State overlay system

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Revision as of 05:28, 8 March 2018 by Necolatis (Talk | contribs) (Background: added Viggen)

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To start FlightGear with an existing overlay add --state=statename to you command line.

For now there is no definitive list of possible states. These are my first suggestions:

  • parking (meaning cold and dark)
  • taxi (all systems running and ready to taxi)
  • take-off (standing on the runway with take-off configuration)
  • cruise (cruise configuration)
  • approach (approach configuration)


overlay file

To add state overlays to your aircraft, create a folder called states. In there you can put your $state-overlay.xml. In the beginning your overlay.xml should look like this:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
  <name type="string" n="1">parking</name>


Now you can put your items, which need to be set between the overlay tags. You only need to put properties in there, which differ from your default setup.

Another rule of thumb is that you use the hierarchy of the property-tree's root. It speeded up my research by quite a bit, when I found out, it's possible to dump the PropertyTree with a nasal command. Open up the Nasal-console from the developer-menu and put in the following: io.write_properties( path: "/home/myName/.fgfs/Export/PropTree.xml", prop: "/" );

Beware! This outputs the entire PropertyTree! This is several thousand lines long. You might want to dump only single folders of the PropertyTree by changing the "/" to sth like "/controls" or whatever folder you want to dump. Now you can simply delete everything from that file, that you don't need and copy&paste it into your overlay.xml.


Now you need to include your overlay.xml in your $Aircraft-set.xml file like this:

    <state include="states/parking-overlay.xml" n="0" />
    <state include="states/taxi-overlay.xml" n="1" />


Wayne Bragg has been working a bit with James on the state overly system.[1]

At this moment, the Citation, the Saab 37 Viggen, the J3 Cub and the Cessna 182s have this implemented.