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Old April 17th 07, 05:47 PM posted to rec.aviation.piloting,rec.aviation.student
rq3
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Posts: 19
Default Question to Mxmanic

Anthony, you've got the issue of compressibility precisely backwards. No
surprise.

Rip

Mxsmanic wrote:
Rip writes:

I don't know, but I'm going to find out! I can envision an aircraft with
light wing loading, like a Cessna for instance, compressing the air
locally as it creates lift. After passage of the wing, the lift created
downwash would rebound upward, kind of like skipping a stone on the
water.


Virtually no compression occurs at the speeds of a Cessna. Compression is
only an issue at high speeds. At low speeds, air behaves very much like an
imcompressible fluid.

The end result is that the downwash stays at a constant altitude,
or sinks MUCH more slowly than theory would indicate.


The downwash does not stay at a constant altitude. It sinks. It has to,
otherwise the aircraft couldn't stay in the air.