Building an electronic Angle of Attack indicator

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.

And after all is said and done, we remind ourselves that we are supposed to
be building inexpensive airplanes that look good and fly well.

So a vane on a synchro? Sure, we had those on the Boeing 3-holer (7-deuce)
at a cost of slightly less than $10k a copy in 1965 dollars. Surplus
synchros? Sure, now you are doing a one-off and how to tell another builder
how to use another brand of surplus synchro isn't feasible...not to mention
the fact that most synchros are set up to use the 115v 3phase power that the
Air Force/Boeing is so pleased with.

Or a gas tank sender with a big flap on it? Well, that looks like hell,
doesn't it? Besides that wirewound pot on the gas gauge needs some REAL
FORCE to push it around and consumes a fair amount of current in the
process.

Or some thermistors inside the pitot? WIthout a little more description you
can't tell exactly what the scheme of that is. One thermistor on the inside
top of the pitot and one on the inside bottom, each thermistor heated
equally (difficult task) and then you hope that the incoming air is laminar
and not swirling around? This might be feasible with a little more
explanation.

Differential pressure sensors? Haven't done the research lately, but the
last time I looked Motorola had stopped making the inexpensive variety and I
don't know if anybody else picked up that ball.

So, let's take it from scratch and think about what the optimum solution for
cost, looks, and reliability might be ... and the rotated yaw string is a
good idea except for the fact that 95% of the homebuilts are tractors and
the prop blast will decalibrate anything we might come up with...

Jim

RST Engineering - JIm wrote:
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.


Nope. It's still very much available in the surface mount package.

"RST Engineering - JIm" wrote in message
m...
And after all is said and done, we remind ourselves that we are supposed
to be building inexpensive airplanes that look good and fly well.

Which is a valid reason to step back from AOA and just build a better basic
stall warning.

Between my aviation and age-induced hearing loss, and the great improvement
in even cheap headsets these days, it is a rare day when I actually hear a
"pennywhistle" stall warning. A simple gizmo that mixes a warning tone into
the intercom audio would be great!

Vaughn

On Sun, 10 May 2009 09:30:02 -0700, "RST Engineering - JIm"
wrote:

And after all is said and done, we remind ourselves that we are supposed to
be building inexpensive airplanes that look good and fly well.

So a vane on a synchro? Sure, we had those on the Boeing 3-holer (7-deuce)
at a cost of slightly less than $10k a copy in 1965 dollars. Surplus
synchros? Sure, now you are doing a one-off and how to tell another builder
how to use another brand of surplus synchro isn't feasible...not to mention
the fact that most synchros are set up to use the 115v 3phase power that the
Air Force/Boeing is so pleased with.

Or a gas tank sender with a big flap on it? Well, that looks like hell,
doesn't it? Besides that wirewound pot on the gas gauge needs some REAL
FORCE to push it around and consumes a fair amount of current in the
process.

Or some thermistors inside the pitot? WIthout a little more description you
can't tell exactly what the scheme of that is. One thermistor on the inside
top of the pitot and one on the inside bottom, each thermistor heated
equally (difficult task) and then you hope that the incoming air is laminar
and not swirling around? This might be feasible with a little more
explanation.

Differential pressure sensors? Haven't done the research lately, but the
last time I looked Motorola had stopped making the inexpensive variety and I
don't know if anybody else picked up that ball.

So, let's take it from scratch and think about what the optimum solution for
cost, looks, and reliability might be ... and the rotated yaw string is a
good idea except for the fact that 95% of the homebuilts are tractors and
the prop blast will decalibrate anything we might come up with...

Jim

Some years back there was a complete discription of a thermistor based
system in Sport Aviation. You might contact the research department or
whatever they call it.

By God, you are correct. When my supplier told me in 1999 that the LM3914
was no longer available, they failed to tell me that the LM3914-1 was a
direct replacement and very much still in the pipeline, even as the larger
18 pin through-hole DIP package. Thanks for correcting me.

