Hi,made a strange experience in FS2004 today. Was taking off from Tokyo to Munich climbing up to FL310 initial cruising altitude. As i reached this altitude there were no contrails. After some minutes of thinking about this i decided to perform some step climbs to see if they would appear anyway. Well, they did over FL320. The day before i was climbing out Munich/Tokyo to FL310. They were there as i was cruising.I'm using the real weather option.Under what conditions do contrails appear? Any temperature or air humidity limits? And the altitude?would be nice to get an answerTom

While I do not know much about this I do know that the temperature "controls" when the contrails appear. Hopefully someone with more knowledge than I will comment here.Philip Olsonhttp://www.precisionmanuals.com/images/forum/supporter.jpg

It's a combination of temperature, humidity and the the presence of condensation cores in the air.Condensation cores can be droplets of air, dust, volcanic ash, etc. etc..

It is unknown what the temp is at which FS decides to turn on the contrails default. But there is a way to modify the temp at which they appear for any aircraft.. In the GENERAL ENGINE DATA section of the aircraft.cfg add the following line and modify to suit.max_contrail_temperature=32Regards,Romanhttp://home.new.rr.com/spokes2112/images/Image2.gif

Volcanic ash? Do they really model volcanic ash? Cool! Now we can look forward to a screen that says "Use real-world vulcanism." Or is that the rubber on the tires? Or maybe the pointy-eared guys on Star Trek?In FS2002, it was a fixed altitude. Although it's nice to push the realism envelope, I'd rather see them devote resources to ATC or Mesh, and let fringe issues like contrail altitude stay fringe issues.

Hi,and thanks for your replys. Is there really no answer? It seems like there can't be a fixed altitude that FS uses to control the contrails.I just thought back and can remember that it was quite hot over Tokyo compared to Munich the day before. The temperature @ cruising altitude was around -28

In FS2002, it was a fixed altitude. Although it's nice to push the realism envelope, I'd rather see them devote resources to ATC or Mesh, and let fringe issues like contrail altitude stay fringe issues.What absolute tripe. It's still pushing the envelope forward and not backwards and yet you still complain...John http://homepage.eircom.net/~eamonnmca/images/logo_ba.JPGwww.bavirtual.co.uk Senior Captain Simflight.com Staff Reviewer

Thanks gents...That's answered a question that I had occasionaly wondered. I'd always tyhought that it was altitude governed; I usualy see contrails from FL270, but that's only if I use a custom weather setting. When using real-world weather I see contrails from FL240 sometimes or not at all...even at FL310 or higher! I think that it's pretty brilliant actualy that someone decided to make it a proper altitude vs. temperature ratio dependant occurance....all adds to the realism :)

Captain,That was pretty funny!Jereon has misread the original question and gave a real world reply. I've never heard the term "condensation core". The meteorlogical term is "condensation nuclei".Bruce

I translated the term from what they use here locally :) But you seem to have understood me well enough...

You can set the temperature for contrails for every plane.I made a program which will do this for all your installed planes.It's called 'AI Contrail Generator' and could be downloaded here http://library.avsim.net/download.php?DLID=37019