Building an electronic Angle of Attack indicator

"Peter Dohm" wrote in message .. .
The idea of the string, or the string on each side, is not that that it is a
true angle; but, if the canopy sides are at a promising height and also an
adiquate distance from the wing, that the positions can be marked as
calibration points for the particular angles of interest--such as best L/D
and minimum sink.


I understand the process. I currently have a yaw string on my glider. The other canopy strings might be somewhat effective; however, I'm spoiled. I flew 13 years in the US Navy with "real" AOA systems. I am not looking for a crude substitute. I'm looking for the real thing.

Wayne
http://www.soaridaho.com/

"Wayne Paul" wrote in message
...

"Peter Dohm" wrote in message
.. .
The idea of the string, or the string on each side, is not that that it is
a
true angle; but, if the canopy sides are at a promising height and also an
adiquate distance from the wing, that the positions can be marked as
calibration points for the particular angles of interest--such as best L/D
and minimum sink.


I understand the process. I currently have a yaw string on my glider. The
other canopy strings might be somewhat effective; however, I'm spoiled. I
flew 13 years in the US Navy with "real" AOA systems. I am not looking for
a crude substitute. I'm looking for the real thing.

Wayne
http://www.soaridaho.com/

I can certainly understand that, and there is no question about which is
"better".

Also, the issue of whether the string(s) can be easily, accurately and
safely read in flight is open to question--and certainly must be resolved
under conditions other than ridge lift. IIRC, you were amoung the
participants, a number of months ago, in a human factors discussion
regarding the effects of head movement while circling and the relationship
of that to an otherwise unexplained glider crash into a mountain side. The
issue is not one that I would take lightly, and anything that requires a
head movement up or down while also turning the head to either side should
probably be avoided; but a cheap and dirty solution could conceivably work
if peripheral vision, or an eyes only glance, is truly sufficient.

OTOH, a true AOA system that can be calibrated over the full reasonable
range of angles is far from trivial--and probably well beyond my design
capabilities.

Peter

"Peter Dohm" wrote in message news

Also, the issue of whether the string(s) can be easily, accurately and
safely read in flight is open to question--and certainly must be resolved
under conditions other than ridge lift. IIRC, you were amoung the
participants, a number of months ago, in a human factors discussion
regarding the effects of head movement while circling and the relationship
of that to an otherwise unexplained glider crash into a mountain side. The
issue is not one that I would take lightly, and anything that requires a
head movement up or down while also turning the head to either side should
probably be avoided; but a cheap and dirty solution could conceivably work
if peripheral vision, or an eyes only glance, is truly sufficient.

OTOH, a true AOA system that can be calibrated over the full reasonable
range of angles is far from trivial--and probably well beyond my design
capabilities.

Peter


The old A-3D and A-6A AOA required a lot of maintenance in order to keep them calibrated.

Speaking of ridge soaring, there is a current video on YouTube that may be enlightening to those who have not explored soaring flight.

Most of my soaring is thermal flight; however, once a year a group of us head to Logan, UT to fly the ridge up into Southern Idaho. The YouTube video is from near the Idaho border heading south toward Logan. Here is the link.
(http://www.youtube.com/watch?v=2Xo6N6_9rNQ)

Wayne
http://www.soaridaho.com/

"Wayne Paul" wrote in message
m...
"Peter Dohm" wrote in message
news

Also, the issue of whether the string(s) can be easily, accurately and
safely read in flight is open to question--and certainly must be resolved
under conditions other than ridge lift. IIRC, you were amoung the
participants, a number of months ago, in a human factors discussion
regarding the effects of head movement while circling and the
relationship
of that to an otherwise unexplained glider crash into a mountain side.
The
issue is not one that I would take lightly, and anything that requires a
head movement up or down while also turning the head to either side
should
probably be avoided; but a cheap and dirty solution could conceivably
work
if peripheral vision, or an eyes only glance, is truly sufficient.

OTOH, a true AOA system that can be calibrated over the full reasonable
range of angles is far from trivial--and probably well beyond my design
capabilities.

Peter


The old A-3D and A-6A AOA required a lot of maintenance in order to keep
them calibrated.

Speaking of ridge soaring, there is a current video on YouTube that may be
enlightening to those who have not explored soaring flight.

Most of my soaring is thermal flight; however, once a year a group of us
head to Logan, UT to fly the ridge up into Southern Idaho. The YouTube
video is from near the Idaho border heading south toward Logan. Here is
the link.
(http://www.youtube.com/watch?v=2Xo6N6_9rNQ)

Wayne
http://www.soaridaho.com/

Very cool indeed!

Perhaps, someday, I'll get to try my hand at that.

Peter

Peter Dohm wrote:
"Wayne Paul" wrote in message
...

"Peter Dohm" wrote in message
.. .
The idea of the string, or the string on each side, is not that that it is
a
true angle; but, if the canopy sides are at a promising height and also an
adiquate distance from the wing, that the positions can be marked as
calibration points for the particular angles of interest--such as best L/D
and minimum sink.


I understand the process. I currently have a yaw string on my glider. The
other canopy strings might be somewhat effective; however, I'm spoiled. I
flew 13 years in the US Navy with "real" AOA systems. I am not looking for
a crude substitute. I'm looking for the real thing.

Wayne
http://www.soaridaho.com/

I can certainly understand that, and there is no question about which is
"better".

