Fuel Quantity IMBAL message ?

[Dumont 9]

I usually have my NGX 60% fuel capacity.When taking off the amount in the wing tanks is equal in both tanks, but after a while the message "IMBAL"The valve cross-flow of fuel is in the "Open Valve" (blue light on)João Alfredo

[xxJohnxx 21]

Hi,It looks like you are empting your wings tanks before the center tank. However first you should empty your center tank. If you have both center tank pumps on this will happen automaticly because center tank pumps have a higher pressure than the wing pumps. When your centertank has 1000lbs you should turn off the pumps and only feed the engines by the wing tanks. However the remaining 1000lbs will be slowly drained to the left wing tank and I think thats your problem here.You may have the center tank pumps switched off and now the drainingpump brings the fuel to the left wingtank. And so you get this imbalance.To avoid this, empty center tank first, than the wing thanks.Jonathan

[Dumont 9]

Hi,It looks like you are empting your wings tanks before the center tank. However first you should empty your center tank. If you have both center tank pumps on this will happen automaticly because center tank pumps have a higher pressure than the wing pumps. When your centertank has 1000lbs you should turn off the pumps and only feed the engines by the wing tanks. However the remaining 1000lbs will be slowly drained to the left wing tank and I think thats your problem here.You may have the center tank pumps switched off and now the drainingpump brings the fuel to the left wingtank. And so you get this imbalance.To avoid this, empty center tank first, than the wing thanks.Jonathan

thank youI'll do a test.João Alfredo

[Paul Deemer 13]

Check the overhead before pushback to be sure all your switches are in the correct positions? Alot of problems could be solved that way. Just like people who forget to turn the packs back on after engine start. If you take your time and verify everthing is correctly setup before you push you will have a smother hassle free flight and will enjoy it more.

[davierosoft 13]

If you load 60% of total fuel capacity, fill fist both wing to the maximum value, then put the remaining fuel in the center tank.The center tank is a passive load while fuel in wings are active loads.What it means? Fuselage is a tube, it has its weight, and it generates when flying something like 0 lift. All the fuselage weights are so called passive weights, they are weights that the gravity want to put down on earth.Wings have their weights, and fuel is a good part of this weight, but wings generates also the lift.This lift is sufficient to create a force greater than the wings and fuselage weight, but, if you think about fources, you can imagine that there will be no torsion forces if all the surfaces from a wing tip to another have its weight balanced by the lift. But, at the center we have only weight, and to balance it the wing must create a lift equal to the weight of the fuselage + the wings. So, more weight is on the fuselage, more the wings will flex and stresses the structure.In your screenshot we can see the issue I'm reporting from the first release about fuel scavenge system.When fuel in the tank no1 decreases to a certain value (around 1900kgs if I remember correctly) fuel scavenge jet pump starts to operate by sucking the fuel from center tank and transferring to the left tank. This fuel transfer rate is too hig, leading, in around 10 minutes or less, in an imbalance.At idle, you will see that fuel in the no1 tank will increase, while on ctr and no2 tank are decreasing.First of all, to solve the issue, load fuel correctly and burn ctr tank first.DO NOT SHUT OFF CTR PUMPS at 1000lbs if you know that you will land with only few kgs (so under the minimums, or near them) in the wings, as as I told before, reducing fuel on left wing will start the fuel transfer from the center tank to the lh wing, this means that all the 1000 lbs will be transferred if you don't land before.Just from the SDS manual:

The jet pump has no parts that move. It is on the left front spar. A fuel scavenge shutoff valve controls fuel sent to main tank 1. When the fuel level in main tank 1 decreases to 4,487 lbs (1,990 kgs) the float valve opens.The minimum fuel transfer rate for the fuel scavenge system is 220 lbs/hour (100 kgs/hour). The fuel transfer rate for the fuel scavenge system is generally between 220 lbs/hour (100 kgs/hour) and 450 lbs/hour (200 kgs/hour).

This is not true on NGX as 200kgs are transferred in less than 10 minutes AND on NGX the system is inhibited on ground, and this cannot be possible as there is no electrical part in the fuel scavenge system. (A venturi jet pump moved (motive flow) by the left fwd wing pump and a float valve in the left wing, plus ducts)