What happened
On 4 February 2019, a DJI Matrice 100 was being operated for aerial work purposes as part of a search for a missing person. The mission involved inspecting a drainage system located in a field near Clough Road, Hull.
Following the completion of pre-flight checks, the pilot navigated the unmanned aircraft toward the search area situated over water. As the aircraft approached the surface, the onboard Collision Avoidance System activated, triggering an automated climb to move the drone away from the water. During this maneuver, the pilot was unable to adjust the flight path sufficiently to avoid obstacles. The aircraft struck branches overhanging the drainage system, which caused it to fall into the water. The impact and subsequent submersion resulted in water ingress and damage to the rotors.
The investigation
The investigation examined the flight sequence and the pilot's response to the automated safety features. It was established that the pilot had intentionally flown the aircraft in close proximity to both the water and the tree canopy to facilitate the search requirements. The investigation also reviewed the operational procedures and the risk assessment used for such missions.
Findings
- The pilot had decided to operate the aircraft at a low altitude near hazards to complete the search task.
- The pilot failed to correct the flight path in time to avoid overhanging branches after the collision avoidance system initiated a climb.
Safety action
- The operating organisation has updated its risk assessment for similar search operations, now mandating that flights must not take place at an altitude below 10 metres when operating over water.