[BUG & DOCUMENTATION] Contact point turning calculations

@FlyingRaccoon I would like to report a severe bug in the ground handling. The bug can be fixed, or documentation updated to help developers avoid the issue.

Here is what is happening. On this image you see:

  • Reference datum point: in the aircraft manual it is measured off of where the forward cockpit firewall is.
  • 3D model origin (pale blue). We put it where the forward cockpit firewall is
  • Contact points (yellow). We matched them to our landing gear

In numbers:

  • The firewall is at 0
  • The datum is 9.833ft forward
  • The nose gear is -9.604ft from the datum, which makes it 0.229ft forward of the origin

With this setup, the plane’s turn radius is wrong and the main gears are skidding sideways during a turn. The orange triangle gives an approximation of where the wheels feel to be for that kind of behaviour.

I tried fixing it by moving the contact points 0.5ft further aft to see how it affects handling. In the next image you can see the new contact point setup in red (slightly exaggerated).

To my surprise the plane started turning opposite to the rudder input when on the ground. Right rudder would give left turns and vice versa! It is as if right rudder would push the tail to the right, and thus the nose to the left!

This led me to the conclusion that ground handling does not use the contact points to calculate a turn radius, but instead tries to turn the model around the 3D model origin. The last image shows how a left rudder input would make the plane’s nose turn right and it is exactly what I experienced.

A very similar bug affected the center of Gravity calculation and was fixed at Sim Update 4. I would like to ask that this bug is either fixed, or clearly documented in the SDK that developers should center their 3D model on the main gears to avoid this kind of issue.

We have been working on this aicraft for 16 months and having to shift the origin & datum could have unforeseen implications in a year’s worth of flight modelling if this bug affects other things as well.


Hello @SWSAlexVletsas !

May I ask you to send us your package to let us investigate on this issue? You can follow the third point of this page to do so.



Hello @GentleLynx ,

Do you want the PackageSources or a community pack?