UAV, Bergen, Norway, 2022
UAV, Bergen, Norway, 2022
Summary
On 26 August 2022, an experienced UAV pilot lost control of a DJI Mavic 3 in central Bergen and it flew at high speed towards a building. The UAV crashed through a third-floor window, slightly injuring a person inside. Why control was lost could not be established, but it appeared to be associated with a fault in the transition between two flight modes. The absence of adequate and timely technical assistance from the UAV manufacturer - which had a European import approval for it - limited the ability to establish the cause of the event, prompting three related safety recommendations.
General
Tag(s)
Root Cause Not Determined,
Unmanned Aircraft Involved
LOC
Tag(s)
Significant Systems or Systems Control Failure
AW
System(s)
Navigation
Outcome
Damage or injury
Yes
Aircraft damage
Major
Non-aircraft damage
Yes
Non-occupant Casualties
No
Off Airport Landing
No
Ditching
No
Causal Factor Group(s)
Group(s)
Aircraft Technical
Safety Recommendation(s)
Group(s)
Aircraft Operation
Aircraft Airworthiness
Investigation Type
Type
Independent
Description
On 26 August 2022, the pilot of a DJI Mavic 3 UAV operated by TV 2 Luftfoto for proficiency prior to covering part of a triathlon competition over Bergen harbour the following day lost control of it in daytime visual conditions (VMC). After it initially performed normally and remained in sight, control of the UAV was lost. After initially moving slowly at the previously controlled height, it suddenly increased speed and tracked towards a harbourside building. The UAV crashed through a triple-glazed third floor window into a room where people were having lunch, one of whom was slightly injured. A colleague of the pilot who was simultaneously operating a DJI Air2S UAV nearby did not experience any similar loss of control.
Investigation
A non-mandatory investigation was carried out by the Norwegian Safety Investigation Authority. The operator had been using the UAV that was the subject of the Investigation for about 10 months, and around 1,130 hours of use had been logged in that time. It was found that although generally experienced in UAV operations, the pilot’s recency was poor. He had recorded just under three hours flown in the 90 days prior to the event and only 5½ hours since the beginning of 2022. The UAV weighed just under 1 kg, had a maximum speed of 37 knots and could be flown in wind speeds of up to 23 knots. It had three operating modes - ‘Normal’ (also known as P-GPS), ‘Tripod’ and ‘Sport’. If satellite signal strength goes below the level which facilitates stabilised flight, it reverts to ‘Attitude’ (ATTI) mode, which means the drone will maintain its orientation, but the stabilisation algorithm will not keep the drone hovering in place. The drone will thus "float" on the wind.
The UAV ground track until control was lost (the return track was the same but continued into the building behind). [Reproduced from the Official Report]
What Happened
With the optical collision avoidance system disabled to avoid interference with the camera and in good visibility and light or calm wind, the UAV was flown over the harbour to check whether flying conditions had changed since a training flight two days earlier. The UAV was positioned about 10–15 metres away over the harbour at a height of around 70 feet, and a colleague then launched a DJI Air2S UAV and positioned nearby. Almost immediately, the DJI Mavic 3 UAV began to move autonomously towards a harbourside building near the pilot’s position. Control was attempted but not achievable despite the remote controller not displaying any indication of faulty communication between the controller and the drone.
The pilot subsequently stated that when control was lost, the UAV initially moved slowly but then accelerated to a speed he considered similar to that achievable in ‘Sport’ mode. Having seen that there were people in the street between the drone’s position and the building it was heading towards, he decided not to cut power to the motors because of the risk of personal injury. The UAV then flew into a window, which broke and continued inside to a terminal impact. Following the event, the operator immediately notified the NSIA and grounded all its UAVs with a weight of over 250 grammes.
