Center tank ran out fuel with fuel switches OFF

[JHepburn 0]

Sorry to bump, but I do hope this at least gets looked at...

[Spin737 102]

The fuel pumps will run dry and begin to heat up. Keeping 1000lbs in the tank would prevent that from happening (the fuel cools the pumps)Beoing has, however, added and retrofitted a system that will prevent that. If a pump runs dry the decreased amperage and increased pump rpm will trigger a shutdown of that pump. That's when the warnings come on.

I haven't heard of that one. I know there are a few AMOC (alternative methods of compliance) on this issue. There's a bit more to it, but you get a LOW PRESSURE and a MASTER CAUTION when the Center Tank starts to go dry. The pumps shut themselves off if the LOW PRESSURE is on for 15 seconds.

[davierosoft 13]

I haven't heard of that one. I know there are a few AMOC (alternative methods of compliance) on this issue. There's a bit more to it, but you get a LOW PRESSURE and a MASTER CAUTION when the Center Tank starts to go dry. The pumps shut themselves off if the LOW PRESSURE is on for 15 seconds.

That's right if the aircraft was produced later than May 2004 or if it incorporates the service bulletin 737-28A1206 wich add this feature.The fuel scavenge jet pump is rated to feed a low rate fuel, less than APU feed when running unloaded, so if with engines your fuel in tank1 is too high, there is a problem.It is strange as in my first tests I tried to see if center tank scavenge was working, and had no fuel transfer or maybe was too low.I'll check again.

[davierosoft 13]

Ok, tested again and found why it didn't work before.PMDG has programmed scavenge system to work only in flight, on ground it will stops.Thats wrong. There are no electrical items in the system on NGs (there was on classic where scavenge was limited to 25minutes)The NGs have a float shut off valve in the wing1 tank that shut off the fuel if the quantity is higer than (around) 2000 Kgs.If fuel goes down, the float opens the valve and scavenge system starts to work. This is valid on ground and in air. The fuel transfer rte is over 30kgs in 30 minutes, maybe 50, maybe 100Kgs, but in half our, not per minute.On pmdg I found that also with high thrust the tank1 was still increasing quantity creating a dangerous inbalance.That's a big issue.