Primary finding
Probable cause
The loss of rotor RPM for reasons that could not be determined based on available evidence.
Investigator assessment
Analysis narrative
The pilot and two passengers were completing an aerial gunning flight. The helicopter was flying at 80 ft above ground level (agl), when the pilot heard the “rotors droop” and the “engine bog down.” He stated that he applied right pedal and increased the throttle input, but the engine did not respond. The helicopter descended into the trees and impacted the ground. The main rotor blades and fuselage sustained substantial damage. The investigation was unable to determine the airspeed of the helicopter and the reason for the loss of rotor RPM based on the available evidence. A postaccident examination and engine functional test run revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation.
Source record
Factual narrative
On February 26, 2021, at about 1540 central standard time, a Robinson R44 helicopter, N7184N, was substantially damaged when it was involved in an accident near Dunn, Texas. The pilot and two passengers were not injured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 91 aerial gunning flight. The pilot reported that he had just refueled the helicopter and departed again with the fuel tanks about half full. While flying at 80 ft above ground level (agl), he heard the “rotors droop” and “engine bog down.” He applied right pedal and increased the throttle input, but the engine did not respond. The helicopter descended into the trees. The helicopter impacted the ground and sustained substantial to the fuselage. The investigation was unable to determine the airspeed of the helicopter based on the available evidence. A postaccident examination and engine functional test run revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation.