Building an electronic Angle of Attack indicator

RST Engineering - JIm wrote:
If somebody can tell me how to convert angle of attack to an electrical
signal, the rest is rather trivial.

Jim


"Mike" wrote in message
...

Has anyone built an electronic angle of attack meter kit. It seems to
be something that would be easy to design but beyond my feeble
electronics background.

I have seen the products that are out there and they are simple
differential pressure gauges and are expensive. I don't like the
round differential pressure gauges that many of the companies offer
for this kind of system. I was wondering if there would be a way to
put something together that would light up different color LED's for
the different levels of lift that we could build at home without
having to pay out hundreds of dollars for a prebuilt one.




We used a reed switch array and a magnet to determine control rod position on my submarine's reactor. You could do the same with an
AOA using a magnet on a vane. You'd only need a few reed switches, one for each angle you were interested in: just before stall, best
angle of climb and best rate of climb corresponding to red, yellow and green LED's. What else do you care about?

--
John Kimmel


I think it will be quiet around here now. So long.

Heck, my first thought was to take the gas gage & sendin unit out of my
'56 chevy , mount the sendin unit inside with some gears outa of my old
alarm clock-(spring busted) sos you get full travel outa the sender with
only ten or 20 degrees motion hang a n aluminium vane on the end of it &
a fishin sinker forward of it to balance it-You could keep the sinker
inside for essthetic reasons. ut then---this was jest my 1st thot--Jerry

RST Engineering - JIm wrote:
If somebody can tell me how to convert angle of attack to an
electrical signal, the rest is rather trivial.

Jim


"Mike" wrote in message
...

Has anyone built an electronic angle of attack meter kit. It seems to
be something that would be easy to design but beyond my feeble
electronics background.

I have seen the products that are out there and they are simple
differential pressure gauges and are expensive. I don't like the
round differential pressure gauges that many of the companies offer
for this kind of system. I was wondering if there would be a way to
put something together that would light up different color LED's for
the different levels of lift that we could build at home without
having to pay out hundreds of dollars for a prebuilt one.




We used a reed switch array and a magnet to determine control rod
position on my submarine's reactor. You could do the same with an AOA
using a magnet on a vane. You'd only need a few reed switches, one for
each angle you were interested in: just before stall, best angle of
climb and best rate of climb corresponding to red, yellow and green
LED's. What else do you care about?

Jerry Wass wrote:
Heck, my first thought was to take the gas gage & sendin unit out of my
'56 chevy , mount the sendin unit inside with some gears outa of my old
alarm clock-(spring busted) sos you get full travel outa the sender with
only ten or 20 degrees motion hang a n aluminium vane on the end of it &
a fishin sinker forward of it to balance it-You could keep the sinker
inside for essthetic reasons. ut then---this was jest my 1st thot--Jerry


That's essentially how a vane type works.

Dan, U.S. Air Force, retired

Hmmmm...for something you could sink your teeth in, Jim, how about a
chip that could be hard mounted inside - with no access to the airflow,
that would keep indicating AoA even with a 1/2 inch of ice over the
entire airframe? $20 gets you a 3-axis accelerometer, which uses
about a couple milliwatts from a 3 volt supply, and provides 300 mV per
g. [ADXL330)
I have it in mind that the arctan [g(vertical) / g(longitudinal)] gives
a useful proxy for AofA, if you process through an op amp ($3), an a/d
on a microcontroller ($25). That way, you could have it play Dixie at
the appropriate angle if you wanted? :-)
That's if a mouth organ reed in a tube from a wing LE aperture is too
low tech?
Brian W

RST Engineering - JIm wrote:
If somebody can tell me how to convert angle of attack to an electrical
signal, the rest is rather trivial.

Jim


"Mike" wrote in message
...
Has anyone built an electronic angle of attack meter kit. It seems to
be something that would be easy to design but beyond my feeble
electronics background.

I have seen the products that are out there and they are simple
differential pressure gauges and are expensive. I don't like the
round differential pressure gauges that many of the companies offer
for this kind of system. I was wondering if there would be a way to
put something together that would light up different color LED's for
the different levels of lift that we could build at home without
having to pay out hundreds of dollars for a prebuilt one.

On Sat, 09 May 2009 19:58:21 -0500, Brian Whatcott
wrote:

Hmmmm...for something you could sink your teeth in, Jim, how about a
chip that could be hard mounted inside - with no access to the airflow,
that would keep indicating AoA even with a 1/2 inch of ice over the
entire airframe? $20 gets you a 3-axis accelerometer, which uses
about a couple milliwatts from a 3 volt supply, and provides 300 mV per
g. [ADXL330)
I have it in mind that the arctan [g(vertical) / g(longitudinal)] gives
a useful proxy for AofA, if you process through an op amp ($3), an a/d
on a microcontroller ($25). That way, you could have it play Dixie at
the appropriate angle if you wanted? :-)
That's if a mouth organ reed in a tube from a wing LE aperture is too
low tech?
Brian W

RST Engineering - JIm wrote:
If somebody can tell me how to convert angle of attack to an electrical
signal, the rest is rather trivial.

Jim


"Mike" wrote in message
...
Has anyone built an electronic angle of attack meter kit. It seems to
be something that would be easy to design but beyond my feeble
electronics background.

