ManaAda,
You are obviously a pilot and as a pilot you are not expected to know a/c systems as well as engineers!!!!!
That is why you fly 'em and we fix 'em.
Ops manuals give a very basic overview of the a/c systems and try to keep it simple so you guys can get your heads around it.
Each boeing a/c have subtle differences but in general are the same. Now what you have said is more or less true but I assure you some a/c have dc pumps some don't.
What had not been covered is how the APU "suction feeds".
That is what my last post was trying to convey.Some of the earlier posts seem to believe that "suction feeding" was due to the weight of the fuel in the tanks and heads of pressure etc. Well it is not.
As I've already explained, suction feeding is caused by fuel being sucked from the left hand tank by a high pressure fuel pump, located on the FCU, which is mechanically driven by the APU gearbox.
The ops manual does not mention a lot of things purely because you don't need to know.
If it is important for you to see written confirmation ask one of you engineers to dig out the a/c schematics manual chapter 49. You will find a very pretty picture of the fuel system.
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and never pause for rest!
With wine, poetry, or vitrtue,
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