• 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.

MSFS Confused with Engine Model (engines.cfg)

Messages
46
Country
spain
Hey everyone,

When I though I had a reasonable understanding of how the engines are being modeled, I find myself bumping against a wall once and again. As has been discussed in several posts, the engines.cfg file now includes the 150x tables from legacy .air files, some variables from the legacy aircraft.cfg file and some other new variables/ parameters.

Having those tables, I though made it possible for us to use the theory and techniques we've all being working with for the past few years. But I was wrong. Not only the models do not behave at all with respect to those tables; if you delete all of them, the model behaves the same as if you have them (with whatever values). It also seems that the new curves are being characterized from the new low-high parameters within engines.cfg (i.e. low_idle_n1. high_n1, idle_FF, etc.).

All in all, I have been testing the A320Neo model at ISA conditions and a Sea Level airport.

  • Idle and Max TO (TOGA) values for N1, N2 and FF are taken from the new low-high variables within engines.cfg, not the table related variables.
  • One thing I tried was to tweak the tables to have idle and maximum n1, n2 and FF values just like the variables in engines.cfg. No joy. At different throttle levels the different parameters do not follow the tables.
  • Taking out ALL table related variables, but maintaining low-high variables, gives exactly the same output as with the Tables. Exception: Thrust is always 0. If we maintain ONLY the table that relates CN1 to Thrust, then we get thrust values back again (although the values do not follow the table).
  • Maintaining Tables, but deleting ALL low-high variables (N1, N2 and FF), actually messes up everything and engine parameters do not follow Tables:
    • N1 idles at 50%
    • N2 idles at 50%
    • FF idles at 16 Kg/h
So in conclusion due to my findings:

  1. Tables do not seem to be needed for engine modeling
  2. Low-high variables seem to be the ones being used to characterize engine behavior
  3. This would mean engine characterization is hardcoded and we are only allowed to give minimum and maximum values for them
Hope this helps out. Also, if anyone has any other experience or feedback, I'd appreciate a challenge to these findings.

Thanks!
 
Messages
46
Country
spain
Well, it seems (as I thought) I am not the first one coming to this conclusion...


... although I haven’t found anywhere within the SDK info regarding legacy vs. modern engine data.
 
Messages
17
Country
unitedkingdom
I am finding exactly the same thing. I cannot get for example any piston twin to feather. Whatever parameters I tweak the feathering does not work, The props just keep rotating even at extremely slow (stall) speeds. In FSX feathering was far from perfect but it did work. There are some new params in the Asobo prop section: named "cx=". Does anyone know what these are?
 
Top