N62073

HISTORY OF FLIGHTOn June 2, 2018, about 1338 mountain daylight time, an experimental, amateur-built North Wing Pulse 10M hang glider, N62073, collided with the ground while participating in an airshow at Mountain Home Air Force Base (KMUO), Mountain Home, Idaho. The commercial pilot sustained fatal injuries and the hang glider sustained substantial damage. The hang glider was registered to and operated by the pilot as a Title 14 Code of Federal Regulations Part 91 flight. Visual meteorological conditions prevailed, and no flight plan was filed for the local flight, which departed KMUO about 1332.

The premise of the pilot's airshow routine was a comedy act in which he would simulate inadvertently flying the hang glider into an active airshow, interrupting another airplane that was performing an aerobatic routine. The plan was for the hang glider, which was equipped with smoke canisters and a series of trailing streamers, to be towed past show center while the aerobatic airplane made a series of close passes, eventually cutting the streamers. Throughout the routine, the rehearsed radio interactions between the hang glider pilot, aerobatic pilot, and the show announcer were transmitted over the public address system.

During a typical airshow, the hang glider was launched by a moving tow-launch system composed of a winch trailer pulled by a truck. The truck and trailer then travelled back and forth down the runway spinning out the tow line while the winch operator maintained line tension as the hang glider climbed to the desired altitude (usually 1,500 ft). The pilot typically released the line once the truck had turned around after the third pass. The pilot would then begin to perform a series of gliding maneuvers down to the ground, while the line, which was equipped with a parachute, was rewound back into the winch spool as it descended.

Most of the accident sequence was recorded on a security camera located on the KMUO control tower in the center of the airport, about 2,100 ft south of runway 12/30, and directly across from show center. Footage from the camera was provided by the United States Air Force (USAF).

On the day of the accident, the performance began and progressed uneventfully until the end of the truck and winch trailer's second runway pass. After being given the all-clear by the hang glider pilot, the truck and winch trailer turned around as planned and began to accelerate along runway 12 in anticipation of the pilot releasing the line. (See figure 1.) The winch operator stated that, a few seconds after the turn, he looked up and noticed that the hang glider was about 500 ft below the altitude at which he would typically expect to see it. The hang glider then performed an aggressive turning maneuver (see figure 2) and descended another 500 ft. The winch operator then released the winch pressure to supply the hang glider with more slack and prevent it from being impeded by line tension. The hang glider then entered a climb, rolled to the left, descended, and impacted the ground in a nose-down attitude. (See figures 3 and 4.)

Figure 1. Hang glider (red circle) and tow truck (green circle) beginning the final pass along runway 12

Figure 2. Hang glider performing aggressive turning maneuver

Figure 3. Hang glider rolling left

Figure 4. Hang glider striking the ground

Multiple witnesses recounted a similar sequence of events, stating that the maneuvers after the second pass were completely unconventional and not part of the routine. The airshow coordinator (air boss), who had seen the routine performed many times before, stated that the performance appeared to be going well and the streamers were cut during the second lap as planned. However, during the final turn, the hang glider was a little lower than normal and it performed a sudden circling maneuver, which he described as a "pinwheel." He commented to one of the crew that something was not right. The hang glider appeared to stabilize and descend, and then performed another pinwheel maneuver before it impacted the ground in a nose-down attitude. A witness saw the hang glider suddenly pitch up before the impact, and based on his experience, assumed that it had encountered a strong wind.

Neither the air boss nor the winch operator saw the line parachute deploy, and when the winch operator arrived at the accident site, the parachute and line were in the immediate vicinity of the main wreckage, appearing to have detached on impact. Multiple airshow attendees reported to news media that the tow line was cut by the aerobatic airplane during the routine, however, examination revealed that the line was intact and undamaged. PERSONNEL INFORMATIONThe 62-year-old pilot had broken his neck in a hang-gliding accident in 1981 and had been a C7 quadriplegic, paralyzed from the shoulders down, since then. He was issued a commercial pilot certificate with a glider rating in February 1996, with limitations for "aero tow" and "hand controls" only.

