Building an electronic Angle of Attack indicator

[Mike]

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.

[RST Engineering - JIm]

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

Jim

"Mike" <michae...@cox.net> wrote in message
news:29d71e7f-b9dd-4aa3...@n8g2000vbb.googlegroups.com...

[Dan]

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

[RST Engineering - JIm]

Those might get me airspeed but I'm not at all sure how you would get theta
from any one of these schemes.

Jim

[Jim Logajan]

"RST Engineering - JIm" <jwe...@gmail.com> wrote:
> Those might get me airspeed but I'm not at all sure how you would get
> theta from any one of these schemes.

I believe he means the vane is lightweight and freely pivots up or down so
that it is always pointing into the relative wind. The angle the vane makes
with some reference line on the wing or fuselage is thus the AoA. I'd post
a link to a picture of what it would look like (pretty simple concept) but
can't see to find one!

Just think of the yaw string on gliders (e.g. the red string in this
picture: http://www.highonadventure.com/Hoa08dec/Steve/GlideYawString.jpg)
but used to show vertical component of the relative wind, not horizontal.

[Jim Logajan]

Jim Logajan <Jam...@Lugoj.com> wrote:
> I'd post a link to a picture of what it would look like
> (pretty simple concept) but can't see to find one!

Okay, found some, like this one:
http://commons.wikimedia.org/wiki/File:Angle_of_attack_indicator_1.jpg

And a simple mechanical kit (looks like no longer available):
http://www.aircraftspruce.com/catalog/inpages/baconsaver.php

My suspicion is that designers get fancy and use things like two non-
parallel pitots and use some mechanism to compute the AoA from their
differential pressures, which is then presented in some fancy digital
display. The irony is that AoA is easy to show, and if one is flying a
glider or pusher, a simple mechanical device could probably be mounted so
it is visible out front (i.e. "heads up") so that one can see the AoA at
the same time one is controlling their approach. But I suppose it'd be too
distracting during crusing flight and mess up the "look" of the airplane.

[John Kimmel]

RST Engineering - JIm wrote:

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
gNuOy_S...@spiretech.com

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

[Jerry Wass]

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

[Dan]

RST Engineering - JIm wrote:

The vane types are self explanatory.

http://www.aircraftmech.com/pics/aoa.jpg

http://spaceagecontrol.com/4239-01image.jpg

The cone type is a bit more complicated. Picture a hollow stainless
cone with two sets of slots running between base and apex. The slots
face towards the front of the airplane. Each set opens to its own
chamber in the cone. The pressure in each chamber is measured and the
cone is rotated until the pressures are equal. The position is then
transmitted to an indicator.

http://www.avionics-specialties.com/images/prodthumb_stat.jpg

The cone types are usually heated to prevent icing.

If I were to build one for small aircraft I'd go with a vane and
resistance strip. In that case a standard d'arsonval meter or column of
LEDs could be used to indicate AOL.

Pressure differential systems have the disadvantages of icing or dirt
contamination.

[Dan]

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.

[cavelamb]

Jim Logajan wrote:
> Jim Logajan <Jam...@Lugoj.com> wrote:
>> I'd post a link to a picture of what it would look like
>> (pretty simple concept) but can't see to find one!
>

My favorite one has no moving parts.

Just two thermosistors in the pitot tube...
and an opamp circuit to read differential cooling.

[jeffreyb...@gmail.com]

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

[Brian Whatcott]

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:

[jeffreyb...@gmail.com]

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

[Charlie]

Something like
http://www.barkeraircraft.com/AOA_kit.html

EAA web site says June 07 Sport Aviation Magazine, but I thought it was
more recent than that.

Charlie

[Dan]

That's a nice set up. It shouldn't be too hard to add an audio alarm
or shaker. I just hope the pitot tube isn't heated.

[cavelamb]

Speaking of which, I have a heated pitot tube head
If anyone is in need of one, drop me a note.

[bildan]

I've worked this problem for a number of years. Let me offer a few
simple points.

Any system of measuring AOA will need to be calibrated. It doesn't
really need to be linear since the major interest is in the region
near stall and Cl max. It just needs to give a variable output that
is related to AOA - and be very repeatable.

If the cockpit is in clean free air flow as with a pusher or
sailplane, an effective AOA indicator can be made with a simple string
taped to the side of the canopy. On sailplanes, these 'pitch strings'
tends to 'over-indicate' by about 2:1 which is fine as it increases
the resolution of the indicator. Stall, Cl max and L/D max can be
marked on the inside of the canopy with grease pencil. It helps to
put one on each side of the canopy as they tend to validate each
other.

