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Guest Voodoo

APU Fuelconsumption?

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Hello,this is my first post here and I am not a frequent reader of this forum but my search didn't find anything.First of all, I have to mention that I got the full PMDG 737NG set plus all the service updates installed on my computer. I found out that when the Auxillary Power Unit is running, that there's no change in any of my fuel tanks even after letting the Simulator running for awhile.I got that problem on any model, so I am not sure if this is a bug or meant to be so. I always thought the APU would get its fuel from the tanks so you should see a decrease after awhile and I think it was so on the older -600/700 versions.What I did to test this is, that I cut off the fuel on the throttle and normally turned on the APU on the overhead panel without any connection of ground power or engines running.Maybe I am getting something wrong here but I hope someone can enlighten me :-).Thanks!Christian

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Hey Christian,It is true, the PMDG APU runs on nothing but fresh air, it doesn't suck fuel at all in the sim.I believe that one of the very first versions did affect the fuel load but problems with the custom fuel system forced PMDG to remove this feature.Personally I'm a bit dissapointed in that regard but there isn't much I can do about it.Hope this helps :)David

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APU burned fuel like the real one back in the dayz (I mean in the first release)...But, apparently, this implementation also led to other problems for some users(I can't remember what was the exact problems 'cuz I never had some)...So PMDG removed it...:( And I was SAD...:( :( Hope this helps a bit.

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The problem caused was a fuel imbalance. I suffered this problem once or twice, but for some reason you couldn't resolve the imbalance. Its a shame that the feature was removed as it added that little extra realism that the pmdg 737's have.

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Hey Alaister,Could the imbalance not be fixed in the standard way once the engines were fired up?As far as I'm aware an imbalance will also occur in real life if the APU is switch on as it only sucks gas from the port main tank and, as there is no tank to tank crossfeed ability in the 737, an imbalance will occur.It won't become an out of limits fuel imbalance for some time (i.e. a couple of hours)Also, a bit of trivia here, if extended APU operation is required on the ground and fuel is loaded in the center tank, leaving the left center tank fuel pump switch ON will preclude a fuel imbalance before takeoff.CheersDavid

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There were more problems than fuel imbalance! For one the a/c started to dance can-can on the apron if you started the APU with no fuel in your tanks. ;-)The APU will create a slight fuel imbalance when used as it uses fuel from the left main tank. The fuel burn for the APU is almost infinitesimal compared to what the main engines burn so at a whole I don't mind PMDG taking that feature away. But I agree it would be nice! Let's see what they have in store for us with the 744. ;-)Cheers,

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Thanks for the informative replies. Too bad it doesn't work but still better than the problems it causes.best regards,Christian

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