Udo wrote:
I broached a subject on the http://soaringcanada.riq.ca/ The Round
Table but not with a direct question about A of A but more general, to
see what the response was. I tought it was interesting and revealing.
I ask "A question on minimizing stall accidents". I wanted to get a
sense of how this critical phase was being taught, in light of an
accident that happened just prior. If you want to see the answer you
my want to read some of the comments.
Udo




On Dec 11, 9:27 pm, "Bill Daniels" bildan@comcast-dot-net wrote:
The threads on this subject has uncovered something that gives me chills.

Internationaly, gliding has an abominable safety record. Many fatal
accidents have as their root cause, failure by the pilot to maintain flying
speed or, stated more directly, control his angle of attack. Clearly, based
on these r.a.s threads on the subject, some do not understand AOA in some
fundamental way and that's chilling.

When I went to collich in the U.S. (1967-1972), even though aeronautical
engineering (what I *really* wanted to major in) had morphed into
aerospace engineering (crummy commies), one forlorn airplane-based
course curricularly remained. Nonetheless, in that one (mostly a nearly
incomprehensible stability and control) aircraft-dominant course, it
became apparent to me that wings cared first about AoA, and only
secondarily about velocity of oncoming air. This was long before I'd
sat in a lightplane, seen a glider, or heard of (the very excellent)
"Stick and Rudder."

Soon after graduating, I bumbled into soaring, and the illness
permanently altered my life. Regrettably, I can no longer remember if
or how my instructor taught 'low speed flight' aspects. Can't remember
if he mentioned AoA, or if he merely said 'maintain flying speed.'

Doesn't matter, because the aforementioned course colored whatever my
instructor also conveyed.

In glider terms, if we assume compressibility isn't an issue (and it
isn't, for glider airspeeds), the wing cares Zero what speed your ASI
displays. Physically, it cares only about AoA of the oncoming air. Of
course, both are (through the stick) inter-related, but one (easier to
reliably measure) falls out in the wash, while the other (AoA),
physically determines what the wing is going to do next.

Now, (glider)pilot training reality demonstrably proves conceptual grasp
of the importance of AoA to the wing's immediate future actions (and
arguably, pilots' near-term lives) isn't required in order to obtain
one's pilot's license. Whether or not that's a good thing leads to this
thread's sort of 'religious arguments.' Fact is, cats can be skinned
multiple ways...

Personally, my brain is most comfortable understanding underlying
physical principles, even if it must (in part) rely on indirect
measurements (e.g. ASI, noise, 'feel,' etc.). I believe if a person
really and truly grasps the underlying physical principles governing the
consequences of his or her actions, s/he's more likely to do the
physically correct thing in moments of crisis, than not. Further,
s/he's less likely to (N.B. Key Word follows!) *inadvertently* go where
no thoughtful risk taker inadvertently wishes to go. (Kids, can you
spell "i*n-p*a*t*t*e*r*n s*t*a*l*l/s*p*i*n?")

Furthermore personally, I'd love to have an AoA gauge in my (flapped)
glider, even if NOT scientifically/numerically accurate. So long as
it's repeatable, I wouldn't care whether it showed my ship stalled at
10-degrees or 30-degrees AoA for 'whatever' flap deflection. That's the
difference between usable engineering accuracy, and scientific (e.g.
wind-tunnel-comparative) accuracy. Absence of the latter doesn't rule
out usefulness of the former.

'Reverently,'
Bob W.