How does the "custom weight and loading system" for the PMDG in MSFS actually work?

User Support Hub Aircraft & Systems
1

Hello,

As you all might know, the MSFS weight and balance tab shows different weights from the weights in the PMDG FMC.

The fuel weights in the MSFS tab do match the FMC input and also change if the FMC input changes.

But the payload figures in the MSFS weight and balance tab and the FMC payload figures are decoupled.

I have been wondering how PMDG has make this work because you would say, that the MSFS weight and balance tab is THE SOURCE for the weight properties and the final weights for the airplane. That is just what a layman would assume, that this MSFS weight and balance tab is the only source in MSFS for the correct weights.

Also, if you change the MSFS payload weights you see the icing% change in the FMC, so there is some kind of connection between the MSFS tab weights and the PMDG FMC weights.

I have ask this question to PMDG customer service, but all they keep on saying is: “we have used a custom weight and loading system for the PMDG 737”. Also this sentence is repeated in this forum.

And I understand this sentence of customer service, in the sense that it tells me “what I am supposed to do”, just use the FMC, and not touch the MSFS weight & balance tab.

But still, I am just wondering, what does this “we have used a custom weight and loading system for the PMDG 737” actually mean?

Does it mean that PMDG has overrided the MSFS weights and thus the MSFS weight and balance tab has become inoperative?

I want to know: how did PMDG make this work in MSFS? That is what I would like to know. Because for me a “we have used a custom weight and loading system for the PMDG 737” just does not explain what PMDG is doing in MSFS to make sure we are getting the correct weights and centre of gravity in the MSFS simulation.

Can anyone explain this, how this works? Without just again stating “what I have to do”, because I know what I have to do, just fill out the FMC weight, and then I have the correct weights in MSFS. But I want to know, what PMDG did, to make sure we get the right weights in MSFS. So I want to know what a “we have used a custom weight and loading system for the PMDG 737” actually means in MSFS.

Does anybody know, and can anybody explain how the PMDG weight system works? Does it override the MSFS weight system? Or does it alter and adjust the MSFS weight system? How did they do it?

I anyone knows, please let me know. Thanks in advance.

Greetings,

Boudewijn

2

I suspect this is the case. You definitely don’t use the default sim weight / load /fuel interface at all. You currently set weights/loads/fuel up via the FMC in the 737. Although this will change when their EFB/UFT/Tablet is released.

For now in FMC:

MENU->FS OPTIONS->FUEL (to set fuel)
MENU->FS OPTIONS->PAYLOAD (to set ZFW etc)

That’s it. The rest is done in the FMC. CG is auto calculated ( press on soft key loads CG value).
The payload and fuel loads are usually all determined by simbrief.

5

It’s of course your choice to buy or not to buy anything, but I totally don’t get the issue. Just don’t use the sims default weigh and balance UI. That’s it. Use the PDMG provided one in the FMC and probably the tablet when they finally release.
It’s exactly the same in Fenix and probably other complex airplanes. Where is the problem?

The thing that matters is that the flight model behaves according to the weight. If that works then what’s the difference where you enter it.

2 Likes
6

Hello,

Well I posted a lot on this topic 2 days ago, but I researched the topic some more. And this is what I found:

  • A PMDG kilogram is around half of the normal MSFS kilogram in the sim.
  • Testing different weights did compress the shockabsorber 100% logical, so the FMC weights seem to work fine.
  • Even tought there is a difference between MSFS weight and PMDG FMC, the CG in the FMC is the same as the CG in the MSFS W&B tab.
  • I tested the take off speed calculations from Virtual Performance Tool with the take off behavior under full load and empty load of the plan, and the calculations where correct, so the behavior is correct.

I assume that PMDG has changed the MSFS kilogram, in order so that the aircraft has a more realistic flight behavior, and because in the end it does net matter how heavy the plane is in MSFS. Nobody is going to put the plane on a scale.

The only thing that matters is how it flies, is that realistic? And if the performance calculations of the real 737 add up with this behavoir. And my small research showed me it did.

So I thought I share it with you, if somebody else someday sees the big difference between the W&B tab and the weight of the PMDG and also asks questions like me.

Greetings,

Boudewijn

7

Out of interest, are you sure you’re not using pounds (lbs) in PDMG? It’s independent of the settings in the sim, depends on the livery you choose and can be changed in the FMS aircraft config pages.
Just guessing because 1kg is more less 2lbs.

8

Hello,

Yeah I took that into account, looks also like a 50% difference, you are right.

But I compared kgs to kgs, and that is what I found.

Greetings,

Boudewijn