Is It Vapor Or Exhaust Fumes?

Sun Dec 10, 2000 6:02 pm

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.

RE: Is It Vapor Or Exhaust Fumes?

Sun Dec 10, 2000 9:19 pm

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  
Posts: 129
Joined: Thu Dec 30, 1999 7:41 am

RE: Is It Vapor Or Exhaust Fumes?

Tue Dec 12, 2000 1:17 am

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
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RE: Is It Vapor Or Exhaust Fumes?

Tue Dec 12, 2000 5:55 am

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).
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RE: Is It Vapor Or Exhaust Fumes?

Tue Dec 12, 2000 8:26 am

Contrails as in condensation!

RE: Is It Vapor Or Exhaust Fumes?

Tue Dec 12, 2000 2:16 pm

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

RE: Is It Vapor Or Exhaust Fumes?

Wed Dec 13, 2000 12:02 am

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.
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Joined: Tue Aug 08, 2000 10:34 am

RE: Is It Vapor Or Exhaust Fumes?

Fri Dec 15, 2000 10:57 am

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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