US experts join team checking jet at centre of grounding crisis

US safety experts and Boeing inspectors have joined a Japanese investigation into the 787 jet at the centre of a worldwide grounding of the technologically-advanced aircraft.

Japanese TV footage showed the American investigators – one each from the Federal Aviation Administration and the National Transportation Safety Board and two from Boeing – inspecting the All Nippon Airways(ANA) jet at Takamatsu airport in western Japan.

The investigation is being led by the Japan Transport Safety Board.

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The pilot of the ANA plane made an emergency landing on Wednesday morning after he smelled something burning and received a cockpit warning of battery problems. All passengers evacuated the plane on emergency slides.

In another incident on January 7, it took firefighters 40 minutes to put out a blaze in an auxiliary power unit of a Japan Airlines 787. The plane was empty of passengers shortly after landing at Boston’s Logan International Airport.

An inspection of the ANA 787 that made the emergency landing in western Japan found that electrolytes, a flammable battery fluid, had leaked from the plane’s main lithium-ion battery. Investigators found burn marks around the damage. Transport ministry investigator Hideyo Kosugi said the liquid leaked through the electrical room floor to the outside of the aircraft.

The release of battery fluid is especially concerning, safety experts have said. The fluid is extremely corrosive, which means it can quickly damage electrical wiring and components.

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The 787 relies far more than any other airliner in operation on electrical systems to function.

The electrolyte fluid also conducts electricity, so as it spreads it can cause short-circuits and ignite fires. Its corrosiveness also raises concern about whether a leak might weaken a key support structure of the plane, even though the 787 is the first airliner to be made primarily from lightweight composite materials that are less susceptible to corrosion than aluminium, safety experts said.

Known as the Dreamliner, the 787 is Boeing’s newest jet, and the company is counting heavily on its success. Since its launch after delays of more than three years, the plane has been plagued by a series of problems including a battery fire and fuel leaks.

Worries over potential fire risks from lithium ion batteries, with their well-known flammability, predate the launch of the 787. In a May 2011 report, the FAA outlined various improvements in containing and preventing onboard fires but also noted that electrolyte leaks could make a fire more hazardous due to the high energy density and power capacity of such batteries.

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The FAA had issued special precautions for installation of such batteries on board the 787s.

Boeing said it was working around the clock with investigators.

“We are confident the 787 is safe, and we stand behind its overall integrity,” Jim McNerney, company president and chief executive said in a statement this week.

GS Yuasa, the maker of the lithium-ion batteries used in the 787s, said it was helping with the investigation but the cause of the problem was unclear.

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The FAA has required US carriers to stop flying 787s until the batteries are demonstrated to be safe. United Airlines has six of the jets and is the only US carrier flying the model.

Aviation authorities in other countries usually follow the lead of the country where the manufacturer is based. On Thursday the European Aviation Safety Agency ordered all European carriers to ground the jetliner. The Indian government ordered Air India to ground its fleet of six Boeing 787s, and Ethiopian Airlines grounded its four 787s “for precautionary inspection”.