What happened
On 24 April 2020, a Yuneable H520 was conducting emergency services operations in Hove, East Sussex. Following an initial flight, the pilot replaced the battery with a fully charged unit and verified it was secure before departing again. During the second flight, while the drone was hovering at approximately 15 metres above the ground, the onboard LEDs began to flicker. Although no warnings appeared on the controller, the pilot observed a second flicker and attempted to return to the landing site for inspections. During a third flicker, the aircraft experienced a sudden loss of power to its six electric motors and fell to the ground. The impact resulted in substantial damage, including broken landing legs and cracks to the aircraft body, camera casing, and battery.
The investigation
The investigation examined flight logs, including ULog and TLog data, and involved an analysis by the manufacturer. Data from the aircraft's internal storage confirmed that the flight log ended abruptly 34 seconds into the mission. At the moment of power loss, the battery's state of charge was recorded at 97.7%. Analysis of the final five seconds of flight showed the aircraft was moving forward at 1 m/s while experiencing significant oscillations in pitch and roll. The manufacturer's review of the hardware and the physical damage to the battery suggested that the battery may have been partially protruding from its housing at the time of impact.
Findings
- The aircraft was operating in turbulent wind conditions.
- The sudden loss of power despite a high battery charge level was consistent with a physical disconnection of the power source.
- The battery became loose and disconnected during flight, likely due to the mechanical stress of turbulent conditions.
- The flickering LEDs observed by the pilot were likely caused by intermittent contact between the battery terminals.
Safety action
- The manufacturer has stated that future iterations of the Yuneable H520 will incorporate software logic to prevent takeoff if the battery clip is not detected as securely engaged.