included flight precautions for icing conditions, instrument flight rules (IFR), and turbulence. Despite these precautions being provided, the aircraft lacked adequate equipment to handle the encountered icing environment effectively. The combination of the lack of deicing systems, the off position of the pitot heat, and the increased carburetor icing potential due to the auto gas modification contributed to the loss of control.
N1291P was not equipped for flight in icing conditions. The aircraft entered a spin and crashed in an open farm field. One fatal injury occurred among those on board.