Description

On 15 March 2009, an Airbus A319-100 being operated by British Airways on a scheduled passenger flight from London Heathrow to Edinburgh experienced an electrical malfunction during the night pushback in normal ground visibility which blanked the Electronic Flight Instrument System displays following the second engine start and produced some electrical fumes but no smoke. The engines were shut down, a PAN was declared to ATC and the aircraft was towed back onto the gate where passengers disembarked normally via the airbridge.

Investigation

An Investigation was carried out by the UK AAIB. It was established that, following the selection of GEN 1 after the start of the second (left) engine the left hand PFD and ND blanked and corresponding electrical cautions were annuciated on the ECAM. When the appropriate reset drill was actioned, a loud noise was heard from behind the right hand flight deck CB panel accompanied by a slight smell of electrical burning.

The damage to AC Bus 1 was found to be most severe directly behind one particular CB where there was erosion of the busbar terminals and burning and distortion of the busbar insulation material. There was evidence of damage from arcing and of some dust deposits between phases on some of the AC Bus 1 exposed connections. It was apparrent that arcing and the associated fire had been short-lived, but that the fire had been "very intense with temperatures in excess of 1084°C". Two exposed terminals on AC Bus 1 had melted and there were ‘pin-like’ protrusions, which were products of the molten copper. A visual inspection of the unaffected wiring found it to be in a good condition and tests of the wiring did not show signs of degradation that could have caused the electrical faults or the fire. The remaining terminals and connections were found to be correctly installed and the examination did not reveal the presence of remaining foreign objects. All the affected CBs3 were tested and found to operate within their published specification.

The soot around the panel consisted of carbon, fluorine, copper and zinc, all of which were to be expected as the products of vaporised material from wiring insulation damage during the fire. Debris collected from around and below CB Panel consisted of molten materials that could be attributed to the materials used on the panel. Chloride levels in the dust were found to be high relative to “normal office dust”, which it was noted would increase its conductivity.

Despite the evidence of a significant electrical overheat in the area behind the right CB panel and the establishing of a potential sequence of events, the origin of the electrical fault and subsequent overheating could not be established. It was considered to be most likely due to the presence of a loose object, probably exacerbated by the presence of dust in the area.

Scheduled maintenance procedures were reviewed and it was noted that the enhanced requirements for the regular inspection of ‘Electrical Wiring Interconnection Systems’ (EWIS) on this aircraft type mandatory from March 2011 had been introduced at British Airways during he course of the investigation.

It was considered that these new EWIS inspection requirements and the associated training already highlighted the need for good housekeeping and cleanliness of electrical connection systems in aircraft and that its introduction into scheduled maintenance should reduce recurrence of electrical faults from foreign objects and debris. Therefore no Safety Recommendations were made.

The Final Report of the Investigation was published on 12 August 2010 and may be seen in full at SKYbrary bookshelf: AAIB Bulletin: 8/2010 EW/C2009/03/02

Further Reading

• Cabin Fumes from Non-Fire Sources
• Operational Fires
• Ageing Aircraft - Electrical Wiring
• Unidentified Fire On Board (OGHFA SE)
• Airworthiness - The System