A surveying drone struck the top of a tower crane at a construction site in the Cheetham Hill area of Manchester in August, then fell 120 m to the ground, according to the Air Accidents Investigation Branch. The incident was notified to the AAIB, but no formal investigation was launched, and neither the site nor the contractor was identified.
Bulletin account
The AAIB's latest bulletin says 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, the bulletin says, but the drone still struck the top of the crane. It then fell 120 m.
Company review
According to the bulletin, an internal investigation by the construction company found that the company and its remote pilots might not have had a full understanding of the avoidance software's limitations. The bulletin attributes that finding to the company's review and presents it as a possibility, not a confirmed cause.
Reporting status
The case was reported to the AAIB, which did not open a formal probe. The bulletin gives an account of the event and the company's internal finding, but it does not identify the site or the contractor involved. It provides the bulletin's account rather than the conclusions of a formal investigation.