YASim Development Tools

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A first version of the YASim development tools is availabel on SourceForge

In order to load the add-on, start FlightGear (fgfs) with the option --addon, like this:

 fgfs <your_usual_arguments> --addon=/path/to/the/YASimDevel/folder

then look at the menubar. :)

You will get a canvas window showing the airplane viewed from top with markers for the CG (the diamond), the desired range as given by the cg-min and cg-max attributes in the XML file and the hard limits for the CG (given by the gear positions). Also displayed are the centerlines of the wings and the MAC. Last but not least a colored chord line is drawn per surface element (yasim generates several surface elements per wing). They will show green for positive lift and magenta for negative lift. The red part indicates drag.

Canvas showing yasim internals

Old models (before FG version 2018.1) often use <wing> + <mstab> to build complex wing geometry. The CG position in %MAC refers to the MAC of the <wing> element and is most likely wrong, when combining <wing> and <mstab> to build the main wing of the airplane.

Canvas showing yasim internals. CG out of range, incorrect MAC due to old model description.

Since FG version 2018.1 you can build the main wing by using multiple <wing> elements (refer to the Yasim main page for details). Now the MAC is calculated for each wing section and then is combinded to a MAC for the wing and CG is expressed relativly to this overall MAC.

Canvas showing yasim internals. CG green, correct MAC calculation using wing sections.