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Here are two pictures of condensation happening above the wing:

Airplane with condensation above wing

Single Wing with condensation

The condensation happens because the pressure drops above the wing which in turn causes the temperature to drop. When the temperature drops below dew point then the condensation will happen. The airplane has to be flying slow enough to allow time for the condensation to happen as well.

Here is my question: How does the condensation affect lift?

I would guess that the temperature does not drop as far because the air would stay at dew point.

Another effect could be that the air is not as dense because the water is now a droplet rather than molecular.

Are there other effects?, and how do they affect lift?

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    $\begingroup$ Does flying through clouds affect lift? $\endgroup$
    – Jim
    Commented Jun 25, 2022 at 6:21
  • $\begingroup$ “The airplane has to be flying slow enough to allow time for the condensation to happen as well.” Not true. Vapes can flash into and out of existence instantaneously under G, and you can see a cone shaped vapor cloud form around a sonic shock wave. $\endgroup$ Commented Jun 27, 2022 at 1:06

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Interesting question, and I will have to speculate when answering.

Condensation changes the lapse rate of air. This makes flying into clouds so effective for gliders. In the early days of gliding some pilots used the higher climb rate in clouds for record flights. But that is not the topic here.

The air above the wing will not cool down as much due to the latent heat freed by condensation. Thus, the air will be less dense compared to drier air which shows no condensation in the same condition. But pressure should not be affected. Therefore, the pressure difference between lower and upper wing surface should not be affected, too.

Lift is the downward acceleration of air, and if this air has less density, lift will also be lower. Now it comes down to how density changes: Moist air is less dense than dry air, so the dry air plus droplets has a higher density. On the other hand, after condensation the air will be warmer, losing some density due to the freeing of latent heat. I would expect that the first effect is larger and lift to be just a tiny bit higher than in a condensation-free condition.

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