I am trying to read flight data from a FDR (Flight Data Recorder, black box) and input some of the data into FlightGear's Replay system to display the flight.

If using the Replay functionality in the FlightGear and I only care some of the values such as:

-Longitude, latitude, altitude, agl
-v_north, v_east, v_down
-phi, theta, psi

All these for displaying the aircraft's attitude, position, trajectory. While I don't care those values such as control surfaces, engines status, instruments related, and etc.

There is a file called acms.xml in FlightGear/data/Protocol/ (base package) which was used for the helicopter playback. Now to play back the data using that file you will have to use the latest version of FlightGear compiled with --enable-sp-fdms

If the file format as described by the acms.xml file corresponds to the data you have you will be able to play the data by running:

fgfs --aircraft=c172p \
      --generic=file,in,1,<path_to_FDR_file>,acms \

I tried to import the data (lon,lat,…) I want to use into the Replay subsystem and "hardcode" those control surfaces, engines/tanks status, and etc. At the beginning, I set the replay_master as true and I got the program started in replay mode. But the problem is, I failed to see the aircraft moving which supposed to be because I have the lon, lat, alt, groundspeed keep changing.

This is because the default FDM will override these values. You will have to use --fdm=null or --fdm=acms

So my question is, how does the Replay subsystem work in FlightGear? Does it use the control surfaces' (and other control elements like engines) changes as the inputs and then use the FDM to recalculate all the outputs again?

With the above description it will only mode the model in the scenery. Lots of stuff can be done by extending the code though.


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