NTSB: “No Obvious Anomalies” in Dreamliner Backup Battery
The backup battery for the Boeing 787 Dreamliner aircraft whose primary battery caught fire while parked at Boston’s Logan Airport had “no obvious anomalies” according to an update issued by the National Transportation Safety Board on Sunday. The findings followed the completion of a “cursory comparative exam” of the battery. The agency said a thorough tear down and test sequence of non-destructive examinations will take place in the coming weeks.
The second battery in the aircraft was identical to the one destroyed in the fire but served a different purpose, namely to provide power for the plane’s startup functions and ground operations and also serves as backup power for the electric brakes. It was in a different location, the nose of the plane.
The NTSB also said it was continuing to study the first battery, which was used to start the aircraft’s auxiliary power unit (APU), a small jet engine that powers the plane while on the ground. That battery was neither being charged nor in a discharged state when the fire occurred. The aircraft was empty at the time.
The batteries in question are rechargeable lithium ion batteries, in which lithium ions move from the negative electrode to the positive electrode during discharge, and back when charging. The batteries have found uses in many electronic devices but the Boeing Dreamliner was the first application in a passenger aircraft.
The Dreamliner fire at Logan was one of two incidents that led to the grounding of all 50 787s worldwide. The second, a fire in a 787 on a domestic flight in Japan, took place on January 16. The battery that backs up the aircraft’s cockpit instruments began smoking shortly after takeoff and forced an emergency landing.
The investigations underway have been inconclusive but investigators have indicated that the problem could be either with the batteries themselves or with the electronics that are used to control them.
The NTSB also said that it had reviewed the two systems associated with the 787’s APU and had found no problems that could have caused the fire. It also reported that it was sending two additional investigators to work with representatives from the Federal Aviation Administration in Seattle to review Boeing’s potential corrective actions and the approval process that the batteries underwent with the FAA.
The NTSB also said it had been given the opportunity to review the circuit boards that were used to monitor the lithium-ion batteries that were on the Dreamliner that had the in-flight incident in Japan. The circuit boards were damaged in the fire, “which limited the information that could be obtained from tests,” although the board added that it had found “no significant discoveries.”
The high-tech Boeing 787 Dreamliner has more electrical systems than earlier aircraft. These systems perform a variety of tasks including de-icing the wings, pressurizing the cabin, and operating hydraulic pumps. In addition, the 787 uses electric brakes while other aircraft have hydraulic ones. The Dreamliner has six generators that produce a total of 1.45 megawatts, enough to power 400 homes.
The first Dreamliner took flight in late 2011 and was operated by launch customer ANA. Boeing has delivered over 50 Dreamliners since the launch.