Engineering news
Japan's All Nippon Airways has said that it replaced lithium-ion batteries on its Boeing 787 Dreamliners 10 times before a battery overheating incident led to the worldwide grounding of the high-tech jets.
Spokeswoman Megumi Tezuka said the airline was not required to report the battery swapping cases to Japan's transport ministry because they did not raise safety concerns or interfere with flights. Boeing was informed.
She said the batteries were replaced because they failed to charge properly or showed other problems.
All 50 of the Boeing 787s in use around the world were grounded after an All Nippon Airways flight on 16 January made an emergency landing in Japan when its main battery overheated.
Earlier, a battery in a Japan Airlines 787 caught fire while parked at Boston's Logan International Airport.
Lithium-ion batteries are prone to overheating and require additional safeguards to prevent fires.
Laura Brown, a spokeswoman for the US Federal Aviation Administration, said in Washington that the agency was checking whether the previous battery incidents had been reported by Boeing.
Japanese and US investigators looking into the Boeing 787's battery problems shifted their attention this week from the battery-maker, GS Yuasa of Kyoto, Japan, to the manufacturer of a monitoring system. That company, Kanto Aircraft Instrument Co, makes a system that monitors voltage, charging and temperature of the lithium-ion batteries.
The US National Transportation Safety Board is conducting a chemical analysis of internal short-circuiting and thermal damage of the battery that caught fire in Boston.
The probe is also analysing data from flight recorders on the aircraft, the board said on its website.