Another incident involving the main lithium-ion battery in a Japan Airlines Boeing 787 just before its scheduled departure from Tokyo on Tuesday has prompted an investigation by the Japan Civil Aviation Bureau, with help from the U.S. National Transportation Safety Board, raising new questions about the integrity of a system redesign devised to mitigate the possibility of fire propagation. Battery overheating in airplanes operated by JAL and fellow Japanese airline ANA led to a worldwide grounding of the 787 fleet early last year, forcing Boeing to develop modifications to the charging system and install containment and venting systems.
The latest event occurred at around 4:15 p.m. Tokyo time, when mechanics witnessed white smoke emanating from the bottom of the airplane’s fuselage through the cockpit window during pre-departure maintenance at Tokyo Narita Airport. An indication in the cockpit of the possible failure of the main battery and main battery charger prompted maintenance crew to open the main battery enclosure. They found that the safety pressure relief valve connecting to one of the eight battery cells had opened and that liquid dispersed in the main battery enclosure.
No other equipment in the forward electrical bay, where the battery main battery sits, suffered any damage, said JAL. The airline said it continues to investigate the reason the pressure relief valve opened.
The airline replaced the airplane in question, operating as Flight JL707 to Bangkok, with another 787. That airplane left Tokyo at 6:12 p.m., seven minutes after the originally intended departure time.
Tuesday’s incident came almost exactly a year after aviation authorities grounded all 787s following two cases of battery overheating, one on January 7 aboard a JAL airplane parked at Boston Logan Airport and the other on January 16 during an ANA flight from Yamaguchi, Japan, to Tokyo.
Asked for its reaction to Tuesday’s incident, Boeing said that it knew of the “issue” and that it appears to have involved the venting of a single battery cell. “The improvements made to the 787 battery system last year appear to have worked as designed,” it concluded.