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AOA in the RV-12

Very interesting stuff. All I know is it works. I flew several landings this weekend at 50kts over the numbers with confidence because I was watching the AOA. I also ran a couple approach stalls at altitude and found that with the airplane clean it mushed at 40kts. With 10 degrees (1/2) flaps it mushed at 33 kts, Any other results like that out there?
Dick Seiders
 
RV-12 AOA

I hate to sound dumb, but I'm still a little confused. You guys are all talking about mounting the AOA tube at 60 Degrees. When I look at Joe's pictures the protractor shows 30 degrees. What do I do? If I drill the hole as he showed will that be the 60 0r 30 degrees?

I like the idea, have all the parts, but I don't want to install it in the wrong place.
 
Looks like 30 degrees DOWN from a line horizontally parallel to the ground, or 60 degrees UP from a line vertical to the ground. Looking at the probe, the slant face is about 30 degrees DOWN from a line measured through the center of the probe.
 
Johns4689, use the layout for the hole location as provided by Joe Gore's post and the angle will take care of itself. It's approximately 30 degrees off the chord and sixty degrees off vertical. Do it as Joe shows and it will be fine.
Dick Seiders
 
I agree with Dick. For the RV-12, use the drawing that I made to locate the hole. It is not necessary to measure any angles. Find the two rivets in the drawing. Hold a straight edge against the bottom flange of those two rivets and draw a horizontal line. Drill a hole on that line. I located the hole far enough away from the stall vane so that the AOA probe would not be in the way for working on the stall vane.
AOA.jpg

For other aircraft, it will be necessary to measure the angle.
Joe Gores
Angle.gif
 
dick seiders said:
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
Click to expand...

Yes, you could. Carrier runways are about 1000 feet and they can cruse into the wind at about 30kts........... So you should use about 100 ft of deck to stop your 15kt touchdown speed..................:eek:
 
Needle Modification

Hey Joe,

Thanks, so much, for sharing your method of getting AOA on a budget. It looks wonderful!! My guess is that you cut off the tips on the needles, to provide a straight shot at the air pressure, instead of trying to use the holes on the sides of the needle, as used for filling sports equipment. Please verify that for me. I plan to start my AOA installation soon.
Thanks, Tom
 
My guess is that you cut off the tips on the needles,
Click to expand...
Tom,
No I did not cut the inflating needles. The ones that I bought already had holes on the end (and on the side). I thought about cutting them for weight savings. But the factory ends are rounded which makes it easier to slide the tubing on.
Joe Gores
 
Seems the UK is a step too far for AOA shipping!

Hi Guys,

Thanks to Bill for posting the bill of materials for the AOA hardware. I ordered this stuff from McMaster but they won't accept my order because I'm in the UK. Any good samariton willing to order this stuff and subsequently mail it to me? Obviously happy to cover your costs...

PM [email protected]

Cheers...Keith Boardman



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
 
I installed the AOA exactly as specified early in this thread - inflation needle, 1/8 inch tubing, disconnect at the wing, etc. I used some silicone to anchor it in the hole (reached in via the stall switch cover plate and smeared some on the inside as well.) Calibrated it in flight. WORKS GREAT!!! Besides the visual element on the screen you begin to get a slow beeping sound as you go below about 55 kts, that gets faster as you continue to increase the AOA (i.e. get any slower with power off). Great and easy mod!
 
Mich48041 said:
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
Click to expand...

Just wondering if anyone has tried using the static port? This would make a nice, neat installation if it works.
 
Refreshing previous post.

Has anybody tried using a rivet for an AOA probe? The idea is very tempting.
 
Dave12 said:
Just wondering if anyone has tried using the static port? This would make a nice, neat installation if it works.
Click to expand...

Isn't static pressure vs. pitot pressure IAS? A good static port should be designed to have the same pressure at all AOAs. I believe you need a third source that provides a dynamic difference with respect to the pitot when the AOA changes.
 
I think that what Dave12 meant was to use a rivet for the AOA probe that is similar to the rivets used for the static ports. I think that using a rivet for an AOA probe is certainly worth a try.
Joe Gores
 
Well, you could always do as I did, this is the Dynon pitot/AOA installed in my 12 wing. Makes it look like a REAL airplane!
vctqfc.jpg
[/IMG]
 
Mich48041 said:
I think that what Dave12 meant was to use a rivet for the AOA probe that is similar to the rivets used for the static ports. I think that using a rivet for an AOA probe is certainly worth a try.
Joe Gores
Click to expand...

