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rsrandazzo

PMDG FUEL IMBALANCE TROUBLE SHOOTING

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Captains-We are still getting reports of wide inconsistencies in the fuel usage between tanks on the airplane, and some users still experiencing engine flamouts when the center tank fuel is exhausted.NEITHER OF THESE THINGS SHOULD BE HAPPENING!I've been trouble shooting this since early July and thought we had a good fix in place with SU1, but apparently that isn't the case.I've tried about 50 different variations to duplicate the flameout and have so far failed to duplicate....I HAVE been able to duplicate the excessive fuel usage from the right side tank but I haven't determined the cause yet.Here are some KNOWN CONDITIONS that each of you should be aware of:1) If the APU is running, our fuel control logic will prevent you from updating the fuel level in the left wing tank.2) We do not use the MSFS default fuel system logic because it does not work effectively for a Boeing airplane. (great for Cessnas tho...)3) Our system uses a series of "states" to define which tank/s to pull fuel from. If your Center tanks are running, you will get fuel from teh center tank, etc.4) There are a number of gates that force the direction of fuel flow given certain conditions. (i.e: when the center tank fuel is less than a certain level- the fuel system logic should force itself into the tank-to-engine configuration.)5) To kill any misconception about Xfeed... Only open the Xfeed valve if you want to draw fuel from the a single side of the airplane. If you aren't actively trying to balance fuel- leave the XFeed shut!6) MSFS will not allow a "tank-to-engine" configuration within the simulator. As such, when the airplane is in the T2E configuration, we have a nice little system that is quietly alternating the fuel valve between left and right tanks at a common timing interval. This simulates the T2E fuel consumption process marvelously. This also explains why you often see LEFT or RIGHT selected in the MSFS fuel valve selector in the FUEL menu. ;-)7) Our airplane SHOULDN'T care whether you change fuel from the external menu or from the internal menu. Some folks have found that they have success with using one menu as opposed to another. From our logic standpoint- it really shouldn't matter....so we'd be interested to hear more about user experience in this regard.8) All of this being the case SOMETHING is causing the fuel imbalance and the center tank flamout..... The question is: what?If you are experiencing the FLAMEOUT and/or the IMBALANCE:1) What version of FS are you using?2) Do you have "unlimited fuel" deselected? (I ask because after tens of hours of testing in FS9 I realized I had this box checked....duh)3) Have you manually set the fuel valve within MSFS before/during your NG flight?4) Which fuel menu did you use to set your fuel leve?5) What was the fuel level in each tank approximately at Takeoff...6) Had you conducted ANY crossfeed operations during the flight?7) Had you operated the APU at any time during the flight? Was it On/Off when the flamout occurred?8) Did you experience IMBALANCE, FLAMOUT or both?9) Please tell me you are running SU1-1, right? ;-)Thanks gents- looking forward to collecting some data from you to see if we can't beat this little bug back into it's hole...

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Robert,I did have severe fuel imbalance problems when running the APU in flight. No flameouts, though. Last night I conducted a flight with APU off and everything worked perfectly. Cross feed worked, no fuel imbalance, fuel only from center tank when sufficient left in that center tank. I switched the fuel switches a lot, but everything worked like a charm. Again, this is only the case with APU off.My data:1) FS2002 on Win XP Pro2) No3) Did not matter4) FS2002 aircraft fuel menu5) 4000 - 1000 - 40006) Did not matter7) APU was on all the time8) IMBALANCE9) Yes, off course. But problem also occured with SU1Hope this helps.Best regards,Henri

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Hi Robert,1) FS9 on WinXP Home2) Unlim Fuel IS deselected3) Centre pumps to OFF when fuel in this tank depleted. ('FUEL' annuciated)4) External5) Wing tanks 100% each, centre 5%6) No7) APU running on ground, off at circa 6000' on climb-out8) Both, but flameout (Eng2 only) only once9) Yes.I say the flameout happened only once but the imbalance occurs everytime. Apart from varying the fuel (question 5) the other steps are common to all my flights.Cheers,Paulhttp://www.strontiumdog.plus.com/sbird.jpgOfficially licenced by British Airways plc for use of name and logo[p]AMD XP2800+ Barton, Gigabyte GA-7NNXP nForce2, 1Gig Crucial PC3200 DDR 400MHz, Gainward 128 MB GF4-4200, SB Audigy, 3 x WD Caviar SE[/p]

