North Wing Pulse accident near Mountain Home, Idaho, June 2, 2018

The NTSB's narrative final · quoted from the NTSB record

The hang glider pilot was performing a routine in an airshow that included the hang glider being towed to altitude by a truck-driven winch trailer. The truck and hang glider typically needed to make three passes along the runway in order to gain the altitude required for the routine; however, at the beginning of the third pass, the hang glider appeared to descend and then made an aggressive turning maneuver. The hang glider then stabilized for a few seconds before rolling to a  nose-down attitude and striking the ground. Postaccident examination did not reveal any anomalies with the airframe or the tow system that would have precluded normal operation. Multiple witnesses reported seeing at least one dust devil on the airfield about the time of the accident. Review of video footage confirmed the presence of a dust devil about the time of the accident along with evidence of low-level wind shift activity. A grass fire on the airfield earlier in the day had resulted in the temporary suspension of the airshow. By the time the accident routine had begun, the fire had been extinguished; however, smoldering areas and hot spots were still present and were being monitored by the fire department. All of the criteria for the development of dust devils were present at the time of the accident except for temperatures above 90°F; however, the burn area from the fire would have resulted in locally warmer temperatures in the vicinity of the accident site and increased the likelihood of eddy or vortices in the area of the accident site. Additionally, while the routine was progressing, a military fighter jet was idling on the ramp with its hot exhaust gases facing the runway toward the location of the ground impact. The jet began to taxi during the hang glider routine, and it is possible that the exhaust gases further exacerbated the conditions and created sufficient eddies to trigger a dust devil event. Based on the available evidence, it is likely that the hang glider encountered dust devil activity while being towed to altitude. The 62-year-old pilot had been paralyzed from the shoulders down due an accident about 40 years prior. He had accumulated extensive hang gliding experience since then and had performed the airshow routine many times before. However, the pilot had been suffering from arthritis in his left shoulder, which in recent months had resulted in a significant decrease in its range of movement. As such, he was experiencing difficulties getting into the hang glider harness, operating his wheelchair, and performing routine daily tasks, and he had discussed the possibility of retiring at the end of the airshow season. Although the autopsy identified evidence of mild coronary artery disease, there was no evidence he ever had any symptoms of ischemia, and it is unlikely that his heart disease contributed to the accident. The pilot's recently degraded shoulder function due to arthritis, likely reduced his ability to perform the control inputs required to recover from the dust devil encounter or release the hang gliders airframe parachute.

The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.