Federal Aviation Administration (FAA) records indicated that the pilot had undergone an FAA medical examination in March 1996, and subsequently was scheduled for a medical flight test in May of that year, but it was not clear if he completed the test or if a medical certificate was ultimately issued.

FAA regulations do not require the pilot of a hang glider to hold a pilot or medical certificate. AIRCRAFT INFORMATIONThe hang glider was composed of a North Wing Pulse 10M wing and a Moyes Delta Gliders Contour model harness. The system was configured with a "softpack" style BRS Aerospace aircraft parachute rescue system mounted to the harness.

The harness was connected to the tow line using a two-point strap, which incorporated a barrel-type quick release on the right side next to the pilot's chest. Operation of the quick release would have required pulling the barrel toward the harness while the strap was still under tension. The strap was connected to the tow line with a weak link, and a small parachute was connected to the end of the tow line.

The winch system included a spool of ultra-high molecular weight polyethylene cord (tow line), which was driven by an electrical motor. The speed of the spool during the towing process was maintained by a hydraulically-controlled automotive disk brake system, the pressure of which was governed by the tow operator. METEOROLOGICAL INFORMATIONA ground pyrotechnic display was scheduled to begin as the show opened, with more pyrotechnics progressively ignited during the day in coordination with approaching aircraft to simulate bombing runs. However, according to the air boss, due to a shift in wind direction, fire from the initial display landed in the other pyrotechnic staging area. Therefore, the decision was made to expend the entire remaining pyrotechnic load in a controlled manner rather than risk it igniting by accident. The subsequent controlled explosion at 1115 started a grass fire on the airfield, and the show was put on hold while the fire was extinguished. During that period the control tower was evacuated, but by 1132, fire command advised that the show could resume. Fire crews continued to extinguish flare-ups and monitor the area for hotspots, and by 1333, 5 minutes before the accident, one of the engines on the field reported that all the fires had been extinguished.

Two witnesses provided statements regarding the weather conditions over the area at the time of the accident. The first was a working volunteer who was also a hang glider pilot, and the second was a pilot who had just been flying a P-51 Mustang in the airshow, and was located immediately east of the accident site, and still in his airplane. Both witnesses described seeing dust devils over the area before and immediately after the accident.

The first witness, who was located about show center, indicated that before the accident pilot started his routine, he observed a dust devil to the west of the runway in a location past the air traffic control tower. He identified that the dust devil had a well-defined vortex and extended to about 200 ft above the ground. He stated that only a small amount of dust outlined the vortex's shape, and that he pointed out the dust devil to a friend who also witnessed the event.

The second witness saw several large dust devils over the airport area during the accident period. He indicated that the winds were light and variable until the pyrotechnic display and related fire started, after which strong vertical wind flows followed. Immediately after the accident, he noticed a dust devil to the south of his position travel across the audience. He described it as a large "lumbering" dust devil with a diameter of 40 to 80 ft that extended from 300 to 1,000 ft high. He noticed it blowing dust and disturbing papers, and people in the audience were holding their hats due to the sudden winds. He was able to observe the dust devil for about 5 to 10 minutes before he lost sight of it. Based on the movement and location of the dust devil, he extrapolated that it was likely over the area of the accident at the time of the event.

The air boss stated that at no time during the show did he see any dust devils, and it was not until the next day that he was told they were present.

Synoptic Conditions

The northwest section of the National Weather Service (NWS) Surface Analysis Chart for 1200 MDT on June 2, 2018, depicted two high pressure systems over Idaho and western Wyoming at 1028- and 1030-hectopascals (hPa) respectively, dominating over the area with a weak pressure gradient. No other significant boundaries were identified over the area.

The station models surrounding the accident site depicted clear skies and temperatures in the 70º F range with surface wind from the east to northeast at 5 knots or less.

A review of the NWS Boise (KCBX) WSR-88D radar imagery surrounding the period did not detect any significant meteorological echoes or boundaries over the ...