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1) What version of FS are you using? FS2004, WinXP Pro SP1 etc.2) Do you have "unlimited fuel" deselected? Yes3) Have you manually set the fuel valve within MSFS before/during your NG flight? No, I only use the valves in your panel, don't use any MSFS fuel related key assignments. I usually fly trips of around 1 hour, so center tank is empty. I fill in 0% in the FS2004 fuel menu of the 'Create a flight' section. Wing tanks are filled according to the fuel needed ofcourse. Then I start with cold&dark, provide power, start APU, switch on left/right fuel pumps, switch off/leave off center tank pump, start engines. All according standard procedures (I hope ;-)) Switch off APU. When I keep it like this, I always get a right tank fuel imbalance warning after some minutes of flight. I then select crossfeed and turn off the right pumps till the imbalance is gone. Then switch on right pumps, switch off crossfeed. From this point on the flow is good. No more imbalance warnings during the remainder of the flight.4) Which fuel menu did you use to set your fuel leve? FS2004 menu5) What was the fuel level in each tank approximately at Takeoff... Left/right at 99%, center tank empty6) Had you conducted ANY crossfeed operations during the flight? Yes, see point 37) Had you operated the APU at any time during the flight? Was it On/Off when the flamout occurred? No, APU off after engine start.8) Did you experience IMBALANCE, FLAMOUT or both? So far no flameout at all occurred, I guess because my short flights do not require center tank fuel? I've only seen the imbalance warning a lot.9) Please tell me you are running SU1-1, right? Sure! Used the remove tool, re-installed base and then SU1-1.Hope it's helpfull. Also, if I'm doing something wrong in my procedures, please let me know!EDIT:I did change Aircraft.cfg to show 'number_of_tank_selectors = 3'Henk-Jan

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Sorry, I should've said 'no' I haven't manually set any fuel pumps from the MSFS menu - only the switches in the PMDG panel.Cheers,Paulhttp://www.strontiumdog.plus.com/sbird.jpgOfficially licenced by British Airways plc for use of name and logo[p]AMD XP2800+ Barton, Gigabyte GA-7NNXP nForce2, 1Gig Crucial PC3200 DDR 400MHz, Gainward 128 MB GF4-4200, SB Audigy, 3 x WD Caviar SE[/p]

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1) What version of FS are you using?FS92) Do you have "unlimited fuel" deselected?yes3) Have you manually set the fuel valve within MSFS before/during your NG flight?No4) Which fuel menu did you use to set your fuel leve?I don't understand this question. I thought there was only one way to set the fuel level, and that is via File/Aircraft/Fuel an Payload. What is the other?5) What was the fuel level in each tank approximately at Takeoff100/20/1006) Had you conducted ANY crossfeed operations during the flight?No7) Had you operated the APU at any time during the flight? Was it On/Off when the flamout occurred?Used APU to start engines, shut it off after start.8) Did you experience IMBALANCE, FLAMOUT or both?Flamout when center tank was empty9) Please tell me you are running SU1-1, right? ;-)Yes of course. LOL

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...>8) All of this being the case SOMETHING is causing the fuel>imbalance and the center tank flamout..... The question is: what?Hi,mmmhhh, now I have a suspect: the running APU, at least for the fuel imbalance. Switching off the Apu immediately after engine startup resulted in a successful test, with no imbalance at the end of the flight, without the need to Xfeed. I was also able to refuel the left tank normally.I'm wandering whether the imbalance is related with the control logic preventing you to refuel the left tank with a running Apu. Anyway here are my answers.All the best, Dino Giannasi>1) What version of FS are you using?FS2004 and FS2002. Same problem. As told before now OK at least for FS2004 (to be confirmed in FS2002).>2) Do you have "unlimited fuel" deselected?YES (i.e. NO unlimited fuel)>3) Have you manually set the fuel valve within MSFS>before/during your NG flight?NO>4) Which fuel menu did you use to set your fuel level?Internal FS>5) What was the fuel level in each tank approximately at Takeoff...Left 51%, Right 51%, Center empty>6) Had you conducted ANY crossfeed operations during the >flight?Yes and no, but it doesn't matter.>7) Had you operated the APU at any time during the flight? Running = imbalance. Switched off = even drainage>Was it On/Off when the flamout occurred?Never experimented a flameout (never filled the center tank)>8) Did you experience IMBALANCE, FLAMOUT or both?Yes. No (see above)>9) Please tell me you are running SU1-1, right?Absolutely YES>Thanks gents- looking forward to collecting some data from>you to see if we can't beat this little bug back into it's hole...You bet... Joint work is the way to go.

