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The crash of a professional drone near Raigmore Hospital, Inverness, sparked an Air Accidents Investigation Branch (AAIB) inquiry

By Philip Murray

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The drone after its second crash in November 2019.
The drone after its second crash in November 2019.

A PROFESSIONAL drone worth more than £5000 fell from the sky close to Raigmore Hospital – sparking an investigation by the Air Accidents Investigation Branch (AAIB).

The 6kg quadcopter, which had been kitted out to carry out aerial surveys, was some 100 metres in the air, and was scouting an area close to the hospital’s helipad, when its parachute suddenly deployed and it fell from the sky in September 2019. Four earlier flights that day had gone by without incident.

AAIB investigators said: “The aircraft motors stopped and the aircraft began to descend under the parachute, drifting in the prevailing light winds. The pilot and observer lost sight of the aircraft as it descended behind a tree line. It was subsequently found on the roof of a nearby house and had suffered substantial damage. The recorded flight time was one minute and six seconds.”

An AAIB investigation found no faults with the drone’s mechanisms, and ruled that its parachute likely deployed because screws securing it might have been loose and vibrations had shaken it free. The drone was otherwise found to be in full working order before the flight and had a nearly full battery at the time of the incident.

The drone was subsequently repaired by its manufacturer – DJI – but crashed again two months later while being used in Montrose, Angus. Before this crash the drone had registered a series of erroneous errors on its system. These included warnings that a propeller blade had fallen off – even though they all remained attached. The AAIB added that the flight logs had not been consistent with a quadcopter which was missing a blade, and labelled them “spurious”.

In its findings the AAIB said: “The first accident most likely occurred due to excessive vibration as a result of the parachute system not being securely attached to the airframe.

“The investigation was unable to establish the cause of the second accident.

“There were several warnings in the recorded aircraft’s flight log, but analysis of this data did not provide any insight into why the flight was abruptly terminated.

“However, the parachute manufacturer considered that the second event involved a valid activation of the parachute system in response to a total aircraft power failure.”

They continued: “In response to the first accident, the parachute manufacturer and the operator amended their respective procedures for securely attaching the parachute system to the aircraft.”

Investigators said it was not possible to say whether there were any links between the two crashes, and that it would be unable to make more informed findings “without additional information from the [drone] manufacturer, particularly about the meaning and validity of the warnings”.

They recommended that drone manufacturers launch a new system to provide “timely technical support” to those state agencies carrying out safety investigations.

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