Message-ID: <000201bf2a11$c5fa7780$97818ed1@pavilion>
From: "J. N. Cameron" <CIC@centurytel.net>
To: "Lancair List" <lancair.list@olsusa.com>
Subject: Reflexing flaps
Date: Mon, 8 Nov 1999 09:10:56 -0600
Mime-Version: 1.0

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My understanding of the purpose of a "reflex" position for flaps is that it
actually reduces the lift of the wing.  Most wing/flap configurations have
essentially two conditions:  flaps up for normal airfoil, and flaps down for
a higher-lift airfoil.  The reflex gives you a "flaps farther up" position
for a lower-lift airfoil, which is just another way of tweaking the
airfoil's lift through a larger range of airspeeds.  At high airspeed, you
don't need as high a lift coefficient, and since lift brings drag with it,
you get better performance by reducing both with a reflex flap position.  In
spam cans the increase in airspeed between stall and cruise is often only
about 50 kts, which may be why nobody bothers with reflexed flaps on 172's.
In the 360, the difference is maybe up to 150 kts, so some extra tweaking at
the top range is worthwhile.  The ideal, of course, would be flying machine
with a continuously variable airfoil, optimized over the whole speed range.
It's called a bird.

Jim Cameron  (once & future ES)

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