Re: N6Q wing problem

[Alan Shaw <wingco@iu.net>]

Tim Crawford wrote:

> Hi Alan!
>
> I got a wing related problem and sure could use your advice.
>
> Today on my 3rd flight at 130 kts, I ran out of down trim and the elevator
> was running trailing edge up about 1/2".  That does not sound correct to
> me.  I am flying in Velocities recomended first flight box with about 30
> pounds of ballast.

At cruise I like a Velocity with 1/2" of reflex single pilot.  This rig makes
for a faster cruise and slower landing.  Your case may be a little extreme and
require 1/2 degree less incidence in the canard.  A quick fix is to put a
1/32" washer on both outboard top wing bolts...thus decreasing the difference
between the incidence angle of the canard and main wing.  This way you can
test fly the change before you go through the hassle of changing the canard.

Like I said, I like a Velocity that requires full forward trim and full
forward stick by the pilot when solo, wide open at sea level.  This will leave
more elevator authority (flare!) when you are slow and loaded.  It should also
trim fine at the lower indicated airspeeds of cruise at 8,000' and above.
It's a common problem with new Velocities that the new owners fly in this
unusual mode of solo, full throttle, low altitude and then re-rig there A/C to
"fix" this quirk that really just makes things better on the slow end of the
flight envelope.

With such a powerful canard some people are worried about deep stall.  Even if
you could "make" it deep stall I doubt that you  push your canard past normal
bucking into the violent bucking and rolling etc. that normally precedes the
"big one".

What prevents deep stall is not just as simple as the difference in wing
loading between the two wings but all there differences in characteristics as
whole.  That means incidence angle, aspect ratio, camber, leading edge radius
and many other lesser factors.  In other words, if you decrease the canard
incidence and/or cut it shorter (lower the aspect ratio) then you have
actually increased two factors for deep stall potential.  On the other hand
this change has increased you wing loading on the canard and also made it
harder for you to pull the nose up too high.  If you are confused so am I.
That's the problem there are so many variables each with different
coefficients of influence over the  wing differential we are trying to
maintain while at the same time trying to get as wide a flight envelope as
possible.

The obvious is to keep the CG in front of the center of lift.  The problem
here is that the main wing/winglet is comprised of four different airfoils,
incident angles and coefficient's of lift.  So where exactly is the center of
lift?....well the experts don't seem to agree unless they simplify with
rounded off  "rules of thumb" that are far from the truth.

That's why the flight test that Dan, myself and especially Jim Patton did were
so important.  When Jim "tickled the dragons tail", as he put it,  he found
the Velocity to have far more low speed stability and aft CG capability than
its other "Easy" counter parts.   As the head of NASA's GA stall spin R&D
program for almost 20 years Jim has pushed everything out there way past it's
limits and should know.  In his opinion the STD wing Velocity is as good as it
gets in the compromise between stall prevention and performance.  Personally I
think the STD Velocity will endure the test of time as one of aviation's more
exceptional designs.

Alan