What happened
In the early hours of 9 February 2024, a DJI Mavic 2 Enterprise Advanced was being operated for emergency services duties in Weybridge, Surrey. The flight, which took place at night, was the fourth deployment for this specific unmanned aircraft. As the pilot prepared for the descent phase of the mission, the aircraft suddenly lost power and fell to the ground. Flight data logs showed an abrupt cessation of recording while the aircraft was still airborne. Prior to this loss of power, the recorded battery health and remaining charge were sufficient for the intended flight. The aircraft and its battery pack landed some distance apart, with the battery still showing active power.
The investigation
Investigators examined the wreckage and found physical damage to the aircraft's body, legs, propellers, and the battery pack. Notably, the plastic latching mechanism on both the aircraft and the battery showed no signs of damage, suggesting that the battery did not detach due to the impact with the ground. While the pilot believed the battery had been installed correctly, they could not be certain.
An examination of the battery casing revealed a split, likely caused by the impact, but also showed evidence of swelling. Research indicated that batteries of this specific model can swell as they degrade, which can prevent them from sitting flush within the compartment. If the battery is not seated correctly, the locking mechanism may appear engaged even if the connection is insecure. The investigation noted that a swollen battery underside could impede the latching process.
Findings
- The loss of power was likely caused by the battery becoming detached during flight.
- The battery may not have been fully latched into position prior to takeoff.
- Evidence of swelling was found on the battery pack, a condition known to compromise secure retention in this model.
- The pilot was unable to definitively confirm the security of the battery installation during the pre-flight phase.