Robinson R44 accident near Ida Grove, Iowa, July 21, 2019

The NTSB's narrative final · quoted from the NTSB record

The commercial pilot of the helicopter was performing an aerial application flight when he noted the engine rpm below "half" and dropping along with the main rotor rpm. The pilot reduced the collective and attempted a high hovering autorotation. Due to the lack of airspeed and altitude, the helicopter impacted a bean field "very hard." The pilot reported that the engine was not operating when the helicopter came to rest on its left side. The pilot reported that he was paying close attention to the carburetor heat temperature during the flight, as he had the carburetor heat lever pulled out "a little over half" and he kept the needle out of the yellow arc depicted on the carburetor temperature gauge. A postaccident examination of the airframe and engine found no preimpact mechanical malfunctions or failures that would have precluded normal operation, and the helicopter had adequate fuel onboard at the time of the accident. The temperature and dew point at the time of the accident were conducive to the formation of serious carburetor icing at glide power settings. However, given that the pilot was monitoring the carburetor temperature gauge, it is unlikely that the loss of engine power was due to carburetor ice. The reason for the loss of engine power could not be determined based on the available information.

The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.