fuel tanks

[doebro2010]

I read that one fuel tank always feed both engines.

I noticed during flights that both tanks 1 and 2 are gradually get empty.

my question is: do they both feed at the same time the engines or is number 1 only feed engine 1

is there someone who could tell me a little more about these tanks?

kr

Doeke

[Litjan]

Not sure where you heard that ;-)

As long as fuel on board is less than 9000kgs it is in both wingtanks. Each wingtank feeds it´s engine, the crossfeed is normally closed.

If fuel is more than 9000kgs, the center tank gets filled and it will then get emptied first and feed both engines.

If fuel gets unbalanced you can open the crossfeed and turn off the boost pumps in the tank which is less full, then the tank with the higher level will feed both engines.

If you dont turn off the boost pumps, one of both tanks will feed both engines, because one pair of boost pumps is always slightly stronger than the other ones and will win the "tug of war" of who can create more pressure.

Cheers, Jan

 

[doebro2010]

That is very helpfull.

to memorize if I understand it correctly, tank 1 and 2 if all pumps on and crossfeed is off , each tank will feed its own engine.

all pumps on and crossfeed is on, the strongest tank feed both engine.

I assume in case of centre tank in filled as you say that one first feed both engine and will not make difference if crossfeed at that time is on or off

till the moment it is empty.

thanks for the clarification.

 

[Litjan]

That is correct!