If you like the pressure differential AOA probes, this is a good one.
http://www.cgmasi.com/aviation/index.html

If you want NASA quality data, the gold standard is the pitch vane
mounted on an air-data nose boom. There are a number of vendors who
sell these for UAV's which are about the right size for homebuilt
airplanes.
Here's an example: http://www.spaceagecontrol.com/Adpmain

Bill D

[Wayne Paul]

In addition to Bill's comments the calibrations process must consider the position of the flaps. Remember you are measuring the AOA of the airfoil, not just the airflow relative to the fuselage.

Wayne
http://www.soaridaho.com/Schreder
.
"bildan" <bil...@comcast.net> wrote in message news:25a743ee-3778-4005...@b7g2000pre.googlegroups.com...

[Dan]

bildan wrote:
> I've worked this problem for a number of years. Let me offer a few
> simple points.
>
> Any system of measuring AOA will need to be calibrated. It doesn't
> really need to be linear since the major interest is in the region
> near stall and Cl max. It just needs to give a variable output that
> is related to AOA - and be very repeatable.
>
> If the cockpit is in clean free air flow as with a pusher or
> sailplane, an effective AOA indicator can be made with a simple string
> taped to the side of the canopy. On sailplanes, these 'pitch strings'
> tends to 'over-indicate' by about 2:1 which is fine as it increases
> the resolution of the indicator. Stall, Cl max and L/D max can be
> marked on the inside of the canopy with grease pencil. It helps to
> put one on each side of the canopy as they tend to validate each
> other.
>
> If you like the pressure differential AOA probes, this is a good one.
> http://www.cgmasi.com/aviation/index.html
>

It occurs to me that a differential system should be fairly simple to
build. Solid state pressure sensors have been around a long time. Since
AOA would be the ratio between the two sensors it should be simple to
make a comparator to voltage converter since actual pressures are
irrelevant as long as they are sufficient to be read. Airspeed would
also not be a factor. I suppose a purely mechanical system could also be
built by a mechanically inclined type. Pressure from each port would be
sent to opposing bellows in an indicator which would position a needle.

[RST Engineering - JIm]

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

<jeffreyb...@gmail.com> wrote in message
news:fdad5d8f-aaba-4385...@m24g2000vbp.googlegroups.com...

[RST Engineering - JIm]

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

[Rip]

RST Engineering - JIm wrote:

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

[vaughn]

"RST Engineering - JIm" <jwe...@gmail.com> wrote in message
news:6YGdncTgBbO9nJrX...@supernews.com...

> 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

[Ed]

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.

[RST Engineering - JIm]

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" <rnospa...@snetnospam.net> wrote in message
news:JiDNl.18235$D32....@flpi146.ffdc.sbc.com...

[Dan]

RST Engineering - JIm wrote:

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.

[Barnyard BOb]

>> 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

[Rip]

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" <rnospa...@snetnospam.net> wrote in message
> news:JiDNl.18235$D32....@flpi146.ffdc.sbc.com...
>> 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
>>>
>>>
>>>
>>> <jeffreyb...@gmail.com> wrote in message
>>> news:fdad5d8f-aaba-4385...@m24g2000vbp.googlegroups.com...
>>>
>>>> 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 here:
http://users.cablemo.net/~jjshultz/sonex/aoa.html

Rip

[cavelamb]

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.

[Maxwell]

"Barnyard BOb" <roo...@barnyard.com> wrote in message
news:9u3e05tblr3o29q5o...@4ax.com...

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 shit to keep your head INSIDE the airplane.
What next, satellite TV?

[Brian Whatcott]

Ed wrote:

> Some years back there was a complete description of a thermistor based

> system in Sport Aviation. You might contact the research department or
> whatever they call it.

I recall reading details of a thermistor sensor autopilot system years ago.
A little air pump blew a small jet towards an array of four thermistors
in a box. If the aircraft pitched, then the jet was deflected more
towards one thermistor than its opposite. Both thermistors went to an op
amp. Another pair of thermistors were responsive to yaw rate and turn.

Such a neat conception! I talked to him on the phone. He worked
(works) for a NASA lab - Ames, if I recall. Still have the article
somewhere.

