Fuel Imbalance?

[geholger 1]

On my flight from KJFK to KSFO, I suddenly received a FUEL IMBALANCE message on the EICAS together with a TANK/ENG message. After cleaning up the TANK/ENG message, the FUEL IMBALACE remained. Reading the QRH and checking the EICAS fuel page did not bring me any further on how to proceed.

Any ideas how to resolve this issue?

Thanks,
Holger

[cannonplug 126]

6 minutes ago, geholger said:

Any ideas how to resolve this issue?

Holger,

What happened here is that you made the change too late. What you can do at this time is open the outer crossfeeds again and turn off the Main2 and Main3 pumps. Now you will be feeding the left engines from Main1 and the right engines from Main4. Keep an eye on things. When your outboard tanks get close to the 8.9 you're seeing in the inboard tanks, the imbalance message will go away and you can reconfigure the pumps as you did above. You should see no more caution messages.

[scandinavian13 5,192]

7 minutes ago, geholger said:

Any ideas how to resolve this issue?

This is caused by ignoring the FUEL TANK/ENG warning on the EICAS for too long.

You can resolve this simply by not allowing it to happen by properly operating the aircraft:

As for resolving it after the fact? You can reopen the crossfeeds and then shut off the inner pumps until they're all equal again, but I will again point to the above. Proper operation will avoid this issue.

There is also a setting in your PMDG SETUP > SIMULATION menu that allows you to tell your computer to handle the FUEL TANK/ENG for you, should you so choose.

[geholger 1]

Thanks a lot for your help. Ok - there should always be at least one crew member in the cockpit and monitor the things while the other one takes a short break on longer flights ;-). I guess I will go with Kyles second advice and let my compute take care of the FUEL TANK/ENG to prevent fuel imbalances in the future.

Greetings and thanks for the prompt feedback!
Holger

[Ralgh 43]

Disregard. I missed a sentence on the previous post. 

[Orbitandy 17]

This happened to me yesterday on a flight from OMDB-YSSY - left the PC running and came back to the advisory "fuel imbalance" EICAS message. 

I learned from the manual that this meant there was a fuel difference of 2,720 kgs between inboard main tanks (2 and 3) and outboard main tanks (1 and 4) after reaching FUEL TANK/ENG condition. Mine had reached a 4 ton difference.
Message no longer displays when difference becomes less than 450 kgs so I proceeded to apply the mitigation.

The manual instructs that fuel may be balanced:
• between main tanks 1 and 4 by opening crossfeed valves 1 and 4,closing crossfeed valves 2 and 3, turning off the fuel pumps in the low tank, and turning off the override pumps in main tanks 2 and 3
• between main tanks 2 and 3 by turning off the fuel pumps in the low tank
• longitudinally by opening all crossfeed valves and turning off the fuel pumps in the low tanks.

I managed to balance the queen after an hour or so and the message went away - interesting lesson learned but rather satisfied I was able to succesfully apply QRH. The logic behind the message was impressively simulated by PMDG, which is why I'm so amazed by the level of fidelity demonstrated by these products.

 

[scandinavian13 5,192]

Again:

The best way to "fix" this is to ensure that it never happens. The TANK/ENG message shows up for a reason. If you don't like the automagic feature we've provided to handle the TANK/ENG switch for you, then look at the LEGS DATA page to find the waypoint (and therefore the time) where you'll have about 120.0 left in the tanks (if you use kgs, do the math to convert 120lbs to kg). That's about when the switch will need to occur.

[Orbitandy 17]

Good tip, thanks Kyle.