Currently fuel and payload data are locked and unable to be accessed by 3rd party devs.
Would be nice to open this up so it can be used by devs to create content with specific mission scenarios.
I am able to access this information via FSUIPC. FSUIPC is just an overlay for SimConnect. So it is accessible I believe. I actually autoload my payload via code. One issue is that the passenger and cargo payload does not update in the MSFS UI, just the fuel.
Hello @DabullAir , thanks for your input.
Ok so it is a workaround that half-works 
We need a official way for third parties to access and manage these data in order to add content to their add-ons.
Fuel is already available. Neofly does access and set fuel data (not payload data though).
@PhantomStreak Yes I know it but wee need something official from Asobo as some add-on developpers don’t do duct tape implementation 
Not sure if Neofly duct tape the fuel in or if it’s through simconnect. My guess (don’t hate me if I’m wrong) is the later in which case any developer could do the same. They have a discord in which you could ask how they do it.
Absolutely! We need this for AddOns like AirHauler and the likes.
Just trying to understand what is being asked for… There are simvars for fuel level, fuel load, and payload station weight defined in the SDK, described as being settable, so those should be accessible using SimConnect. SDK Documentation (flightsimulator.com)
That is about as official as it gets.
So are you asking for something else? Or does that API not work for what you are trying to do?
While it’s possible to set weights on those payload stations, it’s impossible to get any additional data (location, name, max weight) about them via SimConnect.
Setting weights without at least knowing how it affects the CG makes this feature hard to implement anywhere.
I hope we can get that additional data and enable 3rd party add-ons to use it reliably.
Also, it is true that setting the weights via SimConnect doesn’t update the UI in sim
As an additional reference, a variant of this feature was requested in June on the Dev Support portal without any reply from Asobo/MS
https://devsupport.flightsimulator.com/idea/231/payload-station-locations.html
So how exactly can I read and write to fuel and payload with FSUIPC accessing it via SimConnect?
You can, there’s no debating that.
What you can’t do is know anything about the payload configuration in the aircraft, know how it affects CG or see any of those changes reflected in the UI in sim.
I see now. OK.