Brian W

[RST Engineering - JIm]

Hey, Dan, you are posting in rec.aviation HOMEBUILT. I appreciate your
expertise, but your bias towards keeping large jet aircraft running is
showing. Have you BUILT a homebuilt:? Have you MAINTAINED a single engine
aircraft?

With all due respects, sir, if you have not, please refrain from those of us
who have.

Jim

"Dan" <B24...@aol.com> wrote in message
news:GqENl.30219$uD3....@newsfe20.iad...

[RST Engineering - JIm]

The electronics are trivial. The sensors are everything. Please post
detailed information.

Jim

"Rip" <rnospa...@snetnospam.net> wrote in message

news:U5FNl.16033$hc1....@flpi150.ffdc.sbc.com...

[RST Engineering - JIm]

That was "ElectrRO Fluidic Autopilot and my good friend Doug Garner from
NASA Langley wrote it. I haven't heard from him in some years, but he was
damn near 80 the last time I saw him at Oshkosh 20 years ago.

Jim

"cavelamb" <cave...@earthlink.net> wrote in message
news:0L2dnbXQGtX8rprX...@earthlink.com...

[RST Engineering - JIm]

NASA Langley. Doug Garner. Several published articles in Sport Aviation.
cf Fluidic Autopilot.

Jim
"Brian Whatcott" <bet...@sbcglobal.net> wrote in message
news:BNJNl.32907$ZP4....@nlpi067.nbdc.sbc.com...

[Dan]

RST Engineering - JIm wrote:

> Hey, Dan, you are posting in rec.aviation HOMEBUILT. I appreciate your
> expertise, but your bias towards keeping large jet aircraft running is
> showing. Have you BUILT a homebuilt:? Have you MAINTAINED a single engine
> aircraft?
>
> With all due respects, sir, if you have not, please refrain from those of us
> who have.
>
> Jim

Have you not seen synchro repeaters driven by vacuum gyros as used
in home built/ GA aircraft? Heading hold, perhaps? The little 26 VAC
inverter I mentioned is for synchro excitation for such systems. I have
two of them around here somehwere. Neither are mil-spec or STCed or home
made.

As for "large jet aircraft" bias the biggest I ever worked on was
C-141, the smallest was a Cessna 172. You can guess who owned the former
and the owner of the later has probably died of old age by now. I wasn't
aware O-2 would be considered "large jet aircraft" and I have experience
on recips. Most of my experience is on turboshafts or turboprops, this
doesn't make my ideas any less valid than yours.

I have never built a home built, but I have assisted and made several
sub-assemblies including instrument panels.

None of the synchro systems I ever used took 3 phase in. Transmitter
and motors both use single phase for excitation. Perhaps you'd care to
tell us what what Boeing/ USAF aircraft used 115 VAC 400 hz 3 phase power.

I suggested sources for synchros for you or anyone who might want to
play with them. If you don't want to try them, fine, maybe someone else
might.

As for refraining it's not your place to suggest I do anything of the
sort. This isn't a contest between us.

[Rip]

RST Engineering - JIm wrote:

I used a Honeywell ASDXL05D44D on my initial "lift reserve indicator",
mainly be cause I had a spare kicking around.

The true angle of attack design uses 2 Freescale MPXV7002 sensors.

The sensors really aren't that critical.You're after a repeatable
differential pressure signal, rather than absolute accuracy.

[Dan]

I forget who makes it, but there's a commercially available system
that uses ports in the leading edge of a wing. My primary concern would
be how one protects from fouling while parked. I like your probe idea
since one could easily make a protective sleeve with a "remove before
flight" streamer attached.

[cl...@snyder.on.ca]

On Sat, 9 May 2009 05:30:37 -0700 (PDT), Mike <michae...@cox.net>
wrote:

>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.

Buy an electronic differential pressureindicator and put a bar graph
on it.

Not cheap - new Setras are about $400 but they are available surplus
occaisionally at good prices. You want 0-5 volt, not 20ma outputs.

[cl...@snyder.on.ca]

On Sat, 9 May 2009 09:50:56 -0700, "RST Engineering - JIm"
<jwe...@gmail.com> wrote:

>If somebody can tell me how to convert angle of attack to an electrical
>signal, the rest is rather trivial.
>
>Jim
>
>
>"Mike" <michae...@cox.net> wrote in message
>news:29d71e7f-b9dd-4aa3...@n8g2000vbb.googlegroups.com...

>> 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.

