The canyon is called Descent and the maneuver was called the “yo-yo” by Sundance Helicopter pilots and the “Thelma-and-Louise” by Papillon Airways pilots. The trip was a thrilling three-minute helicopter ride over the rim of the Grand Canyon, down Descent Canyon to land at the floor of the canyon. But that maneuver, by any name, resulted in two fatal accidents. On Aug. 10, 2001, the pilot and five passengers perished in the crash of a Papillon AS 350, and a little over two years later, on Sept. 20, 2003, the pilot (nicknamed “Kamikaze”) and six passengers were killed when a Sundance AS 350 crashed. The NTSB last week released a series of factual reports on the most recent crash, which is still under investigation. The Safety Board determined the probable cause of the earlier accident to be the pilot’s decision to maneuver in a high-density altitude in which the helicopter’s performance capability was marginal, “resulting in a high rate of descent from which recovery was not possible.”