What happened
On 22 May 2018, a DJI Phantom 3 Pro was being operated for commercial photography at Railworld, Peterborough. The mission involved capturing images of a local tourist attraction using the aircraft's integrated gimbal camera. Following a standard pre-flight inspection of the propellers and airframe, the pilot initiated a takeoff.
As the unmanned aircraft reached an altitude of roughly 10 to 15 feet, the pilot noted an unusual noise, which was initially perceived to be wind. Shortly thereafter, a second instance of the noise occurred, followed by a rapid descent. The aircraft struck the ground with significant force, resulting in the destruction of the aircraft. During the impact, the battery and camera became detached from the main body. There were no injuries and no damage to third-party property.
The investigation
Investigators examined the wreckage and discovered that one of the electric motors, along with its propeller and mounting screws, had detached from the airframe and could not be located. A detailed inspection of the remaining structure revealed that the attachment points for the motor had suffered from multiple cracks. These cracks had eventually merged, causing the motor mounting bosses to separate from the primary structure.
Further research into the manufacturer's user community revealed that structural cracking at these specific points was a known issue among users, with a 2015 survey indicating that approximately 30% of respondents had experienced similar cracking during normal flight operations without prior impacts. The investigation also noted that while third-party reinforcement kits exist, they are not manufacturer-endorsed.
Findings
- The primary cause of the accident was the structural failure of the motor mounting points.
- Multiple cracks in the airframe around the motor attachment area amalgamated, leading to the detachment of the motor.
- The manufacturer's user manual does not mandate specific structural inspections of these critical areas during pre-flight procedures, only recommending inspections following a crash.
- The loss of the motor during flight led to the immediate loss of control and subsequent ground impact.