I think there are several misconceptions in Jim's post below.

First, we are not talking about "stick shakers" which produce large,
low frequency shaking. No glider would have the electrical power to
operate one. We are talking about "stick vibrators" using tiny cell
phone vibrator motors. These are carefully designed to get your
attention so you answer a call.

Second, if you routinely thermal in the AoA range where they would
activate, you're flying way too slow. There is a fairly large AoA
range between minimum sink and stall so the warning should not
activate in smooth air and rarely in rough air. If it activates
often, you could climb better by lowering the nose and flying a little
faster. For performance, there is no reason to operate in the
airspeed/AoA range between min sink and stall.

Third, I have no doubt Jim can detect an impending stall by feel and
aircraft behavior as he says. Most of us can do that, but we're not
the ones involved in stall/spin accidents - yet. As has been pointed
out, distractions can interfere with our perceptions of impending
stall. Who would say there could not be a situation where they might
benefit from a "buzz in the hand" reminder to lower the nose.

I spent the weekend instructing in an ASK 21 - arguably one of the
most docile gliders ever built. Not one pilot could detect an
impending stall unless I carefully pointed out the glider's
symptomatic pre-stall behavior - it's very subtle and requires some
mental concentration to detect it. It's so docile, a few couldn't
even detect a stall even as it was happening.

For those objecting to a AoA/stall warner, carefully read this story:

http://www.sciencedaily.com/releases...0903142411.htm

Not all objections are based on logic.

Bill Daniels


On Sep 6, 9:11*am, Jim White wrote:
I have changed the subject as we are well passed Idaho now.

I am having trouble with this stall warning stuff. I fly modern gliders:
ASW27, Duo Discus, ASK21 etc. All give clear warnings ahead of a stall.
When they do stall the nose drops, stick forward a bit, dada...stall
recovered. If they were to start into a spin (and the 21 shouldn't with
normal C of G positions), stick forward a bit, maybe a bit of pedal, and
dada...recovered.
None would lose significant amounts of height if recovered straight away.

I compete in the 27 and regularly fly it in thermals near the stall. You
feel for the break in laminar flow on the wings. This actually happens well
before the stall. It would be impossible to climb effectively if the stick
kept shaking!

And what would happen in a fully held off landing? I would also be a bit
****ed if the shaker went off when I was landing as slow as possible into a
very tight field in a light head wind!

This has to be about training and currency in gliders. We are not flying
747s with passengers down the back.

Final turns should be made at a sensible height with sufficient speed and
well banked so that they cannot be ruddered into a spin. This all should be
natural and obvious to a well trained pilot. No need for another mechanical
gadget to go wrong.

At 13:00 06 September 2011, kirk.stant wrote:







Modern gliders give very little indications of a stall (another reason
why training in old clunkers like the 2-33 is counterproductive). *Add
a little distraction or a higher priority task (Bee in the cockpit!)
and you can be in a high-AOA situation without being aware of it. *Add
to that a pilot who flies infrequently, and the benefit of a stall
warning system becomes even more clear.

Kirk
66