Hmm, Andrew, that could be why we are getting eng cutouts then. Once I shut OFF the center tank pumps with less than say 100pds in it, the wing tanks take over and I don't get the dreaded eng. shutdown.

That is the SOP for the 737 as I understand it (has to do with fuel tank fires from dry fuel pumps), but I doubt the engines would cut out in the real plane if the centre ran dry and the wing pumps were on...Greghttp://members.rogers.com/gmoffatt/images/ERJ_CRT.jpg

Yes I was using a *Non normal Procedure* example, which is what a fuel imbalance is ;) and what it means to have no fuel in the center tank under the *FUEL CONFIG* message. There are other reasons to have the pumps on though. Anyways, If BOTH center fuel pump LOW PRESSURE lights illuminated then both center fuel pumps are switched to OFF. [h5]Best Wishes,Randy J. Smith [h4]P M D G 7 3 7 NG[/h4] [h3] Realism on the horizon [h5]AMD XP 2200 |MUNCHKIN 512 DDR RAM |ECS[/b ][i] K7S5A MB[/i] |GF2 MX 32 MEG and still runs GOOD!|WIN XP PRO |MITSUBISHI DIAMOND PLUS 91 19"[/h5]

>Take a look at the manual:> Normal Procedures: page 2:> "Center tank fuel pump switches should be positioned ON>only if the fuel quantity in the center tank exceeds>453kg/1000 pounds."That is right, you allways have to have a little fuel left for that reason in the center tank, it comes from the time with the 747 that had a spark because of a faulty fuelpump rotor.To the other parts of this thread:But it hasnt anything to do with the fuel system not supplying from main tanks i cant explain, you do have a EDP (engine driven pump)as part of the HMU (hydro mechanical unit allso called fuelcontrol) and this can as said supply iys own fuel from the main tanks.A little fuel system explanation is comming up here :-)The center pumps is actually the same pumptype as the main tank pumps, but on the main tank pumps you have put a restricter so it sypply a lower pressure, that way you are allways sure to empy the center tank first, you allso got a little suction s

Gents-Following up on Dennis' Licensed explanation of the airplane (thanks dennis!)...Currently the logic for the fuel system is designed to switch fuel feed to the wing tanks when the center tank reaches 20lbs of fuel remaining.In testing on our end it worked perfectly- but this MIGHT have changed during the process of fixing the fuel Out-Of-Balance problem that was reported in the original version.I'll take a look at it when I have time- but for now, I recommend you be a good captain and make sure you don't let the center tank run dry. ;-)

>Following up on Dennis' Licensed explanation of the airplane >(thanks dennis!)...Hehe i know, im a little technical hehe can you call that a work related damaged and how about being able to see if its an 600-700 or 800 when it flies in the sky hehehe>Currently the logic for the fuel system is designed to switch>fuel feed to the wing tanks when the center tank reaches 20lbs>of fuel remaining.That would be as close as reality as it can get i think, and if you ask me, it will be perfect :-D>I'll take a look at it when I have time- but for now, I>recommend you be a good captain and make sure you don't let>the center tank run dry. ;-)Its called reallife ;-)and if people dont do it right, then the engines will shout down as a penalty, nice feature :-D thats the way to teach themI cant wait, when i get the money from my trip to Nice to work on an Airbus, then i will buy this product myself, atm i have to go to a friends house to try it :-( but im going to take a little look one of these days after the patch, but i allready luv this plane :-)DennisLicensed on the B737NG and the Airbus 319-321 as a technician (B1 and B2)

Hi Dennis,If I understand you and the rest of this thread correctly, are you saying that in a real 737NG, the plane's engines actually shutdown unless the pilot MANUALLY switches fuel tanks (or turns off centre pump?). Is there no safety system in place to crossover or automatically start using the wing fuel tanks once the centre one is empty?John

John,Not at all. The 737 Fuel system, like nearly every other large Twin jet transport with 3 tanks or more, requires boost pumps to lift fuel out of the center or possibly Stabilizer or Bladder fuel cells to get to the Engine Supply lines (because the engines are physically higher than the Tank Plumbing) This is normally done by Fuel boost pumps, in this case called Boost Overide pumps. The pumps in the Center tank on the 737 provide nearly twice as much pressure as the Main tank pumps, and subsequently force the check valves on the output from the Main tank pumps closed allowing only center tank fuel in the manifold. This forces the fuel in the center tank to be burned before using any wing tank fuel. As the fuel level in the Center tank drops to the point that pumps are not getting a good supply of fuel, the pressure will drop and the main tank pumps will now be able to override the check valves and push fuel to the engines via the Supply manifold. In the case where all the boost pumps have failed, there is a manifold Bypass which allows the Engine driven fuel pumps to draw fuel from the wing tanks only via a combination of Gravity and Suction from the Engine Driven pump. Not a complete Description and Operation but a good overview. Hope this clarifies it a bit.RegardsPaul Gollnick :-cool Technical Operations/Customer Operational SupportPrecision Manuals Development Groupwww.precisionmanuals.comhttp://www.precisionmanuals.com/images/forum/devteam.jpg

Thanks Paul. Phew! For a minute there I was terrified at the idea of the 737-700 (which I took to Puerto Vallarta just a week ago) "stopping" in mid-air *grin* ... It was hard to believe there would be no backup switchover mechanism for such a fatal issue as running out fuel in one tank only...John

From previous threads I thought you should always have a minimum of 1000lbs of fuel in the centre tank.

if you watch carefully, you can leave the center pumps on until you get a FUEL warning. if you switch off the center pumps then all will be fine, otherwise the engines will cutout.

As explained above, the engines will not cut out when the center tank runs dry. The Engines fuel supply simply changes from Center fuel in the supply line to Main Tank fuel in the supply line (via the check valves discussed in my previous post). No action required by the pilot except to turn off the center tank pumps to avoid damaging the pumps while running dry. The changeover is transparent as its simple physics. If the pressure from the Center boost pumps is less than the Main pumps then the Main pumps supply fuel. RegardsPaul Gollnick :-cool Technical Operations/Customer Operational SupportPrecision Manuals Development Groupwww.precisionmanuals.comhttp://www.precisionmanuals.com/images/forum/devteam.jpg

The AD Note issued by the FAA after the findings from the TWA 800 crash now require a minimum of 1000 lbs in the center tank for the Center Tank pump cooling (more on the 747). Once you drop below these levels the pumps could overheat. RegardsPaul Gollnick :-cool Technical Operations/Customer Operational SupportPrecision Manuals Development Groupwww.precisionmanuals.comhttp://www.precisionmanuals.com/images/forum/devteam.jpg

I think you will find you should have a minimum of 1,000lbs of fuel in the centre tank. Search the forum this has ben covered befor under fuel planning I think.

edited, double post by mistake