The flight was planned to be a short-range flight (10m) with a hover to execute a maintenance cycle of a set of batteries for the DJI M30T.  Preflight checks were carried out and the aircraft was powered up. Once the home point had been recorded, the pilot completed final checks and throttled the aircraft up to take off.  Immediately on becoming airborne, the aircraft pitched forward and flew rapidly forwards for approximately 4 metres at high speed at a height of under 1m. It then appeared to brake of its own accord. Standard flight procedures involve initiating screen recording prior to take off so the incident was recorded on video. Additionally, the detailed flight logs have been examined and confirm that: a) the home point had been recorded; b) 20 satellites had been locked onto; and c) only the left stick (throttle) was moved by the pilot during this period. The pilot allowed the aircraft to stabilise and then immediately returned to the take off point and landed.

Playback of the screen recording suggests that in the 2 secs immediately prior to take off, the on-screen telemetry was showing a groundspeed of up to 1.5m/s, even though the aircraft was stationary. Because the pilot was carrying out airspace checks in this time, this anomaly was not apparent.

The latest firmware had been applied to the aircraft and controller 4 days earlier, and a total flight time of 90mins had been flown without issue.

Lessons learned: Pilots to confirm speed is registered as zero immediately before lifting and ensure no persons are within 5m of aircraft in any direction at take off / landing

Further Correspondence: There was some very helpful correspondence with the reporter that sheds additional light on what might have happened:

• Q. Were the vision sensors turned on? A. The vision sensors were on (by default)
• Q. What sort of levels of light were there? A. It was dusk, so low light levels.
• Q. If the sensors were switched on, what was the proximity activation distance set to? A. The warning distance was set to 15m, the braking distance was set to 2m.
• Q. How close was the pilot to the aircraft when it took off? A. The pilot was 6m away to the side of the drone.

Further analysis of the flight logs shows a ‘horizontal speed’ of between 1 and 3m/s being logged, even though the aircraft was stationary on the ground, in the seconds immediately before lifting off. The indicated direction of travel was backwards from the lat/long readings. The on-screen display and audio confirmed 20 GPS satellites and home position recorded, leading the pilot to conclude it was safe to take off.

My current working theory looking at the flight log data is that immediately on lifting off, the aircraft believed it was moving backwards, horizontally due to an inconsistent GPS signal. There was a wall approximately 6m behind take off point and so the obstacle avoidance system activated immediately and caused the aircraft to ‘brake’ by pitching heavily forwards. This can be seen in the 25 degree pitch recorded in the flight logs with no pilot input. The physical result was the drone moving rapidly forwards for around 4 metres.

Our pilots have been given extra guidance as follows:

• Ensure (as per the manufactures recommendations for the M30T) that no persons (including the pilot) are within 5m of the aircraft at take-off and landing.
• When taking off in the vicinity of obstacles within range of the obstacle avoidance system, extra care should be taken.
• A final check, immediately prior to taking off, should be carried out to confirm that sufficient GPS satellites are still available and the indicated speed is 0.0m/s

The pilot has logged over 200 flights on the M30T aircraft.

From AAIB report No AAIB-29203. A swarm of 638 UAs took off as part of a planned test of a light display. The preprogramed launch and animation flight were completed without incident. As the UAs switched to ‘return to home’ mode they returned to their grid positions. Several UAs then flew out of formation, before the pilot sent an emergency hold command to which the fleet responded, and all UAs held their position. A manual ‘return to home’ command was sent and the UAs returned to their grid formation. When the swarm began to descend the same UAs again flew out of formation. The swarm was then landed in altitude order, due to concerns about battery endurance. All UAs stayed within the planned geofence. Three UAs sustained broken arms and there were several chipped propellers. An investigation by the operator determined that deviations from the planned flight route were caused by flat batteries in the controller unit, which had been left switched on when stored.

Lessons learned: The Operator has introduced a new procedure to remove all batteries when not in use.

