Building an electronic Angle of Attack indicator

There is one central location that is not subject to prop blast,
exactly: - that's the nose cone of the prop.
Visualize a small hole set about an inch back from the front.
Use a local pressure sensor chip and a wireless transmitter.

The flow from off axis would module the air pressure slightly
one cycle per revolution, with amplitude in proportion to
AofA (maybe :-)

Brian W

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......

On Mon, 11 May 2009 22:44:23 -0500, Brian Whatcott
wrote:

There is one central location that is not subject to prop blast,
exactly: - that's the nose cone of the prop.
Visualize a small hole set about an inch back from the front.
Use a local pressure sensor chip and a wireless transmitter.

The flow from off axis would module the air pressure slightly
one cycle per revolution, with amplitude in proportion to
AofA (maybe :-)

Brian W

The wiring might be a little tricky

Ed wrote:
On Mon, 11 May 2009 22:44:23 -0500, Brian Whatcott
wrote:

There is one central location that is not subject to prop blast,
exactly: - that's the nose cone of the prop.
Visualize a small hole set about an inch back from the front.
Use a local pressure sensor chip and a wireless transmitter.

The flow from off axis would module the air pressure slightly
one cycle per revolution, with amplitude in proportion to
AofA (maybe :-)

Brian W

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

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

"Brian Whatcott" wrote in message
news
There is one central location that is not subject to prop blast,
exactly: - that's the nose cone of the prop.
Visualize a small hole set about an inch back from the front.
Use a local pressure sensor chip and a wireless transmitter.

The flow from off axis would module the air pressure slightly
one cycle per revolution, with amplitude in proportion to
AofA (maybe :-)


Yeah, that sounds eaaaaasssy, and cheeeep, too!

NoT ! ! ! ;-)
--
Jim in NC

Morgans wrote:
"Brian Whatcott" wrote in message
news
There is one central location that is not subject to prop blast,
exactly: - that's the nose cone of the prop.
Visualize a small hole set about an inch back from the front.
Use a local pressure sensor chip and a wireless transmitter.

The flow from off axis would module the air pressure slightly
one cycle per revolution, with amplitude in proportion to
AofA (maybe :-)


Yeah, that sounds eaaaaasssy, and cheeeep, too!

NoT ! ! ! ;-)

I'm the one who likes the mouth organ reed, tube and wing slot approach
- but Experimental class is dedicated to folks who don't take the cheap,
easy approach!

Brian W

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.

"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