AoA keep it going!

"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

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

Bill Daniels wrote:
I'd love to have a quality AOA indicator to make those landings
easier and safer.

What did you think of this idea from my post:

I suggest 5 to 10 proponents of AOA meters, and other interested
pilots, buy some AOA meters (like from Safeflight, DG , Aircraft
Spruce) as a group. This will reduce the cost for each pilot to try
several AOA meters. Have each member of the group try each of the
meter(s) for while, then report their experiences.

Someone has to try some these devices in gliders, so we have some data
that applies to our sport. As the primary promoter of the value of an
AOA gauge, you seem to be the obvious choice to lead an effort that
proves the value. At that point, a few of the clever people in the sport
will likely develop units more suited to gliders, and maybe bring the
cost down.

There are units available, but I don't see anyone buying and using them.
That suggests to me that, while we all agree it's probably a good idea,
we don't think it's good enough to spend the $500-$2000 to actually buy
and install one. So, someone has to just do it and show the results to us.

--
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

Eric Greenwell and Bill Daniels wrote:

I'd love to have a quality AOA indicator to make those landings
easier and safer.

It's more than an issue of safety, an AOA indicator will allow you to
optimize flight in all configurations including circling flight at
different wing loadings. The use and construction of such a device, aka
a lift coefficient meter, was discussed in an article by Daniel J.
Altstatt in Soaring Magazine March, 1975, page 22. No doubt a modern
electronic instrument is now feasible.

Pete Brown




What did you think of this idea from my post:

I suggest 5 to 10 proponents of AOA meters, and other interested
pilots, buy some AOA meters (like from Safeflight, DG , Aircraft
Spruce) as a group. This will reduce the cost for each pilot to try
several AOA meters. Have each member of the group try each of the
meter(s) for while, then report their experiences.

Someone has to try some these devices in gliders, so we have some data
that applies to our sport. As the primary promoter of the value of an
AOA gauge, you seem to be the obvious choice to lead an effort that
proves the value. At that point, a few of the clever people in the sport
will likely develop units more suited to gliders, and maybe bring the
cost down.

There are units available, but I don't see anyone buying and using them.
That suggests to me that, while we all agree it's probably a good idea,
we don't think it's good enough to spend the $500-$2000 to actually buy
and install one. So, someone has to just do it and show the results to us.



--
Peter D. Brown
http://home.gci.net/~pdb/
http://groups.yahoo.com/group/akmtnsoaring/


Going home after a long day
http://farm2.static.flickr.com/1415/...22928754_b.jpg

The fleet at Summit. Mt. McKinley is about 45nm away at 20,320 msl.
http://farm1.static.flickr.com/187/4...cb8d2482_b.jpg

The 170B at Bold near Eklutna Glacier
http://farm1.static.flickr.com/168/4...a216d7bb75.jpg

Here are some links:

http://advanced-flight-systems.com/P...s/AOA/aoa.html

As mentioned, aircraft spruce catalogs this and another, vane based one:

http://www.aircraftspruce.com/catalo...ges/HCIaoa.php
or directly, http://www.hciaviation.com/prod-aoa-a.shtml

And yes, I'd be interested in how well any of these actually work in gliders.
It's not clear the first one has enough resolution for performance info, for example.

--Sarah


Pete Brown wrote:
Eric Greenwell and Bill Daniels wrote:

I'd love to have a quality AOA indicator to make those landings
easier and safer.

It's more than an issue of safety, an AOA indicator will allow you to
optimize flight in all configurations including circling flight at
different wing loadings. The use and construction of such a device, aka
a lift coefficient meter, was discussed in an article by Daniel J.
Altstatt in Soaring Magazine March, 1975, page 22. No doubt a modern
electronic instrument is now feasible.

Pete Brown




What did you think of this idea from my post:

I suggest 5 to 10 proponents of AOA meters, and other interested
pilots, buy some AOA meters (like from Safeflight, DG , Aircraft
Spruce) as a group. This will reduce the cost for each pilot to try
several AOA meters. Have each member of the group try each of the
meter(s) for while, then report their experiences.

