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Re: REFLECTOR: AOA perspective



 'after having many hours in our Velocity, I have no desire for an AOA
guage.  I would rather have it in Cessna 172 than in the Velocity.  Joe
Connally

Al Gietzen wrote:

>  Interesting to see the postings regarding angle of attack meters
> (AOA); especially systems costing over $1400, and mounting in the
> wing. What is it we want from these?  In spite of marketing claims, I
> think its usefulness is pretty much limited to giving a good
> consistent indication of incipient stall, regardless of loading,
> temp., density altitude, etc.  I'd say that this is an instrument that
> is conspicuous by its absence from the panels of standard tractor
> pull; stabilizer-in-the-back airplanes that are subject to the
> stall-spin accident.  But a prime motivation for driving an airplane
> with a wing in the front is that it avoids this type accident. So I
> think its possible usefulness to us is to know when the canard is
> going to stall so we can make consistent landings which aren't any
> hotter than necessary (or not hot enough) for the conditions.  So we
> need it on the canard; not the wing.  I also think that order to
> calibrate these instruments, you need to take the airfoil to stall
> speed, so we could never calibrate one for the main wing without being
> in deep _____ . . . . , you know; stall! Installation of any system
> using differential pressure ports is not so easy in our canards,
> especially if we got the canard from our friends at Dynamic Wing.  Or,
> if you haven't built your canard yet, a very inexpensive installation
> is a differential pressure gauge, a small pressure port (like a static
> port) on the leading edge of the airfoil, and another such port on the
> bottom of the airfoil 12 1/2% of the chord length from the leading
> edge.  Measure the pressure difference between the two; calibrate it
> by marking the reading on your gauge just at the point of incipient
> stall of the airfoil. Now even simpler; since the leading edge port is
> subject to a bug splatter or dirt or ice, one can instead use the
> dynamic pressure you already have from your pitot tube.  It gives you
> less of a differenttial pressure range to work with, but I helped a
> friend with this type installation on his Lancair 360 and it works
> just dandy.  A pitot tube mounted in the slightly disturbed flow on
> the side of the fuselage may be a bit different, but it probably would
> also work. When asked if they thought an AOA (stall) meter would be
> helpful, the guys at the EZ Squadron sort of shrugged and said they
> didn't think so.  If you pressed them, they'd probably say that they
> land hot anyway because otherwise mushy aileron response, adverse yaw,
> and lack of visibility over the nose makes them nervous. What about
> you Velocity fliers (if any of you have read this far)?  Would you
> like to have one of these on your airplane?  I'd like your feedback,
> because I'm giving serious thought to making this installation. Al
> Gietzen  RGE