Pro Member Trainee
b_kennedy Trainee

Hi guys. Have been browsing these forums for a long time but never posted up until now... I need HELP 😞

Here goes... I am using the PMDG 737-700 for my FSPassengers scenario, however I only seem to be able to fly short-mid haul as I run out of fuel. I dont seem to be able to switch between tanks?

I have noticed when the aircraft is idle on the taxiway it uses the centre fuel tank only. When I switch off the centre fuel pumps it begins to use the wing tanks. When I switch them back on again it continues using the centre tank only.

As far as i have discovered from research the wing tanks should be used before the centre tank. Am I correct?

Anyway.. During flight, once my wing tanks are down to around 1500 I switch on my centre tank pumps and nothing changes. It continues to carry on with wings tanks and nothing from centre. Even if I shut off the wing tanks it still uses the wing fuel and not centre.

Hence I am very good at glider landings to emergency airports lol.

I admit im still learning this aircraft as I go along but cant seem to find any information or any other users with this problem after hours of googling 😞

I'm sure you guys will point out a very minor school boy error but would be great for any help or info. Thanks in advance guys,


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Pro Member Chief Captain
Jonathan (99jolegg) Chief Captain

First, you fill the wings and put the trip fuel you need in the centre tank. The reason being is that lift is great; it allows us to zoom around the sky via thrust. However, when you create a shed load of lift (which modern, efficient wing designs are made to do) you create enormous upward stresses on the wing root...where the mass of the fuselage of the aircraft drags down, but the wing has so much lift it deflects upward (wing flex). For that reason, wherever possible, to reduce this force, you leave fuel in the wings so that the mass of the wing is heavier and the force bending upward at the wing root is less.

So...leave the fuel pumps as they are, and on the 737-300 at least, it'll use the centre tank fuel and then revert to the wing tanks. There should be no need to alter the fuel pump system at all (bar crossfeeding for fuel imbalances).

Hope that helps.

Pro Member Trainee
b_kennedy Trainee

That sounds like that would probably work. I will give it a go shortly.
Do you know a route that would use a full fuel load I can test on. I'm not to good with the understanding of the fuel calculator just yet 😞

Thanks for the help

Pro Member Chief Captain
Jonathan (99jolegg) Chief Captain

I don't know where you're from, but Miami to Seattle or Switzerland to Dubai is around 3000nm which is close to the max range of the 737-600/700

Pro Member Trainee
b_kennedy Trainee

I'm from the UK. Work at Heathrow to give a rough location idea Smile

I will try a route tonight and let you know the results.

Thanks again

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