When I was a kid during the sixties it seemed that almost every one had one, now I can't remember the last time I saw one. I assume the answer revolves around efficiency of thrust, but can anyone give a more complete answer?
Interesting....I grew up in Illinois but since 86 I have lived in warmer climates...the coldest was Munich, the warmest the Arizona desert. Perhaps it is as simple as that....
Contrails (short for "condensation trails") or vapour trails are artificial clouds that are the visible trails of condensed water vapour
made by the exhaust of aircraft engines. As the hot exhaust gases cool in the surrounding air they may precipitate a cloud of
microscopic water droplets or, if the air is cold enough, tiny ice crystals.
The wingtip vortices which trail from the wingtips and wing flaps of aircraft are sometimes partly visible due to condensation
in the cores of the vortices. Each vortex is a mass of spinning air and the air pressure at the centre of the vortex is very low.
These wingtip vortices are not the same as contrails.
Depending on atmospheric conditions, contrails may be visible for only a few seconds or minutes, or may persist for many hours
which may affect climate.
It may just be that as a kid you just didn't notice the planes when there was no contrail visible. You are just more observant now.
0 Replies
roger
1
Reply
Sat 9 Jul, 2011 02:07 pm
It may have to do with the type of aircraft. Warplanes fly higher and faster than civil aviation. Also, commercial airliners now use fanjets almost exclusively. I recall that after 9/11, our own isolated section of the sky was filled with them, even when civil aviation was grounded.
I bet Georgeob knows about this kind of stuff.
0 Replies
High Seas
2
Reply
Sun 10 Jul, 2011 07:23 am
@hawkeye10,
hawkeye10 wrote:
Interesting....I grew up in Illinois but since 86 I have lived in warmer climates...
All fuels contain some water, and that water vaporizes from the heat of the engine and becomes visible at the dew point (frost point) in the ambient air. Altitude, speed, type of engine, aren't relevant - only air temperature. It's the same phenomenon with car exhausts, you can see them in cold weather.
It's often been argued that these actually fight against global warming, by reflecting some of the Sun's rays back into space. One of the few positive things to come out of 9/11 was that with the fly ban over the USA scientists could collect valuable data to check out the theory. Apparantly it's true.
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