Why do jets leave a white trail behind them.

Hi everyone,

Me and a friend are wondering why jets leave a white trail behind them. My
guess is that it's moisture being compressed as it passes through the
turbine (because some leave a single trail, while others leave two separate
trails). My friend thinks it's because of moisture being cooled as it
passes over the wing (Bernoulli effect).

While flying a bonanza I have seen a small white trail extending from the
wingtip for a little while right after I break through the clouds
(descending).

Is either one of us right?

AliR.

AliR,

Is either one of us right?


Your friend, partly. There are atmospheric conditions when the pressure
change over the wing or at a wing tip is enough to make the water in
the air visible. But they are rare and don't make long contrails. The
long contrails from jets you see are because the exhaust contains small
particles (soot and other stuff) which cause the water vapor in the air
to condense on them where it wouldn't condense without them.

--
Thomas Borchert (EDDH)

Don't forget that burning any hydrocarbon produces water vapor as well,
so the jet is also adding moisture to the mix. If the air is
relatively dry, the trail disappears rapidly, but if the atmosphere is
near saturation, the contrails can last for many minutes.
tom

Oh it's called Contrails, I didn't know that. I found lot's of info on it
on the web. Thanks.

AliR.



"tom" wrote in message
ups.com...
Don't forget that burning any hydrocarbon produces water vapor as well,
so the jet is also adding moisture to the mix. If the air is
relatively dry, the trail disappears rapidly, but if the atmosphere is
near saturation, the contrails can last for many minutes.
tom

In a previous article, "AliR" said:
Oh it's called Contrails, I didn't know that. I found lot's of info on it
on the web. Thanks.

Just beware of the paranoid lunatics who talk about "chemtrails".


--
Paul Tomblin http://xcski.com/blogs/pt/
Please say this was followed by a very serious discussion on Right and
Wrong involving a blow torch, 220V, a cobra and three East Germans
named Georg... -- Robert Uhl

I ran into that, it was very funny.

AliR.

"Paul Tomblin" wrote in message
...
In a previous article, "AliR" said:
Oh it's called Contrails, I didn't know that. I found lot's of info on
it
on the web. Thanks.

Just beware of the paranoid lunatics who talk about "chemtrails".


--
Paul Tomblin http://xcski.com/blogs/pt/
Please say this was followed by a very serious discussion on Right and
Wrong involving a blow torch, 220V, a cobra and three East Germans
named Georg... -- Robert Uhl

In article , Paul Tomblin wrote:
In a previous article, "AliR" said:
Oh it's called Contrails, I didn't know that. I found lot's of info on it
on the web. Thanks.

Just beware of the paranoid lunatics who talk about "chemtrails".

Well, you know... it is, after all, a *very* dangerous chemical:

Dihydrogen Monoxide (DHMO) -- someone has posted a MSDS (material safety
data sheet) on it:

http://www.dhmo.org/msdsdhmo.html

So...



Best part was the time where city hall in a town in the U.S. actually
passed a law banning DHMO. It stood in force for a day before the very
red-faced city council repealed that ban.

I do, however, have great respect for DHMO in its various forms since it
can cause real problems for GA pilots. :-)

-Dan

(Alternative theory: contrails were invented to give the chemtrail kooks
something to do in their copious spare time. /tongue-in-cheek)

Note to AliR: I'm just kidding in this post. Not poking fun at your
serious inquiry, which has gotten a number of great responses. I'm just
poking fun in passing at the chemtrail kooks.

"AliR" wrote in message
. ..
Oh it's called Contrails, I didn't know that. I found lot's of info on it
on the web. Thanks.

Which is short for "condensation trails."

The water produced from burning lots of gallons of Jet A fuel, producing
water, in vapor form, (lots of it) then exhausting it into very cold air
(20, 30, 40 degrees F, below zero) causes nearly all of that moisture
condense into visible water vapor, pretty quickly.

If you notice, sometimes, you see a space behind the jet where there is no
visible vapor, then it finally cools enough to become visible.

This same thing even happens behind piston engines. They are still burning
fuel, producing water, and having it cool greatly. It is most often seen
behind the high level, heavy bombers of WWII.

I remember the Jimmy Stewart flick, where he was called back into service
after WWII, in the Strategic Air Command. I think that was the name of the
movie, also. Anyway, if you don't get anything else out of the movie, the
flying scenes are "to die for." There are many minutes of seeing the B-36's
flying at very high altitude, with the contrails appearing a few hundred
yards behind the planes.

Kinda neat.

Of course, these planes had jet engines, and gasoline engines, and a lot of
them. Aluminum airplanes, and iron men! Make a point of seeing that movie.
It is worth it.

Extra points, for trivia. What kind/s of fuel did the B-36 carry?
--
Jim in NC

"Morgans" wrote
Extra points, for trivia. What kind/s of fuel did the B-36
carry?

Probably 115/145 AVGAS Purple Stuff

Bob Moore

"Morgans" wrote in message
...

"AliR" wrote in message
. ..
Oh it's called Contrails, I didn't know that. I found lot's of info on
it
on the web. Thanks.

Which is short for "condensation trails."

The water produced from burning lots of gallons of Jet A fuel, producing
water, in vapor form, (lots of it) then exhausting it into very cold air
(20, 30, 40 degrees F, below zero) causes nearly all of that moisture
condense into visible water vapor, pretty quickly.

If you notice, sometimes, you see a space behind the jet where there is no
visible vapor, then it finally cools enough to become visible.

This same thing even happens behind piston engines. They are still
burning fuel, producing water, and having it cool greatly. It is most
often seen behind the high level, heavy bombers of WWII.

I remember the Jimmy Stewart flick, where he was called back into service
after WWII, in the Strategic Air Command. I think that was the name of
the movie, also. Anyway, if you don't get anything else out of the movie,
the flying scenes are "to die for." There are many minutes of seeing the
B-36's flying at very high altitude, with the contrails appearing a few
hundred yards behind the planes.

Kinda neat.

Of course, these planes had jet engines, and gasoline engines, and a lot
of them. Aluminum airplanes, and iron men! Make a point of seeing that
movie. It is worth it.

Extra points, for trivia. What kind/s of fuel did the B-36 carry?
--
Jim in NC



Since it had "six turnin' and four burnin'" did it have to carry AvGas and
JP?

It also carried a nuclear reactor aloft at one point:

http://www.cowtown.net/proweb/nb36h_jde.htm

Jay B