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Angle of attack indicators

Apologies if this has been discussed elsewhere but I didn't see any threads on this topic.

I would like to see what others have to say on installing an AOA indicator on their RV. Specifically, thoughts and opinions regarding how they add to safety, and which products you have installed or rejected and why. Ballpark cost and ease/difficulty of installation would also be helpful.

My wings are finished except for the tips and not yet mounted, so I'd like to run the tubing/wiring before they are completely buttoned up and in place.

Thanks for any advice/experience/suggestions you can share.
 
I think this is mostly dictated by your chosen EFIS. Most of the glass suppliers have their own AOA system and wiring requirements to their pitot and AOA harware on the wing.
 
I think this is mostly dictated by your chosen EFIS. Most of the glass suppliers have their own AOA system and wiring requirements to their pitot and AOA harware on the wing.

Most of the current solutions you just have to run a second line to your pitot tube from your adahrs location.
 
Hi Wyn,

I just installed the Dynon AoA probe in my completed RV-4 in November. I already had a D10A installed so the display component was a none issue.

I had to remove the tank to run the 2nd pitot line to the Dynon instrument. With the Dynon probe, it is necessary to drill and tap the mast portion to attach to the mounting base installed in a flying aircraft.

In addition, I had to run a wire from the Dynon unit to my intercom and install a potentiometer in the panel to allow me to adjust volume of the audio signals in my headset. The Dynon instructions are pretty good.

I'm still learning how to best use it, but I believe it will be a great addition to my aircraft.

Good luck,
 
Apologies if this has been discussed elsewhere but I didn't see any threads on this topic.

I would like to see what others have to say on installing an AOA indicator on their RV. Specifically, thoughts and opinions regarding how they add to safety, and which products you have installed or rejected and why. Ballpark cost and ease/difficulty of installation would also be helpful.

My wings are finished except for the tips and not yet mounted, so I'd like to run the tubing/wiring before they are completely buttoned up and in place.

Thanks for any advice/experience/suggestions you can share.

AOA indicators have been the subject of multiple vigorous discussion over the years on VAF. Try using the search function of the forum to find these threads, there is a ton of info concerning value and use of AOA in the archives.

By the way, I've been flying with the LRI indicator in my RV-6 for over 15 years and consider it a primary part of the panel.
 
Biased AOA opinion

I'm a former Navy carrier guy so including AOA was a no-brainer decision for me. However I screwed up on the display design/placement.

Use it with an AFS 4500 which shows AOA within the display at the top. In my biased opinion, that is not high enough - it requires dedicated eye movement on final to see well enough for real-time trend interpretation. And AOA trends are key to avoiding surprise AOA holes.

Didn't figure out there's a better way display placement until after I started flying it.

One of those while close, but not necessarily unsat, isn't as good as it could be outcomes. I should have opted for the external, top of the panel display.
 
I added AoA to my Dynon D180-equipped RV-12. All it took was a single blind rivet in the wing (sensing port), and tubing to connect it to the Dynon. After using AoA for a few flights, I disconnected the stall warning vane switch. I use and like the AoA indication a whole lot better.
 
I agree that a visual AOA display should be up high - a HUD being best. But several of the EFIS based units also put out an audio warning tone (slow beeps, progressing to rapid beeps, progressing to a solid tone just prior to stall). For stall avoidance these work pretty well imho, and let you keep your eyes outside.

For those not wishing to change their pitot tube to a dual-input one: The GRT HX EFIS offers a choice of AOA, either from dual pitot data, or calculated from EFIS data. I?ve compared the calculated AOA against the Dynon dual pitot data AOA, and they agree quite well.
 
I have an AFS "Sport" AoA. It's a stand-alone unit with a small .040" port on the top of the outboard wing and another on the underside. I mounted the LED bar graph display immediately to the left of my ASI so it's in my peripheral vision while landing. In a Lancair, it's a must-have safety device:

VrxWRN.jpg
 
I am a former Naval Aviator as well (USMC side). We were talk to fly AOA as a performance instrument, not just safety. I always thought it was a better way to fly, but old school electromechanical AOA was expensive and not that reliable.
I have been flying part 121 for over 20 years. They come up will all kinds of god awful cards for different V speeds and approach speeds because of the huge weight range of jets. In reality, you are simply flying AOA, using airspeed as the primary reference.

If you have an EFIS, you already have a pretty good IRS based AOA. The vertical difference between the nose of the airplane, and the velocity vector (flight path marker) as measured on the PFD, is your AOA. I use it all the time in the simulator. When they give me failed or unreliable airspeed in the sim, I just fly AOA. They can't figure out how I do it because they were not trained to do it.

But I will install an AOA above the glare shield on the plane I am building.
 
