A survey 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, the Air Accidents Investigation Branch (AAIB) said in its latest bulletin. The incident took place in August.
According to the bulletin, the unmanned aircraft was carrying out an aerial survey over a construction site in an urban area. It was following a pre-selected flight path.
The AAIB said the drone’s obstacle-avoidance feature was enabled at the time, but the aircraft still hit the top of the crane. It then fell 120 m to the ground.
The incident was reported to the AAIB, but no formal investigation was launched. The bulletin did not identify the site or the contractor involved.
The construction company carried out an internal investigation, which 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 bulletin account indicates that enabling the avoidance function did not prevent the drone from striking the crane in this urban survey flight. The internal review also points to a possible gap in understanding, while the AAIB has not opened a formal investigation.