What happened
On 18 January 1997, at approximately 0900 UTC, a B737-300, registration G-OBMD, was parked at Stand 33 at Dublin Airport for passenger disembarkation. During the process of unloading the 120 passengers on board, a ground maintenance engineer observed smoke and several flashes of flame originating from the connection point between the aircraft and the ground power lead.
Upon noticing the smoke and flames, the engineer alerted the aircraft captain and the onboard crew. Recognizing the potential for a serious fire, a member of the cabin crew initiated an emergency evacuation. Passengers exited the aircraft via the airbridge, the overwing emergency doors, and the rear passenger door using the evacuation slide. The evacuation was completed efficiently, and no injuries or damage to the aircraft were reported.
The investigation
The investigation focused on the ground power equipment located at Stand 33. The ground power lead, which is housed in a fixed pit, was removed and inspected by investigators. The examination revealed that one of the two bolts used to secure the ground power plug had shorted across two different phases (A and B phases).
Findings
- The electrical short circuit was caused by damage to the ground power plug, which had occurred after a vehicle drove over the plug while it was left on the ramp.
- When the ground power lead was connected to the aircraft and activated, the damaged bolt caused severe electrical arcing within the plug.
- This arcing produced the smoke and visible flames witnessed by the maintenance engineer.