Hi,
Bear,
They had to descend from 31000 feet, which took some time. When was this predicted fire supposed to have started?
The event is recorded in FDR. Voltage fluctuated and went to zero. At this moment cells were no longer capable to deliver energy to battery terminals (inter cell connection was open between cell # 3 and # 4).
The danger of fire (outside battery case) IMO reduced after this moment. (Or a little later.) Battery was yet partially discharged, short to ground no longer existed and temperature of battery probably had an inflexion point minutes after inter cell opening.
This is a "model". Can be confirmed later or not.
IMO it´s probable.
All these incidents have occurred aloft, save JAL. JAL problem may have begun while airborne?
I f you look to the time JAL 787 approaching Logan, taxiing, etc. it´s more probable thermal runaway started few minutes before firstly detected. The short circuit (NTSB put as triggering the thermal runaway) would be "visible" if battery voltage is measured before relay/contactor and recorded. I don´t know if it was.
What seems to be lucky, is the proximity of runways and/or Fire departments to allow emergency procedures.
Indeed. But i insist: ANA case was going to be much worse. The short to ground "saved" from a much more serious situation. Similar to BOS thermal runaway consequences. An inside FWD EE bay.
The basis for my post is:
There are many points in common between both cases:
• Same battery
• Not delivering current
• Being charged or being trickle charged
• Thermal runaway
The differences were:
ANA case:
• A short circuit to ground (from cell # 3 region)
• Inter cell connection “broke” (# 3 to # 4)
• Voltage was recorded (fluctuated and went to zero)
• Fire was contained
JAL case:
• Energy was enough to sustain thermal runaway
The rationale is:
ANA battery energy was lost in the external short circuit. The capability to expel fire was reduced and fire was contained inside the battery case. IMO both batteries were going to caught fire.