"Interesting: In all the twins I have flown not
once was a stall an approved procedure. Approach
to stall sure, but never a full stall. So why
must Lancairs be stalled?
Seems that the Lancairs are in the twin
situation. So learn the feel at the approach to a
stall (I have), us an AoA (I do), and the planes
are safe and a joy to fly (they are!)."
Much wisdom there.
I feel compelled to add a bit of technical
content to the discussion. The Lancair IV wing
was tailored to maintain laminar flow as far as
possible over the top and bottom of the wing. The
resulting wing profile has exceptionally low
frictional drag, but an unpredictable stall
performance, a common characteristic of wing
profiles with long reaches of laminar flow.
Laminar boundary layers are just not very
energetic and can separate from the wing in a
flash. The flow may separate at the root and stay
there (conventional stall), or the separated air
flow zone may suddenly spread all the way to the
wing tip in which case a snap roll into a spin
will be the result. And the spin may be
unrecoverable.
The LIV is not certified, and its stall
capability along with many other characteristics
mean it never could be. It is Experimental.
Don't treat it like a certified or aerobatic
airplane. It isn't.
Most airplanes (SNJ's for sure, they are
trainers), most aerobatic aircraft like the
Zlin (which have big fat leading edges which are
highly stall resistant and relatively forgiving)
and certified aircraft are relatively benign in
stall. Aerobatic aircraft and many others are
guaranteed to be spin recoverable. Virtually all
modern certified aircraft) must have wing designs
that are compromised to provide buffet in advance
of stall, they quit flying gently (and only
slightly) with a straightforward relatively benign
stall, and provide normal straightforward
recovery. I flew a friend's Cirrus and it was
even more benign than my old C182. These
airplanes were designed and comprehensively tested
to assure this benign and forgiving behavior each
and every time.
The Lancair IV most definitely was not. It was
compromised in the direction of speed at any
cost. And part of that cost is occasionally
unpredictable and potentially deadly stall
behavior if not carefully and cautiously
handled. It is the nature of the laminar flow
wing design that yields such low drag and high
cruise speed coupled with other of the aircraft's
characteristics and design features.
I was instructed by a 20,000+ hour Qantas
captain who also flew a Lancair IV and was the
Australian national aerobatic champion. This guy
really understands unusual flight attitudes and
aerodynamics. His instructions for the LIV
practice were approach to stall at 10,000 feet in
the landing configuration, an IRONCLAD rule that
the ball be kept EXACTLY in the center, and then
immediate recovery after the initial break. All
this practice was done in the landing
configuration except for a couple of very cautious
approach to stall tests with airplane clean which
we did to establish a calibration point for my
angle of attack indicator. He was adamant: once
that data point is collected, there is no reason
to go back there again.
He emphasized that there are airplanes that you
just don't stall - ever - because they bite.
Many swept wing aircraft are in this category. On
those the stall can progress from root to wing
tip very rapidly and the airplane then
immediately rolls on its back and drops into a
spin. On the Lancair, a deep stall with ball out
of center can on occasion enter an unrecoverable
spin. Let the ball get far enough out of center
and it will almost certainly drop into a spin.
In short, he said, there is absolutely NO
REASON to put a Lancair IV into a deep stall.
Slow flight practice, fine. Nibble at stall
(approach to stall) also fine subject to ball in
the middle and 10,000 feet. Get ball out of
center and/or hold the stall a bit too long and
the outcome maybe fine 9 out of 10 times, but you
may get an unrecoverable spin on the tenth.
Without a spin chute and a personal parachute,
exploring that territory is definitely test pilot
stuff, so you better train and equip accordingly.
Stay away from everything except the approach
to stall with ball centered, use an angle of
attack indicator (should be mandatory in these
aircraft), practice some slow flight maneuvers at
10,000 feet, and practice forced landings.
But deliberately putting the airplane into a
deep stall is Russian Roulette. Many aircraft are
like this. Why go there?
Fred Moreno