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Is It Vapor Or Exhaust Fumes?  
User currently offlineJahthunda From , joined Dec 1969, posts, RR:
Posted (15 years 5 months 2 weeks 6 days 17 hours ago) and read 3566 times:

Hello to everyone, i'd like to know is it exhaust fumes coming from the aircraft engines while flying at high altitudes or is it vapor trails?, I always notice it happens to 4 engines aircrafts and, I've seen two engine aircraft flying very high and there is no smoke or vapor.

Thank you.

7 replies: All unread, jump to last
User currently offlineJsbothe From , joined Dec 1969, posts, RR:
Reply 1, posted (15 years 5 months 2 weeks 6 days 13 hours ago) and read 3531 times:

i think it's trails in which the atmospheric humidity condenses around smoke particles, so it's both, although it's more water than exhaust fumes. it only happens when the humidity is high enough, so that the air cannot keep all the steam in gasious form.
it happens to all forms of aircraft, as for as i know, even to propeller-driven aircraft. it only depends on the humidity in this area.
hope this helps  

User currently offlineF-WWAI From Andorra, joined Dec 1999, 131 posts, RR: 0
Reply 2, posted (15 years 5 months 2 weeks 5 days 9 hours ago) and read 3495 times:

note: water in gaseous form is absolutely transparent!
water steam is tiny little droplets kept in suspension.
aircraft fuel is CnHn+2, a hydrocarbone. If fuel is burned, it produces, essentially, H2O water in gaseous form and the CO2 everybody is talking about.
if it's cold and not extremely dry in the atmosphere, the gaseous water condensates forming the steam you see. It's swirled by the aircraft vortexes. The steam eventually either dissipates amongst the clouds or dries away ..
that's all

User currently offlineTarantine From United States of America, joined Sep 2000, 210 posts, RR: 0
Reply 3, posted (15 years 5 months 2 weeks 5 days 5 hours ago) and read 3472 times:

The trails are not smoke. It is water vapour or ice. The number of jet engines makes no difference at all. I think the word "Contrails" is the correct term for the trails, but I have no idea who thought of that word (maybe people at Convair).

User currently offlineMls515 From United States of America, joined Jun 2000, 3081 posts, RR: 8
Reply 4, posted (15 years 5 months 2 weeks 5 days 2 hours ago) and read 3468 times:

Contrails as in condensation!

User currently offlineWISAZ13 From , joined Dec 1969, posts, RR:
Reply 5, posted (15 years 5 months 2 weeks 4 days 20 hours ago) and read 3455 times:

Hot exhaust fumes + cold air (with moisture of course) = Visibile trail

User currently offlineSHB From , joined Dec 1969, posts, RR:
Reply 6, posted (15 years 5 months 2 weeks 4 days 11 hours ago) and read 3450 times:

F-WWAI is right. Water is a byproduct of combustion. At the low
temperatures at high altitude aircraft engines produce a vapor
trail. The same reason you can see your breath in cold weather
or a car's exhaust produces steam and drips water in the winter.

User currently offlineGreeneyes53787 From United States of America, joined Aug 2000, 844 posts, RR: 0
Reply 7, posted (15 years 5 months 2 weeks 2 days ago) and read 3426 times:

Vapor trails or Condensation trails (contrails) are not vapor, but are visible clouds that are trailing the vapor. These in turn trail the aircraft.

The technical description has already been stated on this post.

Good job everyone.


Ps-there are scores of funny quips from the Convair name. Contrails made up by Convair is a new one for me. Engineers from Convair that landed at Boeing have been called excons and conmen, etc.

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