History of the Flight
On 11 September 2016, an Airbus A320 registered F-HBNK operated by Air France arrived at Bastia Poretta (2B) for a commercial flight. After parking, a ramp agent positioned chocks and informed the crew via ground interphone. The crew released the parking brake. After checking stability, the ramp agent authorized ground equipment and jetways. He then approached the Ground Power Unit (GPU), whose diesel engine was already running. He picked up the connecting cable but found it tangled and asked a ground attendant for help. He connected the ground power connector to the aircraft. Witnesses heard an explosion, saw an electric arc of about 30 cm at the connector, and the ramp agent was thrown to the ground.
Injuries and Damage
The ramp agent sustained injuries to his right ear and left thigh from the explosion and subsequent fall. He did not have burn marks. The GPU connector remained connected to the aircraft. The ramp agent was quickly cared for by emergency services, and the GPU diesel engine was shut down.
GPU Description and Procedure
The GPU supplied three-phase 115 V 400 Hz power (and 28 VDC) via a connector. The procedure required starting the engine, waiting for stabilization, then connecting the connector. After connection, the operator returned to the GPU and held selector switch S10 in the spring-loaded CLOSE position to initiate power. The Generator Control Module (GCM) then authorized self-hold, lighting a lamp above S10. The operator released S10 to the intermediate ON position. The disconnection procedure required setting S10 to OFF before disconnecting.
Examinations
Selector switch S10 was found in the ON position. The control panel was closed and S13 was in AIRCRAFT OUTPUT. The engine start switch was OFF; the emergency stop was not actuated. Continuity and isolation tests of the GPU and GCM revealed no malfunctions; the GPU operated normally with another connector. Examination of the ground power connector showed a short circuit between the three phases, causing copper fusion in the phasings. No defects were found on the neutral. The insulating sheath was absent on the ends of the four cables (three phases and neutral). Pins E and F were in good condition. Tests on the aircraft's ground power receptacle and electrical panel showed no malfunctions; no subsequent issues were recorded.
Witness Accounts
A ground attendant confirmed helping untangle the cable and staying near it. He did not actuate S10. He mentioned that the day before, there was a small discharge when handling the powered connector, which he reported. A visual check of the connector after that incident showed nothing abnormal. After the explosion, the connector remained connected.
Similar Event
A similar occurrence on 15 April 2017 was reported: a ramp agent had difficulty connecting the connector, then asked a ground attendant to power it while his hand was on the cable, resulting in an electric arc and the agent being thrown to the ground. No anomalies were found on the GPU or aircraft.
Cause of the Short Circuit
The absence of insulating sheath on the ends of the phase cables was likely due to damage from repeated pulling on the cables or from a previous incident on 22 June 2016. This lack of insulation led to a short circuit between the three phases when power was supplied by simultaneously holding S10 in the CLOSE position while connecting the connector. The investigation could not determine who actuated S10.