Brian asked:
> I am curious. If the bottom spoiler/dive brake is hinged from the back
> (trailing edge), then that forms a type of a scoop or pocket. How could
this
> cause lift? The air can't exactly flow easily around the device or over
the
> top of it...
You've probably seen those powered beer cans that spin and foam up and
explode or fly? They don't have a very good L/D, but basically they drag
air quickly over the top--reducing pressure--and combined with fwd speed,
they push up a pile of air underneath--increasing pressure--and in a cloud
of suds, the thing flies--sorta. Anyway, a lift killer on the bottom of the
wing does the same thing--increase pressure underneath. The flow will be
all kinds of bad and the D part of L/D will go way up indeed, but there will
be a slight compensation in L, and that's what everyone's getting all
excited about.
Frankly, the purpose of lift killers is to decrease the L/D to the point
where you have a chance at nailing the target. If upper/lower surface
killers are such a big deal, they will be a disadvantage because L/D won't
drop as fast as a plane with the same killer area on the top surface.
Therefore, these god--err CD's--who pontificate about banning them just
cause they feel like it are actually doing a favor to the double-sided
lift-killer flier types. While absolutely none of any of this is based in
objective fact, I wouldn't be surprised if it's mostly hype and 3D
windtunnel tests would show there wouldn't be much discernable difference,
as long as you require all surfaces to move together.
Tony Rogers
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