Glider angle of attack indicator by SafeFlight

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.

Bill Daniels


"Paul Remde" wrote in message
news:aPg6j.222593$Xa3.195325@attbi_s22...
Hi Bill,

It is a very interesting device. I looked at it very closely at the SSA
Convention in the past. I was impressed with the high quality of the
system. If I remember correctly it includes a low friction rotating vane
that is mounted to the side of the fuselage and a variometer like meter
that is mounted in the instrument panel. I don't recall whether or not it
had an audio output. It looked very cool. I don't remember the price,
but I do remember thinking that very few glider pilots would pay the
somewhat high price. Also, it required a hole in the side of the
fuselage.

Paul Remde


"Bill Daniels" bildan@comcast-dot-net wrote in message
. ..
I was very pleased to see the advert in the December issue of "Soaring
Magazine".
See: www.safeflight.com

Does anybody know more about this device - especially the price?

Bill Daniels

On Dec 7, 12:53 pm, "Bill Daniels" bildan@comcast-dot-net wrote:

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

Bill, I think you have presented a case for the benefit of an
effective stall warning system but not necessarily a good case for an
AOA indicator. Unless the AOA sensor is linked to an effective
warning system it is more likely to be an added distraction rather
than a benefit.

Now if someone took that sensor and used it to drive an audio
thermalling speed director I could get interested.

Andy

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

Bill,
I think what we are after is an effective angle of attack indicator to
optimize performance for a rage of flap settings that will also
coincidently act as a stall warning.
Udo


On Dec 7, 2:53 pm, "Bill Daniels" bildan@comcast-dot-net 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.

Bill Daniels

"Paul Remde" wrote in message

news:aPg6j.222593$Xa3.195325@attbi_s22...



Hi Bill,

It is a very interesting device. I looked at it very closely at the SSA
Convention in the past. I was impressed with the high quality of the
system. If I remember correctly it includes a low friction rotating vane
that is mounted to the side of the fuselage and a variometer like meter
that is mounted in the instrument panel. I don't recall whether or not it
had an audio output. It looked very cool. I don't remember the price,
but I do remember thinking that very few glider pilots would pay the
somewhat high price. Also, it required a hole in the side of the
fuselage.

Paul Remde

"Bill Daniels" bildan@comcast-dot-net wrote in message
...
I was very pleased to see the advert in the December issue of "Soaring
Magazine".
See:www.safeflight.com

Does anybody know more about this device - especially the price?

Bill Daniels- Hide quoted text -

- Show quoted text -

Udo, absolutely.

A mere stall warner is just a "stall" or "no stall" binary device. An AOA
indicator, by comparison, gives stall margin or how close you are to a stall
as well as the rate at which you are approaching it. Of course, stall
warning is a part of that.

It also is a performance device that lets the pilot optimize flight. You
can change AOA with the elevator with almost no delay. Airspeed needs more
time to change. Thermalling at a constant, optimum AOA is easy and the
airspeed will be much steadier. The optimum AOA is the same regardless of
wing loading or bank angle.

Unless you have flown with an AOA indicator, it's hard to imagine what it
does. I've never head someone who has used one say they didn' t like it.

Bill Daniels

"Udo" wrote in message
...
Bill,
I think what we are after is an effective angle of attack indicator to
optimize performance for a rage of flap settings that will also
coincidently act as a stall warning.
Udo


On Dec 7, 2:53 pm, "Bill Daniels" bildan@comcast-dot-net 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.

Bill Daniels

"Paul Remde" wrote in message

news:aPg6j.222593$Xa3.195325@attbi_s22...



Hi Bill,

It is a very interesting device. I looked at it very closely at the
SSA
Convention in the past. I was impressed with the high quality of the
system. If I remember correctly it includes a low friction rotating
vane
that is mounted to the side of the fuselage and a variometer like meter
that is mounted in the instrument panel. I don't recall whether or not
it
had an audio output. It looked very cool. I don't remember the price,
but I do remember thinking that very few glider pilots would pay the
somewhat high price. Also, it required a hole in the side of the
fuselage.

Paul Remde

"Bill Daniels" bildan@comcast-dot-net wrote in message
...
I was very pleased to see the advert in the December issue of "Soaring
Magazine".
See:www.safeflight.com

Does anybody know more about this device - especially the price?

Bill Daniels- Hide quoted text -

- Show quoted text -

On Dec 7, 3:36 pm, "Bill Daniels" bildan@comcast-dot-net wrote:

Unless you have flown with an AOA indicator, it's hard to imagine what it
does. I've never head someone who has used one say they didn' t like it.


Agreed. I last flew with an AOA indicator just a few weeks ago but it
was included in a HUD symbology set, not head down. The last thing we
need is for all contest pilots to have a head down indicator that they
depend on to optimize performance while thermalling.

Make it a director, feed it flap position (if applicable) and make it
audible!

Andy

As has been pointed out in the past on RAS, pieces
of wool taped to both front/sides of the canopy perform
quite well as angle of attack indications in unflapped
gliders. The angular change between max LD and stall
is surprisingly noticeable. Once 'calibrated' for
the stall position and min sink and best glide positions
they are helpful for optimizing thermalling technique
but don't grab the attention well enough to be a safety
stall warning.

Certainly good value for money.

John Galloway

On Dec 8, 4:29 am, John Galloway wrote:
As has been pointed out in the past on RAS, pieces
of wool taped to both front/sides of the canopy perform
quite well as angle of attack indications in unflapped
gliders. The angular change between max LD and stall
is surprisingly noticeable. Once 'calibrated' for
the stall position and min sink and best glide positions
they are helpful for optimizing thermalling technique
but don't grab the attention well enough to be a safety
stall warning.

