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Re:Concorde by mcguire on Tuesday October 25, 2016 @10:09AM (#12788104)
To maintain level flight, a plane has to generate lift equal to its weight. It generates lift by forcing a mass of air down. More mass means more air disturbed.
Re:Concorde by nf05papsjfVbc on Tuesday October 25, 2016 @11:24AM (#12788725)
Interesting. I never thought of it this way. Thanks for helping me see the missing part of the picture.
Re:Concorde by mcguire on Tuesday October 25, 2016 @07:46PM (#12792795)
When people explain flight through Bournoulli or whatever, they tend to forget Newton's basic laws, which really are the simplest way to understand flight. It won't make you an aerospace engineer, though.
Re:Concorde by brian_cloutier on Wednesday October 26, 2016 @06:41AM (#12795395)
Ah, you're right, thanks for clarifying. My comment now looks pretty dumb, wish it didn't get so many upvotes.
Re:Concorde by mzs on Tuesday October 25, 2016 @12:48PM (#12789454)
You are describing ground effect not lift.
Re:Concorde by mcguire on Tuesday October 25, 2016 @11:45PM (#12793727)
Note: I am not an aerospace engineer.

Not quite. Outside of ground effect, a downward force is applied to the air mass around the aircraft, resulting in lift on the aircraft. IIUC, this results in compressed, high pressure air below the plane and low pressure air above it. The result of that is a pair of vortices roughly centered on the plane's wingtips. These vortices themselves are Somehow Important to the whole thing. Anyway, you can see the deal when a plane flies close to a cloud top.[1]

In ground effect (i.e. the aircraft is flying within roughly one wingspan of the ground), the proximity of the ground blocks the formation of the wingtip vortices (?) and greatly enhances the efficiency of lift production (by some form of magic, AFAIK).

[1] https://s-media-cache-ak0.pinimg.com/564x/1c/33/e2/1c33e2f2f...

Re:Concorde by mzs on Wednesday October 26, 2016 @12:31PM (#12797884)
You need to sum craft weight and lift when applying Newton's laws in figuring downward pressure, more lift -> less ground pressure across all craft weight.