A drone used for an aerial survey struck the top of a tower crane at a construction site in the Cheetham Hill area of Manchester in August, then fell about 120 m to the ground, according to the Air Accidents Investigation Branch.
The AAIB said the unmanned aircraft was following a pre-selected flight path over an urban construction site. Its obstacle avoidance feature was enabled, but the drone still hit the crane.
The incident was notified to the AAIB, but no formal investigation was launched. The agency’s bulletin did not identify the construction site or the contractor involved.
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, the bulletin said.
The AAIB account does not explain why the avoidance function did not prevent the collision, or whether other factors played a role. It also gives no details of damage or injuries.
The case highlights a practical question for drone survey work near tall structures: how operators verify that automated obstacle avoidance is suited to the specific site, flight path and conditions. The company’s internal finding suggests that familiarity with the software’s limits is part of that operational checks.