Building an electronic Angle of Attack indicator

RST Engineering - JIm wrote:
It is not a biggie if price is no concern. However, if you are trying to
bring it to market it is cost prohibitive.

Jim



"Brian Whatcott" wrote in message
...


The wiring might be a little tricky
A wireless chip to a fixed receiver chip is not a biggie. But getting that
sensor chip and transmitter chip inside the nose cone in dynamic balance
would be an issue, I reckon....

Brian W



Beyond cost I wonder if such a system could be made rugged enough to
survive the sustained g forces.

I would assume the airflow over the spinner would cause near constant
pressure on all sides of the spinner due to centrifugal force. I have
nothing to back this up, but it just seems probable.

There's a lot to be said for simplicity. On F-4E there was a "yaw
string" to indicate yaw. All it consisted of was a length of 550 cord
(parachute cord) with one end attached just behind the radome. The pilot
could see the other end in flight. When it was centered in his view the
aircraft was not yawing. I suppose an enterprising person could install
a similar string mount on a boom mounted scale extending from the front
of the wing within view of the pilot and out of propeller blast. 550
cord is available in several colours if that's what one wishes to use.

Dan, U.S. Air Force, retired

"who cares?" wrote in message
...
In article , rich
wrote:
Well of course, the best is to use an AOA vane, like the jets use. The
biggest problem is where the jets conveniently mount it on the side of
the fuselage, on most singles, that's right in the prop blast,
rendering it useless. If you could find someplace to mount it outside
of the prop blast, then it would work great. But finding that
place......


I would like to see a vain mounted on each wingtip with two indicators on
the
glareshield.

I'd like to see how much difference there is in AA from one side to the
other
during steep turns, slow turns, and less than perfect rudder work.

Sounds like an interesting idea. Encoding the position of the vane would be
needed. One way might be to use minature shaft angle optical encoders ( I
tend to think digitally as opposed to analog) . I've seen prices as low as
$20 each. Put one on each wing tip mounted vane and as Jim says the rest is
easy. (If you know some good electronic tech). If you know the AoA for
stall, the output of the encoder could be compared to a preset number and an
alarm into the head set could easily be produced digitally. I've used a
combination of a modification of one of Jim's circuits produced for
Kitplanes along with some additional digital circuitry for a High/Low
helicopter rotor speed alarm and it works great.



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Stuart Fields wrote:
"who cares?" wrote in message
...
In article , rich
wrote:
Well of course, the best is to use an AOA vane, like the jets use. The
biggest problem is where the jets conveniently mount it on the side of
the fuselage, on most singles, that's right in the prop blast,
rendering it useless. If you could find someplace to mount it outside
of the prop blast, then it would work great. But finding that
place......

I would like to see a vain mounted on each wingtip with two indicators on
the
glareshield.

I'd like to see how much difference there is in AA from one side to the
other
during steep turns, slow turns, and less than perfect rudder work.

Sounds like an interesting idea. Encoding the position of the vane would be
needed. One way might be to use minature shaft angle optical encoders ( I
tend to think digitally as opposed to analog) . I've seen prices as low as
$20 each. Put one on each wing tip mounted vane and as Jim says the rest is
easy. (If you know some good electronic tech). If you know the AoA for
stall, the output of the encoder could be compared to a preset number and an
alarm into the head set could easily be produced digitally. I've used a
combination of a modification of one of Jim's circuits produced for
Kitplanes along with some additional digital circuitry for a High/Low
helicopter rotor speed alarm and it works great.



Good idea, you can use a DIP switch (do they still call them that?)
to set your alarm point.

Dan, U.S. Air Force, retired

I learned a great deal from this thread, especially all the references
cited.
Thanks to everyone for contributing.

I think I may build the Jeff Shultz circuit,
with 8 segments if bar LED, plus a red and yellow bar-like LED.

However, I am not quite sure Shulz's logic of the lights is what I
want.

The display logic that makes sense to me is this:
in cruise many green LED are lit (could be 5-8), All greens
at this point, no yellow or red lit. These progressively
go out as the nose is lifted. Then the yellow comes on...with no
greens lit
then the red comes on. I guess the yellow can stay on when the red is
lit.
might want to make the red flash.

a job for a PIC?

-Jeff

wrote:
I learned a great deal from this thread, especially all the references
cited.
Thanks to everyone for contributing.

I think I may build the Jeff Shultz circuit,
with 8 segments if bar LED, plus a red and yellow bar-like LED.

However, I am not quite sure Shulz's logic of the lights is what I
want.

