What is the minimum fuel left in the center tank to turn the fuel pumps off to maintain CG?

You don't turn the pumps off to maintain CG, you turn them off to avoid overheating the pumps and allowing the fuel to vaporize. For CG concerns, you can't have more than 1000 lbs in the center with less than full wing tanks.

Typically fuel is burned out of the centre tank first before burning out of the wings. CG is not a concern.

Typically fuel is burned out of the centre tank first before burning out of the wings. CG is not a concern.

Which is the reason behind that ? Thx

Think it's got to do with MZFW and wing bending moments. You want the fuel balance to be "wings heavy", "fuselage light" if you wish. Basically a heavy fuselage and light wings would increase the stress at the wing root due to bending. Would need to look it up though to get a definite.

Think it's got to do with MZFW and wing bending moments. You want the fuel balance to be "wings heavy", "fuselage light" if you wish. Basically a heavy fuselage and light wings would increase the stress at the wing root due to bending. Would need to look it up though to get a definite.

Not 100% positive on that myself, but I think you got that pretty much right on. Also, the centre tank pumps have further to travel to the engines so they pump at a higher pressure, this ensures that the center tank fuel is used before the main tank fuel, even though all the fuel pumps are operating. This is a big generalization, but typically you see the centre tank empty either in the later stages of the climb, to the early portion of cruise on alot of 737 flights, depending of course on length of flight, payload, etc etc. I also believe on the new builds of the NGs; the center tank pumps will automattically shut off, when the pumps sensor detects low output pressure. Not sure if the PMDGs do so or not.

So you can leave the pumps on and run the center tank dry then turn off the pumps and feed off the wing tanks? Thanks for the help so far.

Nevermind

Nevermind also

Thats helpful. LOL.

I also believe on the new builds of the NGs; the center tank pumps will automattically shut off, when the pumps sensor detects low output pressure. Not sure if the PMDGs do so or not.

I believe it's an option, but I'm convinced the NGX will do so.

So you can leave the pumps on and run the center tank dry then turn off the pumps and feed off the wing tanks?

Well that's what you'd do anyways. Once the centers are low you'd switch them off and hence each main tank will feed its corresponding engine. As long as you ain't x-feeding of course. But if you meant to leave the main pumps on as long as the center is still feeding, yes you should do that as well. Whenever each tank carries some fuel you'd leave the gate with all pumps running. As stated above the system is designed in a way that would empty the center first by higher pump output pressure.

In answer to your question, yes you can, an annunciation warning will light up when the tank is almost empty. In my other post i said something like: I always thought the center tank has to be emptyd first because of safety reasons. With fuel only in the wings the fire will burn outside the hull incase of a crash landing,.Giving passengers the best chance of survival.

Alrighty thanks for the help!

I always thought the center tank has to be emptyd first because of safety reasons.

No, Etienne above in #5 has the right answer.

So in real life they don't land the 737 with any fuel in the center tank?