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asked by (15 points)
I want to test an autopilot algorithm using X-Plane, but for a generic aircraft model with certain properties, (Moments and product moments of inertia, mass, lift and moment coefficients, etc.), and would not want to build a complicated (or any, if possible) plane in Plane-maker for it. Can this be done by assigning datarefs?

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answered by (148 points)
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You can fully disable the flight model and move the aircraft with datarefs. You can also add forces to the flight model.  More info here:

You cannot edit the properites of the aircraft inside X-Plane via datarefs; X-Plane needs to analyze and cache information about the airplane at load time.

The best work-around for running an automated simulation is to script writing of a .acf file (text inv 10) replacing values, then reload the aircraft.
commented by (15 points)
That's great information, thank you. Editing the aircraft properties is really my ultimate goal, since in flight dynamics an aircraft can be described by matrix equations with different variables (phi, theta, psi,etc.), in terms of the properties and control surface inputs, or any other inputs from gusts, etc.

Where could I find an overview of the anatomy of an .acf file, and what each property string means?
commented by (148 points)
The ACF file format is -not- documented and it is not our general intention that it be an open file format. The only supported way to modify it is via Plane-Maker.

With that in mind, the correlation between Plane-Maker settings and the text file is relatively straight forward.  What you could do is diff the .acf file after editing in Plane-Maker manually and note the changes, then automate that change.