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Thread: Plane condensation

  1. #1
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    Plane condensation

    This is my first time to share photos, so I'm not absolutely sure I've done it correctly.

    Yesterday I was in downtown Tokyo and I noticed from an app that planes on approach to Haneda were flying over the city center (it's a new route that just started this spring). It was partly clouded, and I noticed (it's the first time I ever really remember seeing this so clearly) that the planes created their own clouds (I guess condensation trails?) as they descended through the cloud layer, even when there wasn't a cloud there. These are two pictures I took with my iPhone, so they are not great quality and one is pretty blurry.
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    As above, so below

  2. #2
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    It doesn’t take much airflow with cold soaked wings.
    Usually you see cones in the transonic range.

    Now watch someone say the chem trail folks swapped in humidifiers by mistake...

  3. #3
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    Cool! It doesn't take all that much speed, just humidity and compressive effects. We watched a Formula 1 race from Hungary yesterday and you could see little condensation trails coming off the rear wings. That's at speeds of 200mph or less.
    Cum catapultae proscriptae erunt tum soli proscript catapultas habebunt.

  4. #4
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    I think temperature and RH have to be just right for this vapor condensation to appear on commercial airliners but it's very commonly seen with fighters performing moderate-to-high g maneuvers.
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  5. #5
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    These low pressure clouds over the wings are a little different from contrails. Contrails generally form in high, dry air from the water in engine exhaust, and can persist for a long time as ice crystals. Condensation over the wings (and in vortices shed by wingtips and flap edges) usually appears transiently at lower altitude, when warm, humid air is temporarily cooled below its dew point as it expands in a low pressure region created by the passage of an aerofoil surface.
    The farther from the dew point the air mass, the more severe the pressure drop has to be to induce condensation, which is why it appears more readily when fast jets are manoeuvring abruptly. I always look out for condensation over the wings if I'm a passenger in a plane descending towards cloud. You can usually catch sight of a little burst of it just before the plane enters the cloud.

    Grant Hutchison

  6. #6
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    Here's a video that nicely shows the effect, as well as wingtip vortices: MACH LOOP MEGAFLUFF 4K

    It depicts US F-15E Strike Eagles maneuvering the Mach Loop training area in Wales. Although I believe low-res options are available, those with limited bandwidth may be challenged by the video.
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  7. #7
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    Quote Originally Posted by Trebuchet View Post
    Cool! It doesn't take all that much speed, just humidity and compressive effects. We watched a Formula 1 race from Hungary yesterday and you could see little condensation trails coming off the rear wings. That's at speeds of 200mph or less.
    Yeah, I don't remember exactly, but the photos I took are of jets on approach to Haneda, so I'm guessing they were about 2,000 feet and about 180 knots at that point.
    As above, so below

  8. #8
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    When they descend, they put on the flaps on the leading and trailing edges, to give extra lift at lower speeds, for safety, and maneuverability. Doing so reduces the streamlined airflow, and disturbs it a lot, giving the compression and subsequent expansion Grant mentioned, and it depends on the relative humidity of the air. That's a thing a school kid can check with an ordinary alcohol thermometer. Just read the thermometer after it reaches thermal equilibrium ( dry bulb temp.)...then attach a piece of damp cloth or damp paper towel, or damp cotton, to the bulb with tape or a rubber band....and swing it around in the air ( without breaking it) for about 15 seconds. Evaporation cools the bulb if the air is real dry, but less so if it's humid, and that is the wet bulb reading. The difference is looked up in a chart, and it gives the relative humidity.
    A house heated with hot air heat on a bitter cold New England day can be drier than the Sahara. The easy fix is make pasta, and let some of the water boil away.
    See:https://www.google.com/search?sxsrf=...k0I4ZB5USjD-QM
    Last edited by trinitree88; 2020-Aug-04 at 03:05 AM.

  9. #9
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    Some of the airbus models seems to have substantial condensation inside the aeroplane while it's on the ground . . .

  10. #10
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    Quote Originally Posted by Rolling Stone View Post
    Some of the airbus models seems to have substantial condensation inside the aeroplane while it's on the ground . . .
    Some Boeings have that problem in flight as well. "Rain in the Plane" it's called!
    There's also an area over the aft end of the central wing box where the wing shape curls down and then the pressure vessel kicks back up over the wheel well. It's known as the Guppy Pond.
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