Boeing faces new safety probe over battery fears

Joan Lowy and Joshua Freed

The US government should reassess its safety approval of the Boeing 787's lithium ion batteries, America's top accident investigator said, casting doubt on whether the airliner's troubles can be remedied quickly.

Switching to a different type of battery would add weight to the plane – and fuel efficiency is one of the 787's main selling points.

Boeing received permission yesterday to conduct test flights under limited circumstances with special safeguards – a critical step toward resolving the plane's troubles. The airliners have been grounded for the past three weeks.

The National Transportation Safety Board (NTSB) is investigating last month's battery fire in a Japan Airlines 787 Dreamliner while it was parked in Boston. The results so far contradict some of the assumptions that were made about the battery's safety at the time the system won government approval, said the board's chairwoman, Deborah Hersman.

The NTSB investigation shows the fire started with short-circuits in one of the battery's eight cells, she said. That created an uncontrolled chemical reaction known as 'thermal runaway', characterised by progressively hotter temperatures. That spread the short-circuiting to the rest of the cells and caused the fire, she said.

The findings are at odds with what Boeing told the Federal Aviation Administration when that agency was working to certify the company's newest and most technologically advanced plane for flight, Hersman said. Boeing said its testing showed that even when trying to induce short-circuiting, the condition and any fire were contained within a single cell, preventing thermal runaway and fire from spreading, she said.

Boeing's testing also showed the batteries were likely to cause smoke in only one in 10 million flight hours, she said. But the Boston fire was followed nine days later by a smoking battery in an All Nippon Airways plane that made an emergency landing in Japan. The 787 fleet has recorded less than 100,000 flight hours, Hersman noted.

Boeing issued a statement saying it is working to address questions about its testing and compliance with certifications requirements, "and we will not hesitate to make changes that lead to improved testing processes and products".

hnews@herald.ie