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ZSOFN
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Joined: Fri Jun 24, 2005 5:20 pm

What Atmospheric Conditions Cause This?

Wed Oct 30, 2013 10:30 am

Hi all,

I landed in Munich on SQ327 last week (77W) and noticed a large amount of water vapour being generated over the wings on final approach:

http://www.youtube.com/watch?v=ReJOhVv4N6U

I've noticed this before particularly on videos of landings at ZRH and AMS, so I was wondering if there was a particular temperature or humidity range in the atmosphere in that causes this?

N.B. Ignore some of the rather inane chatter between my friends & I during the video..!
 
airbuster
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RE: What Atmospheric Conditions Cause This?

Wed Oct 30, 2013 10:56 am

What i believe happens is that with very moist/damp air being accelerated over the wing the temperature drops and cold air can hold less moisture than hot air, therefore you see a release of moisture over the wing.

Something like that.
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oly720man
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RE: What Atmospheric Conditions Cause This?

Wed Oct 30, 2013 11:31 am

What you see is the expansion of the air as it accelerates over the wing. As it expands the temperature decreases and if the temperature is reduced sufficiently, to the dew point or below, any water vapour in the air will condense and you'll see it as clouds over the wing.

When this happens will depend on the speed of the aircraft, the size of the aircraft (to some extent) and any manoeuvre g loading as well as atmospheric conditions.

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Humidity and the dew point temperature relative to ambient temperature are the main atmospheric factors, though.

Judging by this, people are looking for a definitive answer.

http://www.aviationplatform.com/surv...ect%20over-wing%20condensation.pdf
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nomadd22
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RE: What Atmospheric Conditions Cause This?

Wed Oct 30, 2013 11:33 am

Quoting airbuster (Reply 1):
What i believe happens is that with very moist/damp air being accelerated over the wing the temperature drops and cold air can hold less moisture than hot air, therefore you see a release of moisture over the wing.

Something like that.

You get less that ambient temperature and pressure on top of the wings so air at close to 100% humidity can't hold the water anymore.
Anon
 
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ZSOFN
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RE: What Atmospheric Conditions Cause This?

Thu Oct 31, 2013 9:17 am

Quoting oly720man (Reply 2):
Humidity and the dew point temperature relative to ambient temperature are the main atmospheric factors, though.

Perfect - thanks! I knew the theory of why condensation occurs but I think that's the key piece of info above. Wasn't necessarily looking for exact ambient temperatures etc necessarily.

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