This morning I noticed a large, fairly low-flying, 4- engined passenger
jet go overhead through a clear blue sky (it appeared to be still in
takeoff mode from Stansted).

What immediately struck me was that it was creating a large sheet of
condensation (?) in its wake, the sheet forming a delta shape, with the
apex somewhere just under the body of the aircraft. The condensate only
lasted a few seconds before it evaporated, but the continuous production
of it looked as if the plane was trailing a large white sheet behind it.

I've seen planes form short-lived vortices of condensation from the
wingtips, but never anything as extensive as this.

It looked quite spectacular as it went overhead. I assume that pressure
differences over the wings was reducing the temperature in air that was
close to saturation(?)

- Tom
Blackmore, Essex.

"Tom Bennett" wrote in message
...
This morning I noticed a large, fairly low-flying, 4- engined
passenger
jet go overhead through a clear blue sky (it appeared to be still in
takeoff mode from Stansted).

What immediately struck me was that it was creating a large sheet of
condensation (?) in its wake, the sheet forming a delta shape, with
the
apex somewhere just under the body of the aircraft. The condensate
only
lasted a few seconds before it evaporated, but the continuous
production
of it looked as if the plane was trailing a large white sheet behind
it.

.... see the FAQ Q/A 2A.11

I've actually seen military aircraft with full fuel load (having
difficulty lifting clear by the end of the runway) just after dawn (high
RH ... 96%), actually feeding into a pre-existing sheet of shallow fog
(MIFG) and temporarily thickening same to 'proper' fog (BCFG), though by
the same token, the wake of the a/c then causes turbulence which mixes
down unsaturated air from just above the fog layer and the entire sheet
disappears!

Martin.


--
FAQ & Glossary for uk.sci.weather at:-
http://homepage.ntlworld.com/booty.weather/uswfaqfr.htm

"Martin Rowley" schreef in
bericht ...

"Tom Bennett" wrote in message
...
This morning I noticed a large, fairly low-flying, 4- engined
passenger
jet go overhead through a clear blue sky (it appeared to be still in
takeoff mode from Stansted).

What immediately struck me was that it was creating a large sheet of
condensation (?) in its wake, the sheet forming a delta shape, with
the
apex somewhere just under the body of the aircraft. The condensate
only
lasted a few seconds before it evaporated, but the continuous
production
of it looked as if the plane was trailing a large white sheet behind
it.

... see the FAQ Q/A 2A.11

I've actually seen military aircraft with full fuel load (having
difficulty lifting clear by the end of the runway) just after dawn
(high
RH ... 96%), actually feeding into a pre-existing sheet of shallow
fog
(MIFG) and temporarily thickening same to 'proper' fog (BCFG), though
by
the same token, the wake of the a/c then causes turbulence which mixes
down unsaturated air from just above the fog layer and the entire
sheet
disappears!

Martin.


--
FAQ & Glossary for uk.sci.weather at:-
http://homepage.ntlworld.com/booty.weather/uswfaqfr.htm



In the old days, 1946 etc., DC3's starting their flight from Medan,
Sumatra, to Batavia -now Jakarta- Java, in the early morning when RH
was high, produced condensation rings behind the propellors. Visible
only for a short distance. Trying to visualize the picture, I think that
the extent was not more than the diameter of the propellor circle.
Good old days ;-(

Sytze Stel

What you describe, Tom, is condensation in high humidity air experiencing
the reduction of pressure (and therefor temperature) as it is accelerated
over the lifting surface of the aircraft. The resulting condensate flows off
the trailing edge of the wings before evaporating in a sub-saturated
environment.

--
Bernard Burton
Wokingham, Berkshire, UK.

Satellite images at:
www.btinternet.com/~wokingham.weather/wwp.html







"Tom Bennett" wrote in message
...
This morning I noticed a large, fairly low-flying, 4- engined passenger
jet go overhead through a clear blue sky (it appeared to be still in
takeoff mode from Stansted).

What immediately struck me was that it was creating a large sheet of
condensation (?) in its wake, the sheet forming a delta shape, with the
apex somewhere just under the body of the aircraft. The condensate only
lasted a few seconds before it evaporated, but the continuous production
of it looked as if the plane was trailing a large white sheet behind it.

I've seen planes form short-lived vortices of condensation from the
wingtips, but never anything as extensive as this.

It looked quite spectacular as it went overhead. I assume that pressure
differences over the wings was reducing the temperature in air that was
close to saturation(?)

- Tom
Blackmore, Essex.