Originally Posted by
svhar
We had to turn off the center tank pumps with 500 kg remaining in the center tank after this (757, 767). One day we no had to do it anymore. Same pumps. Same tanks.
Are you sure there were no changes? Boeing developed a center fuel tank inerting system in direct response to the TWA 800 accident. It uses engine bleed air, separates out the nitrogen from the oxygen - the nitrogen is pumped into the center fuel tank while the O2 is dumped overboard. It keeps the O2 concentration in the center tank low enough that ignition is extremely unlikely even with an ignition source. Installation of the center fuel tank inerting system was mandated for all 757 and 767 aircraft. My memory is a bit foggy on the dates, but I think it had to be done by around 2015.