DJI Mavic – Accident – 2018-07-01

Drone Manufacturer: DJI
Drone Model: Mavic
Country: United States of America
Type: Accident
Date: 2018-07-01
Applies: Daytime
Pilot Qualifications: Unknown Status
Pilot Flight Experience: Unknown Hours
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Night operations were being conducted for situational awareness {SA} at the northern expansion zone {beach lot area} of the Kilauea volcanic eruption that began May 2018. UAS launch site was in the vicinity of Kapoho Lava Flow of 1960 at Lat: 19.46066 Long: -154.85166 in an area known locally as 4-corners. Daytime recon of the site prior to night ops, revealed a topographic rise to the SE of the launch site that was estimated to be between 160 to 180 feet above home elevation. This elevation was determined to require an increase in RTL altitude from 70 meters {230 ft} used at previous launch sites to 85 meters {279 feet} at the new 4 corners launch site. The possibility of the rise creating a loss of link situation was also discussed, with the final recommendation being that pilots should keep an eye on the RSSI signal strength during flight, and maintain visual line of site if possible during night ops Following launch, the UAS was guided to ascend approximately 200 feet altitude and pitch forward to the South about 200 ft over the road, where a 20/20 test of telemetry, stick control and gimbal function was conducted. A live feed was initiated and the UAS was determined to be ready for the situational awareness {SA} flight. Following the 20/20 check the UAS was controlled by manually manipulating the controls in GPS mode, yawed to the ESE and guided in a full forward pitch while climbing to ~750 feet. DJI GS Pro App was used to monitor the position of the UAS and view video footage of the lava flow margin with an oblique gimbal as it came into view. A brief loss of link {about 5 seconds} was experienced when the UAS passed about 2500 feet beyond home and beyond the identified obstruction. The UAS initiated its own RTL, but the link was reestablished so RTL was aborted in DJI GS Pro and the mission was continued on to a maximum distance from home of about 7400 feet. RSSI was noted at this point to be degraded to 2 bars. The decision was made to initiate an RTL to avoid a loss-of-link situation. As the drone approached 5000 feet, RSSI was normal again {full 5 bars}, so RTL was again aborted by canceling the RTL on the DJI GS Pro app screen. The PIC walked down the road about 100 meters to improve direct line of site, and regain connection. SA began again over the lava flow margin, images and videos were acquired on a slow-guided, manually-controlled look around the flow expansion zone. The UAS was pointed towards the NW and moving towards home with the gimbal pointed down to slightly oblique. Once the end of the flow zone was reached at approximately 3500-4500 feet from home and about 690 feet altitude, an RTL was initiated to conserve battery {approximately at 41-44 at that time} and come home. A descent was being simultaneously provided on the sticks along with the UAS controlled RTL. The PIC began walking back towards the launch site to prepare for landing, and this could have impacted the RSSI. However, the landing site appeared to have a better visual line of site for the RTL heading, but maybe that was not the case. The last known distance from home before loss of link was noted to be about 1700 feet with an altitude of 490 feet, and battery at 31. RSSI began changing erratically from near full to no bars and intermittently displaying red. No visual line of site was confirmed at this time. DJI GS Pro app screen was locked and RTL was greyed out. Also the option to cancel RTL by clicking on an ‘x’ adjacent to RTL icon was unavailable. The blue arrow on the app that indicates UAS location and heading turned to grey and was not moving on the display. The app screen froze, so the controller became the only source for updating information regarding the UAS. The center of the controller display, which usually displays ‘GPS mode’ during flight, had changed and was displaying a left-scrolling banner that repeated the message ‘Sys error – close app’. The DJI GS Pro app was closed and reopened but remained completely greyed out without any updated location information {lat, lon, altitude}. The controller stopped displaying the sys-error message about 30 seconds to 1 minute after it was initially observed, and began displaying the message: ‘connecting’, then ‘GPS mode’. Distance from home on the controller displayed 1702 feet with an altitude of 0 feet. The UAS was assumed to have landed in place, possibly due to a loss of link, caused by a topographic obstruction along the UAS path to home. Following landing, a second drone was launched to try to get eyes on the landed UAS, while inflight lights may still have been on and battery operating. The tablet that was running the DJI GS Pro app was still frozen and no precise estimate of location existed at this time. The UAS location identification mission was unsuccessful. Equipment was packed up and the night ops team determined that an attempt at recovery would not be possible until daylight. The tablet that was frozen eventually came back online after about 30-45 minutes and was broadcasting the last known position of the UAS at latitude: 19.5061139, longitude: -154.8180277. The night operation team returned to base to meet with the field team, and a plan was made to visit the site and make a daylight recovery if the location was deemed safe for a recovery mission. The decision to recover the aircraft was pushed back a day to take advantage of longer daylight. A follow up will be included if recovery is successful.

Reported Cause

Loss of control. Software and controller issues.