A surveying drone struck the top of a tower crane at a construction site in the Cheetham Hill area of Manchester in August, then fell 120 metres to the ground, according to the Air Accidents Investigation Branch (AAIB).
The incident was reported to the AAIB, but no formal investigation was launched, and neither the site nor the contractor was identified. In its latest bulletin, the AAIB said the unmanned aircraft was carrying out an aerial survey on a pre-selected flight path over a construction site in an urban area.
The drone had its obstacle avoidance feature enabled, the bulletin said, yet it still hit the crane. The AAIB reported that an internal investigation by the construction company found the company and its remote pilots may not have fully understood the limitations of the obstacle avoidance software.
The account is limited to the bulletin's summary and the company's internal findings. It does not identify the drone operator, the equipment model or the extent of any damage on the ground. The bulletin places the flight in an urban setting and records the fall after impact, but gives no further details about the flight or the site. The AAIB's bulletin records the event and the internal conclusion without opening a formal probe.