The broken window after the UAV entered the building. [Reproduced from the Official Report]
UAV Ancillary Information
It was noted that communication between the UAV and its pilot used the frequency 5.8 GHz and that other signals using this frequency in the vicinity are liable to cause interference. The pilot-specified ‘Failsafe Return To Home’ (FRTH) feature of the UAV can automatically take control of the UAV if communication between the pilot and the UAV is lost. It was set prior to the flight to return at an altitude equivalent to 328 feet.
It was also noted that the UAV model involved and its control and operating systems had been declared as ‘CE’ compliant, which required that it meet a series of EU Directives covering Radio Equipment, Hazardous Substances, Waste from Electrical and Electronic Equipment and the Registration, Evaluation, Authorisation and Restriction of Chemicals.
Why It Happened
Actual wind velocity information from the vicinity where control was lost was obtained from the flight record of the operator’s other UAV positioned near to the loss of control point. This was because the UAV did not record sufficient wind data before it crashed. This data showed that during both its controlled and uncontrolled flight, the wind at a height of around 50 feet had been north westerly at 7-9 knots.
The UAV manufacturer analysed the flight data record from the UAV and concluded that loss of a useable GPS signal had occurred, and although it initially switched to ATTI mode, it had subsequently obtained a sufficiently strong signal to switch to Tripod mode. However, the signal received was not strong enough to enable this mode to work but strong enough to prevent a switch back to ATTI mode.
Norwegian UAV Regulatory Issues
Regulation of UAV operations was confirmed by the European Union Aviation Safety Agency to be a State responsibility outside its jurisdiction with the Norwegian CAA, in its capacity as the ‘State Marked Surveillance Authority’ responsible for aviation products in an EEA State in accordance with Regulation EU 2019/947. Although this responsibility included a responsibility to “propose actions if a product does not comply with applicable requirements from the regulation." However, the Norwegian CAA in its capacity of Marked Surveillance Authority stated to the NSIA that they “do not have the capability to perform an investigation needed to pursue and resolve the findings of this report."
Key Findings from the Investigation
- The pilot involved was qualified to fly the UAV.
- The investigated flight was not in compliance with the applicable regulations for its UAV category.
- The UAV stopped responding to input from its pilot.
- One person sustained minor injuries as a result.
- It is unlikely that the UAV was jammed or that someone else took over control.
- It is probable that the UAV had a flaw that caused it to switch from Attitude mode (a default mode if contact with GPS positioning satellite is lost) to Tripod mode (one of three normal operating modes) without verifying that it had a regained sufficient GPS signal strength for safe flight.
Related Occurrences
It was noted that previous investigations into malfunctioning DJI UAVs carried out by two other European Safety Investigation Agencies had resulted recommendations to DJI in respect of support for such investigations but similar problems had been encountered in the NSIA Investigation:
- In 2021, the UK AAIB investigated a UAV event in Scotland which, albeit in occurred in unrelated circumstances with unrelated consequences, resulted in a Safety Recommendation that “DJI should introduce an effective system for providing timely technical information to support State Safety Investigations”.
- In 2023, the Dutch Safety Board investigated a loss of control event with similar third party risks to the current event which resulted in a Safety Recommendation that DJI “should ensure Safety Investigation Authorities and operators are provided with timely technical support and relevant information for the purpose of safety investigation regarding UAS manufactured by DJI".
Three Safety Recommendations were made based on the findings of the Investigation as follows:
- that the European Commission implement legislation where all manufacturers of unmanned aircraft systems can be subject to sanctions for failing to support safety investigations regardless of the category where the unmanned aircraft system was operated. [Aviation No 2024/04T]
- that the European Commission mandate an authority to conduct a technical review of DJI’s unmanned aircraft systems in which DJI present documentation (to show that) their systems maintain the expected aviation safety standard. [Aviation No 2024/05T]
- that the CAA Norway inform users of DJI Mavic 3 UAVs in Norwegian airspace about (the identified) design flaw which can result in losing control of the drone after it switches out of ATTI mode. [Aviation No 2024/06T]
The Final Report was completed on 14 May 2024 and published online the following day.