Jim


"Rip" wrote in message
...
RST Engineering - JIm wrote:
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.


Nope. It's still very much available in the surface mount package.

RST Engineering - JIm wrote:
And after all is said and done, we remind ourselves that we are supposed to
be building inexpensive airplanes that look good and fly well.

So a vane on a synchro? Sure, we had those on the Boeing 3-holer (7-deuce)
at a cost of slightly less than $10k a copy in 1965 dollars. Surplus
synchros? Sure, now you are doing a one-off and how to tell another builder
how to use another brand of surplus synchro isn't feasible...not to mention
the fact that most synchros are set up to use the 115v 3phase power that the
Air Force/Boeing is so pleased with.

Or a gas tank sender with a big flap on it? Well, that looks like hell,
doesn't it? Besides that wirewound pot on the gas gauge needs some REAL
FORCE to push it around and consumes a fair amount of current in the
process.

Or some thermistors inside the pitot? WIthout a little more description you
can't tell exactly what the scheme of that is. One thermistor on the inside
top of the pitot and one on the inside bottom, each thermistor heated
equally (difficult task) and then you hope that the incoming air is laminar
and not swirling around? This might be feasible with a little more
explanation.

Differential pressure sensors? Haven't done the research lately, but the
last time I looked Motorola had stopped making the inexpensive variety and I
don't know if anybody else picked up that ball.

So, let's take it from scratch and think about what the optimum solution for
cost, looks, and reliability might be ... and the rotated yaw string is a
good idea except for the fact that 95% of the homebuilts are tractors and
the prop blast will decalibrate anything we might come up with...

Jim


Every aircraft synchro I have ever seen uses 26 VAC 400 hz single
phase. I have seen power supplies for them on e-bay for around $25 or
so. It's been awhile since I have looked, but they were there. In any
event synchro systems don't seem to be sine wave particular so a simple
power supply should be easy.

If you want cheap aircraft synchros find a shop that repairs jet
aircraft. The 1" "peanut" pressure indicators contain a synchro that
usually outlasts the internal lighting. I have found them on e-bay also.
Compass amplifiers such as used in the C-12 compass system contain a
multitude of synchros since they use a gear train to drive several
synchros. Vertical scale instruments such as those used on C-141 also
contain synchros. I have seen those for sale on e-bay also.

Dan, U.S. Air Force, retired

And after all is said and done, we remind ourselves that we are supposed
to be building inexpensive airplanes that look good and fly well.

Which is a valid reason to step back from AOA and just build a better basic
stall warning.

Vaughn

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

AMEN.

First learn to fly with competency and K.I.S.S. in mind.

If you fly honest inexpensive safe machines and you're and honest
pilot, you can grow old without a gadget to stare at whist you forget
to fly the plane to an untimely demise. :-)

Barnyard BOb - 55 years of licensed powered flight w/o AOA

RST Engineering - JIm wrote:
By God, you are correct. When my supplier told me in 1999 that the LM3914
was no longer available, they failed to tell me that the LM3914-1 was a
direct replacement and very much still in the pipeline, even as the larger
18 pin through-hole DIP package. Thanks for correcting me.

Jim


"Rip" wrote in message
...
RST Engineering - JIm wrote:
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.

Nope. It's still very much available in the surface mount package.


My pleasure. This topic is timely, since I recently built myself a
"Lift Reserve Indicator" based on the LM3914 and a Honeywell sensor.
Now I'm doing a "true" angle of attack indicator based on the Maxim
4210 multiplier (and an op amp) to correct for airspeed ram pressure.

A terrific treatise on the subject (with one inconsequential math error)
can be found he
http://users.cablemo.net/~jjshultz/sonex/aoa.html

Rip

Ed wrote:


Some years back there was a complete discription of a thermistor based
system in Sport Aviation. You might contact the research department or
whatever they call it.

Might refer to "Electo Fluidic Autopilot" article.