Certainly good value for money.

John Galloway

John,

I tried this technique on an LS4. While you could see the difference
in angle of attack quite clearly, there was a huge difference when any
yaw was introduced, with the yarns showing significant differences in
relative airflow on opposite sides of the canopy. In effect, with
this system, you are really showing the instantaneous airflow over the
canopy, and deriving AOA from that indication - which is not much
better than just using airspeed, really, and effectively impossible to
use due to yaw effects and the flapping of the yarn masking the small
AOA changes you are interested in.

Having some time in airplanes that used AOA (gauge, lights, and
variable audio cues) in preference to airspeed during low speed flight
(F-4s, in my case) I can vouch that it's a much better way to fly -
especially when the AOA is coupled with an audio signal. But in a
glider, I thing the working AOA range that we are interested in is a
lot smaller than the AOA range that low aspect ratio jets use, so in
practice it may be more difficult to implement.

What I would like to see is a simple AOA indicator that would tell me
when I am at the optimum AOA for efficient thermalling. No fancy
indicator, just a bright LED that would be on steady at thermalling
AOA. Have it start flashing when approaching the desired AOA, and
have a different flash rate when below the desired AOA (which would
also function as a stall warning, since there is really no reason for
ever flying below min sink, especially in the pattern.

To use, pull into the thermal and set your attitude to the approximate
AOA, glance at the LED to adjust to the exact AOA, then fly that,
occasionally crosschecking the light. No figuring for bank angle or
ballast required, the wing takes care of that. Sweet...

AOA is really not that useful in cruise, since we are really more
concerned with the appropriate MC speed, and rarely fly at L/D max.
But again, that would be a single AOA point to measure, and could use
a different color LED.

Obviously, with a flapped ship, flap position would have to be sensed
and compensated for.

Since I'm really only concerned about one angle of attack, a moving
vane should not be necessary - I think it can be done with
differential pressure ports, so no moving parts or drag. Flaps may
complicate things, but even if there has to be a different set of
ports for each thermalling flap position, it may still be easier than
a mechanical AOA vane. Or just pick your favorite flap setting, and
TLAR it from there...

Comments from smarter people out there are welcome!

Kirk
LS6b "66"

"kirk.stant" wrote in message
...
On Dec 8, 4:29 am, John Galloway wrote:
Kirk,

I agree with your assessment. A simple LED index system of three lights.
One indicating "fast", another "on speed" (Max Cl) and finally one that
flashes when nearing stall. Sound familiar from your F-4 days?

Wayne
Retired A-6 Bombardier.
http://www.soaridaho.com/Schreder

John,

I tried this technique on an LS4. While you could see the difference
in angle of attack quite clearly, there was a huge difference when any
yaw was introduced, with the yarns showing significant differences in
relative airflow on opposite sides of the canopy. In effect, with
this system, you are really showing the instantaneous airflow over the
canopy, and deriving AOA from that indication - which is not much
better than just using airspeed, really, and effectively impossible to
use due to yaw effects and the flapping of the yarn masking the small
AOA changes you are interested in.

Having some time in airplanes that used AOA (gauge, lights, and
variable audio cues) in preference to airspeed during low speed flight
(F-4s, in my case) I can vouch that it's a much better way to fly -
especially when the AOA is coupled with an audio signal. But in a
glider, I thing the working AOA range that we are interested in is a
lot smaller than the AOA range that low aspect ratio jets use, so in
practice it may be more difficult to implement.

What I would like to see is a simple AOA indicator that would tell me
when I am at the optimum AOA for efficient thermalling. No fancy
indicator, just a bright LED that would be on steady at thermalling
AOA. Have it start flashing when approaching the desired AOA, and
have a different flash rate when below the desired AOA (which would
also function as a stall warning, since there is really no reason for
ever flying below min sink, especially in the pattern.

To use, pull into the thermal and set your attitude to the approximate
AOA, glance at the LED to adjust to the exact AOA, then fly that,
occasionally crosschecking the light. No figuring for bank angle or
ballast required, the wing takes care of that. Sweet...

AOA is really not that useful in cruise, since we are really more
concerned with the appropriate MC speed, and rarely fly at L/D max.
But again, that would be a single AOA point to measure, and could use
a different color LED.

Obviously, with a flapped ship, flap position would have to be sensed
and compensated for.

Since I'm really only concerned about one angle of attack, a moving
vane should not be necessary - I think it can be done with
differential pressure ports, so no moving parts or drag. Flaps may
complicate things, but even if there has to be a different set of
ports for each thermalling flap position, it may still be easier than
a mechanical AOA vane. Or just pick your favorite flap setting, and
TLAR it from there...

Comments from smarter people out there are welcome!

Kirk
LS6b "66"

Wayne Paul wrote:
I agree with your assessment. A simple LED index system of three lights.
One indicating "fast", another "on speed" (Max Cl) and finally one that
flashes when nearing stall. Sound familiar from your F-4 days?

Using either a vane on a shaft encoder, or differential pressure ports,
the hardware and software are pretty trivial (well under $100US in
parts). The aerodynamics, however, are not. Where does one put the
vane or ports such that one doesn't get large errors due to tiny
variations in yaw?

My DG-600 had an AOA meter (it looked to be a modified electronic
variometer) and two cross connected sets of static ports immediately
above the wing root, one set near the leading edge, and the second set
roughly mid-chord. I never got it to do anything useful.

Marc