Synthetic vs. measured AOA

It would be great of one of you test pilots would compare Synthetic vs. measured AOA under various circumstances to see if I can avoid the plumbing required for a measured AoA. :)
 
Use the tone

I installed the Dynon AOA in my -4. Had to pull the left tank and install the new probe, wiring, and pitot / static lines. I put the heater module on the inside of the access panel but mounted the probe in the skin against the rib.

AOA is a very important tool and the ability to install it relatively cheaply in our experimental airplanes makes it a slam dunk. Just do it, you won't regret it.

As others have mentioned, having a display in your line of sight is helpful but only if that means while you are looking outside. Don't worry about the display. I almost never look at mine on the Skyview. Just set up the tones properly and you listen to those for AOA while keeping your scan primarily out the window.

I find AOA most useful in the landing pattern but it provides some benefit during aerobatics as well.
 
It would be great of one of you test pilots would compare Synthetic vs. measured AOA under various circumstances to see if I can avoid the plumbing required for a measured AoA. :)

Did that years ago....bottom line is that they compare well for things like approaches, where bank angle is low and things aren't;t changing rapidly. During heavy maneuvering, with all axes changing rapidly, synthetic can get lost.

Paul
 
I have dual Dynon Skyviews in my -10. It has the AOA display, but is almost useless. It is a tiny wiget on the screen and you definitely do not want to look for it in the pattern. The audio is good, but not a great.

I have suggested the following to Dynon and have been ignored to date.

At a user selected airspeed, say 90 knots for my -10, have the program expand the AOA wiget to the size of the airspeed tape and put it just to the right of the tape.

Now it is easy to find and of a size that can be seen at a glance when you mostly need it. If you want it all the time, just set the airspeed selection to a high number.
 
Synthetic vs. measured AOA

Did that years ago....bottom line is that they compare well for things like approaches, where bank angle is low and things aren't;t changing rapidly. During heavy maneuvering, with all axes changing rapidly, synthetic can get lost.
Thanks Paul - sounds like you recommend installing the measured AOA, which I will do.
 
I ordered my Dynon with AOA after reading how carrier pilots use it, and getting to ride right seat with a fellow RV'er in his day-job machine; a Lear 45. After he explained Mach stall and the unfamiliar gauges and controls, I asked "where is your airspeed indicator?" He chuckled, and said "don't need one, the GPS tells how fast you are going, the Mach gauge tells you not to to go too fast, and the AOA tells you not to go too slow". "But the rules say you need one!" I protested. "Oh that" he said, and opened a little cubby with emergency gauges such as airspeed, compass, and gyro horizon. "Never had to use them for real, and pray I never do" he replied.

The Dynon AOA installed easily with two plastic lines coming from the wing mounted pitot; no more difficult than routing a single line behind the wing tank and back to the ADAHRS in the fuselage. It was also easy to calibrate, just sneak up on a stall at altitude, and press a button at the break.

I don't like the Dynon AOA display, it is too faint, and too low on the panel to look at on short final. However, after a year of flying fast approaches I hooked up the audio signal to my intercom and wow, what an amazing device! It uses variable frequency beeps to provide AOA feedback for approach, landing, aerobatics, and canyon turns. The steady warning tone always comes on just before stalling for fun, no matter what airspeed, flap setting, or orientation the plane has. It helps me come in slow when visiting my friend's farm strip lightly loaded, and reminds me that the safe IAS for approaching hot and heavy is about 25 knots faster. I can't imagine how I could accidentally stall while the device is working properly, and because of the feedback, I have a better sense of lift even without instruments. (I lost pitot and AOA pressure twice, once by hitting a big bug, and once in VMC snow without pitot heat - my bad)

This is the only AOA I have used, so I don't have an opinion as to which brand is best. Like a previous post said, the device needs to readily visible or audible, or it won't do any good when you need it most.

Jay
 
Convinced

Thanks Gents,
After reading these posts I am convinced to install an AOA. I love this site!
 
I ordered my Dynon with AOA after reading how carrier pilots use it, and getting to ride right seat with a fellow RV'er in his day-job machine; a Lear 45. After he explained Mach stall and the unfamiliar gauges and controls, I asked "where is your airspeed indicator?" He chuckled, and said "don't need one, the GPS tells how fast you are going, the Mach gauge tells you not to to go too fast, and the AOA tells you not to go too slow". "But the rules say you need one!" I protested. "Oh that" he said, and opened a little cubby with emergency gauges such as airspeed, compass, and gyro horizon. "Never had to use them for real, and pray I never do" he replied.

The Dynon AOA installed easily with two plastic lines coming from the wing mounted pitot; no more difficult than routing a single line behind the wing tank and back to the ADAHRS in the fuselage. It was also easy to calibrate, just sneak up on a stall at altitude, and press a button at the break.

