No passengers or crew were aboard the 787 at the time but a firefighter received minor injuries combating the blaze says the safety agency.
Despite a small area of the aircraft involved, limited to within 20 inches of the auxiliary power unit (APU) battery rack says the NTSB, it took emergency crews approximately 40 minutes to completely extinguish the fire.
The APU battery is described as having severe fire damage. Initial indications are the APU was running while cleaning and maintenance crews were servicing the airplane. The APU battery pack is located in the aft electronics bay.
According to the update issued by the NTSB, initial investigative findings include:
• The NTSB investigator on scene found that the auxiliary power unit battery had severe fire damage. Thermal damage to the surrounding structure and components is confined to the area immediately near the APU battery rack (within about 20 inches) in the aft electronics bay.
• Preliminary reports from Japan Airlines representatives indicate that airplane maintenance and cleaning personnel were on the airplane with the APU in operation just prior to the detection of smoke in the cabin and that Boston Logan Airport Rescue and Fire Fighting were contacted.
• Rescue and fire personnel and equipment responded to the airplane and detected a fire in the electronics and equipment bay near the APU battery box. Initial reports indicate that the fire was extinguished about 40 minutes after arrival of the first rescue and fire personnel. One firefighter received minor injuries.