Incident Overview
On 31 January 2011, at 10:45 p.m., a cabin crew member on an Airbus A380-800 flight from Hong Kong to Singapore heard a loud bang while in lavatory LM35. The lights went out and he noticed an electrical burning smell. He saw smoke emitting from the base of the wall panel under the sink and discharged a fire extinguisher into the area. The smoke cleared about 10 minutes later. The aircraft landed without further incident. No passengers or crew were injured.
Background
Earlier on the same day, during departure from Singapore, the Electronic Centralised Aircraft Monitoring system displayed an alert message "ELEC GEN 1 FAULT". The No.1 Variable Frequency Generator (VFG) was reset and the message cleared. In Hong Kong, the alert reappeared and could not be cleared. Engineering staff interchanged the No.1 Generator and Ground Power Control Unit (GGPCU) with the No.6 GGPCU (APU generator controller). A subsequent test was satisfactory, and the aircraft departed Hong Kong.
Damage to Aircraft
Post-landing inspection in Singapore revealed signs of burning at the feeder terminal block for the No.1 VFG, located in the forward cargo compartment below lavatory LM35. Feeder cable lugs were melted, and there was soot on surrounding components. Insulation blankets adjacent to the terminal block were burnt. The Lightning Protection Units (LPUs) connected to the terminal block showed signs of melting.
Investigation Findings
The Main Excitation Cable for the No.1 VFG was found to be degraded. The sheath and shielding of the cable and the insulation of the negative (blue) Main Excitation Wire were damaged. There was no heat or stress damage nearby, and no maintenance had been performed on that cable since aircraft delivery.
Probable Cause
The investigation concluded that a degraded Main Excitation Cable likely caused an over-voltage across the Lightning Protection Units attached to the feeder terminal block, resulting in a short circuit between the three-phase feeder cables and structural grounding. This short circuit caused excessive current to flow through the feeder cables, leading to overheating and damage. The operation of over-current protection limited the damage.
Subsequent Event
After repairs, the aircraft was released for flight on 20 February 2011. During take-off, the "ELEC GEN 1 FAULT" message reappeared at take-off power, causing the crew to abort the take-off and return to the bay. Further troubleshooting identified the degraded Main Excitation Cable.
Safety Actions
The operator conducted fleet inspections and updated operating procedures. The aircraft manufacturer addressed fast over-voltage protection and troubleshooting procedures.