OPNLguy From United States, joined Jun 1999, 13092 posts, RR: 83 Reply 1, posted (6 years 2 months 3 weeks 6 days 23 hours ago) and read 2439 times:
I'll make this short and sweet, and then go call my bookie and place a bet on how long it'll be before someone starts the "chemtrail" conspiracy BS...
Contrails are formed much in the same way that your car exhaust is visible on a cold morning. At the altitudes jets commonly cruise (31,000 feet to 43,000 feet), it's obviously -cold- and contrails will last (or dissipate) based on the actual temperature, and dewpoint. A large coverage area of contrails that linger and only partially disspiate and then all merge together due to the winds aloft can also mimic clouds, i.e. psuedo-cirrus clouds versus cirrus clouds.
Hope this helps...
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
TARANTINE From United States, joined Sep 2000, 210 posts, RR: 0 Reply 2, posted (6 years 2 months 3 weeks 6 days 15 hours ago) and read 2239 times:
The odd thing with the trails is that some days they will fill the sky up & other days you will see none at all even though the temp & humidty are the same.
Rick767 From United Kingdom, joined Jan 2000, 2662 posts, RR: 57 Reply 4, posted (6 years 2 months 3 weeks 6 days 13 hours ago) and read 2231 times:
"The odd thing with the trails is that some days they will fill the sky up & other days you will see none at all even though the temp & humidty are the same."
It must be some kind of conspiracy.....
Sorry guys
I used to love the smell of Jet-A in the morning...
Positive rate From Australia, joined Sep 2001, 2143 posts, RR: 0 Reply 5, posted (6 years 2 months 3 weeks 6 days 11 hours ago) and read 2212 times:
I love it when the sky is clear blue and there is an aircraft passing overhead leaving a bright contrail going for miles. Just looks so neat especially if it's a 747.
Tadex From Vatican City State (Holy See), joined Sep 2002, 91 posts, RR: 0 Reply 6, posted (6 years 2 months 3 weeks 5 days 3 hours ago) and read 2106 times:
THVGJP From Ukraine, joined Mar 2002, 157 posts, RR: 0 Reply 8, posted (6 years 2 months 1 week 6 days 23 hours ago) and read 1894 times:
Is there any way mechanical way for a jet to not put out contrails, sort of contrail cancellation. I have seen refeuling operations where the tanker puts out no contrails and the receiving aircraft puts out contrails. Any explanations??
Dab920 From United Kingdom, joined Jul 2001, 95 posts, RR: 1 Reply 9, posted (6 years 2 months 1 week 6 days 22 hours ago) and read 1892 times:
That doesn't really explain it. At altitude, the air is cold and dry. Hot air from the engine exhaust cools down and condenses? I assume there is a lot of moisture in jet exhaust is there? If this is the case, why does the trail dissapate? It's not as if the air warms up again. It stays just as cold, to the relative humidity of that patch of air should stay high enough to remain as a trail.
I was once told that it was because there is moisture in the air, but with no condensation particles for the moisture to cling to, it remains in the air. A jet provides condensation particles which the water immediately cling to. Sounds strange also.
Avioniker From United States, joined Dec 2001, 1098 posts, RR: 15 Reply 10, posted (6 years 2 months 1 week 6 days 22 hours ago) and read 1909 times:
The engine compresses whatever goes into it and expells that compressed matter from the tailpipe. It uses hydrocarbon based fuel to run and the exhaust also goes out the tailpipe. Water is made of oxygen and hydrogen.
There is no such thing as perfectly dry air so any water in the air will be compressed and condensed and become visable after it cools behind the engine exhaust.
Did I mention HYDROcarbon? There is also some hydrogen and oxygen combination happening within the exhaust byproducts so you get a little more water vapor which becomes visable in the exhaust stream.
Now will you paranoid conspiricy freaks go play on your own website and let those of us who want to discuss reality issues alone?!
One may educate the ignorance from the unknowing but stupid is forever. Boswell; ca: 1533
Bobrayner From United Kingdom, joined Apr 2003, 2227 posts, RR: 10 Reply 12, posted (6 years 2 months 6 days 19 hours ago) and read 1794 times:
I remember hearing there is a way to tell the weather from the length, and width of contrails. Anyone care to explain?
To a limited extent, yes.
Contrails will be thicker, and more persistent, in air where the humidity is high (relative to the solubility of water in air at that temperature and pressure). However, the fact that there are three variables behind the system makes it quite difficult to get useful information by counting / measuring contrails.
Also, the contrail is only telling you about weather conditions 10km up. If you want to know about terrestrial weather, you can get much better quality information just by looking around you rather than up in the sky.
Contrails could also help a little with prediction of weather, but tbh in order to extract much information from them you'd need to have a good weather chart handy anyway.
Aloges From Germany, joined Jan 2006, 5853 posts, RR: 52 Reply 13, posted (6 years 2 months 6 days 14 hours ago) and read 1794 times:
With my rather little knowledge of meteorological issues, I'll try anyway...
"It uses hydrocarbon based fuel to run and the exhaust also goes out the tailpipe. Water is made of oxygen and hydrogen."
Quite exact. Remember the combustion of a hydrocarbon, I'll use methane for it's the simplest (doesn't matter it's gaseous at room temperature):
CH4 + 2 O2 -> CO2 + 2 H2O
That works similar for longer hydrocarbon chains, like decane. So whenever Jet A is combusted, the exhaust gases will contain water; and they'll be hotter than the environment at FL330.
As hot air can absorb more humidity than cold air (ever breathed on that -15°C day?), the exhaust of the engine will contain more humidity than the surrounding cold air up there could ever absorb.
Neither can the water vapour from the exhaust be dispersed to a volume of cold air that could absorb it fast enough to prevent it from condensing or re-subliming. The result is a contrail mainly composed of dipersed water droplets or ice crystals.
When there are no contrails in the sky, the temperature differences between exhaust and environment might not be sufficient for condesation; however, this is just a guess.
Then, there might be those secret substances being sprayed from aircraft on behalf of the CIA...
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Just looks so neat especially if it's a 747..gif){kind=small}
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