X-Plane "Reality Check": Evaluating time dilation

[Daniel Neugebauer]

If you are an X-Plane user you surely are well aware of the recent discussions about time dilation (simulation rate slow-downs) and the effects it has to other users when flying online. Over the past weeks, you've most-likely have read about or even experienced disconnects first-hand due to low frame rate detection introduced to experimental pilot client releases.

 

During the discussions that happened on the VACC Germany forum, Andreas Fuchs asked if it wouldn't be better to simply observe the effects by altered ground speed instead of relying on frame rate measurements. Over the past week I developed a simple FlyWithLua script called "Reality Check" as a proof-of-concept which, in addition to frame rate calculations, uses the great-circle distance of points taken at ~1 second intervals to calculate the externally (as by other users) perceived ground speed and the comeulative distance error resulting from time dilation.

 

The idea is that a small amount of time dilation, i.e. speed and distance error, should be tolerable in the same way as other causes for deviations such as non-uniform winds would be. Serious issues in online networks only arise if separations cannot be maintained such as two aircraft with identical reported/indicated ground speeds closing in on each other while on final.

 

The latest version can be downloaded from GitHub

 

Detailed docomeentation is also available.

 

The script requires FlyWithLua 2.7.0 or later and was tested with X-Plane 11. Compatibility with X-Plane 10 has not been checked yet.

 

When installed, Reality Check will show a warning message if it detects that time dilation has specific effects (see full docomeentation). It also adds a few options to your FlyWithLua menu: You can at any time open an analysis window to show detailed information (regardless of any warnings being active), you can disable the notification texts if they get too annoying and you can also record your data to a series of CSV files which can easily be opened in spreadsheet applications such as LibreOffice/OpenOffice or Excel.

 

Please keep in mind that the script is inofficial. While I hope the results will help pilot client developers to find a better, more acceptable solution to reduce the number of false positives and unjustified disconnects (e.g. due to very low speed errors), I do not have any influence over VATSIM nor any pilot client. Nevertheless, swift has already started evaluating the results and discusses them on their Discord channel. Before sending logs to client developers please check if and what information they want to receive.

 

I uploaded a quick test flight to

to demonstrate the script; stutters due to forced weather changes occur around 2:20, 3:10, 3:45 and 5:25.

 

Happy testing!