OTXSIM debugging tool

Last updated 12 August 2022 - Mike Shellim


OTXSIM is a tool for debugging your setup without the need for an actual model, so saving time and effort. It runs in the Companion simulator, using a profile for the Taranis X9D. (It can also be run on an actual X9D transmitter.)

OTXSIM displays a virtual view of the control surfaces, responding to virtual stick and switch commands from the simulator console.

It supports most common aircraft layouts, and can configure itself automatically.

Control surface deflections are determined by the aggregated mixer values rather than the output values, making it ideal for validating and debugging your mixer scheme.

Key parameters are displayed, and different GVAR values can be simulated.



OTXSIM version 1.3 (29 Dec 2021)

For Companion 2.2 and higher, with X9D profile




  1. Download the script, and change the file extension from '.txt' to '.lua'
  2. Copy the script into the \SCRIPTS\TELEMETRY folder of the SD Structure path (specified in Companion settings).
  3. Start Companion and select a profile for X9D/X9D+
  4. Open an .otx file and select the target model
  5. In the Telemetry menu, scroll to bottom, set the first screen to 'script' + otxsim
  6. Save the .otx file

The screen definition for OTXSIM is now saved with the model.


To run the script:

  1. Start Companion and select the model
  2. Start the OpenTX simulator
  3. From the splash screen, press {long PAGE} until OTXSIM is displayed.


Drawing conventions

The surfaces are drawn using the following convention:

Individual surfaces can be shown reversed (see the Configuration page).

Auto configuration

At startup, OTXSim looks at the channel names and makes an informed guess as to their function. For example, a channel name containing 'v' and 'r' is mapped to the right V-tail panel. Suggested control surface names for auto-configuration:

If the auto configuration fails, surfaces can be manually assigned in the configuration page.


OTXSIM is designed as a developement tool only. It's recommended to remove it from the final setup before flying.