What happened
On 11 September 2016, an Airbus A320, registration F-HBNK, was parked at Bastia Poretta airport for ground operations. After the aircraft had come to a halt and the engines were shut down, a ramp agent began the process of securing the aircraft and connecting ground support equipment. After positioning the chocks, the agent proceeded to connect a Ground Power Unit (GPU) to the aircraft.
While attempting to connect the power cable, the agent found the cable tangled and requested assistance from a colleague to untangle it. As the agent connected the ground power connector to the aircraft's receptacle, an explosion occurred. Witnesses observed an electrical arc approximately 30 cm in size. The force of the blast threw the ramp agent to the ground. The connector remained attached to the aircraft following the event.
The investigation
The investigation focused on the condition of the GPU, the power cable, and the connection procedure. Technical examinations of the GPU's control panel and electronic components, including the Generator Control Module, revealed no functional malfunctions. The unit operated normally when tested with a different connector.
However, a physical examination of the ground power connector revealed a short circuit between the three phases inside the connector itself, which had caused the copper to fuse. Investigators also found that the insulating sheath was missing from the ends of the four cables where they met the metal pins. The investigation also looked into the sequence of operations, noting that the electrical supply was likely activated at the same moment the connector was being inserted into the aircraft.
Findings
- The primary cause of the short circuit was the absence of insulating sheath on the cable ends at the connector pins, likely caused by mechanical damage from repeated pulling on the cables or a previous ground incident involving the GPU.
- The electrical arc occurred because the three-phase power was present in the connector at the moment of connection.
- The investigation could not definitively determine who activated the power switch, but the mechanical action of setting the switch to the "CLOSE" position appeared to occur simultaneously with the physical connection of the plug.
- The ramp agent sustained injuries to his right ear and left thigh due to the explosion and the subsequent fall; notably, his gloves did not provide electrical protection.