AoA keep it going!

On Dec 17, 12:37 pm, "Bill Daniels" bildan@comcast-dot-net wrote:
"Eric Greenwell" wrote in message

news:UCz9j.4239$Xh1.3090@trndny03...

Bill Daniels wrote:

Maneuvering for landing in gusty wind shear is exactly where I'd want an
AOA. It will show the maximum gust induced AOA so the airspeed can be
increased just enough that no gust stalls the glider but not so much that
you'll need to dump a lot of energy in ground effect.

Bill, have you used an AOA indicator in the conditions you describe? What
one was it? And how did you know the "maximum gust induced" AOA it showed
you was the maximum you were going to encounter before landing?

Yes, Eric. I've flown with very high quality instruments in airplanes and
jury-rigged "pitch strings" in gliders. The pitch strings don't work as
well as the expensive units but, aside from the hassle, they are nonetheless
very useful.

There's no big mystry about AOA indicators, they go back to the very
beginnings of aviation. They aren't common because of cost and difficulty
implementing them on small airplanes. Until now, nobody gave much thought
to gliders.

Just look at the jitter or swing in the needle/string. The max swing in the
positive direction is the max gust induced AOA. By the time you have flown
the pattern and are on short final, you should have a pretty good idea about
the level of turbulence you are dealing with and have selected a minimum
safe margin for the "over the fence" airspeed.

I've seen pilots who have no real knowledge of just what their gust-stall
margin is so they keep adding airspeed until it's a problem for them on roll
out. It does no good to have a wide margin over stall in the air only to
hit a fence on rollout. Just standing on the ground watching glider
landings shows a wide range of techniques. Some patterns look like a ground
attack fighter rolling in on a target. Others float around the pattern tail
low. I have to believe if they had an AOA indicator, they be more
consistent - or at least, have rational excuses.

In off field landings especially, it's a balance between stall margin in
the air and rollout distance on the ground. I practice a short landing on
every flight - partly to be ready for a possible off field landing and
partly because my trailer is near the approach end and I hate pushing back.
I'd love to have a quality AOA indicator to make those landings easier and
safer.

Bill Daniels

This is a life saving discussion and the best I've heard or read.
Most, or too many instructors do not know how to teach the subject.
Most cannot tell you why "relative wind" exists,. much less how to
anticipate the maximum aoa. Airfoils are much more forgiving now, but
there is a video of a DG spinning in on final. It's late now and I
don't have the link. The ship that spun in on my field in 68, ended
with bones sticking out and no bleeding. Some of the pieces are still
there to remind skepticks. Bless all of you that care .Fred