Re: REFLECTOR: Empty Weight

[David Doshay <ddoshay@cisco.com>]

>>really force buck it it will never deep stall.

>Please explain "force buck" a little better for us novice flyers

If you slow down a Velocity and apply full aft stick
attempting to maintain level flight at progressivly slower
airspeed, eventually the canard will stall. If you continue to
hold full aft stick the nose will drop due to the canard being
stalled but the main wing still generating the 'normal'
amount of lift. As the nose drops, the angle of attack of the
canard decreases until the canard is no longer stalled, and
the canard begins to pull the nose back up. If full aft stick is
maintained, the nose bobs up and down at about 1 Hz. 
This is known as the pitch buck.

On my test flight, with Duane and myself in the front and my 
wife and small daughter in the back and about 25 gal of fuel,
in full pitch buck with full aft stick and 1500 rpm the plane
was moving down at 500 fpm with the nose moving up and
down about 2 feet. The ailerons and rudders were responsive. 
The plane felt perfectly controllable, although having the
nose bobing 2 feet once a second really gets one's attention.

But what can happen at aft CG is that a pilot can abruptly
pull the stick back into an accelerated stall. The momentum
of the rapid pitch up of the nose can rotate the nose far
beyond the point where the nose would normally start
dropping. I think this is what Alan meant by "really force." In
this case it is possible that the rotation will take the plane
out to where the main wing has stalled. Not a good thing in
most folk's minds. ;^o

While it is possible that an improperly designed canard
airplane could immediately go tail down (a generally fatal
thing), a few older Velocities instead settled into a flat
attitude, slowly going straight down with no aileron or 
elevator effectiveness. That was the "deep stall."  

I do not know exactly where the Velocity sits on this one, but
most canard planes have between 6 and 10 degrees of
difference between the angle of attack where the canard
stalls and the angle where the main wing stalls. Duane is
rightfully tired of all the press and worry about the "deep
stall problem" in the Velocity, because it has clearly been
fixed. Besides, what is a real pilot doing by whipping a canard
plane into a hard accelerated stall anyway? A Velocity is not
supposed to be a Pitts, and should not be flown like one.

Cheers,
David