According to a report by the Air Accidents Investigation Branch, on 20 December 2017, a 46-year-old commercial operator with 52 hours of experience was flying a DJI Matrice 210 near Albert Bartlett’s potato export facility on a routine training flight.
During the flight, the device – which can cost up to £10,000 – intermittently lost its connection with GPS satellites and the pilot changed modes to resolve the issue.
Shortly after, the operator began to bring the drone down for landing and noted that his controller was indicating 12 minutes of flight time remaining.
When it reached a height of 84 metres [275 feet], a ‘low-voltage battery warning’ began showing, all four of the drone’s electric motors stopped and it began rapidly losing altitude. The motors then restarted.
The report said: ‘The pilot tried to apply full power to arrest the descent but the unmanned aerial vehicle crashed into a field at “considerable speed”.’
The drone was then sent to its Chinese manufacturer, DJI, for repairs and to have its data – recorded from the flight – analysed.
According to DJI, despite the pilot receiving a low-voltage battery warning, the data revealed that the batteries had been charged up to 23.4 volts, 2.9 volts less than its maximum charge capacity and that there was sufficient power for continued flight.
The data also revealed anomalous measurements for one of its two batteries, which despite being used indicated 22.6 volts throughout the flight.
The report added: ‘The UAS manufacturer could not explain this anomaly but stated that it was aware of a battery firmware issue that results in actual battery levels being “ignored” and power to the motors being cut because the system considers the battery level too low.
‘The manufacturer issued a firmware update in January 2018 to address this issue.’
