A battery that overheated on a Boeing 787 flight in Japan and forced the plane to make an emergency landing was incorrectly wired, an investigation has found.
The All Nippon Airways (ANA) Dreamliner touched down in Takamatsu when the lithium ion battery sparked an on-board fire, prompting the worldwide grounding of the Boeing 787 jets due to safety concerns.
Japan’s Transport Safety Board has said the battery for the aircraft’s auxiliary power unit was improperly connected to the main battery, which overheated during the flight.
The board’s report said a protective valve would have prevented power from the auxiliary unit from causing damage, the Huffington Post said.
The fact that lights on the aircraft’s tail and wings were flickering after the emergency landing, and that the main battery was switched off, led investigators to conclude there was an abnormal current travelling from the auxiliary power unit.
This was down to miswiring, the report said.
The Transport Safety Board will carry out further analysis to determine what caused the main battery to overheat and begin smoking.
The incident on January 16 came days after a battery exploded on a Dreamliner parked at Boston’s Logan International Airport.
A mechanic conducting a routine post-flight inspection on the Boeing 787 jet discovered smoke in the cockpit.
Passengers had disembarked the plane just 15 minutes before the blaze broke out.
After the fault on the ANA domestic flight on January 16, the Federal Aviation Administration and aviation authorities in other countries took the decision to ground 787 fleets.
The Boeing 787 is the first airliner to make extensive use of lightweight lithium ion batteries.
The batteries are quicker to charge and contain more energy than conventional batteries of the same size, but are also more susceptible to overheating.
Aircraft manufacturer Airbus has switched from lithium ion batteries to traditional nickel-cadmium batteries for its new A350 passenger jet in the wake of the problems plaguing competitor Boeing’s Dreamliner fleet.
It said it had taken the decision to prevent further delays in delivering its new new passenger jet amid uncertainty over whether the investigations into Boeing’s battery problems will lead to a regulation overhaul.