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AOA in the RV-12

todehnal

Well Known Member
I know that the Dynon is capable of displaying the "Angle of Attack" indicator. Why in the world would you not use it? Oh well. That's just one more reason that I want to build mine as an EAB.

Anyone else want AOA?

Tom
 
AOA and wing removal

I don't think that hooking up a couple of pitot lines would complicate the wing removal very much, or for that matter, a few extra wires. The O2 industry has some pretty nice quick connectors that should solve small tubing connection issues nicely. Also, in my case, daily removal of the wings is not a consideration.

Tom
 
Good luck with that.

I can tell you that those connectors do cause a little scoring on the tubing. repeated use on and off over lots of cycles will cause definate leaks.
 
I know that the Dynon is capable of displaying the "Angle of Attack" indicator. Why in the world would you not use it? Oh well. That's just one more reason that I want to build mine as an EAB.

Anyone else want AOA?

Tom

why could you not have the AOA sensor through the prop shaft and spinner I am sure there is enough room for two tubes, does it have to be on the wing??

Tony
 
why could you not have the AOA sensor through the prop shaft and spinner I am sure there is enough room for two tubes, does it have to be on the wing??

Tony

Odds are the AOA of the wing is not the same as the AOA of the spinner.
 
AOA - RV-12

I agree, the AOA would be useful and not a lot of added trouble to hook up. The connectors (of which ever type) could be replaced as they wear out - not a factor in my mind. How about it, Van's?:cool:
 
I believe one of the Trutrak autopilots (i.e with the artificial horizon indicator) has a slow warning alarm feature that would act like AOA.
 
FlightDEK D180 AOA

It looks like the Dynon FlightDEK D180 is going to be installed in the RV-12. The D180 has the capability to display Angle of Attack using a single combination Pitot - AOA probe that is 3/4 inch in diameter according to the drawing on Dynon's website. http://www.dynonavionics.com/docs/D180_Feature_AOA.html Does anyone know if Van's will be supplying that probe? If not, is it feasible to install it in place of the pitot tube in the spinner? (Assuming EAB or previously certificated E-LSA).
Joe
 
Remember that the Van's RV-12 pitot tube has a "custom" bevel on it to make it work properly. That would need to be engineered on any replacement.

--Bill
 
AOA probe bevel

If Van's pitot tube has a bevel, then maybe it is the Dynon combination airspeed and AOA probe that has one straight port and one angled port.
Joe
 
It's just a tube. Here are a couple of Jerry's Sun 'n Fun pictures:

100_5071.jpg


100_5420.jpg


--Bill
 
Homemade AOA probe for Dynon

I installed a homemade AOA probe on my RV-12 wing and connected it to the Dynon D-180. It works great! Total cost is about $10.
Parts list:
2 sports ball inflating needles
1 plastic plug with 1/8" NPT threads
1/16" I.D. 1/8" O.D. Tygon tubing available here:
http://www.usplastic.com/catalog/search.aspx?search=57102&page=1
See pictures for location of hole to be drilled in leading edge of wing. Put a dab of 5-Minute epoxy glue on the needle, and stuck it into the hole from the outside of the wing. A piece of tape held the needle in place until the glue set (24 hours). The hole should be drilled in the same rib bay that is accessible through the stall vane access cover. The Tygon tubing is a tight fit over the inflating needle. No clamp is necessary. The plastic plug is used to make a bushing to adapt the inflating needle to the AOA port on the back of the Dynon D-180. After cutting the square head off from the plastic plug, ream out the hole in the plug to 1/4". Put the inflating needle in a vise, threaded end up. Use wood to protect the needle from the vise jaws. Briefly heat the needle with a torch. Push and turn the plastic plug down onto the needle threads. Too much heat will damage the needle or plastic. The object is for the needle threads to melt their way into the plastic plug. A tap could be used instead of heat, but the taps are an odd size, difficult to find, and expensive.
http://www.tapsndies.com/catalog/item/6890755/6851684.htm
I routed the Tygon tube along the inside of the fuselage instead of through the center tunnel.
Another needle (with the threads cut off) can be used as a coupling at the wing root if desired.
After calibrating the AOA per Dynon D-180 installation manual, the AOA indication appeared on the screen and I began using it. Even though I have never used AOA before, I found the display easier to interpret than airspeed numbers. On that very first flight using AOA, I was able to land on a very short private strip without floating off the end of the runway.
Joe Gores
Advantages of AOA:
http://www.oshkosh365.org/saarchive/eaa_articles/2001_04_20.pdf
IMG_0725.JPG

