Ok, who's up for a silly question? How does the cross feed prevent an imbalance if we are leaving all pumps on?
We had a serious fuel incident some years ago where the cross feed was turned on but the low tank pumps were left on (all engines running). As these were the stronger pumps, the fuel used for both engines came from this low tank and it nearly ran dry (I wasn't there but this was the washup). So how, with one engine running, is the balance maintained purely by use of the cross feed.