The pilot of the helicopter was conducting his third air tour flight of the day, transporting six passengers to the operator's plateau landing site, known as Quartermaster, on the south bank of the Colorado River within the Grand Canyon. He was appropriately rated for this flight and was experienced executing approaches and landings at Quartermaster. Following an uneventful flight to the area, the pilot began a descent and approach from across the river to a ravine on the west side of the landing site. The accident helicopter was the ninth of ten helicopters scheduled to land at the site that afternoon, and because all of the pads on the east side of the site were occupied, the pilot initiated a descending left turn toward a landing pad located on the west side of the site, aligning the helicopter on an east-northeasterly heading. Photographs of the landing site windsock near the time of the accident indicated winds at magnitudes of 15 kts or greater from the north-northwest, resulting in tailwind conditions during approaches to the west pads. A pilot on the ground at the landing site reported that the accident helicopter began to decelerate as it approached the landing pads and entered a nose-up attitude, then turned left toward the landing pads, transitioned through several pitch oscillations, and drifted aft. The left turn continued through 720° of rotation before the helicopter descended into a canyon just west of the landing pads and impacted terrain. Photos indicated that the helicopter’s final impact in the canyon was immediately followed by a postcrash fire. Postaccident examination of the helicopter and engine revealed no evidence of mechanical anomalies that would have precluded normal operation.
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We determined the probable cause(s) of this accident to be a loss of tail rotor effectiveness, the pilot’s subsequent loss of helicopter control, and collision with terrain during an approach to land in gusting, tailwind conditions in an area of potential dondrafts and turbulence.
