A pilot carrying out a construction survey with an unmanned aerial vehicle collided with an unmapped crane, a report has found.
The Air Accidents Investigation Branch, which examines and produces reports on air accidents in the UK, has revealed that the UAV struck the crane as the pilot, who had previously flown the pre-programmed mission at the site, had not taken into account the addition of a new crane.
The 43-year-old pilot had planned the drone flight with four reference points above 400ft, higher than three existing cranes on the site. Following the safety visit, a new crane was erected and undetected by the pilot until their system collided with the jib.
The collision took place in June during a during a survey of a construction site in Kent using a 3DR Solo with a Go Pro Hero 4 camera mounted on a gimbal below the aircraft.
The report said: “The crane had not been at the site during the previous flight, and from where the pilot was situated in the car park it was difficult for him or his observer to tell that it was about to strike the crane because of a lack of perspective.”
The unmanned device fell to the ground and is reported to have been damaged but there was no damage to the construction site.
The report continued: “The pilot stated that the accident was caused by the incorrect programming of autonomous waypoint mission which had not taken into account the new crane at the site.
“He stated that future missions would be planned such that the UA ascended vertically to 400ft shortly after take-off, in a safe corridor, before surveying the site and would avoid intersecting the working radius of any of the cranes.
“He also decided to split the mission in two and to survey the southern boundary by taking off from a new position on the south side. This would avoid flying directly across the site and would afford him a better view of the UA’s relative location to the cranes.”
It is the fourth report by the Air Accidents Investigation Branch which investigates a drone-based collision.