JAL's grounded Boeing Dreamliner leaks fuel in tests

An advertisement of Boeing Co's 787 Dreamliner jet is seen at New Tokyo international airport in Narita, east of Tokyo Janauary 9, 2013.

TOKYO/SEATTLE (Reuters) - Japan Airlines Co (JAL) (9201.T) said on Sunday that a Boeing Co (BA.N) 787 Dreamliner jet undergoing checks in Tokyo following a fuel leak at Boston airport last week had leaked fuel during tests earlier in the day.

An open valve on the aircraft caused fuel to leak from a nozzle on the left wing used to remove fuel, a company spokeswoman said. The jet is out of service after spilling about 40 gallons (roughly 150 liters) of fuel onto the airport taxiway in Boston due to a separate valve-related problem.

In Boston, a different valve on the plane opened, causing fuel to flow from the centre tank to the left main tank. When that tank filled up, it overflowed into a surge tank and out through a vent. The spill happened as the plane was taxiing for takeoff on a flight to Tokyo on January 8. It made the flight about four hours later.

The causes of both incidents are unknown, the JAL spokeswoman added. There is no timetable for the plane to return to service.

On Friday, the U.S. government ordered a wide-ranging review of Boeing's 787 Dreamliner, citing concern over a battery that caught fire on January 7, also on a JAL plane in Boston, and other problems. The government and Boeing insisted the passenger jet remained safe to fly.

The 787 represents the boldest bet Boeing has made on a new plane in more than a decade, and because the aircraft required billions to develop, much of the company's financial performance is riding on its success. Boeing is trying to double production to 10 jets a month this year to cash in on nearly 800 orders.

The eight airlines that operate the 50 jets delivered so far have expressed support for it, saying the mishaps are teething problems common with most new airplanes, and the 787's fuel savings make it an important addition to their fleets. JAL and local rival All Nippon Airways Co (9202.T) fly 24 Dreamliners.

The review follows a slew of incidents that have focused intense scrutiny on the new plane. While many of the issues that have dogged the 787 are typically considered routine, their occurrence in quick succession on an aircraft that incorporates major new technology and has not seen wide use yet has sparked concerns about safety.

In December, a 787 operated by United Airlines (UAL.N) and bound from Houston to Newark, New Jersey, was forced to land in New Orleans after a warning light in the cockpit indicated a generator had failed.

Boeing later said a faulty circuit board produced in Mexico and supplied by UTC Aerospace Systems, a unit of United Technologies (UTX.N), had produced a false reading in the cockpit. A UTC Aerospace spokesman declined to comment.

Also in December, two other 787s suffered problems with electrical panels. The fire on January 7 started when a lithium-ion battery used in an auxiliary power system ignited while the plane was parked at the gate. It burned for about 40 minutes before firefighters put the flames out, and smoke entered the cabin. Passengers and crew had already left the aircraft. <ID:L1E9C8B0V>

On December 5, U.S. regulators said there was a manufacturing fault in 787 fuel lines and advised operators to make extra inspections to guard against engine failures.

Last week, the plane had seven reported incidents, ranging from the fire to a cracked cockpit window.

(Reporting by James Topham in Tokyo and Alwyn Scott in Seattle; Editing by Jeremy Laurence, Catherine Evans and Dale Hudson)