[cl...@snyder.on.ca]

On Sat, 09 May 2009 12:35:38 -0500, Jim Logajan <Jam...@Lugoj.com>
wrote:

>"RST Engineering - JIm" <jwe...@gmail.com> wrote:

>> Those might get me airspeed but I'm not at all sure how you would get
>> theta from any one of these schemes.
>
>I believe he means the vane is lightweight and freely pivots up or down so
>that it is always pointing into the relative wind. The angle the vane makes
>with some reference line on the wing or fuselage is thus the AoA. I'd post
>a link to a picture of what it would look like (pretty simple concept) but
>can't see to find one!
>
>Just think of the yaw string on gliders (e.g. the red string in this
>picture: http://www.highonadventure.com/Hoa08dec/Steve/GlideYawString.jpg)
>but used to show vertical component of the relative wind, not horizontal.
>
>>> 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
>>
>>
>>

See
http://www.pegazair.on-the-net.ca/ClareSquared/pictures/airframe/lri.htm
and use electronic differential pressure in place of the DWYER
MINIHELIC II.
The diagram of the probe dissapeared, sorry.

[cl...@snyder.on.ca]

On Sat, 09 May 2009 19:58:21 -0500, Brian Whatcott
<bet...@sbcglobal.net> 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" <michae...@cox.net> wrote in message
>> news:29d71e7f-b9dd-4aa3...@n8g2000vbb.googlegroups.com...
>>> 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.

[cl...@snyder.on.ca]

On Sun, 10 May 2009 21:43:15 -0500, Dan <B24...@aol.com> wrote:

>
>
> I forget who makes it, but there's a commercially available system
>that uses ports in the leading edge of a wing. My primary concern would
>be how one protects from fouling while parked. I like your probe idea
>since one could easily make a protective sleeve with a "remove before
>flight" streamer attached.
>
>Dan, U.S. Air Force, retired

Any reason not to incorporate the LR sensor ports in a custom main
pitot pylon?

[Brian Whatcott]

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

[rich]

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 Sat, 9 May 2009 05:30:37 -0700 (PDT), Mike <michae...@cox.net>
wrote:

>Has anyone built an electronic angle of attack meter kit. It seems to

[Dan]

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......
>

Kitplanes once did an article on a boom mounted vane called "bacon
saver." No reason a similar set up couldn't be used.

[Rip]

Thanks Dan, but credit where it's due. The page I linked to is by Jeff
Shultz, who went through the same exercise I went through, and was kind
enough to make a web-page out of his research.

[who cares?]

In article <kt8g05hrk3i4c3tna...@4ax.com>, rich <ric...@rocketmail.com> 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.

[jan olieslagers]

who cares? schreef:

> I would like to see a vain mounted on each wingtip

Great idea, yes. Any preference of vains in the glossy magazines?
For myself I'd much like Madonna and Prince - if they are more or less
balanced.

(or could it be you meant a couple of vanes? That's a whole another
story...)

[Frank Stutzman]

Could be worse. He could have said 'veins' ;-)

--
Frank Stutzman
Bonanza N494B "Hula Girl"
Boise, ID

[Dan]

Frank Stutzman wrote:
> jan olieslagers <adelco_g...@skynet.be> wrote:
>> who cares? schreef:
>>> I would like to see a vain mounted on each wingtip
>> Great idea, yes. Any preference of vains in the glossy magazines?
>> For myself I'd much like Madonna and Prince - if they are more or less
>> balanced.
>>
>>
>>
>> (or could it be you meant a couple of vanes? That's a whole another
>> story...)
>
> Could be worse. He could have said 'veins' ;-)
>

Vain vanes, something in that vein?

[Morgans]

"rich" <ric...@rocketmail.com> 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 a mast like a pitot tube, out on the wing.

I propose 4 or 5 microswitches with a mechanical linkage to go from the vane
to the switches in the wing. Send the signal to some led's, and you are
done. Cheap and easy.
--
Jim in NC

[Dan]

That should be fun to calibrate, but once everything is secured it
should be reliable.

[Brian Whatcott]

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

[Ed]

On Mon, 11 May 2009 22:44:23 -0500, Brian Whatcott
<bet...@sbcglobal.net> 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

[Morgans]

"Brian Whatcott" <bet...@sbcglobal.net> wrote in message

news:Dh6Ol.29825$YU2....@nlpi066.nbdc.sbc.com...

> 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

[Brian Whatcott]

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]

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

[RST Engineering - JIm]

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" <bet...@sbcglobal.net> wrote in message

news:AvdOl.22177$as4....@nlpi069.nbdc.sbc.com...