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Uhmmm Henri, I guess you did not know this but PMDG has modeled the APU to suck fuel from the left tank while running. Why you are having fuel imbalance problems is because of operator error. If you keep the APU on during flight, you WILL have a fuel imbalance problem with the left tank draining faster than the right tank.

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Well,Than it is even worse, because the RIGHT tank was being drained much faster than the left tank. Furthermore, the imbalance was much more than ever could be attributed to the APU, or does the APU use more fuel than the two engines together ;-)Best regards,Henri

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Robert,With 2) = No I meant no unlimited fuel selected, i.e. did you have unlimited fuel DEselected = yes. Sorry for reading so poorly. It isn't even a Florida ballot. ;-)Best regards,Henri

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Here's an interesting one- I'm not seeing the imbalance with the 1-1 update, however I have seen a consistient flameout when the center tank runs dry, but it did not happen last night for the first time!Flameout only seems to happen to me if I've used teh APU for engine start.I have unlimited fuel unchecked.Tim

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1. 20022.na3.no4.FS 20025.7500,2000,75006.no7.only startup -off when flameout occurred8.Flameout9.SU1-1This is the first time that I have had flame out -I believe because Idid not notice the warning and did not turn off the centre tank pumps.If I do that when warned no flame out occurs and - I notice that the centre tank empties itself.David Pedder

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Most peculiar thing... When I took a test ride to answer these questions just now, it seems everything worked fine! However, I started a flight with the engines running, 1% fuel in the center tank and 50% in the wingtanks. Shut down fuel pumps for the centertank as soon as the flight started (had 280 lbs in it), and started the APU, configured and set the overhead panel, and turned the APU back off (I've flown with the APU running all the time earlier). When I arrived, no fuel had been drawn from the centertank (still 280 lbs left), and the other tanks had an almost equal amount left (1900 and 1890 left to right).Just to test - after landing I turned on the center tank fuel pumps and gave full throttle to empty it. Guess what? The engine(s) did not flame out! I kept throttling, and as long as the center fuel pumps were on, the right tank fuel flow rate was much higher than the left. As soon as I turned the center pumps back off, fuel were drawn equally from both wing tanks.So I guess everything is normal with me all of a sudden then? Well, my plane anyway... *:-* At least when starting the flight with engines running (through the 'Create a Flight'-menu).Anyway, here are my answers:1. FS92. Deselected yes3. No, not through MSFS, only your panel4. The FS menu before starting the flight ('Create a Flight')5. 1% in the center tank and about 45% in each wing tank6. I did not touch the crossfeed valve this time (since everything went ok), and I think that is a first. I've always switched this several times during earlier flights when I had the flame outs and imbalance.7. The APU was off when I started the flight (with engines running), then I turned it on and 'pushed the right buttons' (I think) on the overhead panel, and turned the APU back off. It was running for about a minute.8. For the first time, no imbalance (well 10 pounds. Probably from when the APU was running) and no flameout, even when the center tank was empty. The APU was not running at the time the tank was empty.9. Running the latest service update yes.Final note: I've been running the APU through the whole flight earlier, and just recently learned that it was supposed to be off after engine start (well I sort of knew, but didn't bother to turn it off earlier). This was the first PMDG flight I turned it off during flight.When I started the APU before engine shut-down upon arrival, I noticed the fuel flow rate from the right tank was much higher than the left, so that has probably caused the imbalance for me (and others) earlier. I think maybe the APU is not supposed to drain that much fuel in real life...?Ok I'll stop now...Good luck sorting out the problem, and thank you for a great piece of software!Best regards,Bj

