DraggieDriver posted:
Centre tank is the warmest tank, so significant quantities of ice are unlikely to accumulate there.
According to the AAIB special report, the right MLG punctured the centre tank. I infer from this that the CT extends into the wings, outside of the fuselage profile. An empty tank in the wing will very quickly cold soak. On descent, moist incoming air will deposit ice on the tank walls. Where is the outboard CT boundary?
psalm139_9 posted:
...inlets for the center tank pumps are not located at the lowest point of the tank. In fact, there is a substantial amount of residual fuel which they can't touch.
Where are the pickups? Fwd or Aft of cruise attitude lowest point? How high above tank floor?
From the AAIB special report: "
Samples from the
centre tank had been contaminated by fire fighting
foam and hydraulic fluid: this contamination was a
consequence of the rupture of the right rear wall of the
centre tank." So couldn't check to see if in spec.
Green-dot
The amount of water for the center tank message is approximately 138 gallons.
That is an outrageous amount of water. Is that right? What's the system design philosophy there? The unsubstantiated American "leak" stated that a centre tank water warning occurred on the 2 previous departures. How is the water sensed?
I've not seen anything yet that invalidates my theory in post 216, but then I've very little info on the 777 fuel system. If anyone can post or PM system schematics, system description, training notes etc. I could make another late night of it and maybe invalidate it myself. Otherwise I'll just have to wait for the final report, and where's the fun in that?
Couple more things.
Stratification: no chance. (following para is general, not 777-specific) Apart from the scavenge jet pumps (if they're not full of FOD), the boost pumps cause plenty of mixing, through their own bypass/cooling flow discharged back into the tank, through swirling/entrainment near the inlet and through collector cell feed/overflow. There is also often fuel returned to tanks from other systems heat exchangers.
Does the 777 have collector cells?
Does the 777 have capacitative FQI probes ?