DUAS29

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.