Bill Daniels wrote:
Cost and installation issues are a real hurdle as is just how well the
device performs in actual use.

However, we seem to pay large sums for safety devices like transponders and
ELT's when it is at least argueable that stall/spin accidents kill far more
pilots than mid-airs or exposure after a landout. It's possible that on a
"bang for the buck" basis, an AOA indicator is a better deal. This is
especially true if the AOA indicator actually improves our soaring
performance while increasing safety.

It's even possible to argue that one offsets the other. i.e. If your AOA
indicator prevents a spin in on the ridge, you have avoided, at least in
that instance, the need for an ELT, saved your glider and maybe yourself in
the bargan.

I can't think of any device that would have more impact on accident numbers
than a really practical AOA indicator.

I wonder if a stall warning is more complicated than an effective AOA
indicator mounted on or near the fuselage. Sure, it'd work for straight
ahead stalls, but how often do those cause accidents, compared to stalls
while turning? My experience in stall/spins while turning is the root
isn't stalled, it's the outer wing portions (likely from the tip inward
for a few feet) that stalls and precipitates the spin.

And perhaps we are chasing the wrong parameter. Separation of the
airflow is a better indicator of a stall in progress; in fact, I think
Johnson's indicator worked by detecting separation, not AOA. This might
work without the need for sensing flap position, simplifying things.

One way to detect separation would be to flush-mount a microphone out
near the tip of each wing, positioned on the chord where separation
begins as that section gets near stall. The cockpit indicator might just
be the signal from the microphone, amplified and fed to a speaker. LEDs
could be used instead or in addition to the sound, of course.

The microphone could be very small, and a small tube (say, 0.1"
diameter) could lead the sound from the wing surface, through the wing
skins, to the microphone. A thin membrane covering the outer end of the
tube would prevent water and dirt from affecting performance.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org