Government UAS pilots reported an unknown failure caused one UAS to have a rapid descent to the ground. During the descent the UAS crashed into another hovering UAS causing major damage to both UAS aircraft.
Synopsis
Government UAS pilots reported an unknown failure caused one UAS to have a rapid descent to the ground. During the descent the UAS crashed into another hovering UAS causing major damage to both UAS aircraft.
Narrative
Two state agencies held a joint flight practice day at Location A; Day 0; beginning at XAAM. Groups were spaced out with access to an open grassy field near the field station. Our 3-person crew completed our pre-flight checklist for our sUAS; and took off at XA:43AM. We were in manual control for the duration of the flight. RPIC completed tests on all controls at low altitude - max altitude 21 ft AGL. RPIC was walking a new crew member through landing; drone was descending at 15 ft AGL over the landing pad when UAS #2 (Small UAS) fell out of the sky and collided with our drone at XA:49AM. The other operator said they were hovering at 120 ft AGL when they lost connection with their drone; controller screen went black and drone fell from the sky. There were no injuries; and only property damage was the drones themselves. Both drones sustained damage to frame and props and cameras snapped off. Primary corrective action would be better airspace management to avoid aircraft overflying other aircraft or occupying the same airspace.
Second reporter narrative
While attending a state government UAS training session our Small UAS collided with another participating UAS; severely damaging both drones. As the RPIC I oversaw the preflight procedures; witnessed the UAS show a fully warmed-up status; and green light conditions for manual flight. I proceeded to fly the aircraft for about 2 minutes in various directions to a maximum altitude of about 30'AGL. After I was satisfied with the UAS's performance I switched roles with my visual observer; so that he had a training opportunity to operate the UAS while I acted as his visual observer. He initially made a series of lateral maneuvers at about 30' AGL; then proceeded to climb to a max altitude of about 320' AGL. There he hovered briefly; while manipulating the gimbaled camera and rotating the UAS. Next; he descended to a hover at about 120' AGL; while also continuing to manipulate the gimbaled camera while rotating slowly. It was at this point that I noticed the drone begin a slight roll to the port-side while starting to lose altitude. Seconds later I observed the drone falling rapidly; colliding with another group's UAS (Small UAS); which appeared to be hovering near the ground. As our UAS fell; I glanced at the controller screen to notice that it was completely black. The drone operator claims at the time of the incident; he was attempting to hover at 120' AGL and had not initiated a port side roll or any change in altitude. When the drone fell unexpectedly; he remembers the controller screen becoming black and a warning flashed that the 'connection with the drone had been lost'. Fortunately; no one was injured in the collision. It is my assumption that there was an issue with the battery; causing the UAS to plummet without any warning. In the past I have had one incident occur where the connection to the drone was lost temporarily; however it remained hovering then reconnected without incident. I probably should have also directed him away sooner; from the vicinity of the other UAS.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.