I don't like the Dynon AOA display, it is too faint, and too low on the panel to look at on short final. However, after a year of flying fast approaches I hooked up the audio signal to my intercom and wow, what an amazing device! It uses variable frequency beeps to provide AOA feedback for approach, landing, aerobatics, and canyon turns. The steady warning tone always comes on just before stalling for fun, no matter what airspeed, flap setting, or orientation the plane has. It helps me come in slow when visiting my friend's farm strip lightly loaded, and reminds me that the safe IAS for approaching hot and heavy is about 25 knots faster. I can't imagine how I could accidentally stall while the device is working properly, and because of the feedback, I have a better sense of lift even without instruments. (I lost pitot and AOA pressure twice, once by hitting a big bug, and once in VMC snow without pitot heat - my bad)

This is the only AOA I have used, so I don't have an opinion as to which brand is best. Like a previous post said, the device needs to readily visible or audible, or it won't do any good when you need it most.

Jay

Nice writeup Jay. The AOA tones are definitely the best way to fly the airplane. And, as you note, the beauty of AOA is that you don't have to calculate a stall speed. The aircraft ALWAYS stalls at the same angle of attack. The airspeed may vary greatly depending on many factors but the AOA will always be the same. When that tone goes solid, the airplane is going to stall. It's a great tool!
 
I have been using on speed aoa for around a year now and really like it .
You can find info on it by typing on speed aoa on you tube.
It uses an arduino board that uses info from a dynon or other products that are similar .
After I got used to using and trusting it I hardly look at the airspeed indicator, which keeps my vision primarily outside where it should be.
 
DIY - Test install

I read the threads on adding a DIY port for AOA input to EFIS (e.g. Dynon), some using a pop rivet under the wing, some a inflation needle.

Since I'm not eager to drill extra holes in the wing skin, this just occurred to me:
In the RV-3 and RV-4 (and probably other RVs) the tie-down hole is just next to the pitot fitting. Drill a small hole in the tie-down bracket (W-422) that will reach near the top of the 3/8" threaded hole. Fit a needle or something into that small hole and tube to AOA port on EFIS

Now you can add a temporary 3/8" fitting of some kind with an alu tube you can bend until you get an acceptable angle (for the EFIS to be able to be calibrated).

By 3/8" fitting I mean something that will screw into the tie-down hole.

When you have found the right angle and are tired of screwing in and removing the test probe to instal the tiedown ring, make a permanent install next to the pitot tube.

Just an idea I'll try out on my Flying RV-3B that has a Dynon 10A in it.

Finn
(too cheap to spend $ on a Dynon pitot tube)
 
Hi Wyn,

I just installed the Dynon AoA probe in my completed RV-4 in November. I already had a D10A installed so the display component was a none issue.

I had to remove the tank to run the 2nd pitot line to the Dynon instrument. With the Dynon probe, it is necessary to drill and tap the mast portion to attach to the mounting base installed in a flying aircraft.

In addition, I had to run a wire from the Dynon unit to my intercom and install a potentiometer in the panel to allow me to adjust volume of the audio signals in my headset. The Dynon instructions are pretty good.

I'm still learning how to best use it, but I believe it will be a great addition to my aircraft.

Good luck,

Did you replace the stock Van's pitot tube with the Dynon AOA pitot tube? That's what I want to do in my RV-8. It has the stock Van's pitot tube and need to know if the mount will work or if I have to buy a new mount.

I want to buy this style AOA pitot tube one from Dynon as it looks like the one I have now

https://www.dynonavionics.com/includes/guides/Boom_Mount_AOA_Pitot-Dimensions.pdf


but if I have to replace the mount I might go with the L style which doesn't extend so low under the wing.
 
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Did you replace the stock Van's pitot tube with the Dynon AOA pitot tube? That's what I want to do in my RV-8. It has the stock Van's pitot tube and need to know if the mount will work or if I have to buy a new mount.

I want to buy this style AOA pitot tube one from Dynon as it looks like the one I have now

https://www.dynonavionics.com/includes/guides/Boom_Mount_AOA_Pitot-Dimensions.pdf


but if I have to replace the mount I might go with the L style which doesn't expend so low under the wing.

My -4 had a standard AN5812 (L-shaped) pitot tube. The mount for this pitot accepted the Dynon (L-shaped) AoA probe.

My mount looks like this one: https://www.aircraftspruce.com/catalog/inpages/gretzbrackets.php?clickkey=5714

It was necessary to drill and tap 4 holes into the probe to make the attachment to the mast.

