Sender: <marv@lancaironline.net> (Marvin Kaye)
To: lml
Date: Tue, 09 Jul 2002 08:08:14 -0400
Message-ID: <redirect-1622499@logan.com>
From: J H Webb <airmale@bright.net>
MIME-Version: 1.0
Subject: Stall recovery and spin avoidance
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>Re: Paul Davis' post about trying to pick up a stalled (or nearly
stalled)
>wing with ailerons.

>No argument here, Paul, your post is right on! I might only add that
besides
>increasing the drag, and therefore the adverse yaw into the down wing,
>trying to pick up the down wing with a downwardly deflected aileron
>increases the angle of attack of that wing. If it ain't stalled, but is
very
>close, when the aileron goes down the increase in AOA for that wing
will
>kick it over the threshold. All the additional aileron in the world
after
>that will only make matters worse.

Guys

   This is beginning to sound like a discussion about the 'boggy man'.
First consider the loss of lift at the full stall.  Approximately 10% of
the total.   Second consider the loss of Q from a couple of knots above
the stall to stalled.  Less than 2 %   Third consider the stall
progression.  Trailing edge root to tip.  Finally in a Lancair you do
not have all the aileron in the world and you don=92t have much
deflection.  The ball in your turn coordinator or turn and bank is big,
biggest black indicator on the panel and this is for a reason as applies
to pilots.  Coordinate. This does not mean =91all the aileron in the
world=92 or only rudder.

   Now armed with that knowledge consider why the ailerons would
suddenly have horrible characteristics with the reduction of a couple of
knots when the lower portion is still in the airflow no different than
before the slight speed reduction.  Much more important by an order of
magnitude is the proper coordination.  Why because this will cause a
root stall to progress outboard rapidly or if well coordinated not
rapidly progress toward the tip and AILERON.  This conversation about
huge increases in drag with aileron deflection is at best silly, if we
are talking a fairly well designed GA airplane. The reason that that
some aircraft designs have poor to awful stall characteristics is that
the manufacturer had other goals (Read in general Military {high speed,
high mach, high gross wt, manufacturing costs}).

  Now in addition to the above making the comparison to the decathlon is
very much like comparing a Porsche=92s handling characteristics to a mode=
l
T and then making decisions about how to handle the Porsche because of
corning problems with the model T.  Now if you want to compare, look at
the aileron deflection of the two aircraft, look at the aileron chord
length, look at the type of aileron, look at the way the ailerons are
hinged, look at the aileron type, look at the aileron gap (which by the
way can be more than significant at high AOA) and etc. We are talking
different designs here. This is not a good extrapolation!

  Summing up and adding one thing, be coordinated (no more than 1/4 ball
out of coordinated), be smooth, use all three controls (I could give
much data on this and
some is very surprising in favor of using ailerons), and fly at a
forward CG (ailerons will improve the recovery but an aft CG (and I have
seen several of these airplanes being flown at or behind of the
designers aft limit) will kill you and make it hard to recover both from
the stall and especially from a spin if you allow it to develop. Finally
it has not been mentioned here before but be smooth and not abrupt with
the power as this aircraft type will do a torque roll from abrupt power
applications at low Q (airspeed).

  I say this from much stall and spin experience in Experimental flight
test in GA aircraft, plus a degree in Aeronautical Engineering with a
focus on low speed aerodynamics. If you want to know more about CG and
stalls, consider first the reduction in moment arm for the rudder as the
CG moves aft.  It is like trying to do more with a shorter crow bar.
Sorry that this is so long but there is so much that could be said.

Jack Webb, BSAE
ATP, CFI A&I
L 360, L IV
Ohio