I have seen the products that are out there and they are simple
differential pressure gauges and are expensive. I don't like the
round differential pressure gauges that many of the companies offer
for this kind of system. I was wondering if there would be a way to
put something together that would light up different color LED's for
the different levels of lift that we could build at home without
having to pay out hundreds of dollars for a prebuilt one.




Won't indicate RELATIVE AIR FLOW, only absolute attitude - useless as
AOA or lift reserve (iminent stall) indicator.

wrote:
On Sat, 09 May 2009 19:58:21 -0500, Brian Whatcott
wrote:

Hmmmm...for something you could sink your teeth in, Jim, how about a
chip that could be hard mounted inside - with no access to the airflow,
that would keep indicating AoA even with a 1/2 inch of ice over the
entire airframe? $20 gets you a 3-axis accelerometer, which uses
about a couple milliwatts from a 3 volt supply, and provides 300 mV per
g. [ADXL330)
I have it in mind that the arctan [g(vertical) / g(longitudinal)] gives
a useful proxy for AofA, if you process through an op amp ($3), an a/d
on a microcontroller ($25). That way, you could have it play Dixie at
the appropriate angle if you wanted? :-)
That's if a mouth organ reed in a tube from a wing LE aperture is too
low tech?
Brian W

RST Engineering - JIm wrote:
If somebody can tell me how to convert angle of attack to an electrical
signal, the rest is rather trivial.

Jim


"Mike" wrote in message
...
Has anyone built an electronic angle of attack meter kit. It seems to
be something that would be easy to design but beyond my feeble
electronics background.

I have seen the products that are out there and they are simple
differential pressure gauges and are expensive. I don't like the
round differential pressure gauges that many of the companies offer
for this kind of system. I was wondering if there would be a way to
put something together that would light up different color LED's for
the different levels of lift that we could build at home without
having to pay out hundreds of dollars for a prebuilt one.



Won't indicate RELATIVE AIR FLOW, only absolute attitude - useless as
AOA or lift reserve (iminent stall) indicator.


In case there are folks who can't see it: it is possible to stall out
'flat' - in fact a few WW1 era pilots did it and walked away. The air
flow is 50+ degrees to the long axis - from underneath.

Brian W

On Sat, 9 May 2009 09:50:56 -0700, "RST Engineering - JIm"
wrote:

If somebody can tell me how to convert angle of attack to an electrical
signal, the rest is rather trivial.

Jim


"Mike" wrote in message
...
Has anyone built an electronic angle of attack meter kit. It seems to
be something that would be easy to design but beyond my feeble
electronics background.

I have seen the products that are out there and they are simple
differential pressure gauges and are expensive. I don't like the
round differential pressure gauges that many of the companies offer
for this kind of system. I was wondering if there would be a way to
put something together that would light up different color LED's for
the different levels of lift that we could build at home without
having to pay out hundreds of dollars for a prebuilt one.


Generally "lift reserve" is more accurate than angle of attack as a
description.

I would start with two small ports in the leading edge of the wing,
with capillary tubes running to a MEMS differential pressure sensor.

Since the purpose of the device is to tell the pilot how
close the AOA is to the stall value these ports should be
placed straddling the stall stagnation point. (maybe plus-minus 1/2
inch?) Then
the pressure difference is zero at stall, at any airspeed.

The differential pressure IC can feed an LED bar graph.
This should give very good stall prediction accuracy.

Isn't there a voltage-to-LED-bar-graph IC? I seem to
remember such a thing. That would make the circuit simple.

When approaching
an accelerated stall (at higher airspeed than while landing)
the unit would tend to overestimate angle. Actually, it measures
something more like "lift reserve" than angle of attack. But isn't
that
the better quantity to report to the pilot?

Anyway. the feel of the controls is very different in these two
cases,
so I think most pilots would learn to adjust their interpretation
of the reading, as long as the yellow light comes on, then red, then
the
plane stalls.

-Jeff

On May 9, 8:35*pm, wrote:
I would start with two small ports in the leading edge of the wing,
with capillary tubes running to a MEMS differential pressure sensor.

Since the purpose of the device is to tell the pilot how
close the AOA is to the stall value these ports should be
placed straddling the stall stagnation point. (maybe plus-minus 1/2
inch?) Then
the pressure difference is zero at stall, at any airspeed.

The differential pressure IC can feed an LED bar graph.
This should give very good stall prediction accuracy.

Isn't there a voltage-to-LED-bar-graph IC? *I seem to
remember such a thing. *That would make the circuit simple.

When approaching
an accelerated stall (at higher airspeed than while landing)
the unit would tend to overestimate angle. *Actually, it measures
something more like "lift reserve" than angle of attack. But isn't
that
the better quantity to report to the pilot?

Anyway. the feel of the controls is very different in these two
cases,
so I think most pilots would learn to adjust their interpretation
of the reading, as long as the yellow light comes on, then red, then
the
plane stalls.

-Jeff

The LED bar graph chip used to be call LM3916, now replaced by
NTE1549

Yes. It was made by National Semiconductor and you could get it linear or
logarithmic. It was obsoleted by National about fifteen years ago, but
there are still a few of them in the pipeline at a pretty hefty price.

Jim



wrote in message
...

Isn't there a voltage-to-LED-bar-graph IC? I seem to
remember such a thing. That would make the circuit simple.