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gilles.thesee(at)free.fr
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 Posted: Thu Apr 12, 2018 7:16 pm Post subject: Diy AOA, anyone ? |
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Hi all,
One of my building buddies just challenged me concerning the following
Pitot angle of attack (AOA) device
https://www.thingiverse.com/thing:1121786
Of course 3D printing the device is the easiest part. But does anyone
here happen to have implemented, programmed, etc. an AOA indicator, and
with what success ?
BTW, some years ago I had the opportunity to make a study for such a
device based on differential pressure between upper and lower wing
surface. At the time the study involved a University wind tunnel,
hotwire profiles, several students, but nowadays my approach needs to be
much much "lower tech" as I no longer have access to such facilities.
Thanks for your inputs,
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
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andymeyer
Joined: 31 Mar 2015
Posts: 54
Location: SW MI
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BARRY CHECK 6
Joined: 15 Mar 2011
Posts: 738
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| Posted: Fri Apr 13, 2018 5:15 am Post subject: Diy AOA, anyone ? |
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Hi Andy:
I worked on an RV6A which had this AOA unit:
http://www.aircraftspruce.com/catalog/inpages/aoasportsystemaluminum.php?clickkey=5477
It required and used sensing holes on the top and bottom of the wing. Maybe... If you give them a call... NOT ACS! They maybe able to answer the question.
Barry
On Fri, Apr 13, 2018 at 8:34 AM, andymeyer <meyerkc135(at)gmail.com (meyerkc135(at)gmail.com)> wrote:
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echristley(at)att.net
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| Posted: Fri Apr 13, 2018 5:28 am Post subject: Diy AOA, anyone ? |
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I cut the corner off a piece of 1/2" plate of aluminum. With it oriented so the 90 degree angle is at the top right, I drilled a 1/4" hole halfway through from the top, and a 1/16" hole from the left that intersected with the 1/4" hole. I got the "homebuilder's pitot/static" from ACS. It's the one with two pieces of 1/4" tube tack welded into a base. I drilled a 1/4" hole through the base behind the others, then ran a 8" or so length of 1/4" tube through it and into the top of the triangle. Situated it so that the triangle touched the bottom of the previous tubes, then buried the assembly in a peanut butter thick mix of micro. Let it set, sanded it to an "airfoilish" shape, and wrapped it in a 9oz layer of glass.
Works fine with my Dynon-100 AoA.
On Thursday, April 12, 2018 11:17 PM, GTH <gilles.thesee(at)free.fr> wrote:
--> AeroElectric-List message posted by: GTH <gilles.thesee(at)free.fr (gilles.thesee(at)free.fr)>
Hi all,
One of my building buddies just challenged me concerning the following
Pitot angle of attack (AOA) device
https://www.thingiverse.com/thing:1121786
Of course 3D printing the device is the easiest part. But does anyone
here happen to have implemented, programmed, etc. an AOA indicator, and
with what success ?
BTW, some years ago I had the opportunity to make a study for such a
device based on differential pressure between upper and lower wing
surface. At the time the study involved a University wind tunnel,
hotwire profiles, several students, but nowadays my approach needs to be
much much "lower tech" as I no longer have access to such facilities.
Thanks for your inputs,
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.= the many List utilities such as List Un/Subscription,
http://www.matronics.com/Navigator?AeroElectric-List
http://forums.matronics.com
http://w -Matt Dralle, List Admin.
t="_blank">http://www.matronics.com/contribution
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user9253
Joined: 28 Mar 2008
Posts: 1927
Location: Riley TWP Michigan
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| Posted: Fri Apr 13, 2018 6:10 am Post subject: Re: Diy AOA, anyone ? |
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An AOA probe can be made using only a single pop rivet with the mandrel removed. Connect the rivet to the AOA sensor with Tygon tubing. The sensor will compare the pressure differential between the pitot tube and the AOA port (pop rivet). Vans Aircraft uses this rivet probe in the latest version (iS) of their RV-12. The picture shows where I located the AOA rivet port in my wing. I drilled the rivet hole at the point where the 30 degree line is tangent to the wing. Although Van's tested different locations and determined that the optimum location is slightly farther down and and aft. Exactly where, I do not know.
