Enviro-controlled wingtip contrail gauge

[microlight]

Hi all.

A while ago, I wrote an invisible gauge for FS9 that provides wingtip contrails dependent on atmospheric conditions (beat you to it, FSX!). It's always worked fine, except that I'm not sure I've got the atmospheric conditions right, since it only comes on occasionally! Never does come on in summer, of course!

What with global warming, can anyone help me out with some recommended conditions for condensation to occur? My current parameters are more than 50 feet off the ground, less than 220 kts IAS, less than standard atmospheric pressure and less than 40 degrees F.

Thanks!

[Groundbound1]

Do you have dew point in the equation anywhere? I've seen vapor vortecies on extended flaps of airliners when it's 60+ degrees, but it would have to be pretty humid for that.