AOA.jpg

IMG_0721a.JPG

IMG_0705a.JPG

IMG_0704.JPG

IMG_0703a.JPG
 
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I took the easy way out Joe, since I had to relocate my pitot anyway because of the Honda engine, I found Dynon sells a pitot/AOA fixture. I found a gal wanting to sell a brand new one over in the classified section and it became mine.
I still have to screw it on the wing and run some tubing with disconnects for the wing junction. I never had one either, but since it was already on the Dynon display, what the heck! I have been reading for years how great they are.
 
how much of the tubing does it take to make the run from the wing to the D180? thanks Harold Irvine
Harold,
I did not measure the tubing. A rough estimate is 15 feet. Tygon does not cost much. I would buy 20 feet.
Joe Gores
 
Setting up the AOA alarm

I installed a fuel pump switch so that it is not necessary to pull the fuse anymore when I want to play with the Dynon. Not wanting to listen to the fan noise while setting up the AOA alarm on the Dynon, I donned my Bilsom Thunder T3 ear muffs.
I entered the EFIS > SETUP > AOAALM menu and set the alarm to go off at the top of yellow chevron. There is a test button to see what it sounds like. I pushed it but nothing. Those Dynon menus can be confusing. Maybe I did something wrong. Then I noticed that the intercom was on isolate. I switched it to ICS. Still nothing. So then I turned on the com radio and pulled the squelch knob out. Still nothing. Hmm, what is wrong with the sound in my airplane? Well duh, how could I expect to hear anything while wearing my Bilsom Thunder T3 ear muffs? :D I took them off and put on my headset and pushed the test button again. A woman's voice said, "STALL", and there was a steady lower-pitched alarm tone.
Joe Gores
 
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Installed the Joe Gore's AOA deal last weekend, and calibrated it today. A very easy installation and works like a charm. Thanks Joe! I used the volleyball inflating tubes and 1/8" Tygon tubing. The only change I made was to use slip fittings as offered by Mcmaster Carr to make the tubing connections. A coupling at the wing and a 1'8" npt connector at the Dynon connection. THe 1/8" tubing can be pulled thru the 1/4 bushings installed in the wing ribs earlier using the string we all left there when building the wing. The calibration was interesting as you really have to be aggressive to get the stalls w/i 45 seconds. I had to do that with a couple restarts. I strongly recommend that whoever follows thru on this take a helper along on the calibration as it gets busy flying aggressive (power on ) stalls.
I did not set up an alarm on the Dynon as my stall warning provided with the 12 was perfect with each stall. I saw no need to have more than one horn sounding off. While I tried only a few stalls after calibration I can clearly see where the AOA feature will allow me to accurately get my across the numbers of 50 kts as well as providing a picture view of where I am relative to a stall in any flight mode. I heartily recommend that all 12 drivers take advantage of this feature which is provided by the Dynon 180.
Thanks again Joe.
Dick Seiders
 
Dick,
I'm pleased to read about your success with the AOA. I suggest that you enable the alarm on the AOA and give it a try. A beautiful woman says, "STALL".
It is hard to beat the price of the probe, about one percent of the cost of the commercial model. And it does not stick out past the leading edge of the wing where it could be damaged.
Here is a link to the Push-to-Connect fitting that Dick used:
http://www.mcmaster.com/#push-to-connect-tube-fittings/=etnqlc Part number: 51025k171. They also sell bulkhead fittings for a wing to fuselage coupling. Or you can make your own with another inflating needle.
The hardest part of the installation is routing the tubing. Dick and I cheated by going through the cockpit along the left side. That 1/8" tubing can fit through small holes.
While reading Dick's post, I again noticed Don's remark above. I had intended to post a smart comeback but forgot. Maybe he is right. :D
Joe Gores
 
