VATSIM has recently instructed the development teams for our X-Plane clients, (xSquawkbox, xPilot, and swift), to add code which will automatically disconnect users who are unable to maintain an average of 20 frames per second while connected to VATSIM. These users will be welcome to immediately reconnect to the network after adjusting their rendering settings.

The reason for this is a programming decision by Laminar Research in which X-Plane will automatically slow the simulation rate when frame rates drop below 20 frames per second as a requirement to maintain flight model stability. This feature is transparent to the end user outside of their flight taking twice as long or more to complete. 

Unfortunately, this feature is very disruptive to other users of the VATSIM network as the slow rate is very evident to our Air Traffic Controllers who are expecting the aircraft on their radar scopes to perform as the information on their radar scope indicates. When this does not happen, in cases of X-Plane  simulation rate change, sequencing these users during busy times or events becomes extremely difficult if not impossible.

This feature is also disruptive to other pilots as they are put in situations where they face unneeded delay or have to conduct a missed approach to accommodate an X-Plane user who cannot maintain 20 frames per second.

Future versions of xSquawkbox, xPilot, and swift will have code that will poll a users average framerate and users will have a set amount of time below 20 frames per second before the pilot client will automatically disconnect them. If the frame rate improves to 20 frames per second or better during this time the user will not be disconnected. Previous versions of xSquawkbox, xPIlot, and swift will no longer be able to connect to the network.

X-Plane users who are having trouble maintaining frame rates above 20 frames per second are advised to turn down their rendering settings until they are at a setting that can maintain 20 frames per second. VATSIM recommends using the 3jFPS script along with the FlyWithLua plugin, which will automatically adjust the rendering settings of the user to maintain 20 frames per second so that users can have the higher rendering settings they desire when in areas that their computers will allow for it. Another option is FPS Boost + Auto LOD  You can find links for these options in the postscript.

VATSIM does not recommend the use of the autospeed plugin, which uses X-Plane’s time compression feature to attempt to counteract the slowdown effect of low framerate. This simply compounds the the sim rate problem, and causes issues with the climb and descent profiles. It also does not adjust the frame rate, which will result in the disconnection scripts in the pilot clients to activate. 

We understand that this decision will not be very popular with a lot of our X-Plane users. After collecting data over the past year and a half about this issue from both our air traffic controllers and pilots, we have seen this issue continues to impact our users and action needs to be taken. Most X-Plane users are unaware of this issue which can be easily fixed by manually lowering rendering settings or automatically with the use of 3jFPS. In many cases, the visual quality of the simulator is minimally affected, as the largest frame rate penalty comes from 3D object level of detail, and the scripts work very intelligently to remove distant 3D drawing when at lower altitudes near busy airports.

The disconnect is not punitive and users will be able to immediately reconnect. Instead it serves as an alert to the user that his rendering settings are too high at the moment and that he is impacting other VATSIM users because of it. We thank you for your understanding and thank you for being a VATSIM member.

Best Regards,

VATSIM’s Board of Governors

Setting the Rendering Options for Best Performance in X- Plane

FlyWithLua (Needed for 3jFPS)

3jFPS Wizard

FPS Boost + Auto LOD