if there's a bit of documentation that explains this, please let me know, but:for some reason, sometimes, after having fueled, the 4 valves which control fuel flow between tanks (x-flow valves I guess) are set so that fuel will not flow.ok, so, use the buttons to control the valves you say?well, half easy, half hard, it seems.the two outer buttons on the overhead control panel are functional for the two outer valves, no problem, however, the inner buttons are non-functional for some reason.why is that, and, how do I control the inner set of fuel x-feed valves?please advise...

ok, I figured it out. open the button cover before trying to push the button!!doh!I'm still a little puzzled as to why the valves would end up in a closed position after having landed, refueled, and then taking off again.weird.

You shouldn't need to touch the inner crossfeed valves in normal operation, and you should use the outer crossfeeds when going from Tank to Engine.Rob

ok, 'should' is one thing, but, what I'm talking about is where, after having landed at egll, shut down the engines, refueled, restarted the engines, takeoff and then flaps up, I still ended up with the inner x-feed valves set the wrong way.now, until I figured out how to raise the protective covers on the inner buttons, I didn't have the ability to change these inner valve settings.so, tell me, what happened?what series of events could have caused the valves to be set the wrong way?and please don't tell me 'it shouldn't have happened', because it did.you guys have the code for this aircraft, and should be able to understand the various scenarios that might happen that could lead to the inner x-feed valves ending up being set the wrong way.please advise in a helpful manner.

In normal operations you do not touch the 2 and 3 crossfeed valve switches (the guarded ones). the valves will be open until you select takeoff flaps at which time they will automatically close. Once the flaps are retracted the valves will automatically open again. That is how the system is designed. From your post I am not sure if that is what you are seeing or it is something else. It is all detailed starting on page 44 of the Systems documentation that came with the plane.

Hey hold up! I am not a devolper just another customer tryin to help. I never it said shouldn't have happened I said you should never need to push those buttons in normal operations. read my post more carefully and Read the manual!Rob

Rob,I certainly do appreciate your willingness to help a fellow flier, and I did not gather from your post that you were not a PMDG staffer.Sorry about that.it's rather an easy leap to make given the way the avsim forum titles are set up 'commercial support' gives the impression that you're really talking with people that are pmdg staffers.also, since you were using a very corporate PMDG looking tag, it's not too surprising.again, thank's for your help, but I'm still wondering what it was that caused the inner valves to stay closed.regards,Peter Belbin.

No problem Peter, The Development staff have special sigs that say what there position is within PMDG . I'm sure they will check to see if you have bug with the 747X.Rob

"again, thank's for your help, but I'm still wondering what it was that caused the inner valves to stay closed."What fuel did you have in each tank for the second flight? Could you post a screenshot of the fuel panel and the EICAS fuel synoptic at the point where you think it is wrong?Thanks.Cheers.Q> イアン

I may be able to do that next time this issue surfaces.regards,peter.