[Dan]

RST Engineering - JIm wrote:

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.

[Stuart Fields]

"who cares?" <dead...@verizon.net> wrote in message
news:OgYNl.543$5F2...@nwrddc01.gnilink.net...

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.

__________ Information from ESET NOD32 Antivirus, version of virus signature database 4068 (20090512) __________

The message was checked by ESET NOD32 Antivirus.

http://www.eset.com

[Dan]

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

[jeffreyb...@gmail.com]

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

[Dan]

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.

[bildan]

On May 13, 6:21 pm, Dan <B24...@aol.com> wrote:

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.

[Dan D]

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

"RST Engineering - JIm" <jwe...@gmail.com> wrote in message news:1I-dndOkFIfGJ5jX...@supernews.com...

> 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 D]

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

"Mike" <michae...@cox.net> wrote in message news:29d71e7f-b9dd-4aa3...@n8g2000vbb.googlegroups.com...

[Dan D]

"Maxwell" <nom...@nospam.net> wrote in message news:4a073833$0$31194$882e...@news.ThunderNews.com...
>
> "Barnyard BOb" <roo...@barnyard.com> wrote in message
> news:9u3e05tblr3o29q5o...@4ax.com...
>>
>>
>>>> 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 shit 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....

[Wayne Paul]

> "bildan" <bil...@comcast.net> wrote in message news:787f9245-a4c5-4290...@d39g2000pra.googlegroups.com...

>
> 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

[bildan]

On May 14, 7:30 pm, "Wayne Paul" <wa...@soaridaho.com> wrote:
> > "bildan" <bil...@comcast.net> wrote in messagenews:787f9245-a4c5-4290...@d39g2000pra.googlegroups.com...

Yes, there would have to be additional hardware/software to do it with
flaps. But, as long as the AOA system knew what flap setting was
being used, it could still display AOA data for that flap polar. Of
course, a continuously variable system like yours could be
complicated.

To simplify the system, min sink is only of interest at thermalling
flap settings and best L/D only at zero flap. (I'm guessing if you
are in negative flap, you're not interested in flying at best L/D.)

Also, the newer airfoils have made non-flapped gliders just about as
good as flapped ones so the flap issue may be becoming moot anyway.
It could be that a glider without flaps but flown with the precision
possible with an AOA indicator might not be at much of a disadvantage.

[Peter Dohm]

"bildan" <bil...@comcast.net> wrote in message
news:787f9245-a4c5-4290...@d39g2000pra.googlegroups.com...

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.

----begin new post--------OE got confused again-----------

Presuming that a moving/rotating vane system would work for you, you might
consider an all mechanical system.

One possibility might involve canibalizing an old VW fuel guage assembly for
some of the parts--the 1965, and possibly the 1964, VW "Beetles" had a
mechanical fuel guage activated through a push/pull cable that was similar
to the throttles on lawnmowers and the hand brakes on bicycles.

Actually, with a little thought and considering that the vane could be
located on the side(s) of the forward cockpit area, it should be possible to
devise a system that would be lighter, simpler, and also having less
friction. You could even make the indicating needle move vertically--which
would seem to me to be more intuitive.

By the way, a pair of "pitch strings" mounted on the lower portion of the
canopy sides would possibly work as well and would be a trivial
installation; but I suspect that they could be difficult and distracting to
read unless they happened to fit well with your use of peripheral vision.
That issue greatly exceeds my "human factors" knowledge.

Peter

PS: I was an electronic technician, and occasionally design technician, for
many years and I am confident that I could devise an electronic "lift
reserve" or similar indicator with two or three angles marked for reference;
but I strongly suspect that a simple mechanical system would be simpler and
equally functional on a glider--where there should be no ice and no tractor
propeller.

[cavelamb himself]

Doug Garner! That's his name.
His AOA sensor was the soul of simplicity - and, IIRC, worked very well.
It was a fascinating project.

RST Engineering - JIm wrote:

> That was "ElectrRO Fluidic Autopilot and my good friend Doug Garner from
> NASA Langley wrote it. I haven't heard from him in some years, but he was
> damn near 80 the last time I saw him at Oshkosh 20 years ago.
>
> Jim
>
>
>
>
> "cavelamb" <cave...@earthlink.net> wrote in message
> news:0L2dnbXQGtX8rprX...@earthlink.com...
>> 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.
>
>

[Charlie]

You can configure the LM3914 LED driver to light the LEDs as shown in
the article, or one-at-a-time, like climbing a ladder. (Bar or dot mode)

You can also daisy-chain 2 or more drivers if you need finer resolution.

http://www.national.com/mpf/LM/LM3914.html

[Dan D]

"Peter Dohm" <left...@bellsouth.net> wrote in message news:ONnPl.41152$i9.2...@bignews7.bellsouth.net...

