Robinson Helicopter Company R44 II accident near Alpine, Texas, November 13, 2015

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

The commercial pilot and crewmembers were conducting wildlife surveys and predator control at the time of the accident. The pilot did not have any recollection of the accident sequence. Crewmember statements and GPS data indicated that the pilot was maneuvering the helicopter about 40 ft above ground level when the low rotor speed warning activated. The pilot attempted to regain rotor speed by descending into a small canyon. However, his efforts were unsuccessful, and the helicopter subsequently impacted trees and terrain. A review of GPS data revealed that the pilot had completed a low-speed, 360-degree turn followed by a gradual descending left turn immediately before the impact. One crewmember reported that the pilot told him that, during the takeoff on the morning flight, the helicopter "wouldn't go" and that the low rotor speed warning came on. A postaccident examination of the helicopter did not reveal any preimpact failures or malfunctions. Postaccident calculations revealed that the helicopter was operated within the gross weight and center-of-gravity limitations. However, the flight was operating at or near the helicopter's out-of-ground effect hover ceiling performance limit. It is likely that the main rotor speed decayed as the pilot maneuvered the helicopter while it was at or near its performance limit and that the pilot decided to conduct the flight knowing the helicopter was near its performance limit. Insufficient altitude was available to allow the pilot to lower the collective and recover the rotor speed before impact with trees and terrain.

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.