In article ,
Denis wrote:

Derrick Steed a écrit :
since induced drag increase due to airbrakes is=20
high=20

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Don't you mean "form" drag? I thought induced drag resulted (crudely)
from the wingtip vortices.

No. Wingtip vortices are only the visible part of the iceberg ;-)

Induced drag is the result of lift itself and is lower when the span is
higher and when the spanwise lift repartition is close to elliptic. And
with the airbrakes out, the lift repartition is very bad, closer to 3
wings of 5 m of span separated by no lift (at the airbrakes) than to 1
27 m wing !

This appears to be confused.


Also, are you sure that drag is proportional to lift?

Induced drag is proportionnal to square of lift, while form drag don't
vary much with lift. Total drag definitely increases with lift, but to
quantify it that's where we need the proportion of induced drag...

And this is clearly totally mistaken, or misspoken. Two gliders flying
have twice as much lift as one glider, but they have four times as much
induced drag as one glider? And ten gliders have one hundred times as
much induced ddrag as one?

--
Bruce | 41.1670S | \ spoken | -+-
Hoult | 174.8263E | /\ here. | ----------O----------