An All Nippon Airways Boeing 787 Dreamliner equipped with Boeings updated lithium ion battery system experienced a minor electrical issue during a test flight earlier this month, Flightglobal.com reports.
The problem was traced to a loose fastener on an electrical distribution panel, not the new battery or its charging system.
The issue happened on a May 4 proving flight between Tokyos Haneda Airport and Chitose. ANA is extensively testing the Dreamliners modified electrical systems before returning its 18 Dreamliners to commercial operations.
The airliner was carrying only a pilot and a co-pilot on the test flight. The crew was alerted to the issue by several warning lights. The plane landed without incident at Chitose.
A later examination showed a nut holding the panel hadnt been tightened sufficiently causing heat damage to the electrical panel.
The panel was replaced, and the plane was returned to test flights.
ANA was one of two Japanese airlines affected by problems with the Dreamliners lithium ion battery system. An ANA plane on an internal Japanese flight in January suffered a battery meltdown and was forced to make an emergency landing. No one was injured in the incident.
That incident and another issue with a battery on a Japan Air Lines plane on the ground in Boston cause worldwide aviation regulators to ground the Dreamliner fleet for more than three months.
Boeing modified the batteries to separate the individual cells, built a stainless steel box to contain the batteries and modified the battery charging systems to prevent overcharging. The boxes containing each Dreamliners two batteries are vented to the outside to prevent smoke from a battery thermal runaway from entering the cabin.
ANA plans to return its Dreamliner fleet to commercial service next month.