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Guest tcable

A different fuel bug

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Right now I'm facing a situation that when ever I run the center tank to empty, my engines flame out, requiring an air restart!All of my fuel pumps are on, but the flow of fuel to the engines should be uninterrupted.That and I have VNAV climb issues :)Tim

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I wonder why I haven't hit this bug. I have purposely departed with 1000lbs in the center tank and had it run dry, and everything went as expected with transition to the wing tanks.Lee Hetherington (KBED)

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Lee,I bet that Tim's has not positioned the cross-over switch to open. Since it is set at closed when you first start, this could happen very easy and a flame out would occur.Tim, can you check this out and let us know if the problem still occurs. I have had the center wings go to zero on several flights without the problem AFTER the patch. Prior to the patch this would happen no matter what.CheersBob

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Cross switch is open- and it never happened to me before the patch! Frustrating when you have only 1-2k in the center tank and you go dry on climbout...I also cannot transfer fuel across the ship- even if teh pumps are off on that wing tank.I've noticed that the tank with the pumps off will also deplete at teh same rate as if the pumps are on, making any fuel imbalance continue.Tim

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My cross switch is closed (I believe as it should be--need to check). The cross switch has nothing to do with this situation, anyways. I thought it had to do with an engine feeding off the opposite wing.If I open the cross switch and turn off the left pumps, I can get the left engine to feed off the right tanks, as expected.Lee Hetherington (KBED)

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I thought that SOP was cross feed closed- unless trying to cure a fuel imbalance in the wings. Now with SU1 I don't get the massive imbalance that I used to with the original version, but the APU no longer has a mind of its' own either!I have fuel pressure on the wings, with both pumps on, so ther should be no fuel starvation at all. AFAIK, the pumps will not pump air, so as soon as the pressure on the center pumps drops, the wing pumps will automatically pump fuel to the manifold- it's the same basic Boeing system on all of their twins. and it works becuase of the simplicity- kinda like Cessna gravity feed :)I just reinstalled SU1 to see if that cures the issue. It's easy to duplicate :)Tim(KTAN)

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Tim,To confuse what I wrote before, I just did a flight from Denver to Seattle. My fuel load was 22180 pounds. That had full wing tanks and about 20% in the center wing. I had the crossfeed open. When the center wing tank emptied, I too had a engine flame out, which requiared a air start.Let me understand that SOP is that the crossfeed should be CLOSED? The fuel diagram would suppor the notion that when fuel is no longer available in the center wing the wing tanks will still feed the engines with the cross feed closed.I am going to do a return trip tomorrow from Seattle to Denver and this time I will keep the crossfeed closed to see if I can prevent this fuel starvation problem. On a long flight one would have to know where the center wing tank goes empty to keep from crashing.With the PIC 767, when the center tank emptied, you get a warning that you had low pressure, but the engines were then feed from the wing tanks, which I think is the normal SOP.Anyone on the PMDG team, what is the logic that you programmed the tank feed seqence? That info sure would help with keeping this from being a problem.Thanks GuysBob JohnsonKDEN

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I've seen the same thing happen on my side as well. I was running in FS2002 and BEFORE the patch, I never had the center tank run dry/engines fail issue. I DID have the fuel imbalance issue. AFTER the patch, my imbalance issues are cured (I believe PMDG said to always PAUSE the sim if you adjust any fuel loads), but now I have the issue where my engines fail if the center tank goes to zero. My crossfeed valve is CLOSED as it is supposed to be. I've used the crossfeed valve prior to the patch to cure my fuel imbalance issues while in-flight and it worked just fine. But, normal procedure is to leave the valve position at CLOSED.Anyone else with these issues?

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My understanding of the fuel system is that the center tank feeds both fuel manifolds- L & R. the wing tanks feed their respective manifold unless the cross-feed valve is open, then both manifolds are tied together in order to allow for the curing of a fuel imbalance or to allow for feeding from the opposite wing tank.Since the center tank pumps are at higher presure than the wings, they feed after the pressure from the center tank drops to less than the center tank pumps, and there should be no interruption of fuel to the engines :)Tim

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