Background
The flight was intended to provide airplane familiarization to a recent purchaser of the aircraft. A flight instructor (CFI) had flown with the owner's son approximately one hour before the accident, during which no discrepancies with the airframe or powerplant were noted.
Pre-Accident Flight
On that earlier flight, the CFI had the owner's son perform a simulated engine-out procedure in the same box canyon where the accident subsequently occurred. The flight profile was similar to that described by witnesses for the accident sequence. During the simulation, the son terminated the procedure, informing the CFI that he was uncomfortable with being so low over the canyon.
Accident Flight
A witness observed the accident airplane turn into the box canyon, flying flush with the top of a bluff, approximately 100 feet above the canyon floor. The airplane then executed a tight left turn, followed by a dust cloud from the impact. The witness did not hear any change in engine sound or sputtering, and described the engine as producing power throughout.
Emergency Response
Emergency response personnel flew to the accident site within an hour of the crash. They reported encountering swirling, turbulent winds as they descended below the canyon rim, which made their approach into the box canyon very difficult.
Investigation
After obtaining witness statements, the flight crew flew the described flight path. They noted that as they initiated and subsequently completed the turn, the helicopter was pushed by the winds downward and toward the accident site. The airframe and powerplant were inspected, and no discrepancies were noted.