The display logic that makes sense to me is this:
in cruise many green LED are lit (could be 5-8), All greens
at this point, no yellow or red lit. These progressively
go out as the nose is lifted. Then the yellow comes on...with no
greens lit
then the red comes on. I guess the yellow can stay on when the red is
lit.
might want to make the red flash.

a job for a PIC?

-Jeff



If you make your own bar graph you can use a flashing red LED.
Either that or use a yellow bar graph with separate flashing red LED. I
think Radio Shaft carries them. I'd wire the yellow such that they
remain lit as they climb until all are lit just before red illuminates.

There are commercial systems available to the homebuilder. Look at
their displays for ideas. If you find an array you like it shouldn't be
too difficult to make one similar.

I have the feeling no two people will agree on what's best.

Dan, U.S. Air Force, retired

On May 13, 6:21*pm, Dan wrote:
wrote:
I learned a great deal from this thread, especially all the references
cited.
Thanks to everyone for contributing.

I think I may build the Jeff Shultz circuit,
with 8 segments if bar LED, plus a red and yellow bar-like LED.

However, I am not quite sure Shulz's logic of the lights is what I
want.

The display logic that makes sense to me is this:
in cruise many green LED are lit *(could be 5-8), All greens
at this point, no yellow or red lit. *These progressively
go out as the nose is lifted. *Then the yellow comes on...with no
greens lit
then the red comes on. *I guess the yellow can stay on when the red is
lit.
might want to make the red flash.

a job for a PIC?

-Jeff

* * If you make your own bar graph you can use a flashing red LED.
Either that or use a yellow bar graph with separate flashing red LED. I
think Radio Shaft carries them. I'd wire the yellow such that they
remain lit as they climb until all are lit just before red illuminates.

* *There are commercial systems available to the homebuilder. Look at
their displays for ideas. If you find an array you like it shouldn't be
too difficult to make one similar.

* *I have the feeling no two people will agree on what's best.

Dan, U.S. Air Force, retired

The interest for me is a sailplane installation where AOA is a
performance issue in addition to a safety issue.

My glider can be flown at 1000 pounds up to 1433 pounds gross weight
and spends a lot of time in 2G turns thermalling. The AOA for minimum
sink is always the same but the airspeed at which that happens changes
a lot. The same thing with best L/D.

A very 'slippery' glider takes a while for the airspeed to settle down
after a pitch change. Flying to an exact AOA would be easier than
chasing airspeed.

An AOA indicator that shows minimum sink and maximum L/D as well as
stall would be quite useful.

Didja ever look at the nose of the x-15? The "ball" was a bit of magic!




"RST Engineering - JIm" wrote in message ...
Those might get me airspeed but I'm not at all sure how you would get theta
from any one of these schemes.

Jim


Use variable capacitance, variable reluctance, resistor strip or
synchro connected to a vane. For a real giggle do as some Air Force
systems and employ a slotted, rotating cone for a probe. It involves a
feedback loop.

Dan, U.S. Air Force, retired

Use the airdata computer to derive AOA from it's accelerometers...



"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.

"Maxwell" wrote in message m...

"Barnyard BOb" wrote in message
...


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


And another F'ing a Bubba.

If you can't fly your aircraft well enough to shoot safe approaches without
an AIR SPEED indicator, you need to surrender your ticket and go back in to
training. Much less an angle of attack indicator.

That's just what we need, more **** to keep your head INSIDE the airplane.
What next, satellite TV?




I wanna go to FlightAware.com and watch my flight progress across the USA while I am doing it....

"bildan" wrote in message ...

The interest for me is a sailplane installation where AOA is a
performance issue in addition to a safety issue.

My glider can be flown at 1000 pounds up to 1433 pounds gross weight
and spends a lot of time in 2G turns thermalling. The AOA for minimum
sink is always the same but the airspeed at which that happens changes
a lot. The same thing with best L/D.

A very 'slippery' glider takes a while for the airspeed to settle down
after a pitch change. Flying to an exact AOA would be easier than
chasing airspeed.

An AOA indicator that shows minimum sink and maximum L/D as well as
stall would be quite useful.

Bill,

I tatally agree! It would also be nice to have the AOA measure units instead of degrees and be calibrated so to give the same readings for max L/D and Min Sink at all flap settings.

When I was flying A-6 Intruders 21 units of AOA was the Max Range value (best L/D) at all flap settings. I don't believe you can develop an effective unit for aircraft with flaps without integrating the flap setting into the system. This requires knowing the performance curve for each setting in order to calculate a single Max L/D (Max Range) indicator reading and a single Min Sink (Max endurance) indicator reading.

This isn't as simple of a problem as some seem to think it is.

Wayne
HP-14 with flap settings from -5 to +90.
http://www.soaridaho.com/Schreder