During normal flight should the crossover valve be open or closed?

Did you check the manual? :-)http://forums.avsim.net/user_files/164088.jpg

As an added bonus question, why is it closed for take-off?A: If you spring a leak (noted by a "significant" fuel imbalance), all your fuel won't cross over to the leaking tank, leaving you with TWO fuel starved engines.Consequently, if you do get a fuel imbalance, your best bet is to examine WHY you have an imbalance before you hit the crossfeed switch.