Thanks for reading my mind Joe.
 
Rivet for AOA probe

Installed the tubing for an AOA probe and used an LP4-5 rivet for the probe. Positioned it per Joe Gores' recommendation. After calibration, performed power-off stall and landing. AOA functioned very well. Leading edge is clean, rivet looks like it belongs there.
 
Hey Joe Gores. On 11/6/2011 you suggested I configure the Dynon to get the lady to say STALL along with the buzz. Today I did so as a follow up. Interestingly enough she also says STALL during takeoff roll (very briefly) and again when I am landing. It's not a problem , just a tad disconcerting while doing both T.O. and landings. I set the Dynon to top of AOA yellow as you said. Have you experienced the same? By the way how do you know she is beautiful? Thanks for feedback.
Dick Seiders
 
Dick Seiders,
No, I have not gotten a stall warning on takeoff. Maybe you climb at a slightly steeper angle than I do. Maybe we did the calibrating differently. Or maybe I don't know. You could change the alarm set point if it continues to be a problem. Anyone else have an alarm on takeoff?
By the way how do you know she is beautiful?
Click to expand...
Haven't you seen her? :D
Joe Gores
 
Actually Joe, I think my nosewheel was still on the ground altho maybe not. I will watch closely next flight.

I am still looking for the lady.
Dick Seiders
 
Configuration and interpretation

Thanks fellas, for getting the instructions (and the parts) to me for my AOA system.

I have installed it and calibrated it so now I can see the display.

How do I get the lady to call "stall"?

And what does the display exactly mean? What is the yellow sector? What is the red sector?

Cheers...Keith
 
Keith, to get the lady to say stall go to Joe Gores 10/15/2011 post on this thread.
To understand how the AOA works regarding the colored chevrons as I recall that would be explained in the calibration process in the Dynon instructions.
Dick Seiders.
 
Dynon manual excerpt

I have posted the relevant paragraphs for the Dynon installation guide. The instructions for getting the lady to speak are explicit.

There seems to be some vagueness about the display bar itself. The text below suggests you "might" get a stall just after the yellow/red boundary. What indication do folk look for when requiring to land at the lowest safe airspeed?

Cheers...Keith

Here's the text:

This calibration should result in the lowest angle of attack stall occurring just above the red/yellow boundary. If this is not the case please repeat the AOA user calibration, including flight configurations that resulted in stalls with incorrect indications. If the user calibration continues to be unsuccessful, please contact Dynon Avionics technical support.

ALARM SETUP

Enter the EFIS > SETUP > AOAALM menu and press any of the buttons beneath the AUDIO label to select the point on the AOA bar at which you wish the alarm to sound:

AUDIO: ALWAYS OFF
AUDIO: ON IN RED
AUDIO: START YLW TOP
AUDIO: START YLW MID
AUDIO: START YLW BTM

The latter three alarms (the ones that begin with START) are progressive, meaning the audio will start at the top, middle, or bottom of the yellow sction of the AoA bar.

Setting audio to ON IN RED configures an intense alarm to occur only when the AOA indicator is in the red. To reduce nuisance audible AOA alarms ? such as when taxiing, taking off and landing ? the alarm can be inhibited below a selected airspeed. While in the menu, press MINSPD to configure the minimum airspeed at which an AOA alarm can occur.Anytime airspeed is below the MINSPD value, AOA alarms will not occur; anytime it is above the MINSPD value, alarms can occur. If the AOA alarm is already sounding as airspeed falls below this threshold, it will continue to sound until the high AOA condition is resolved.
 
Interestingly enough she also says STALL during takeoff roll (very briefly) and again when I am landing. It's not a problem , just a tad disconcerting while doing both T.O. and landings
Click to expand...
Dick Seiders,
Have you set the minimum airspeed "MINSPD" for the AOA setup? Mine is set at 35 knots to prevent the AOA alarm below that speed. If MINSPD is set much higher than that, there might not be an AOA stall warning when the plane is lightly loaded.

What indication do folk look for when requiring to land at the lowest safe airspeed?
Click to expand...
Keith,
If I want to land on a short field, I keep the AOA in the yellow, but not slower than 55 knots per the Pilot Operating Manual. If the woman's voice yells "STALL", I lower the nose to shut her up. Since each of us may have installed or calibrated the AOA probe differently, it is up to the pilot to determine the safe AOA on approach.
Joe Gores
 
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More Chatty Patty warnings; Useful?

