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Guest Kianok

Cross Feed 737NG

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Guest Kianok

This is probably a really dumb question but how do you get the cross feed to work?I have flicked the cross feed switch to on so it lights up blue but i still get a fuel warning light when the center tank is close to empty.Where am i going wrong??

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Guest svedman

I don't think the cross-feed does much to the center tanks, but seperates the wing tanks when closed?When the center tanks give the warning, just turn the center pumps off and the Low press light will extinguish. This is perfectly fine. You do have fuel in your wing tanks, right? ;)Best regards,

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Guest Kianok

Yes, tons of the stuff, just couldn't work out how to get to it!Thanks i'll give that a try.

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Guest tmetzinger

You would normally use the crossfeed valve if you had an imbalance between the amount of fuel in the left and right wing tanks. This could be due to an engine failure, or a fueling error.When I get home this afternoon I'll pull the fuel system diagram and double check, but if I remember correctly one would open the crossfeed valve, and turn off the pumps on the lower of the two wing tanks. The higher pressure in the tank with the pumps on would ensure that it was used to feed the engine(s) running. Then, one would switch tanks periodically by changing which tanks had the pumps running, to keep the fuel levels close.I also think that somewhere PMDG may have had problems with the fuel system logic in FS9, so I don't know if the sim works "correctly".More this evening,http://online.vatsimindicators.net/874487/2716.png

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Guest svedman

>Yes, tons of the stuff, just couldn't work out how to get to>it!You don't need to "get to it", the airplane will use fuel from the wings automatically.Best regards,

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The Crossfeed does work in the 737NG simulation.Always use the fuel in the Center tank first. when the Center tank pump low pressure lights illuminate, turn them off. Fuel will now flow from both wing tanks to the engines.Use the crossfeed to balance fuel levels between wing tanks 1 and 2. Crossfeeding does not transfer fuel from one wing tank to the other tank or even the center tank. It only sets up a situation to use fuel from only one wing tank to balance fuel with the other wing tank.To Balance fuel:-Open the Crossfeed Valve-Turn off both main fuel pump switches on the low fuel quantity side.-When fuel levels are equal in the wing tanks... -Turn both main tank fuel pump switches back on-Crossfeed valve close.Floyd


John Floyd

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Guest tmetzinger

>To Balance fuel:>>-Open the Crossfeed Valve>-Turn off both main fuel pump switches on the low fuel>quantity side.>-When fuel levels are equal in the wing tanks... >-Turn both main tank fuel pump switches back on>-Crossfeed valve close.>In the event of single engine ops, once you have the levels balanced, turn on all fuel pumps and keep the crossfeed valve open, and you should drain fairly from both wings to the single engine, I think.

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Sounds good but not a standard 737NG procedure. The cross feed should never stay in the open position except to balance fuel, even during single engine flight. If a fuel leak develops in either engine with the cross feed open, all fuel will be lost. To help identify a potential fuel leak, the cross feed must be closed. Identify an engine fuel leak by observing one main fuel tank quantity decreasing faster than the other. During single engine flight it is OK to let an imbalance occur and then balance however many times it requires until landing. This would be a good task for the PNF.By the way, in this airplane, the primary reason to keep the wing fuel balance is to avoid unequal bending moments on the wing root which short en


John Floyd

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Guest Kianok

Thanks for all your help chaps, it all makes sense now.Just out of interest why does the FMC say insufficient fuel even though when i do reach my destination i still have both wing tanks full and the centre tanks at about 10% full?

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Guest 102301636

you might be getting the insufficient fuel message in the climb because the aircraft is using a higher thrust setting (and thus more fuel) so the logic predicts that at this rate of fuel usage you will not have enough fuel to reach your destination...you should plan to arrive at your destination with at least 2000lb of FOB

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Guest Kianok

Is it normal? or should i reduce the climb rate and air speed?

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Guest tmetzinger

Thanks, I found the same thing when I hit the books last night when I got home. Unfortunately my daughter then hit the fireplace so I was unable to post.

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