A surveying drone struck the top of a tower crane at a construction site in the Cheetham Hill area of Manchester and fell 120 m to the ground, according to the latest bulletin from the Air Accidents Investigation Branch (AAIB). The incident occurred in August.
The AAIB said the unmanned aircraft was carrying out an aerial survey using a pre-selected flight path over a construction site in an urban area. The drone's obstacle-avoidance feature was enabled at the time, but the aircraft still hit the top of the crane.
The incident was notified to the AAIB, but no formal investigation was launched. The site and the contractor were not identified in the bulletin.
Internal findings
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 AAIB bulletin.
The account highlights a gap between having an avoidance function switched on and understanding what it can reliably detect and avoid in a complex urban construction setting. The bulletin does not say what obstruction, flight-path condition or software limitation contributed to the collision.
The drone fell from the crane top to the ground after the impact. The AAIB bulletin provides no further detail on damage, injuries or regulatory action.