Robinson Helicopter Co R66 N117TW accident near Wikieup, Arizona

Probable cause

An encounter with turbulence due to updrafts and/or dust devils that resulted in mast bumping and an in-flight break-up.

NTSB analysis

The commercial pilot and the pilot-rated passenger departed on a cross-country positioning flight. The helicopter was reported overdue when it did not arrive at the destination, and the wreckage was located the following morning. There were no witnesses to the accident, no recorded radar data, and no recorded radio transmissions from the pilot.

Examination of the wreckage revealed no evidence of any preexisting anomalies that would have precluded normal operation of the helicopter. There was evidence that a mast bumping event had occurred and that the main rotor blades had contacted the airframe, which resulted in an in-flight break-up. There was no recorded information available that could be used to determine the helicopter's airspeed, altitude, or the pilot's control inputs.

A weather study indicated that conditions were conducive to the development of significant updrafts or thermals of rising air and dust devils, and people near the accident site reported that there were numerous dust devils in the area.

It is likely that the helicopter encountered turbulence due to updrafts and/or dust devils, and the pilot lost control of the helicopter, which resulted in mast bumping.

Text from the NTSB. Open the NTSB docket for WPR16FA130 for the full record.