Japan Airlines Co.’s fuel leak on a Boeing Co. 787 plane at Boston last month was probably caused by a foreign object that caused a valve to temporarily open.
Either a valve to prevent fuel flowing backward in the left tank, or a valve between the main and left tanks was temporarily open, causing the overflow, Japan’s transport ministry said in a statement today.
The ministry said checks should be made on the central pump to prevent a similar problem happening again, according to the statement. About 40 gallons of fuel spilled onto the ground from a Japan Airlines 787 when it was taxiing for takeoff at Logan International Airport on Jan. 8.
“We estimate that an object about 1.5 millimeters (0.06 inch) in size was in the tank,” Tatsuyuki Shimazu, a chief airworthiness engineer at Japan’s Civil Aviation Bureau, told reporters in Tokyo today. “We haven’t been able to determine what that was.”
A separate fuel leak on a Japan Airlines 787 at Tokyo’s Narita airport the following week was caused after a microswitch was painted with an insulating coating that wasn’t needed and a hair from a brush had stuck to it, causing it to lock, Shimazu said.
To avoid a repeat incident Japan has agreed with Boeing on measures to prevent the U.K.-made switch from being incorrectly painted again, and to improve the system that alerts the cabin when the valve is open, according to the government.
All Nippon Airways Co., the biggest operator of 787 jets, Japan Airlines, and six other operators have canceled thousands of planned Dreamliner flights since two separate lithium-ion battery incidents last month, which led to a fire on a parked Japan Airlines plane and the emergency landing of an ANA plane.
“Our main priority is to solve the problems and then return to service,” Taro Namba, a spokesman for Japan Airlines, said by telephone from Tokyo today.