Voidhawk, I think that you have nailed it !!Collector (feed box)keeps pumps submerged and primed.and available for both engines (crossfeed) Ref.F27-all series,also F50 (F27-Mark-50)and Fairchild notes (yank version) Nasty accident not long ago where the supply switch was left off and the engines stopped a few minutes after take-off.(Jeez I'm getting old)
Cheers