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Joe Gores |
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BARRY CHECK 6
Joined: 15 Mar 2011
Posts: 738
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| Posted: Fri Apr 13, 2018 6:24 am Post subject: Diy AOA, anyone ? |
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Joe:
Guessing: But, probably 3 hole diameters behind the high point (Max profile) of the wings profile. Three diameters is a negative pressure point in open end resonance.
Barry
| Quote: | Although Van's tested different locations and determined that the optimum location is slightly farther down and and aft. Exactly where, I do not know.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=479309#479309
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alec(at)alecmyers.com
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| Posted: Fri Apr 13, 2018 6:45 am Post subject: Diy AOA, anyone ? |
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How is “optimum” determined?
You would have to calibrate for different airspeed and AoAs and creative some kind of algorithm or lookup table, regardless of location, no?
On Apr 13, 2018, at 10:23, FLYaDIVE <flyadive(at)gmail.com (flyadive(at)gmail.com)> wrote:
Joe:
Guessing: But, probably 3 hole diameters behind the high point (Max profile) of the wings profile. Three diameters is a negative pressure point in open end resonance.
Barry
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bob.verwey(at)gmail.com
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| Posted: Fri Apr 13, 2018 7:34 am Post subject: Diy AOA, anyone ? |
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Hey Joe,
Thanks for providing a KISS solution for a change!
No disrespect intended to any lister, but sometimes it seems (to this neophyte anyway) that the more complicated the solution, the better it is deemed?
Best...Bob Verwey
082 331 2727
[img]https://docs.google.com/uc?export=download&id=0B5d7rgAInTuTUUZsUjY4QmJsdVU&revid=0B5d7rgAInTuTdDJDaXRFZVh3b3lMa3FWL0s3MFdzc01YRlNvPQ[/img]
On 13 April 2018 at 16:10, user9253 <fransew(at)gmail.com (fransew(at)gmail.com)> wrote:
| Quote: | --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>
An AOA probe can be made using only a single pop rivet with the mandrel removed. Connect the rivet to the AOA sensor with Tygon tubing. The sensor will compare the pressure differential between the pitot tube and the AOA port (pop rivet). Vans Aircraft uses this rivet probe in the latest version (iS) of their RV-12. The picture shows where I located the AOA rivet port in my wing. I drilled the rivet hole at the point where the 30 degree line is tangent to the wing. Although Van's tested different locations and determined that the optimum location is slightly farther down and and aft. Exactly where, I do not know.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=479309#479309
Attachments:
http://forums.matronics.com//files/angle_167.gif
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errer" target="_blank">http://wiki.matronics.com
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====================================
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user9253
Joined: 28 Mar 2008
Posts: 1927
Location: Riley TWP Michigan
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| Posted: Fri Apr 13, 2018 11:18 am Post subject: Re: Diy AOA, anyone ? |
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Here is a link to the VansAirforce thread about AOA in the RV-12.
http://www.vansairforce.com/community/showthread.php?t=34040
I do not know where is the optimum point to measure air pressure. All I know is that I looked at the angle on Dynon's AOA probe and thought that 30 degrees looked about right. I drilled a hole and hooked up some tubing and it worked. Several other RV-12 builders followed my lead and they are all happy. When Van's came out with a new and improved version of the RV-12, they used my idea. But they did flight testing to determine the best location for the AOA port.
The AOA needs to be calibrated during flight by performing a series of stalls, with and without flaps. AOA is displayed on the EFIS screen. There is also an audio indication that starts out as tone pulses. As stall approaches, the tone pulses get closer and closer together until at stall, there is one solid tone.
A stall can occur at any airspeed depending on wing loading. A heavily load aircraft in a steep turn will stall at a much higher airspeed then when the plane is lightly loaded and flying straight. That is why many planes have stalled and crashed while in a traffic pattern. The pilot keeps the airspeed where he normally does, not taking into consideration the higher wing loading in a steep turn. A wing will always stall at the same AOA, regardless of wing loading. Now that I have AOA, I use that instead of airspeed. The FAA should mandate AOA and eliminate the requirement for airspeed indicators.
