B737-738 center tank

[boeing738driver]

limitations of the Fuel system of B737 and 738 we have this note "Main tanks 1 and 2 must be full if center tank contains more than 453 kgs" Is there anybody knows why we have to transfer center to main if we have more than 453kgs.Or why we have to full of both main tank?If we have 600 kgs on center and main tank is not full.We should call ground stuff for fuel transfer to the main tanks at least 200kgs.Is that right???

Thanks...

[IRRenewal]

Historically I believe this has something to do with bending moment on the wing attachments. All other things being equal less fuel in wings and more in center tank increases stress on wing attachments.

However, Boeing got a bit nervous about center fuel tanks and we now take off with up to 2300 kg of center tank fuel with the center tank pumps off until FL100. By then you are definitely outside the limits you quoted in bold.

[I-2021]

Hello,

now take off with up to 2300 kg of center tank fuel with the center tank pumps off until FL100.

Why is that ?

[RAT 5]

The 2300kgs in centre tank is to do with keeping the pumps submerged until they are updated with modified system.

However, there is a limititation that you can have a max of 2300kgs, but centre tank fuel should be added to the 'load' total to ensure that max ZFW is not exceeded.

In you case of 600kgs in CTR tank, if the pax/cargo/ctr fuel/DOW is total less than max ZFW there should be no structural problem.

[I-2021]

Hi RAT 5,

Thanks for the explanation. But this has to do only with the NG series ?

[Wing_Bound_Vortex]

Use of centre tank pumps depends on if yours has had the mod to the pumps or not. In either case you can use the centre tank fuel after you have started accelerating to a climb speed of 250kts or higher, you don't have to wait untill FL100. All to do with the pitch ( body ) angle, to keep the pumps submerged.

If you have less than 2300 kg before T/O centre tank fuel pumps must be off. Use of fuel after T/O depends on quantity in the centre tank, greater than 950kg both pumps can go on, less than 950kg the alternate fuel proc must be used.

WBV

[HAWK21M]

This is applicable to all B737 series.
regds
MEL

[Port Strobe]

RAT5
However, there is a limititation that you can have a max of 2300kgs, but centre tank fuel should be added to the 'load' total to ensure that max ZFW is not exceeded.
Is this limitation from the -800 manual? It's not in -700 Vol 1, never seen it before, but I can see why you might consider doing so.