A drone conducting an aerial survey struck the top of a tower crane at a construction site in the Cheetham Hill area of Manchester in August, according to an AAIB bulletin. The unmanned aircraft then fell about 120 m to the ground.
The flight was following a pre-selected route over the urban construction site. The AAIB said the drone’s obstacle-avoidance feature was enabled at the time of the collision.
No formal investigation
The incident was reported to the Air Accidents Investigation Branch. However, no formal investigation was opened, and the bulletin did not identify the site or the contractor involved.
An internal investigation by the construction company examined the circumstances. It concluded that the company and its remote pilots may not have fully understood the limitations of the obstacle-avoidance software, according to the AAIB bulletin.
Operational questions
The case highlights a gap between having an automated safety feature and understanding how it performs around complex structures. A pre-planned survey route over a construction site can bring an aircraft close to cranes and other tall equipment, while obstacle-avoidance systems may have operating limits that are not obvious to remote pilots.
The AAIB’s bulletin records the event and the company’s internal findings without a formal safety investigation. It does not provide further detail on the drone’s make or model, the software involved, or the conditions at the site. The site and contractor remain unidentified in the bulletin.