At CHIRP we are in touch with several other Human Factor reporting entities, including NASA and their Aviation Safety Reporting System (ASRS) who perform the confidential reporting function in the United States. We are grateful for their permission to reproduce below an HF occurrence that was reported to them in October of 2023 as report ACN: 2951851. I have summarised the report below, but for those that are interested to see the whole report and the level of detail NASA manage to get reporters to fill out, follow this link to the site: https://asrs.arc.nasa.gov/search/database.html. To find drone related reports within their online database choose Federal Aviation Regs (FAR) and select: Part 107 or Public Aircraft Operations (UAS) or Recreational Operations / Section 44809 (UAS).

I was operating my UAS on a mapping mission with a base station for RTK (Real-Time Kinematic Positioning) corrections. I was running an automated mapping mission using the KMZ file using the app. This was my first operation of the KMZ file as opposed to a KML file. As per the KMZ file, I was having the mission fly to remain no more than 400 feet AGL to the terrain, and in order to maintain a visual line of sight I would move throughout the hilled/undeveloped area in order to maintain VLOS.

I would have to remove the cap on the application in order to allow the drone to fly the 400 feet AGL over the hilled areas. This mission became lengthy as I would return to the home start point, move a few hundred feet to a good vantage point that would keep a VLOS, then start the drone and move with it. I would then have to return the drone to home and I came along with it, which proved to be fatiguing. Part of this fatigue was caused by me being hypervigilant to the nearby airport, as there were airplanes practicing landings/touch and goes, (across the highway, but still close by) and I wanted to ensure no airplanes were moving towards the south (towards me).

Towards the end of the mission, the drone began the return to home. During this the drone began to rise to 1000 ft. I was keeping visual line of sight directly and realized it was becoming increasingly difficult to see. I looked at the remote and realized it was at 1000 ft AGL. I then ceased the operation and took manual control and brought the drone down as quickly as possible. Upon investigating the issue, I soon realized that because I set the return to home safely at 1000 feet, the drone automatically went to that height. My error was not setting it at the 400 feet that I normally set it to. I set the max altitude in the application to 1000 feet, in order to move along the hillsides. (this height would only happen in relation to the altitude). This was also my first operation in a hilled/varying terrain area which added another layer of difficulty. I mostly run mapping missions on smaller flatter terrain.

Lessons learned: For future flights with varying terrain areas, I will set the return to home altitude no more than 250 feet, which is one of the highest points in the area above my start point. I will also manually fly the drone home at a much lower altitude instead of letting the drone automate itself for a return to home when it comes to unfamiliar sites or varying terrain sites.

From AAIB record-only UAS investigations reviewed October to November 2023, published within AAIB Bulletin: 1/2024. The remote pilot had planned a series of automated mapping missions. On the third day of conducting this mission, the UA lost real time kinematic signal which caused the UA to pause during a turn away from a wind turbine. The remote pilot resumed the flight and the UA initially reversed along its previous flight path, flying into the wind turbine. The remote pilot was not aware the turbine had the ability to rotate 360° around its vertical axis. This required a larger area to avoid for the UA to maintain 50m clear of the turbine in all positions, which was not taken into account when planning. The UA sustained significant damage and was replaced. There was no visible damage to the wind turbine.

Performing Beyond Visual Line of Sight (BVLOS) flights with visual mitigation (observers positioned out along the flightline who are in touch with each other and the pilot) for the purpose of data capture, we flew through cabling between two pylons a total of 4 times and only noticed they were there when looking at the photographs after the flights. The pylons were obscured from the TOAL site because we were in a cutting. We had previously flown an adjoining section of the same infrastructure in the opposite direction and the pylons at the end point of the two sections were obscured from the TOAL at both ends of each section, even if the aircraft always remained VLOS. The electricity cables were across the infrastructure rather than parallel with it. This meant they were much more difficult to see. The first photo I attach is a general view from aircraft. The pilots were located on the right-hand side, away from the track. There was little visibility of the cables that were across the track and the pylons were obscured from view. The previous flight was flown towards the road bridge, from the far end. The cables were between 30 and 45m high and crossed over this side of the road bridge. The second photo is an approximately 11X zoomed picture looking under the road bridge.

Lessons learned: When checking for electric cables, it is not sufficient to just look for pylons alone. Electric cables are difficult to see and the site inspection should include the start and end point.