David Culp:

Here are files to get automated contrails working.  I've set up contrails for
the 737, using my simple, untextured contrail model.  Vivian has made another
contrail model, but I'm still trying to get his to work.  I'm hoping others
will try to make contrail models also.

Here's some code that defines a top to thermals.  When the top of a thermal is
reached the strength is phased-out linearly over the next 100 feet of
altitude.  At first I tried just capping the thermal at the top, but the
change in thermal strength was too fast for the FDM to handle well.

Included is a new version of the thermal scenario that includes a top
(height-msl) to the thermal.  The default value is 5000 feet.

Data/AI/thermal_demo.xml

@@ -9,8 +9,9 @@
    <type>thermal</type>
    <latitude>37.61633</latitude>
    <longitude>-122.38334</longitude>
-   <strength-fps>8.33</strength-fps>
+   <strength-fps>13.49</strength-fps>
-   <diameter-ft>4000.0</diameter-ft>
+   <diameter-ft>4800.0</diameter-ft>
+   <height-msl>5000</height-msl>
   </entry>
 
  </scenario>

preferences.xml

@@ -441,6 +441,7 @@ Started September 2000 by David Megginson, david@megginson.com
   <params>
    <real-world-weather-fetch type="bool">false</real-world-weather-fetch>
    <control-fdm-atmosphere type="bool">false</control-fdm-atmosphere>
+   <contrail-altitude>30000</contrail-altitude>
   </params>
 
  </environment>