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Joe - I am VERY interested because I will eventually be operating off a short grass strip. Is it correct that the wing sensor must protrude as opposed to using a standard static port like this? http://www.aircraftspruce.com/catalog/inpages/staticports2.php How did you get that very even gray glue bead? And did you just route the tubing in the wing through the large lightening holes or did you pull it through the bushings with the wires?
The unheated dynon probe is $200 and requires a $125 mounting bracket. The description of the Dynon probe says that the AOA port is "especially sensitive to AOA" but it looks like just a hole on a polished ~30 degree surface which is why I was wondering about using a static port. http://www.dynonavionics.com/images/AOA_new_unheated.jpg
 
Bill,
I do not know if the probe needs to protrude or not. The way that I did it works. A flush port may or may not work. If you install the 15160 static port and it does not work out, there will be a 1/4" hole in the wing. You could try using a rivet like those installed on each side of the fuselage for the static system. The advantage of the inflating needle is its perfect size for connecting the 1/8" Tygon tubing. Another option is to cut the threads off from the needle so that it looks like a nail. There would not be much sticking out. But who knows if a flush probe will work? It is worth a try. You could always replace it. Nobody notices my AOA probe because it is slightly under the leading edge of the wing. When I want to show it off, I have to point out its location. A protruding probe is less likely to be filled with paint or wax.
As for the glue bead, I waited for the glue to thicken before applying so that it would not run. I spun the inflating needle in the hole to get a uniform glue bead. If I were to do it again, I would use a much smaller amount (one drop) of epoxy glue so that it would not show.
During construction I had installed extra plastic bushings in the wing ribs for future projects like this. The tubing can be pulled along with wires and share the same bushings if there is room. That should not be a problem unless the wires need more room for ventilation. I doubt that the wires get that warm though.
Joe Gores
 
One nice thing about your choice is that - with that small protruding portion - with a close-fitting rubber tube you can attach a bug-eliminating remove-before-flight streamer.
 
Stall speed

Dick, about a year ago in another thread you made the comment that the flaps down stall speed in your RV-12 was in the 30's. You didn't get any feedback so you dropped the subject. I am curious if you have further thoughts on the subject in light of the installation (no pun intended) of your AOA indicator.
 
Alan, I answered your question on a PM as you requested yesterday. Since it's on the forum now as well I will say essentially the same thing. Probably mis-read the IAS while trying to keep the ball centered on the power on stall. Additionally I did a few months later discover a static leak on the left side which also may have influenced the numbers. As stated in the PM I never flew the airplane with the low stall numbers as I preferred to use Van's published stall figures. Regarding the AOA the AOA indicator and the airspeed numbers are totally in sync. I think I could probably land it on a carrier now. Do it (AOA) if you have a 12, and you will appreciate it I'm certain.
Dick Seiders
 
My apologies, Dick. I assumed the response would be coming in the form of an email. Now I see the private messages in the upper right corner. When you say the AOA and the IAS are totally in sync can you clarify what you mean? One of the advantages of the AOA indicator is that if the plane is heavier or lighter or in a bank, it will let you know how close you are to a stall even though the airspeeds may be quite different. When you talk of 'landing on an aircraft carrier' are you suggesting your approach speed is lower now? I am reading 'Stick and Rudder' and I can see that the author heavily favors some kind of AOA indicator.
 
No apologies necessary Alan. You are correct in your description of the function of the AOA. My comment of being in sync refers to the AOA indicator position and airspeed on an approach stall. I was informed by a former (USMC) F4 back seater that the U.S. Navy likes the AOA so much that it is employed in all carrier landings. Yes, my carrier comment here is in reference to the positive low approach speed control the AOA provides.
Dick Seiders
 
To me a big benefit of the AOA indicator is lower touchdown speeds and less likelihood of bending the nose gear. I still wonder if it would be possible to run a split tube through the spinner. From your knowledge of how it works do you think this could be made to work, Dick?
 