OK, I am ready to be flamed. LOL
For aircraft without an EFIS, a Dwyer Minihelic II 2-5002 Differential Pressure Gauge, Range 0-2.0"WC might work for a display, although I have never tried it. I would also add an audio pulsing tone.
To andymeyer, I think the pressure differential for AOA is about 2" of water. 0.57psi converts to 15.7 inches of water.
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alec(at)alecmyers.com
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| Posted: Fri Apr 13, 2018 1:19 pm Post subject: Diy AOA, anyone ? |
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i use the airspeed indicator as an AoA indicator - you just have to mentally adjust the scale for weight and load factor. A bit like those airspeed indicators that have a sliding scale for true airspeed. My airspeed indicator has a sliding scale (in my head) for AoA.
On Apr 13, 2018, at 15:18, user9253 <fransew(at)gmail.com> wrote:
Here is a link to the VansAirforce thread about AOA in the RV-12.
http://www.vansairforce.com/community/showthread.php?t=34040
I do not know where is the optimum point to measure air pressure. All I know is that I looked at the angle on Dynon's AOA probe and thought that 30 degrees looked about right. I drilled a hole and hooked up some tubing and it worked. Several other RV-12 builders followed my lead and they are all happy. When Van's came out with a new and improved version of the RV-12, they used my idea. But they did flight testing to determine the best location for the AOA port.
The AOA needs to be calibrated during flight by performing a series of stalls, with and without flaps. AOA is displayed on the EFIS screen. There is also an audio indication that starts out as tone pulses. As stall approaches, the tone pulses get closer and closer together until at stall, there is one solid tone.
A stall can occur at any airspeed depending on wing loading. A heavily load aircraft in a steep turn will stall at a much higher airspeed then when the plane is lightly loaded and flying straight. That is why many planes have stalled and crashed while in a traffic pattern. The pilot keeps the airspeed where he normally does, not taking into consideration the higher wing loading in a steep turn. A wing will always stall at the same AOA, regardless of wing loading. Now that I have AOA, I use that instead of airspeed. The FAA should mandate AOA and eliminate the requirement for airspeed indicators.
OK, I am ready to be flamed. LOL
For aircraft without an EFIS, a Dwyer Minihelic II 2-5002 Differential Pressure Gauge, Range 0-2.0"WC might work for a display, although I have never tried it. I would also add an audio pulsing tone.
To andymeyer, I think the pressure differential for AOA is about 2" of water. 0.57psi converts to 15.7 inches of water.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=479319#479319
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rickofudall
Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA
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| Posted: Fri Apr 13, 2018 3:02 pm Post subject: Diy AOA, anyone ? |
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Here's an article one of the members of EAA Chapter 88 wrote for our newsletter a few years ago. Seems to be the same idea y'all are talking about.
Rick Girard
On Fri, Apr 13, 2018 at 4:18 PM, Alec Myers <alec(at)alecmyers.com (alec(at)alecmyers.com)> wrote:
| Quote: | --> AeroElectric-List message posted by: Alec Myers <alec(at)alecmyers.com (alec(at)alecmyers.com)>
i use the airspeed indicator as an AoA indicator - you just have to mentally adjust the scale for weight and load factor. A bit like those airspeed indicators that have a sliding scale for true airspeed. My airspeed indicator has a sliding scale (in my head) for AoA.
On Apr 13, 2018, at 15:18, user9253 <fransew(at)gmail.com (fransew(at)gmail.com)> wrote:
--> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>
Here is a link to the VansAirforce thread about AOA in the RV-12.
http://www.vansairforce.com/community/showthread.php?t=34040
I do not know where is the optimum point to measure air pressure. All I know is that I looked at the angle on Dynon's AOA probe and thought that 30 degrees looked about right. I drilled a hole and hooked up some tubing and it worked. Several other RV-12 builders followed my lead and they are all happy. When Van's came out with a new and improved version of the RV-12, they used my idea. But they did flight testing to determine the best location for the AOA port.