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1. FS92. Yes3. No4. FS9 menu from full screen using ALT key5. 80%, 0%, 80%6. No7. On till 5000ft after takeoff8. Imbalance only L=35%, R=30%9. Clean re-nstall after removal with tool. Patched using SU1.1Flight time 1 hr.Paul Gardner

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1) What version of FS are you using?FS92) Do you have "unlimited fuel" deselected? (I ask because after tens of hours of testing in FS9 I realized I had this box checked....duh)Unlimited fuel is deselected3) Have you manually set the fuel valve within MSFS before/during your NG flight?No4) Which fuel menu did you use to set your fuel level?Fuel/Payload menu5) What was the fuel level in each tank approximately at Takeoff...L 99.9% C 12.0% R 99.9%6) Had you conducted ANY crossfeed operations during the flight?Yes7) Had you operated the APU at any time during the flight? Was it On/Off when the flamout occurred?APU for cold/dark start. Shutdown APU prior to taxi.8) Did you experience IMBALANCE, FLAMOUT or both?Flameout when center tank goes empty. I usually shut down the center tank pumps with about 120lbs remaining in the tank. Imbalance is slight with crossover open for entire flight, however I recall imbalace can get to be quite severe without it constantly open. I'll make a couple of flights later tonight and update with my findings.9) Please tell me you are running SU1-1, right? Of course :)Carl MooreSystem specs:WinXP Pro SP1P4 2.4ABIT BD7 RAID 512 Corsair DDR 2100ATI Radeon 9800 Pro Cat 3.6Hercules Game Theater XP Driver 6.09

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All right, Did some testing last night and this is what I found. When the center tank runs dry the engines die. After the center tank pumps are shut down and the engines restarted, you can turn the center tank pumps back on without the engines dying. The imbalance issue appears to be caused by running the APU. It pulls about 10lbs or so a minute from the right wing tanks. I started cold and dark,used the APU to power up the aircraft until after engine start. I noticed in the time it took to get everything up and running and get my flight plan loaded into the FMC the APU had consumed 230lbs of fuel from the right tank. The imbalance stayed at 230lbs with the APU shutdown. About 20 minutes after takeoff I fired up the APU to see if the imbalance would increase in flight. Sure enough, with the APU running for about 7~8 minutes, the imbalance went from 230 to 300 lbs.Hope this helps.Carl Moore

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G'dayHere are my settings.I experienced a No 2 flameout on expiration of fuel in the centre tank.My data:1) FS2004 on Win XP Home2) Yes3) No4) FS2004 aircraft fuel menu5) 6500-500-65006) No7) APU on ground prior to start.Turned of prior to t/o.8) Flameout at centre tank expiration.9) Yes i have SU1.1All the best and keep up the great work on the NG of flight sims.Darren Howie

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1.) FS2K22.) No unlimited fuel3.) Yes, shutdown and start-up on a second leg, did not use the center pumps and the first.4.) Fuel menu?? I only know of one within FS, not fuel settings at start-up.5.) Full-1500-Full6.) no, not on 2nd leg, on first leg yes about 1hr prior to balance the wing tanks after APU operations.7.) yes, it was off when flameout occured.8.) Right engine flameout.9.) YESSIR.Eddie Doloughty

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To add to my post on imbalance.I suffered from continual engine shutdowns with no fuel in centre tanks and I thought it was pilot error. I appear to have solved the flameout problem - not the imbalance by doing the following.I loaded up the default 737-400, powered up and started engines. I then did a complete shutdown (ctrl+shift+F1) to shut of the fuel and turned all power off. I saved this flight as a "cold and dark pre PMDG" flight.Now when I'm in FS9 and want to fly I select the above flight and then go to the PMDG 737. So far I've had no flameouts. This may well be a red herring but there may be something in this which will give a clue to the problem, I don't know.Just my two pennys worth.Paul gardner

