Air accident investigators believe a modification to a bar unit on a passenger jet may have been responsible for a fire in electrical wiring which forced the crew to make an emergency landing.
A preliminary report into the serious incident on board a Virgin Atlantic Airbus A340 en route from Heathrow to Chicago last month was published today. There were 143 passengers and 13 crew on board when the rescue services responded to a full-scale emergency on January 11th last.
The aircraft made an emergency landing at Shannon airport after the crew reported a small fire in the bottom of a waste bin storage compartment of the bar unit in the first class section of the plane. Virgin Atlantic said at the time there had been no fire on board.
The fire was located in a hole in the floor of the compartment, the report by the Air Accident Investigation Unit (AAIU) said today.
Cabin crew noted that a damaged electric cable loom appeared to be sticking out of the hole and there was ‘arcing’ in the hole – a phenomenon that can result from an electrical fault.
The cockpit crew turned off power circuits, but the fire and arcing persisted, the report said.
“The captain declared an emergency and diverted to Shannon, where the aircraft landed safety some 30 minutes later.”
As the plane diverted, five 1kg fire extinguishers were used by the cabin crew in efforts to stop the fire. These subdued the flames but the arcing persisted. After each application, the fire restarted after about five minutes.
The flames were not large but were described by witnesses as “licks of flame”.
After landing, the airport fire service tackled the fire with a 5kg extinguisher, but a glow continued to be observed at the bottom of the hole, the accident report said.
Fire chiefs discussed the situation with the crew and the aircraft was powered down. The glow then disappeared and no further arcing was observed.
Investigators found the cable loom in the bottom of the waste bin compartment had been “completely severed” and bore “strong evidence of burning/arcing”.
The wiring loom in question consisted of 10 wires in a protective sheath and was used to provide power and dimming circuits for “mood” lighting in the bar unit counter top.
It appeared the lower edge of the metal waste bin made contact with the wiring loom.
Investigators said there was “no evidence” of a protective metal cover and rails that should have been present to keep the bin above the wiring loom.
“Initial inspection indicated the possibility that they were never fitted,” the report said.
The bar unit itself was a modification, specific to Virgin aircraft. It was installed three years ago, seven years after the aircraft was manufactured.
Investigators said a fleet inspection of Virgin’s A340-300 and A340-600 aircraft found that a number of them also had problems relating to missing covers, rail screws and cable routing in this area.
Damage to the same wiring loom was found on one other aircaft.
The AAIU report said a similar bar is installed in Virgin’s Boeing 747-400 fleet, but the same potential for cable damage did not arise in that aircraft.
“While the cause of the wiring damage to this aircraft has been determined, significant other issues are being examined by the investigation.
These include the difficulties faced by the crew in isolating the damaged circuits, the emergency checklist, the design of the modification and the standards relating to such modifications,” the report stated.
The investigation is ongoing and a final report will be published by investigators in due course.
Virgin Atlantic said it immediately launched an investigation and a thorough inspection of its aircraft in full co-operation with the AAIU after the incident.
“A few minor issues were found and were immediately rectified,” said a spokesman.
“The installation of the bar was carried out in accordance with all relevant regulations. Virgin Atlantic continues to assist the AAIU in their investigation and looks forward to the full report with interest.”
Additional reporting: PA
A Virgin Airbus A340
Investigators in Ireland have found wiring problems in several Virgin Atlantic Airbus A340s as part of their investigation into a fire on board one such aircraft that was forced to divert to Shannon Airport. 

The Virgin jet was headed from London Heathrow Airport to Chicago with 143 passengers and thirteen crew on January 11 this year. A small fire was noticed in a waste bin storage area in the first class section's bar unit.

A damaged wiring loom could be seen sticking out of a hole in the compartments floor, and there was visible electrical arcing in the area. An attempt was made to control the situation by switching off electrical circuits, but both the fire and the arcing continued unchecked.

The aircraft's captain declared an emergency and diverted to Shannon, which the airliner reached thirty minutes later. During that time, the crew used five 1kg fire extinguishers upon the fire, but each time the arcing continued and after about five minutes the fire reignited. Witnesses described the fire as consisting of “licks of flame”.

After performing a safe emergency landing the airport's Aircraft Rescue and Firefighting department tackled the fire with a 5kg extinguisher but met with similar results. After consulting with the crew the jet's power was completely shut down, after which the fire was finally put out. Virgin initially claimed the fire had never occurred.

Investigators with Ireland's Air Accident Investigation Unit (AAIU) inspected the loom and found it to be “completely severed” and exhibiting “strong evidence of burning/arcing” according to a preliminary report released on Friday. The loom was identified as providing power and dimming circuits for mood lighting in the bar.

The AAIU says that it seems the loom had contacted the metal waste bin in the compartment above. There should have been rails to hold up the bin and a protective metal cover, but “no evidence” of these was found and the report notes that “Initial inspection indicated the possibility that they were never fitted.”

The bar unit is a modification exclusive to Virgin. The AAIU ordered all 36 of the airline's A340s worldwide inspected, with both France and the United Kingdom assisting with this. The UK has identified four other aircraft with faulty wiring, it has now been revealed. Virgin says that “A few minor issues were found and were immediately rectified,” and adds that “The installation of the bar was carried out in accordance with all relevant regulations. Virgin Atlantic continues to assist the AAIU in their investigation and looks forward to the full report with interest.”

The AAIU says that "significant other issues are being examined by the investigation" in addition to the wiring defects. “These include the difficulties faced by the crew in isolating the damaged circuits, the emergency checklist, the design of the modification and the standards relating to such modifications,” said the report.

Virgin's Boeing 747-400 fleet also has a similar bar installed on it, but there was not considered to be a risk to the aircraft's wiring on that model. The fire involved a bar added three years ago, with the aircraft manufactured in 1998.