The AOA needs to be calibrated during flight by performing a series of stalls, with and without flaps. AOA is displayed on the EFIS screen. There is also an audio indication that starts out as tone pulses. As stall approaches, the tone pulses get closer and closer together until at stall, there is one solid tone.
A stall can occur at any airspeed depending on wing loading. A heavily load aircraft in a steep turn will stall at a much higher airspeed then when the plane is lightly loaded and flying straight. That is why many planes have stalled and crashed while in a traffic pattern. The pilot keeps the airspeed where he normally does, not taking into consideration the higher wing loading in a steep turn. A wing will always stall at the same AOA, regardless of wing loading. Now that I have AOA, I use that instead of airspeed. The FAA should mandate AOA and eliminate the requirement for airspeed indicators.
OK, I am ready to be flamed. LOL
For aircraft without an EFIS, a Dwyer Minihelic II 2-5002 Differential Pressure Gauge, Range 0-2.0"WC might work for a display, although I have never tried it. I would also add an audio pulsing tone.
To andymeyer, I think the pressure differential for AOA is about 2" of water. 0.57psi converts to 15.7 inches of water.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=479319#479319
====================================
-
Electric-List" rel="noreferrer" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List
====================================
FORUMS -
eferrer" target="_blank">http://forums.matronics.com
====================================
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errer" target="_blank">http://wiki.matronics.com
====================================
b Site -
-Matt Dralle, List Admin.
rel="noreferrer" target="_blank">http://www.matronics.com/contribution
====================================
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nuckolls.bob(at)aeroelect
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| Posted: Sun Apr 15, 2018 3:01 pm Post subject: Diy AOA, anyone ? |
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At 08:52 AM 4/12/2018, you wrote:
| Quote: | --> AeroElectric-List message posted by: GTH <gilles.thesee(at)free.fr>
Hi all,
One of my building buddies just challenged me concerning the following Pitot angle of attack (AOA) device
https://www.thingiverse.com/thing:1121786
Of course 3D printing the device is the easiest part. But does anyone here happen to have implemented, programmed, etc. an AOA indicator, and with what success ?
BTW, some years ago I had the opportunity to make a study for such a device based on differential pressure between upper and lower wing surface. At the time the study involved a University wind tunnel, hotwire profiles, several students, but nowadays my approach needs to be much much "lower tech" as I no longer have access to such facilities.
Thanks for your inputs, |
We had some discussions here on the List about
various AOA sensor/display options about 15 years
ago. During and since that time I'd collected some
articles on the topic which I posted here
https://goo.gl/5XdU1y
One of the articles cloned a sensor mast that
was popular with Piper as I recall. Don't recall
the manufacturer off hand.
[img]cid:7.1.0.9.0.20180415175131.0642aaa8(at)aeroelectric.com.0[/img]
This probe was mounted under a wing on an inspection
plate. Pretty easy to build. I recall that I offered to carve
one out for a builder . . . but he never took me up on it.
Something I've found quite useful before launching
on any new development effort is to explore history
of the practice. Patents are a useful place to lay foundations
for refining the next generation . . .
Bob . . .
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gilles.thesee(at)free.fr
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| Posted: Tue Apr 17, 2018 10:04 am Post subject: Diy AOA, anyone ? |
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Le 16/04/2018 01:01, Robert L. Nuckolls, III a crit:
| Quote: |
We had some discussions here on the List about
various AOA sensor/display options about 15 years
ago. During and since that time I'd collected some
articles on the topic which I posted here
https://goo.gl/5XdU1y
One of the articles cloned a sensor mast that
was popular with Piper as I recall. Don't recall
the manufacturer off hand.
|
Hi Bob and all,
A big thank you for your inputs, docs etc. !
We now have to do our homework. Nevertheless the project is still at the
initial build stage, and we are still in the process of (slowly)
reducing drag on our present 4-seater, so it may be some time til we are
ready for the AOA flight tests.
Thank you everyone !
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
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