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jbcallender

Center Tank Empty, L & R Wing Tanks not feeding fuel

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Have had an odd problem for the last two flights.  After the center tank empties, the left and right wing tanks are not feeding fuel, thus the engines starve out.  I have probably 25 flights in the NGX prior to this with no fuel flow issues.  I have all fuel pumps on, so that is not the problem.  I don't have any of the random maintenance and failure issues activated.

 

The first flight I could not get a restart.  Last night, I reloaded the center tank via the FMC (not very realistic) and executed a crossbleed restart - at 13,000 feet - and finished the flight.  I have obviously done something, but I can't figure it out.

 

Any suggestions would be welcomed. 


Jeff Callender

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No, loading 737NGX first.  I think I have solved it, but not sure why.  This morning, I disengaged the center tank fuel pumps just before it was empty and it correctly began drawing from the wing tanks. 


Jeff Callender

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That's actually what you are supposed to do, per the FCTM.

Although the wing tanks should start feeding automatically when the Center tank is empty, even if the Center fuel pumps are still running.

In any case, if you are able to reproduce the problem, send a ticket to PMDG at support.precisionmanuals.com


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That's actually what you are supposed to do, per the FCTM.

 

That's an old procedure, most of the airplanes have been modified.  Our procedures changed a while ago and we don't turn the center pumps off until the low pressure lights come on.  The center tank usually indicates zero by then.  The AD no longer applies to airframes that have been modified.


Joe Diamond

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That's actually what you are supposed to do, per the FCTM.

Although the wing tanks should start feeding automatically when the Center tank is empty, even if the Center fuel pumps are still running.

In any case, if you are able to reproduce the problem, send a ticket to PMDG at support.precisionmanuals.com

 

 

That's an old procedure, most of the airplanes have been modified.  Our procedures changed a while ago and we don't turn the center pumps off until the low pressure lights come on.  The center tank usually indicates zero by then.  The AD no longer applies to airframes that have been modified.

 

IIRC, there are a few AMOCs (Alternate Means Of Compliance) in the mix. One is burn down to 1000lbs, and shut them off and just tanker the 1000lbs. Another is burn down to 1000lbs, open the crossfeed and turn of 1 center pump until you get the master caution with the empty tanks. The last is with the center tank pumps mod.


Matt Cee

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Thanks for all the input.  It's very interesting to hear the RW pilot input.  What PMDG has accomplished with their products continues to amaze me.


Jeff Callender

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IIRC, there are a few AMOCs (Alternate Means Of Compliance) in the mix. One is burn down to 1000lbs, and shut them off and just tanker the 1000lbs. Another is burn down to 1000lbs, open the crossfeed and turn of 1 center pump until you get the master caution with the empty tanks. The last is with the center tank pumps mod.

 

I can only speak for our fleet but all our planes have been modified.  We used to go to one pump at 2000 lbs remaining in the center tank.  Our procedure is simple now, if there is fuel in the center tank the pumps are on.  The only exception is that if we get the low pressure lights in the climb due to the pitch angle with fuel remaining in the center tank we shut the pumps off.  Upon leveling off the center pumps are turned on again until the low pressure lights illuminate.


Joe Diamond

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One is burn down to 1000lbs, and shut them off and just tanker the 1000lbs.

 

Isn't there a scavenger pump in there somewhere? IIRC there was supposed to be a feed to L wing tanks.


--Peter Fabian 
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Isn't there a scavenger pump in there somewhere? IIRC there was supposed to be a feed to L wing tanks.

Yeah, it'll pump out around 150lbs from the center before the flight is over. I'm guessing that's accounted for in the AMOC.

Matt Cee

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That's an old procedure, most of the airplanes have been modified.

In that case, we still use the "old procedure" in real life. ;-)


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In that case, we still use the "old procedure" in real life. ;-)

 

As I said, I can only speak for our fleet.


Joe Diamond

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In that case, we still use the "old procedure" in real life. ;-)

Does your fleet consist of different options/versions 737? I know some airlines that in this case use same procedures so not to confuse pilots. This procedures would be downgrade (switch fuel pumps off on 1000lbs, even on newer aircraft where it's not needed; switch ignition to CONT even if equipped with AUTO position, but there are also older airplane, etc).

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Does your fleet consist of different options/versions 737? I know some airlines that in this case use same procedures so not to confuse pilots. This procedures would be downgrade (switch fuel pumps off on 1000lbs, even on newer aircraft where it's not needed; switch ignition to CONT even if equipped with AUTO position, but there are also older airplane, etc).

 

While our fleet was in the process of being modified the old procedure applied to all airplanes, modified or not.  Once the entire fleet had the mod the old procedure went away.


Joe Diamond

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