What happened
On 29 January 2019, a DJI Matrice 210 was engaged in aerial work as part of a police-led search for a missing person near Little Hulton, Manchester. The flight took place under overcast conditions with light snow and winds between 8 and 10 mph.
Following several successful sorties, the aircraft was performing its final flight of the mission. At approximately 1,000 feet from the operator and at an altitude of roughly 250 to 300 feet AGL, the pilot attempted to return the aircraft to the launch point. As the drone approached within 400 feet of the operator, it suddenly entered a rapid, tight spiral descent. The pilot noted that the propulsion motors sounded significantly louder and were spinning at a higher speed than usual, yet no error messages appeared on the control screen, and the battery level remained at 40% during the descent.
The aircraft struck a small stream upside down, resulting in the drone being destroyed. The impact caused the landing gear to break, the batteries to detach, and the loss of almost all propeller blades.
The investigation
Investigators examined the flight data recorded by the unmanned air system. The manufacturer performed a technical analysis of the internal logs to determine the sequence of events leading to the loss of control.