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Guest lbowes

Fuel

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Guest lbowes

Hi all,I have now started doing longer trips in the fantastic 737. I did a flight which had a distance of 2000nm in the b737-800. I checked with the FMC that I had enough fuel (left & right tanks 100% and ctr 30%). On approach the two wing tanks were empty and the engines shutdown, so I quickly filled the left and right up again and restarted the engines (to land safely). I thought once the left and right tanks were depleted it should automatically switch to the ctr tank. What do I have to do to make sure that the centre tank is used?Thanks to anyone in advance for answering my rather dumb question,Luke

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Luke,Did you make sure that the center fuel pump switches were ON? If they were, and there was fuel in the center tank, there is no reason why your engines shut down.Also, I have been informed by different sources that it is unsafy to let any of the tanks run dry. So, if there is less than about 800Kg of fuel in the wing tanks, turn those switches to OFF position to keep the pumps submerged in fuel.Cheers,


Balint Nagy
 

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Hmmm...I'm sure I'm gonna be corrected if I'm wrong but I'll take the risk. ;-) I think all the pumps are located in the centre tank. They just draw fuel from different tanks. Thus you should be fine draining the main tanks and leaving enough fuel in centre to keep the pumps submerged i.e. 1000 lbs or 500 kgs.Oh. And to the original question. You use your centre tank fuel first, down to minimum. This is accomplished by turning all pumps on. The centre tank pumps provide a higer output pressure and will "overpower" the main tank pumps. Then you switch off the centre fuel pumps and main tank pumps will feed the engines.Hope it helps,


Mats Johansson
PMDG Flight Test Dept
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Luke,Fuel management in the 737NG, always burn fuel from the center tank first and then from the wings. This is for a structural limitation for a bending moment on the wing root area.Before takeoff if there is fuel in the center tank then turn all the fuel pumps on, center and wings. Fuel will be taken from the center tank first because center tank pumps produce higher preasure than wing tank pumps.Floyd


John Floyd

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Guest lbowes

HiThanks all for the great replies. I'll follow your advice and burn from the center tank first and then from the wing tanks. Now all I need to do is make sure I flick the right fuel pump switches :-)Thanks,Luke

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as the centertank runs dry the warning lights for the pumps will come on telling you which switches to flip :)

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Guest tmetzinger

>as the centertank runs dry the warning lights for the pumps>will come on telling you which switches to flip :)But because of recent concerns about exposed wiring, the proper practice is to leave 1000 LBS in the center tank, so pay attention to the fuel status, and shut the center pumps off when you get down around 1000 lbs.

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Tim,Actually the lastest procedure now with non modified fuel systems is during climg or cruise when center tank fuel reaches 2000 lbs, open the crossfeed and turn one center tank pump off. When center tank is empty, turn off the other center tank pump.For takeoff, both center tank pump swithches must be off if fuel in the center tank is less than 5000 lbs. Position both center tank pump swithches on passing 10,000 feet or after the pitch attlitude has been reduced to begain acceleration to a climb speed of 250 knots or greater, if more than 2000 lbs remain in the center tank.For descent turn one center tank pump switch off at the begining of the descent if less than 3000 lbs of fuel remain in the center tank. Open the crossfeed valve to minimize imbalance. When the center tank is empty, turn the other center tank pump switch off and close the crossfeed valve.So much fun.Floyd


John Floyd

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