reply to the posts above, I'm still not convinced. For me it is impossible to use right tank, even with crossfeed open and right pumps running.
Only looking at the feed pipes you can indeed say you can use right tank through crossfeed, but it's the electric control that does not allow to use right tank.
If the left AC pump and DC pump send a signal "I'm not running" , the APU will not start, even with crossfeed open and right pumps on.
1/ left ac pump running = apu gets fuel from left tank
2/ left ac pump off due to no AC power= DC pump takes over = apu gets fuel from left tank
3/ left ac pump and DC pump not running = APU controller doesnt allow fuel to go to the APU, shutoff vlve stays closed. If you would try to start the APU here, the only action you get is an EICAS message.
otherwise, the Boeing schematics we have are wrong. Pity no a/c here to test it.
Last edited by Piper19; 28th Jun 2009 at 16:51.