I have the stuff to install the AOA, but I am wondering whether it would be useful or distracting for me in the 12.

How are you using it? Short fields? Practicing airmanship? Carrier Ops?

Tony
 
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For me it is solely for training in anticipation of moving the plane from the airport to my short 1260 foot runway after the grass grows in. I'm practicing low speed approaches and the AOA audio is very helpful. The visual indicator is not so much helpful because it's heads up on final. The beeping gets faster the higher the AOA and so you can correlate that with a 55kt approach (or whatever speed you are using) and not have to even glance down at the airspeed. If you don't like it you can just turn it off by telling the Dynon "No AOA installed."
 
Below are links to EAA magazine articles about Angle of Attack.

Better Way to Fly - May 1998 http://www.oshkosh365.org/saarchive/eaa_articles/1998_05_06.pdf
Carrier Pilots' Secret - July 1999 http://www.oshkosh365.org/saarchive/eaa_articles/1999_07_31.pdf
Test Pilot: Angle of Attack - April 2001 http://www.oshkosh365.org/saarchive/eaa_articles/2001_04_20.pdf
Test Pilot: Angle of attack and lift/drag - May 2001 http://www.oshkosh365.org/saarchive/eaa_articles/2001_05_19.pdf
Aircraft wings will stall at various airspeeds depending on how heavily the aircraft is loaded and angle of bank. AOA is NOT affected by those factors. Thus it is safer to watch AOA instead of airspeed.
The stall warning vane switch works on the AOA principle. However it is only on or off. There is no progressive warning as the wings approach the stall AOA. That is like having an "empty switch" on the fuel tank instead of a fuel gauge.
The AOA should be a required instrument instead of airspeed. One AOA manufacturer aptly named his product, "Bacon Saver".
Joe Gores
 
AoA vs Stall Warner

"That is like having an "empty switch" on the fuel tank instead of a fuel gauge."

Slightly unfair, I believe. The empty switch is really a low-fuel switch. "You need to get gas soon". The stall warning vane is an AoA indicator that says you need to lower AoA soon.

Cheers...Keith
 
Joe, I did not set minspd. I don't recall seeing it in your post, and being a good soldier followed orders. (blindly). I will go back and set it if I can find it.
Dick Seiders
 
Reading list...

Joe,
Thanks for the links to AOA information. I need to do some reading, having never flown with an AOA indicator. Sounds worthwhile, and as Bill said it can be turned off if one wishes to.

Tony
 
For the aeronautical engineers in the crowd.

To calibrate the Dynon D-180 AOA indicator, Dynon has one perform a series of 4 stalls. Two power on (full flaps and no flaps) and two power off (full flaps and no flaps). Then the Dynon looks at the data and calibrates the AOA indicator for the stall that gives you the lowest AOA at stall.

I understand why they ask for the flaps and no flaps configuration. The maximum coefficient of lift (the lift at stall) changes due to the change in the wing.

But theoretically, would power have any effect??

As such, following the Dynon procedure, the AOA indicator would be accurate with full flaps (the normal landing configuration) and would be conservative with no flaps (as in steep turns). I may have this reversed?? I base my conclusion of the EAA articles referenced in Joe's post The articles show a higher coefficient of lift but a lower AOA with full flaps compared to the no flap case.

Looking for answers to both questions!
 
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answers

Having read the various article, I agee with you Marty.

Power should make no difference.

AoA is calibrated for full-flaps case.

Cheers...Keith
 
Power makes a difference in a Cessna where power on and power off stalls sure seam different.

Power changes the AOA in the wing root Area.

Power changes the effectiveness of elevator/stabilator.

Power changes rudder demand.

Power can change the aircraft's pitching moment.

So it might be possible that power would make a difference in the RV-12's stall characteristics but not in the AOA that the stall occurs at?

Don't really know the answer, just adding to the confusion.
 
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If my head is on right. Power changes where the relative wind is for a "power on" stall. Nothing about AOA is changed. That creates a whole new breed of stall as gravity is not acting so perpendicular to the cord line anymore.

We shouldn't confuse AOA with "deck angle".
 
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pilottangocharlie said:
Power changes where the relative wind is for a "power on" stall.
Click to expand...