Also, the issue of whether the string(s) can be easily, accurately and
safely read in flight is open to question--and certainly must be resolved
under conditions other than ridge lift. IIRC, you were amoung the
participants, a number of months ago, in a human factors discussion
regarding the effects of head movement while circling and the relationship
of that to an otherwise unexplained glider crash into a mountain side. The
issue is not one that I would take lightly, and anything that requires a
head movement up or down while also turning the head to either side should
probably be avoided; but a cheap and dirty solution could conceivably work
if peripheral vision, or an eyes only glance, is truly sufficient.

OTOH, a true AOA system that can be calibrated over the full reasonable
range of angles is far from trivial--and probably well beyond my design
capabilities.

Peter


I would think a simple solution would be to have an indicator with
range marks for common flap settings. It's not perfect, but if you
usually use one setting for take off, one for landing and clean for
flight you should be able to SWAG other settings based on those range
marks.

Dan, U.S. Air Force, retired

"Peter Dohm" wrote

OTOH, a true AOA system that can be calibrated over the full reasonable
range of angles is far from trivial--and probably well beyond my design
capabilities.

Should not be a big deal. I have in mind how to do the whole thing (with
angles of attack and stall angles with and without flaps) mechanically. No
electronics involved, other than some switches, linkages and led lights.
--
Jim in NC

"Dan" wrote in message ...

I would think a simple solution would be to have an indicator with
range marks for common flap settings. It's not perfect, but if you
usually use one setting for take off, one for landing and clean for
flight you should be able to SWAG other settings based on those range
marks.

Dan, U.S. Air Force, retired

A thought just crossed my mind. When you change the flap setting the angle between the fuselage and the effective chord of the airfoil (angle of incidence) changes. At the optimum L/D speed at various flap setting, I bet there is little change in airflow relative to the fuselage.

If you are flying with the fuselage nose down, or nose up relative to the airflow, drag is created. So my guess is that a well designed sailplane fuselage flies at an angle of 0 degrees to the airflow at best L/D regardless of flap setting.

This is just a gut feeling. I'll have to tape a string to my canopy and mark its' location at best L/D with a zero flap setting and see what speed I achieve maintaining that mark at various flap setting.

Wayne
http://www.soaridaho.com/

On May 17, 6:30*pm, "Peter Dohm" wrote:
"Wayne Paul" wrote in message

...

"Peter Dohm" wrote in message

.. .

The idea of the string, or the string on each side, is not that that it is
a
true angle; but, if the canopy sides are at a promising height and also an
adiquate distance from the wing, that the positions can be marked as
calibration points for the particular angles of interest--such as best L/D
and minimum sink.

I understand the process. *I currently have a yaw string on my glider. *The
other canopy strings might be somewhat effective; however, I'm spoiled. *I
flew 13 years in the US Navy with "real" AOA systems. *I am not looking for
a crude substitute. *I'm looking for the real thing.

Waynehttp://www.soaridaho.com/

I can certainly understand that, and there is no question about which is
"better".

Also, the issue of whether the string(s) can be easily, accurately and
safely read in flight is open to question--and certainly must be resolved
under conditions other than ridge lift. *IIRC, you were amoung the
participants, a number of months ago, in a human factors discussion
regarding the effects of head movement while circling and the relationship
of that to an otherwise unexplained glider crash into a mountain side. *The
issue is not one that I would take lightly, and anything that requires a
head movement up or down while also turning the head to either side should
probably be avoided; but a cheap and dirty solution could conceivably work
if peripheral vision, or an eyes only glance, is truly sufficient.

OTOH, a true AOA system that can be calibrated over the full reasonable
range of angles is far from trivial--and probably well beyond my design
capabilities.

Peter



Having used "pitch strings" on several gliders, I can assure there are
no 'human factors' issues whatsoever. The "pitch strings" are in easy
view and not any more distracting than a yaw string which they
complement. It would be equally absurd to claim that an airspeed
indicator is 'distracting'.

In fact, the indications are so intuitive that all pilots who have
used them feel they had a much better understanding of what the glider
and the atmosphere was doing. Think of them together as a "3D yaw
string"

They actually help with thermalling reacting 3 seconds or so ahead of
a vario indication. The strings flick upward as you enter a thermal.
One pilot told me that the strings "got him home" by improving his
'dolphin flying' technique.

Let me add that if a pilot DOES find them distracting, he would fail
that part of the Practical Test Standards dealing with pilot
distractions.

AOA indicators are 100% a good thing. There are no downsides to
having one. There is nothing "open to question". While there are
many crashes that are arguably due to the pilot NOT having AOA
information, there are probably NONE where having that knowledge was a
contributing factor.

"Wayne Paul" wrote in message ...

"Dan" wrote in message ...

I would think a simple solution would be to have an indicator with
range marks for common flap settings. It's not perfect, but if you
usually use one setting for take off, one for landing and clean for
flight you should be able to SWAG other settings based on those range
marks.

Dan, U.S. Air Force, retired

A thought just crossed my mind. When you change the flap setting the angle between the fuselage and the effective
chord of the airfoil (angle of incidence) changes. At the optimum L/D speed at various flap setting, I bet there is
little change in airflow relative to the fuselage.

If you are flying with the fuselage nose down, or nose up relative to the airflow, drag is created. So my guess is
that a well designed sailplane fuselage flies at an angle of 0 degrees to the airflow at best L/D regardless of flap
setting.

This is just a gut feeling. I'll have to tape a string to my canopy and mark its' location at best L/D with a zero
flap setting and see what speed I achieve maintaining that mark at various flap setting.

Wayne
http://www.soaridaho.com/



That is where I was hoping this would go...a little experimentation. ;-)