Robinson Helicopter R44 N7187B accident near Fielding, Utah

Probable cause

The pilot's failure to maintain rotor rpm while traversing a canyon in high-density altitude and gusting wind conditions.

NTSB analysis

The student pilot reported that, upon entering the mouth of a canyon, he slowed the helicopter to between 70 and 75 knots because he had experienced turbulence going through the canyon with his instructor the day before the accident. About halfway through the canyon, the helicopter dropped about 100 feet, and the main rotor rpm was between 80 and 85 percent. He lowered the collective and rolled on the throttle to regain rotor rpm and then turned toward a field to set up for a precautionary landing. During the turn, the main rotor rpm rose to about 90 percent, but, after leveling out, the pilot observed the rpm decrease again to between 80 and 85 percent. The pilot stated that, after he cleared a set of wires and landed the helicopter in the field, the front skid caught on something, and the helicopter tipped over on its left side, which resulted in substantial damage. The calculated density altitude at the time of the accident was 8,830 feet, which could have reduced the available engine torque and, subsequently, the rotor rpm. A postaccident examination of the helicopter's engine and airframe revealed no anomalies that would have precluded normal operation.

Text from the NTSB. Open the NTSB docket for WPR13LA295 for the full record.