I would think it very possible. If you pull up the Dynon AOA/Pitot that I bought and simply copy the nose of it, you should be able to adapt it to the spinner hole. This photo is upside down actually, the hole in the slanted portion is the AOA, the big hole is the airspeed. I am not sure just how it works, but one would assume that the airflow difference over the slanted portion makes the AOA come alive. Certainly would be worth trying.
There are no real instructions for installation, but the affair would appear to be parallel to the bottom of the wing.

2eulbvb.jpg
[/IMG]
 
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Can't say Alan, one tube is pointing 30 degrees down and one horizontal. That is a tall order in one opening. I do know what does work, and that is Joe Gores method described here earlier.
Dick Seiders
 
Wait a Minute Here:

I got to looking over my fancy AOA/PITOT from Dynon, and there is more than what it appears at first look. As you can see in this photo, there are two holes at the rear of the tube, which share the galley with the hole on the slanted front. Just copying the front for a thru the spinner sensor would probably not work.
6gct40.jpg
[/IMG]
 
Don, I believe those two holes are for water draining, and don't affect the pitot function unless of course you are flying in rain. I think it would be a challenge to get that setup onto the 12 spinner pitot, but I've been wrong before. One thing for certain is you would'nt want that pc of metal braking loose and going into the prop. Also doesn't that cost about 200 bucks?
Dick Seiders
 
ELSA Retrofit

Those holes might be for drainage.

Joe's solution is very elegant for other reasons, particularly if you are approaching this as a retrofit post-ELSA (as I am) as opposed to initially installing it as EAB. (For EAB just hang in on the wing and get a couple of tubing quick-connects for the wing root.)

For E-LSA retrofit:

a> There are two tubes that must be run from the Dynon back to the tail tube into the ADHARS for AOA. Running another tube from the nose would be more difficult than bringing it in from the wing.

b> The existing pitot's mounting bracket on the rear of the prop gearbox would no longer work and something else would have to be fabricated. The existing Dynon tube is not long enough to be prop-mounted and it would have to be modified. It might also be too large in diameter - remember, it is surrounding two separate air tubes.

c> Adding the whole pitot and mounting bracket on the wing (with a backing plate) will be much more involved that Joe's solution - which can be accomplished through the stall switch inspection plate. (I had been considering this.) Particularly if the wing is already painted.

Note - I would be sure that - in Joes solution - the tubing continues "up" for a bit inside the wing (secure the tube to the underside of the top wing surface) to make it self-draining.

Adding AOA for less than $50? Priceless!
 
...one tube is pointing 30 degrees down and one horizontal....

Dick, I think you must mean that the AOA probe is 60 degrees down (30 degrees up). At least that is the way it appears in the photo above.
 
To be a little more clear...

...one tube is pointing 30 degrees down and one horizontal....
Dick, I think you must mean that the AOA probe is 60 degrees down (30 degrees up). At least that is the way it appears in the photo above.

The AOA tube is 60? down from horizontal and 30? forward from vertical. Or another way, 60? down from the pitot tube.
 
Yeah, 200 bucks and then you get to spend some more on a mount for the darned thing. I got a bargain over in the classified section on mine, since I had to have something and Joe had not shared his cheapskate idea with me:mad:
If one goes here, you can get a nice primer on how the darned thing actually works, was educational to me: http://www.dynonavionics.com/docs/D180_Feature_AOA.html

Don, I believe those two holes are for water draining, and don't affect the pitot function unless of course you are flying in rain. I think it would be a challenge to get that setup onto the 12 spinner pitot, but I've been wrong before. One thing for certain is you would'nt want that pc of metal braking loose and going into the prop. Also doesn't that cost about 200 bucks?
Dick Seiders
 
Sure looks like 60 deg. down. Dang, I thought I remembered my geometry, but this is not the first time I jangled my angle.
Dick Seiders
 
Here is what I bought. I buy online 'cause I live way out in the boonies without good hardware stores nearby. So these part numbers might be of use thos those in a similar situation.