>
> "bildan" <bil...@comcast.net> wrote in message
> news:787f9245-a4c5-4290...@d39g2000pra.googlegroups.com...
>
>
> 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.
>

The glider solution could be a simple as the piece of yarn along the side of the canopy...

[Peter Dohm]

"Dan D" <nospamblu...@charter.net> wrote in message
news:SbVPl.89686$ew.8...@newsfe24.iad...

Someone's trimming of messages needs work!

My post, immediately above yours, included the following:

"By the way, a pair of "pitch strings" mounted on the lower portion of the
canopy sides would possibly work as well and would be a trivial
installation; but I suspect that they could be difficult and distracting to
read unless they happened to fit well with your use of peripheral vision.
That issue greatly exceeds my "human factors" knowledge."

That seems similar, except that I had suggested a string on each side.

[Dan D]

"Peter Dohm" <left...@bellsouth.net> wrote in message news:yuVPl.42613$b9.2...@bignews6.bellsouth.net...

Sorry, didn't see it...it does seem great minds think alike!

[Wayne Paul]

"Dan D" <nospamblu...@charter.net> wrote in message news:SbVPl.89686$ew.8...@newsfe24.iad...
>

>> 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.
>>
>
> The glider solution could be a simple as the piece of yarn along the side of the canopy...
>

It isn't that simple. The string will show the angle of flow relative to the fuselage, not the airfoil. The fuselage angle of max L/D and minimum sink change with the flap setting. (Thermal at 15 degrees, cruise between zero and -10 degrees.)

A true AOA would supply a single given Max L/D indication no mater what the flap setting. The software to do this isn't difficult if you know the airflow relative to the fuselage, the angle of incidence of the wing, and the wing's performance curves for various flap setting.

From my perspective a reliable low-drag encoding vane is the tall pole in the tent. The airfoil performance/angle of incidence can be derived from sailplane's handbook. The cockpit indicator can be the designer's/owner's choice.

Wayne
HP-14 N990
Flap range -10 to +90.
http://www.soaridaho.com/Schreder/HP-14/N990/N990.html

[Peter Dohm]

"Dan D" <nospamblu...@charter.net> wrote in message

news:hHVPl.89691$ew....@newsfe24.iad...

No problem, and I'm glad to have a second on a simple solution.

[Peter Dohm]

"Wayne Paul" <wa...@soaridaho.com> wrote in message
news:momdnb0bMddV3I3X...@supernews.com...

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.

[Wayne Paul]

"Peter Dohm" <left...@bellsouth.net> wrote in message news:dK0Ql.43781$19.2...@bignews2.bellsouth.net...

> 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/

[Peter Dohm]

"Wayne Paul" <wa...@soaridaho.com> wrote in message

news:GoOdnSZmdN-5Po3X...@supernews.com...

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

[Wayne Paul]

"Peter Dohm" <left...@bellsouth.net> wrote in message news:DP1Ql.42016$i9....@bignews7.bellsouth.net...

>
> 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/

[Peter Dohm]

"Wayne Paul" <wa...@soaridaho.com> wrote in message

news:rYWdnTVlrfWDKo3X...@supernews.com...

Very cool indeed!

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

Peter

[Dan]

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.

[Morgans]

"Peter Dohm" <left...@bellsouth.net> 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

[Wayne Paul]

"Dan" <B24...@aol.com> wrote in message news:cm3Ql.26145$ho7....@newsfe10.iad...

>>
> 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/

[bildan]

On May 17, 6:30 pm, "Peter Dohm" <lefty...@bellsouth.net> wrote:
> "Wayne Paul" <wa...@soaridaho.com> wrote in message
>
> news:GoOdnSZmdN-5Po3X...@supernews.com...
>

> "Peter Dohm" <lefty...@bellsouth.net> wrote in message

>
> news:dK0Ql.43781$19.2...@bignews2.bellsouth.net...
>
> > 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.

[Dan D]

"Wayne Paul" <wa...@soaridaho.com> wrote in message news:utOdnQQ2w8-bTY3X...@supernews.com...

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