Someone has to try some these devices in gliders, so we have some data
that applies to our sport. As the primary promoter of the value of an
AOA gauge, you seem to be the obvious choice to lead an effort that
proves the value. At that point, a few of the clever people in the
sport will likely develop units more suited to gliders, and maybe
bring the cost down.

There are units available, but I don't see anyone buying and using
them. That suggests to me that, while we all agree it's probably a
good idea, we don't think it's good enough to spend the $500-$2000 to
actually buy and install one. So, someone has to just do it and show
the results to us.

On 17 Dec, 20:37, "Bill Daniels" bildan@comcast-dot-net wrote:

I'd love to have a quality AOA indicator to make those landings easier and
safer.

I generally find that my attention is fully occupied while landing. If
I had an AoA indicator, I would have to take attention away from
something else to look at it (I always have the audio vario and radio
off for the final approach). Would an AoA also indicator free up some
of my attention, and if so, from what?

Ian

I generally find that my attention is fully occupied while landing. If
I had an AoA indicator, I would have to take attention away from
something else to look at it (I always have the audio vario and radio
off for the final approach). Would an AoA also indicator free up some
of my attention, and if so, from what?

Ian

Ian, do you look at your airspeed indicator while landing (well,
during the approach, of course - no one looks at their airspeed while
actually landing, do they?)? If you do, then a properly designed AoA
indicator could make your approaches easier and safer. Remember,
airspeed is just an inaccurate way to show angle of attack - the AoA
gauge shows it directly.

Now, if all gliders had AoA gauges, you could jump from one glider to
another and not worry about what the right approach speed is for the
glider you happen to be in. Ditto min sink, etc. Sure would be nice
with ballasted two-seaters, that can have a significant difference in
approach and thermalling speeds depending on crew and ballast weight.

Right now, the closest we have is the yellow triangle on german
gliders - approach speed at max gross, I think? (please correct me if
I'm wrong on that one).

Still dreaming...

Kirk
66

On Dec 19, 2:38 pm, "kirk.stant" wrote:
I generally find that my attention is fully occupied while landing. If
I had an AoA indicator, I would have to take attention away from
something else to look at it (I always have the audio vario and radio
off for the final approach). Would an AoA also indicator free up some
of my attention, and if so, from what?

Ian

Ian, do you look at your airspeed indicator while landing (well,
during the approach, of course - no one looks at their airspeed while
actually landing, do they?)? If you do, then a properly designed AoA
indicator could make your approaches easier and safer. Remember,
airspeed is just an inaccurate way to show angle of attack - the AoA
gauge shows it directly.

Why might an AoA guage be any more accurate than an ASI?



Now, if all gliders had AoA gauges, you could jump from one glider to
another and not worry about what the right approach speed is for the
glider you happen to be in.

But you might be concered about what the correct AoA was for them?



Right now, the closest we have is the yellow triangle on german
gliders - approach speed at max gross, I think? (please correct me if
I'm wrong on that one).

*minimum* suggested approach speed. Assuming the dial is marked
correctly.

Cats wrote:



Why might an AoA guage be any more accurate than an ASI?





Because an AoA gauge responds directly with "relative wind"
Airspeed indicators respond to ram air pressure measured against static
pressure. Have you ever noticed that your airspeed indicator seems to
read higher in the winter due to denser air (assuming you live in a
climate with vastly different temps between summer and winter). Also,
have you ever noticed your airspeed indicator reads lower at higher
altitudes (due to less dense air)? AoA is accurate regardless of the
above mentioned differences.

--
Scott
http://corbenflyer.tripod.com/
Gotta Fly or Gonna Die
Building RV-4 (Super Slow Build Version)

Scott wrote:

Have you ever noticed that your airspeed indicator seems to
read higher in the winter due to denser air
....

Which is a very good thing, considering that the aerodynamic behaviour
of an airfoil changes with the air density. Back to field 1.