• Which the release of FS2020 we see an explosition of activity on the forun and of course we are very happy to see this. But having all questions about FS2020 in one forum becomes a bit messy. So therefore we would like to ask you all to use the following guidelines when posting your questions:

    • Tag FS2020 specific questions with the MSFS2020 tag.
    • Questions about making 3D assets can be posted in the 3D asset design forum. Either post them in the subforum of the modelling tool you use or in the general forum if they are general.
    • Questions about aircraft design can be posted in the Aircraft design forum
    • Questions about airport design can be posted in the FS2020 airport design forum. Once airport development tools have been updated for FS2020 you can post tool speciifc questions in the subforums of those tools as well of course.
    • Questions about terrain design can be posted in the FS2020 terrain design forum.
    • Questions about SimConnect can be posted in the SimConnect forum.

    Any other question that is not specific to an aspect of development or tool can be posted in the General chat forum.

    By following these guidelines we make sure that the forums remain easy to read for everybody and also that the right people can find your post to answer it.

FSXA .AIR file confusion!!!

ozzman1997

ozzman1997

Messages
665
Country
us-illinois
Okay, I'm officially confused. :confused: I've been messing around with Aircraft Airfile Manager and a lot of the tables and values relate to the position of a certain feature of the aircraft. I see the term CoG a lot, (Center of gravity, I presume). Now, I thought that positions were dependent on the Reference_Datum_Position in the aircraft.cfg file. :confused: Does the "RDP" only go for things in the CFG file, or do some things in the .AIR file go off of it as well? I'm a newb with flight dynamics so if anyone could explain, that would be great.
 
As far as I know, only the aircraft.cfg entries are based on the RDP, which would make sense because some of the aircraft.cfg stuff is based on the .air file's parameters, not the other way around! :D
 
Thanks for clearing that up, Bill. :) Now is there a way to change the CoG within the .AIR file? I don't see an entry for that in AAM...
 
I don't think it can there is because of the way FS calculates the CG position during the flight.

The calculation's based on the empty_weight, empty_weight_cg_position, station_load(s) (which incudes their positions) together with the positions and contents of the fuel tanks. The positions and empty_weight are set in the .cfg file and the fuel contents vary in flight.
 
The important part is Center of Lift in .air. If this is wrong, then your weights don't matter.

Table 1204 and 1514 can set the CoG, but are overrode by the .cfg.

Table 1534 does not have a .cfg duplicate and must be set correctly. Moving the wing around won't show any effect because the CoL in 1534 is referenced from the CG_ref. What affects flight balance is the change in the distance from CoG to CoL. CoL, being referenced from CG_ref does not change (sim world), while CoG, being calculated dynamically, changes with weight distribution.

You will need to know your aircraft's dry and empty CoG position (CG_ref), and the CoL position (based on the same RDP).

Subtract the two and set this distance in 1534 from CG_ref and you should be able to load the aircraft like the real thing and get the correct CoG and performance (assuming the rest of the airfile is good.)


Note: There is a misconception that the difference between the RDP and the CoG in the .cfg will account for the CoL and this isn't true. RDP is just an arbitrary reference point in space, that is used to reference the positioning of all values in the .cfg. Lights, engines, fuel tanks, CG, etc.
 
Last edited:
You must log in or register to reply here.
Back
Top