Center tank booster pumps on A320 series

[mirkoni]

Hello All,

If I understood well from airbus cbt and Park airbus notes, center booster pumps on A320 not working when slats are down?
Anybody know what is the reason? AFAIK, 737 doesn't have this kind of "complication".
Thanks in advance.

[Goldenrivett]

Hi mirkoni,

You are correct.
The reason is because of Airbus AUTO logic setting of the center tank pump switches. Take off with all engines being fed with the fuel from just one tank is not permitted. Therefore the center tank pumps stop running when the the first flap setting for take off is selected.

[mirkoni]

Thank you for the propmpt answer.

But then again, why is this rule - why is it forbidden to use only one tank during take off? And presumably, landing too? Safety reasons? In what way?

Maybe relatively low level of fuel present in the center tank during t/o or land would leave the pumps dry in some high pitch or roll attitude? Therefore engineers don't want to risk that and ensure engines drinking from wing boosters that are "safely" submerged into fuel.

Wouldn't it be possible that wing booster pumps work together with center tank boosters and prevent such occurence? Making the center booster pumps higher flow, as in B737.

[Rick777]

The center boost pumps do operate at a higher pressure just like a 737. Generally for multi engine airplanes you don't all engines fed from the same tank on takeoff in case of fuel contamination. I haven't flown the 737 for 25 years or so, but I don't thing taking off with center tank fuel to both engines was allowed. The 320 just does it for you.

[MD83FO]

Its a certification requirement, Each engine from its independent source.

[Ollie Onion]

What happens if there is some sort of contamination in the center tank. Could be for a number of reasons, this requirement just guards against a double engine failure at a critical stage of flight due to fuel contamination or some other issue with the center tank.

[mirkoni]

OK I think this is more clear now, let's summarize

- While in critical flight phase (T/O or landing), center tank fuel pumps inhibited, "Tank-to-Engine" principle used (even if there is significant amount of fuel in center tank)
- When out of critical flight phase, center tank fuel pumps automatically turn on (if there is suff. fuel in) and operate at higher flow, so that center tank is emptied before wing tanks
- When below certain fuel low limit, center tanks again off, and we are left with wing fuel.

Thanks to everyone for participation in this topic!