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Ok, here we go:-startup at ksea on runway with engines shut down.- running Fs9- no unlimited fuel (I can run out ouf fuel and then engines should shut down)- I didn't set any fuel valves in the menu of Fs9. Inside the cockpit all fuelpumps were "on" and no crossflow applied- I used the pulldown menu from Fs9 to adjust the amount of fuel to- both wingtanks to a full 100% and the center tank to only 5% (for test reasons only)- again no crossfeeding- I used the APU to start engines and after both engines running I shut the APU down. This resulted in a slight imbalance between the right and left wingtank. (left lower than right = normal)- takeoff with full power... both engines pulling fuel out of the center tank... when this went dry, flameout of both engines... No imbalance except for the slight difference between left and right because of apuLuc "Glaudrung" BrusselmansBelgium

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By the way...is there some other way to adjust the fuel, other than the pull down menu from Fs9 to adjust fuel and payload...???I have been wondering about this since I first read this thread...Luc

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Hiafter looking to the default Boeing 737-400 from FS9 I notice, that in the aircrfat.cfg the number of tank selector is = 1After changing our PMDG to the number 3 I got back to 1.And ?I tested ( 2 times only ) and it works.When the center tank goes dry, you get the message "fuel", I shut down the pumps of the center tank and the engines run now from the wing tanks, without any problems.Try it !Gerhard / Vienna

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Why is it that the left tank is hard limited to 29% of capacity with APU on? Technically if all tanks are full and the APU is drawing off left, from 100% there will be an imbalance and why no other pumps are turned on except aft 1. Once APu is cut out, xfeed oughta balance the 2 wing tanks in flight.APU should not be drawing fuel at a high rate or constant rate even if left on in flight since fuel economy varies with altitude.Can you check this out. I try to fill left tank for flight but hard limited to 29% max until I shut it down.

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"Can you check this out. I try to fill left tank for flight but hard limited to 29% max until I shut it down."This is a known bug, Mr ...er... "Buff". It has been mentioned many times in the forum. Pausing the sim with the "P" key before refilling the tanks will allow you to put in as much fuel as you want ;-)Regards.Ian.

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** If you already have this post apologies.Robert,I have had the flameout problem many times and seem to be able to re-create it. Basically I tend to load the flight from create flight and once loaded adjust the fuel. Now my logic here is based on a PSS and I think Dreamfleet issue, but don't quote me. Basically in one of them if I set the centre to zero and the wings to say 30% the engines would shut down. To avoid this I always left 5% in the centre and the problem goes away.Tonight I tried two flights from EGCC runway 24R with Activesky running (I hope this isn't too much detail). I ran this up from create flight and once loaded altered the fuel to 30% 5% 30%.I then spent some time setting up the FMC to fly to EGNM (A very short trip of 40nm). After doing that and setting the MCP I taxied to the runway. It seemed to be burning centre tank fuel very fast as I was down to 200LB by this point. I only came to this conclusion when I did the whole thing again and it burned more slowly.Anyway, with everything setup I got onto the runway and started to roll. Between 80kts and V1 the centre tank emptied and I lost engine 2 (As always). Due to my piloting ability I veered right and game over. One point here, I never get an audible alarm and I don't know if I should. If not I would like to recommend one to Boeing.After all this excitement I did the whole thing again, however the centre tank lasted much longer so I took off. Part way into the flight the centre tank emptied and engine two died. On this occassion I restarted and landed safely at EGNM as you will be glad to hear.I took screen shots of the panel and overhead during both flights if you would like them for reference. Please let me know and I can email them. I wasn't sure what the protocol is here regarding attachments. I will now answer you settings questions:1) What version of FS are you using?20022) Do you have "unlimited fuel" deselected? (I ask because after tens of hours of testing in FS9 I realized I had this box checked....duh)Yes3) Have you manually set the fuel valve within MSFS before/during your NG flight?Before flight4) Which fuel menu did you use to set your fuel leve?Inside flight sim before take off5) What was the fuel level in each tank approximately at Takeoff...30% 3% 30% and second time30% .5% 30% 6) Had you conducted ANY crossfeed operations during the flight?No7) Had you operated the APU at any time during the flight? Was it On/Off when the flamout occurred?No and off8) Did you experience IMBALANCE, FLAMOUT or both?Flameout9) Please tell me you are running SU1-1, right? YepI hope this helps solve the problem.RegardsGeoff

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