Why do jets sometimes produce vapour trails and sometimes dont?
Answers:
Vapor trails left by aircraft are actually ice crystals. Condensation trails (contrails) are of 2 types, exhaust, and aerodynamic. Exhaust contrails are formed as a result of the addition of enough moisture in the air to form ice crystals. These are prevented in military aircraft by injecting sand into the exhaust trail. Aerodynamic contrails are formed in moist air by the reduction or air pressure around airfoils. They don't stay around as long as exhaust contrails, but under the right conditions, will trigger the formation of a layer of cirrus clouds.
There are also dissipation trails, (distrails) although they are not as common as contrails. They are caused when a jet flies through a thin layer of clouds and evaporates a trail through them.
lol . google "chemtrails"
Depends on the moisture content in the air.
the tempurature at which they are flying. hows that :)
It has to do with the temperature and humidity of the air that they are flying through
Give Corky the points.
It depends on how high they care
When they produce vapour trails they are in the Stratosphere above the normal atmosphere we have around us (troposhere) and the water vapour in the fuel condenses into cloud as soon as it's exausted from the plane. When they are lower (in the troposphere) it's slightly warmer and the water vapour disperses before it has time to condense.
Because some are flying in conditions that are favorable to contrails and some are not.
The heated air from the exhaust mixes with the surrounding air and forms the vapors you are observing. From the air (I have seen this from there) these “trails” look way different from that prospective. Another of these type of trails were something many saw during WWII (No not me) from many of the bombers during the winter (Cold weather) and when they were able to get high enough in the air to reach the cold air. Bottom line if the difference between the exhaust temperature and the surrounding cold air.
It happens past 30,000 ft. the result of the hot thrust in the cold upper atmosphere. A lot like the vapor your breath creates in very cold weather.
The aviation fuel is hydrogen based when it burns with the oxygen from the air it produces the vapour. If you have a clear sky you see the vapour. But a cloudy sky that already has a lot of vapour in it doesn't show up vapour trails so easily.
it has to do with the humidity, tempature and the speed of the jet, also you have to take in to consideration the size and wing span etc
When they like they do when they dont like they dont ,simple,
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