A surveying drone struck the top of a tower crane at a construction site in Manchester before falling 120 metres to the ground, according to the Air Accidents Investigation Branch. The incident happened in August at a site in the Cheetham Hill area of the city.
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, but it still hit the top of the crane and fell.
The incident was notified to the AAIB, but no formal investigation was launched. The site and the contractor were not identified in the bulletin.
The construction company carried out an internal investigation. It found that the company and its remote pilots may not have fully understood the limitations of the obstacle avoidance software, according to the AAIB bulletin.
The case highlights a practical safety issue for drone surveys near tall structures: an automated avoidance function is not a guarantee that an aircraft will detect and avoid every obstacle in a complex urban site. The bulletin records the sequence of events but does not set out any regulatory findings or enforcement action.