APU fails to start when center tank shows nearly empty

[pbelb 0]

ok, so I land at an airport with almost no fuel left in the center tanks, and none in the stabilizer tanks.I'm under the impression (perhaps wrongly) that the pumps are supposed to make sure that there is fuel in the center tank (the wings have plenty) so that the APU can run.However, having set everything the way I normally do, and tried to start the apu, the eicas status display shows absolutely no joy at all with the APU.what's up with that?I'm guessing it's because there's too little fuel in the main center tanks.how am I supposed to cause fuel to be moved to the center tank so that the apu will start?any help appreciated.

[cavaricooper 2,613]

Peter:It is my understanding that the APU draws from the #2 Main (wing) tank- so the center tank having no fuel is unimportant- and a correct condition for most/all landings!Are you following the recomended checklist flows? Right click on the APU knob to Start (2 clicks) and it should spring back to center. After a minute or so you should have APU innunciated on the EICAS and 1 and 2 gen avail on the upper panel..... Have you waited a bit to see if it turns on? Normally it is started on taxi in, that way it is on and gens available on stand......Best-Carl F. Avari-Cooper BAW0225http://online.vatsimindicators.net/980091/523.png

[BAW9DV 2]

Peter,Carl is correct. Bring up the lower EICAS and click the STATS button. Then bring up the overhead panel and click the APU start button TWICE so that it springs right across to START and then back to the middle. With the EICAS STATS page showing, watch the APU steadily increase as it starts.When it reaches around 99%, you should see the two AVAIL buttons light up. Click these buttons and also turn on the APU BLEED as well. The upper EICAS should show the APU RUNNING message.Note that the APU cannot be turned on above 20,000 feet and it does indeed draw fuel from TANK No.2If you are not getting the APU to run, check the overhead panel and ensure you have estblished electrical power.Hope this helps,regards,Lee

[pbelb 0]

thank you for the responses guys!ah, tank #2. ok, so, same question:lets suppose I land and tank #2 is empty, but I have fuel in other tanks.how do I cause fuel to flow into tank #2 so that I can start the APU?the problem is not how to click the button, the problem is evidently the fuel level.I thought I read somewhere that there were pumps that were supposed to help ensure that the tank was able to get fuel from other tanks so that the APU would be able to be started and run.is this not correct?

[mburkhard 23]

>lets suppose I land and tank #2 is empty, but I have fuel in>other tanks.Peter,you should never be airborne with main tank #2 empty. If you are you either made an error during fueling or during flight with fuel management.Have a look at the FUEL section of the 744's manual, all possible fuel configuration scenarios are listed there together with the proper management of those.ORyou wait for the MD-11, she's doing that all automatically, no need to push ANY fuel panel button during normal operation ;)Regards,Markus

[Qavion 19]

"Note that the APU cannot be turned on above 20,000 feet and it does indeed draw fuel from TANK No.2"Depends on the model and what fuel pumps are running and what crossfeeds are open. Later aircraft allowed fuel to be drawn from the #3 tank also (on the ground). In PMDG, if the APU is selected ON (with main bus power available), which PRESS lights go out? Just #2... or #3 also?In theory, any fuel pump which is feeding the left fuel manifold, will feed the APU (including the CWT)Cheers.Q> イアン

[BAW9DV 2]

Peter,Are you loading fuel via the PMDG menu - or by the FS Menu? Never load fuel into the PMDG 747 by using the Flight Simulator's own menu, always use the PMDG/FUEL option.Just a thought - not attempting to teach you to suck eggs....!cheers,Lee

[pbelb 0]

yes, I'm using the pmdg fuel loader.I'll try and pay attention next time to what is going on next time I encounter it.given I tend to fly long distances (10 - 12 hours with holds on top of that) I tend to encounter it quite a bit.for example:one time, I landed with barely 4000lbs of fuel remaining.the aircraft had been on hold so long, that the fmc claimed there wasn't enough fuel remaining to reach the destination.indeed, if I had flown the remainder under power, that would have been true, however, I glided most of the way down, and used a spurt of thrust just prior to landing to get on the ground gently.