DENIS SMITH wrote:

Sometimes we bury ourselves with numbers.  In the
regime most of us fly a stall is defined by a
situation where the angle of attack of a lifting (read
wing) surface exceeds a point where smooth airflow is
possible and separation of the airflow over the top of
the wing causes loss of lift and that sinking
sensation most of us have experienced.  The reason
canard type aircraft claim to be stall proof is that
the mechanism they use for pitch control has
insufficient authority to put the wing at a high
enough angle of attack to cause the wing to stall
during normal (whatever that means) operations.
Typically, angle of attack required to stall an
airfoil is the same regardless of airspeed.  Your spam
can will stall at 45, 100, or 150mph if that angle of
attack is exceeded.  Whether it is caused by control
input, wind shear, updraft, or whatever, it is angle
of attack that is critical.  Paul is right that any
airfoil can be stalled.  Usually the "Stall Proof"
folks are just saying that whatever pitch mechanism
they are using has insufficient authority to put the
main airfoil at an angle of attack where a stall will
occur.

Stone Tool wrote:

The statement that the control surfaces on a canard such as the VariEze have
"insufficient authority" to put the aircraft into a stall is really not
accurate...... or rather it glosses over the real situation which is that
the canard stalls before the main wing.   When the canard begins to
experience flow seperation this seperation interferes with elevator
authority.......Add to this that there is a significant percentage of the
weight supported by the canard which becomes more or less unsupported when
it loses lift, and there will be a pitch down moment when the canard breaks
which exceeds the ability of the elevator to overcome it.

    This is a far more complex situation than simply "not enough elevator
authority"..... a gross oversimplification which suggests that the EZ series
use a limited elevator like the Ercoupe which they do not.

                                H.W.

 
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