ONE inflation needle (in a pack of 2 at the hardware store)

All of these are the part numbers from mcmaster.com:
1 each 5047K12 Moisture-Resistant Acetal Sngl-Barb Fitting Adapter for 1/16" Tube ID X 1/8" NPT Male Pipe $1.10 each
This is the fitting that adapts from the tube to the 1/8 NPT female fitting on the Skyview ADHRS. It was available in a single quantity. In Joe's original post, he made this by melting another inflation needle into a plug.

1 pack 51525K211 Plastic Quick-Turn (Luer Lock) Coupling Nylon, Female X Barb, for 1/16" Tube ID, packs of 10 $3.41 per pack
1 pack 51525K121 Plastic Quick-Turn (Luer Lock) Coupling Nylon, Male X Barb, for 1/16" Tube ID, packs of 10 today $3.83 per pack
This is the disconnect fitting that I will use at the wing root. It was not available in a single quantity so I will have 9 left over...
I'll pull the wing out a few inches, then disconnect the fitting.

25 ft. 5006K51 Abrasion-Resistant Clear PVC Tubing 1/16" ID, 1/8" OD, 1/32" Wall Thickness, $0.15 per foot.
Total of all from mcmaster.com $12.00 plus shipping
 
Dick it IS 60 degrees down. You had said 30 degrees down earlier and I corrected it to avoid confusion for others. I figured you meant 60 degrees. :)

Technically I am not sure that it matters what the angle it is as long as it is significantly larger than the maximum angle of attack.

It looks to me like whatever the angle is you can calibrate it. Does anybody know?
 
You're probably right.

Technically I am not sure that it matters what the angle it is as long as it is significantly larger than the maximum angle of attack.
It looks to me like whatever the angle is you can calibrate it. Does anybody know?

I just tried to get mine close to the 60? that I found on the Dynon unit because I wasn't sure how much calibration range they have.
 
I think that we all agree on how the AOA probe should be orientated. The number of degrees depends on what is used as a reference. It is a matter of semantics.
The Dynon has no idea what the angle is. It measures pressure. In cruise attitude, the pressure is low. As the angle of attack increases, the pressure in the probe increases because the relative air strikes the probe more directly. The maximum pressure is reached just before a stall. During the calibration procedure, the Dynon records the minimum and maximum pressure at the AOA port. After calibration, the Dynon linearly interpolates the display between these points and displays AOA pressure as bars and chevrons, green bars at the bottom and yellow and red chevrons near the top. Starting at the bottom, the bars and chevrons disappear as the pressure goes up. The pilot can choose in the setup menu at what point the alarm goes off, if at all.
The fittings that Bill and Dick found will make installation easier.
Joe Gores
 
The Dynon has no idea what the angle is. It measures pressure.

True, But, the angle is what determines the pressure of the AOA tube.
The greater the delta angle of the tubes, the greater the delta of the pressure.
 
True, But, the angle is what determines the pressure of the AOA tube.
I agree with you.
The greater the delta angle of the tubes, the greater the delta of the pressure.
It would seem that the AOA is determined by the pressure differential between the airspeed port and AOA port because they are located in the same Dynon probe. But that might not be the case. I had assumed that the Dynon compares the pressure between the static port and the AOA port. But I have no knowledge of the internal architecture of the Dynon on which to base that assumption. Regardless of the theory, a working AOA display is what counts.
Joe Gores
 
I am sure you are correct about the two pressures being compared, Joe. I also think that 60 degrees is good from theoretical considerations because when you are in full stall you are still about 30 degrees away from 0. As you get close to 0 degrees to the air stream, the resolution approaches zero. Between 60 and 30 pressure changes are fairly linear and large enough to be measurable.
 
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