A surveying drone struck the top of a tower crane at a construction site in the Cheetham Hill area of Manchester, according to the latest bulletin from the Air Accidents Investigation Branch.
The incident occurred in August. It was notified to the AAIB, but no formal investigation was launched, and neither the site nor the contractor was identified in the 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 obstacle-avoidance feature was enabled, but the aircraft still hit the top of the crane and fell 120 m to the ground.
An internal investigation by the construction company found that the company and its remote pilots may not have fully understood the limitations of the obstacle-avoidance software, according to the bulletin.
The account points to a gap between the presence of an automated safety function and the operators’ understanding of what it can reliably detect and avoid. It does not establish why the system did not prevent the collision, and the AAIB bulletin does not identify the equipment or the operating arrangements beyond the details above.
Because no formal probe was opened and the site and contractor were not named, the bulletin provides a limited public record of the event. The 120 m fall and the strike on the crane top are the principal technical details disclosed, alongside the company’s internal finding about possible limits in operator knowledge.