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Attention: JSBSim ground reactions code

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Attention: JSBSim ground reactions code

Postby erik » Sun Feb 09, 2014 2:00 pm

This is a heads up for JSBSim aircraft maintainers that user their own ground detection and handling code.
As of today JSBSim, just like YASim, supports ground effects like bumpiness, solid-ground detection and adjusting of friction actors.

Actually JSBSim supports an extra feature, BOGEY contact points sink in a non-solid ground surface but STRUCTURE contact point do not, making it easy to define floats using STRUCTURE contact points.

In order not to pollute /fdm/jsbim too much I've added the following properties:

A user defined property which if defined and set to a something higher than 0 will disable the JSBSim ground reactions code completely and the following properties are set to false:

Otherwise the following applies:
* is set to true

* is set to true if there is a valid material available or set to false otherwise (the material defaults are set).

The following properties are set to their respective values:

* flag which defines if the surface is solid not

* defines the bumpiness factor

* maximum allowed force for this surface

* rolling friction factor - applies to rolling friction

* static friction factor - applies to static friction and dynamic friction

These properties are also set for the appropriate gear and contact units.

If you want to keep your old behaviour just set sim/fdm/surface/override-level to 1 somewhere in the configuration files, for Nasal this becomes:
setprop("sim/fdm/surface/override-level", 1);

I've updated the Nasal code for the following aircraft in the base package:

Not that some of these might actually be YASim aircraft but YASim will just ignore the property.
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Re: Attention: JSBSim ground reactions code

Postby Gijs » Sun Feb 09, 2014 2:16 pm

Thanks for working on this Erik; it's been a long standing feature request! I've added a short pointer to our aircraft maintenance wiki, so aircraft authors (including those not in fgdata) can find what to do.

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Re: Attention: JSBSim ground reactions code

Postby erik » Sun Feb 09, 2014 2:25 pm

Good idea, thanks!
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