When has the aircraft landed?

[mikeindevon]

X-Plane has sloping runways and to make the external views of the aircraft realistic, XView has to take account of this.  We don't want the plane hovering or with its wheels stuck in the concrete!

The problem starts when the wheels first touch the ground, hopefully the rear ones.  As the plane drops, the gear compresses and the attitude reduces until the nose wheels are supprting the aircraft.  As the plane slows, the lift from the wings will reduce, resulting in more gear compression.  "When has the plane landed?" is not such a simple question as it sounds.

To get this to work convincingly I found it necessary to ignore PSX altitude data when the plane was in contact with the ground and set the plane altitude directly from the runway height.  For realism, I lower the plane somewhat and set the gear compression to maintain the wheels at ground level.

All this completely ignores Hardy's flight model and even his grounded setting ("G" on the Boost Server).  Some of you may notice a slight discontinuity in the scenery display when the transition is made between Hardy's flight model and my grounded algorithm.

My model of gear compression takes no account of the weight of the aircraft or its airspeed.  It is simply based on altitude and attitude.  This is a shame, but any workaround that I make for this would just use visually pleasing values, but have no aerodynamic basis. 

A similar approach is taken to wing-tip deflection.  I increase this with airspeed, but only in an arbitrary but visually satisfactory amount.  Hardy and I discussed this in the past, but now as I update PSX Plane to XP11, I have a chance to do something more accurate if the data is there.

Mike

[Flex]

Mike,

Interesting insight and something I have wondered for sometime. Can't wait to try the updated version for X-plane 11. Great work. The future for X-plane looks bright!

Felix.

[cagarini]

Interesting indeed, and I have invested a bit on this particular matter when trying to fine tune some aircraft for XP10 and 11.

There's an "old" article by Chuck here:

https://forums.x-plane.org/index.php?/forums/topic/61282-landing-gear-dynamics/

Depending on the landing, the gears can bounce for sure. I do not know if there are Q-variables for the "gear compression" and or if Hardy can publish the damping and Spring constants used in PSX's gear model ?