I see the LIGHT! MAYBE! Just returned from our EAA chapter meeting and one of the members used an extreme example. Consider the high powered aerobatic airplane that is flying straight and level, at very high power down the flightline, hanging on its prop. He is at an extreme AOA. The prop, creating thrust is influencing the critical angle of attack. Could make an argument that the propwash is changing the direction of the relative wind, but, what about the jet team that performs the same maneuver??

BUT, I think we can conclude that power level must change the critical angle of attack for a given airfoil.
 
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By hanging on the prop an acro pilot is utilizing the vectoring of thrust to surpass the stall. Thrust can be vectored from anything that creates thrust (prop or jet blast).

Not saying I know what is going on. I am learning too. I love forums for this reason. A sharing place and wealth of knowledge.
 
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AOA Report

Installed the AOA modification in accordance with the direction provided by Joe Gores (Mich48041). Used the football needle, some 1/8" O.D. tubing, the quick connectors at the wing root as suggested and the fitting on the backside of the Dynon as suggested. Part numbers can be seen earlier in this thread.

It is amazingly accurate!!

This evening did a series of landings and stalls. I have the AOA set to start to alarm (beep slowly) when it is in the middle of the yellow band. On landing it started to beep slowly when I stopped the descent, and then a solid tone just when the wheels touched. My normal stall warning never sounds on landing with only me in the plane, it only sounds when nearer to gross weight.

When doing the full stalls at altitude, the AOA starts to beep just before the stall and the solid AOA tone sounds right at stall. If I slow just a bit more (with only me in the plane) the normal stall warning sounds. (My stall warning vane alarm may be coming in a bit late.)

Will have to do a bit more testing and determine the TAS, with full flaps, when the AOA just starts to beep slowly. More testing to come.

One suggestion..... Do not turn the AOA function on until it has been calibrated per the instructions in the Dynon manual. I turned it on prior to my 1st calibration flight. The AOA alarm blared in my ears as soon as I passed 35 knots just prior to liftoff.

Thanks Joe!! A $20-$30 modification that is well worth the insignificant cost.
 
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Good going Marty, getting the AOA working.
For those who have the Dynon D-180 and installed AOA but do not hear the woman's voice when approaching stall AOA, it seems that it is necessary to have either the AP74 of HS34 in order to hear the voice alarms. And the voice must be enabled in the AP74 or HS34 setup menu.
Joe Gores
 
Does the installation in the Skyview have the AOA hooked up or does a similar type of mod need to be done like previously mentioned for hooking up a AOA probe?

Thanks,

Bob
 
The E-LSA Skyview instructions and parts do NOT include the AOA parts or installation. It is very easy to add per the instructions in this thread.
 
If you want to install the AoA sensor (and/or pitot) in (on) the wing, and are not comfortable with the twist-lock fittings recommended earlier, I can highly recommend these quick-disconnect fittings:

http://www.mcmaster.com/#standard-quick-disconnect-tube-fittings/=lj5z09

They are a bit (O.K., a LOT) more expensive, but they have O-ring seals and really do disconnect (and connect) quickly. They are also vibration resistant, and you can get bulkhead mount versions that may be useful in this application.
 
I can highly recommend the KQ2 line of fittings from SMC. I replaced my entire pitot/static system with new hoses and KQ2 fittings when I installed my Dynon. O-ring seals, vibration resistant, bulkhead mounts available.

SMC even makes a Flame Resistant line, the KR series. Not sure why you'd need them in the engine compartment, but if you're anal about flame resistance you could use them in the cockpit too.
 
Has anyone tried to silence the woman yelling STALL and still been able to keep the side tone beep?

I just set mine up to start the side tone at the top of the Yellow. The stall warning alarm comes in just before the solid tone, but I find the woman yelling STALL to be distracting.
 
Try deleting the stall switch from the Skyview input configuration. I am thinking that the AV5000 is actually generating the tone, not the Skyview. If that works you can then delete the display widget from the engine screens (100% 50% and 20% sizes) Do a backup first and also make a note about the specific input it is on. You can add it back if needed.
 
I forgot to mention that I have the earlier Dynon 180. I think the audio comes via the auto pilot or hsi.:confused:
 
rv3flier,
See FlightDEK-D180 Installation Guide page 8-23
EFIS > SETUP > AP menu, scroll down to AUDIO ALERTS, and press SEL
Joe Gores
 
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