PMDG 737 NGX increasing in fuel in left tank?

[BlueSwurl 32]

So I've recently started noticing fuel increases happening in my #1 wing tank during flight, this causes imbalances and i have to try balance them again every flight. I have discovered, however, that when i use the preset fuel inputs such as 2/3 it doesn't happen. This is quite a head scratcher for me as this only happens when i input specific units manually such as 1.4 reserves in my wing tanks. The left wing tank will go up eventually to almost 2000 kg if i don't stop it.

 

Any help?

Note:

not loading any panel states

 

Thanks,

Chris.

[downscc 1,327]

Hi Chris... please note PMDG forum rules require our full names on all posts in their forums.

Your wording "when I input specific units manually such as 1.4 reserves in wing tanks," bothers me.  I cannot tell from this problem description how you are manually loading fuel but it sounds like you are filling the center tank before wing tanks are full.  Wing tanks fill first, only when wing tanks are full do you add fuel to the center tanks.

[BlueSwurl 32]

Yeah, i am filling the center tanks first. I'll give that a whirl.

[scandinavian13 5,192]

1 hour ago, BlueSwurl said:

Yeah, i am filling the center tanks first. I'll give that a whirl.

Make sure you are only using the FUEL menu under FS ACTIONS > FUEL on the CDU MENU page.

[Bob Scott 7,715]

This is correctly modelled behavior in an incorrectly-operated system.  What you are seeing is the center tank scavenge pumps moving fuel to the #1 tank, as they are designed to do with any fuel in the center tank, the #1 tank below half full and the #1 fwd pump turned on.  Once the scavenge pumps are activated, they remain on for the remainder of the flight.  The scavenge pumps move fuel at a rate of 220-500 lbs/hr, usually closer to 500 than 220.

So if the system is operated correctly--wing tanks filled first before loading center tank fuel, and center tank burned first before burning wing tank fuel, then the scavenge pumps will activate after the center is empty and the wings are at half full, and then it will only move the small amount of residual fuel in the center tank to the left tank without much of an effect on fuel balance.

Regards

 

[BlueSwurl 32]

59 minutes ago, w6kd said:

This is correctly modelled behavior in an incorrectly-operated system.  What you are seeing is the center tank scavenge pumps moving fuel to the #1 tank, as they are designed to do with any fuel in the center tank, the #1 tank below half full and the #1 fwd pump turned on.  Once the scavenge pumps are activated, they remain on for the remainder of the flight.  The scavenge pumps move fuel at a rate of 220-500 lbs/hr, usually closer to 500 than 220.

So if the system is operated correctly--wing tanks filled first before loading center tank fuel, and center tank burned first before burning wing tank fuel, then the scavenge pumps will activate after the center is empty and the wings are at half full, and then it will only move the small amount of residual fuel in the center tank to the left tank without much of an effect on fuel balance.

Regards

 

As my 737 already loads in with fuel i wasn't sure if it would still occour even if i had loaded the wing tanks first, put fuel in wing tanks first (with fuel already being in somehow) and its still happening. Anything i did wrong? Here's what i did in order:

-loaded in

-connected jetway, set up passengers, payload, GSX and all that jiffjaff

-went to fuel page, my friend told me i can just put my total fuel into the 'TOTAL KGS' box so i calculated total fuel (rounded from 8827 to 8800) so i put that in

-units went all wrong and proceeded to put the wing tank fuels in first, then the center tanks

-fly out and issue still occours 

[scandinavian13 5,192]

11 minutes ago, BlueSwurl said:

connected jetway, set up passengers, payload, GSX and all that jiffjaff

What is contained in "jiffjaff"? FS Passengers? Any other add-ons?

11 minutes ago, BlueSwurl said:

-went to fuel page, my friend told me i can just put my total fuel into the 'TOTAL KGS' box so i calculated total fuel (rounded from 8827 to 8800) so i put that in

Don't need to round on the fuel page. Just enter the number.

You're referring to the fuel page of the CDU, correct?

12 minutes ago, BlueSwurl said:

-units went all wrong and proceeded to put the wing tank fuels in first, then the center tanks

"Units went all wrong..."

What do you mean by this?

 

Full names - first and last - in the forum, please.

[BlueSwurl 32]

14 minutes ago, scandinavian13 said:

What is contained in "jiffjaff"? FS Passengers? Any other add-ons?

Don't need to round on the fuel page. Just enter the number.

You're referring to the fuel page of the CDU, correct?

"Units went all wrong..."

What do you mean by this?

 

Full names - first and last - in the forum, please.

1.JiffJaff as in programming the route and getting the APU set up, as well as preparing for push back later on.

2. Oh, didn't know that. Thanks!

3. Yes, the CDU fuel page.

4. The CTR fuel tank had 920 KGS but the wing tanks both had 1300

Unless i have to start from a panel state, or just be careful to insert the wing tanks first i'm not really sure why this annoying thing keeps happening >:c
 

[downscc 1,327]

Just enter the total fuel you desire, the simulation will correctly fill the tanks.  Each wing holds about 3900 kg so unless your total is greater than 7800 kg you should not have any fuel in the center tank.  If the wing tanks have 1300 kg each your center should be empty.

I am getting the feeling that this discussion is not addressing the problem.  Have you flown the Tutorals yet?

[BlueSwurl 32]

21 hours ago, scandinavian13 said:

What is contained in "jiffjaff"? FS Passengers? Any other add-ons?

Don't need to round on the fuel page. Just enter the number.

You're referring to the fuel page of the CDU, correct?

"Units went all wrong..."

What do you mean by this?

 

Full names - first and last - in the forum, please.

When scandinavian13 said "Don't need to round on the fuel page. Just enter the number." I tried that, it turns out that, indeed, it had worked as it should. Although my CTR fuel tanks were low, i still had fuel in my wing tanks and i made it from ENBR - EKVG with fuel to spare. Thanks for the support guys, will make sure to either fill tanks first or enter total fuel.