What happened
On 5 December 2022, a DJI Mavic 2 Enterprise Zoom was being operated for commercial purposes to conduct an aerial survey of a construction site in Garstang, Lancashire. The mission involved capturing imagery of the site's progress within agreed boundaries. During initial flight control checks at head height, the pilot noted that the battery level, which had started at 95%, dropped quickly to 88%.
Despite this initial fluctuation, the pilot proceeded with the flight, maintaining an altitude between 50 and 60 metres. During the operation, the aircraft issued a critically low battery notification and immediately initiated an automatic landing sequence. During this descent, the drone's flight behaviour became erratic, and the pilot lost the ability to maintain lateral control. The aircraft drifted toward houses under construction and eventually struck a site worker on the arm before falling into cement and hitting the ground. The uninvolved person sustained no injuries.
The investigation
Investigators examined the aircraft and its battery at an authorised repair facility. The battery, which had 43 recorded cycles, showed no physical defects and appeared to be seated correctly. Post-flight, the battery's internal indicator showed a charge between 50% and 75%, though the cause of the discrepancy between this reading and the in-flight readings could not be identified.
Analysis of the flight logs provided no data to explain the sudden loss of power or the erratic flight behaviour. The investigation also confirmed that the flight was planned in accordance with UK regulations, including the required safety distances from people and structures; however, the loss of control caused the aircraft to breach these safety margins.