Aux fuel system of the 737BBJ

[chksix]

I've tried searching....

I have a specific question about the aux system directed at pilots of the type.
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From the 737 Cockpit Companion by Bill Bulfer:
FWD/AFT AUX fuel transfer valve switches
AUTO
-closes fuel vent valves
-arms forward and aft aux fuel transfer valves to begin fuel transfer
-fuel transfer begins if there is sufficient space in the center tank
-lower level float switches in the center tank must be dry
-as center tank reaches full, the upper level float switches close the aux transfer valves; when there is space in the ctr tank the cycle repeats.
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What I'd like to know is at what level is the switch going dry and aux valves opened?
And how fast is the tank refilled?

This is for simulation purposes....
Thank you in advance for quick replies :O

[Flight Detent]

Hi chksix,

Our B737-700 aircraft have the four cell auxiliary system, one in the front and three in the aft cargo compartment.

Thats 1665kg/4794kg capacity.

After t/o, when the center tank gets down to 10,886kg (24,000lbs), but no sooner than 10 minutes after t/o, the transfer of fuel from both aux cells starts automatically, if selected to AUTO.
When the center tank is again full, transfer stops until that 24K level is reached again and the whole thing repeats over.

The rate at which this occurs is dependent on the rate of fuel useage. Remember, both engines are being fed fuel from the center tank.

I understand that about 40 minutes is required to refill the center tank in cruise flight, thats the combination of fuel useage from the center tank, and the fuel being transferred into the same tank.

Cheers, FD :\

[chksix]

Thank you very much! This info will help our BBJ become more realistic :ok:

And I'd send you a nice bottle of single malt if I could ;)