Good luck,

Dean
 
I am considering jury-rigging an AOA indicator on my plane. I already have a Skyview with an ADAHRS controller, with an open port for AOA. And I already have a heated pitot tube that works great. I suppose all I need to do is drill a small hole in my leading edge just under the cord line, and run a pneumatic tube from the hole to the AOA port? Any tips on how to mount the tube to the inside of the wing skin? I'm guessing the hole should be just near the pitot tube and just below the chord line. Curious if anyone has done this and could share building tips.

I could also install the Dynon product but I'm a little reluctant to mess with the heated pitot that I already have, that works fine.
 
delrin block

I am considering jury-rigging an AOA indicator on my plane. I already have a Skyview with an ADAHRS controller, with an open port for AOA. And I already have a heated pitot tube that works great. I suppose all I need to do is drill a small hole in my leading edge just under the cord line, and run a pneumatic tube from the hole to the AOA port? Any tips on how to mount the tube to the inside of the wing skin? I'm guessing the hole should be just near the pitot tube and just below the chord line. Curious if anyone has done this and could share building tips.

I could also install the Dynon product but I'm a little reluctant to mess with the heated pitot that I already have, that works fine.
I have the advanced systems aoa sport which came with some delrin blocks, threaded into a hose connector. Photo here. Glued on with proseal. It also came with some hyper long rivets which I also glued in, but didn't squeeze or buck - too chicken, and seriously not needed. The tubing is very flexible rubbery material - not 100% sure what.

img_8791.jpg
 
... I already have a heated pitot tube that works great. I suppose all I need to do is drill a small hole in my leading edge just under the cord line, and run a pneumatic tube from the hole to the AOA port? Any tips on how to mount the tube to the inside of the wing skin? I'm guessing the hole should be just near the pitot tube and just below the chord line. Curious if anyone has done this and could share building tips. ...
My situation was similar to yours: heated pitot tube and AOA-ready Dynon SkyView but no AOA probe. I fabricated one in the style of the plans-specified pitot tube and bent the end to a "pleasing angle" downward. It's not really critical; the SkyView AOA calibration compensates for the angle. You can see it in the center of this image along with the pitot tube.

AOA%20Probe.jpg



Of course the AOA probe is not heated and it's the first thing to collect ice (and sounds an AOA warning) but that's a feature, not a bug <g>.

--
Joe
 
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My situation was similar to yours: heated pitot tube and AOA-ready Dynon SkyView but no AOA probe. I fabricated one in the style of the plans-specified pitot tube and bent the end to a "pleasing angle" downward. It's not really critical; the SkyView AOA calibration compensates for the angle. You can see it in the center of this image along with the pitot tube.

AOA%20Probe.jpg



Of course the AOA probe is not heated and it's the first thing to collect ice (and sounds an AOA warning) but that's a feature, not a bug <g>.

--
Joe

Interesting. I will probably do something like this. If it freezes over, wouldn’t that lock in the pressure, rendering the AOA more or less invalid? I would imagine if the AOA is frozen or clogged but the pitot is not, AOA would measure lower than actual as one descends after the freeze and higher than actual if one climbs after the freeze. Have you frozen it before and did it alarm right away?
 
...If it freezes over, wouldn’t that lock in the pressure, rendering the AOA more or less invalid? I would imagine if the AOA is frozen or clogged but the pitot is not, AOA would measure lower than actual as one descends after the freeze and higher than actual if one climbs after the freeze. Have you frozen it before and did it alarm right away?
It happened to me twice, once in level flight and once in a climb (trying to get on top). Both were solid IMC and the AOA alarm was my first indication of icing as I was "on the gauges" and not looking at the wing leading edge or the windscreen. Pitot heat was doing its job taking care of the pitot probe and all pitot-static "gauges" (SkyView) were working normally.

The sound was so annoying/distracting that I had to disable AOA audio in the Setup menu so I could focus. Not fun in IMC.

I do not know the physics involved but I do know that bad things happen when the AOA line is blocked. I had a tubing kink inside the wing and on some occasions the SkyView PFD would shut down because it failed a self-test that Dynon added somewhere around version 10. I believe Dynon has changed the software's behavior; I certainly found and fixed the kink in my AOA line.

My comment about it being "a feature" should not be taken literally -- I would prefer a heated AOA probe .
 
So I'm getting ready to start building this, as my plane will be in the shop for February as my mechanic builds some new wheel pants and performs the conditional. Currently juggling a few options.

Option 1 - Joe's Solution - Fab a new tube

I am consulting my RV-6A plans for building the pitot tube. It looks like an AN-832-4D union protrudes from the wing and is coupled to a flared aluminum tube on both ends.

My parts list:

1. Vans pitot tube kit. Includes flared aluminum pipe, AN-819-4D sleeve, An-818-4D nut. I would probably bend this downwards and maybe cut it a little bit. Or just get some aluminum tubing. Vans part # VENT-P-100 https://shop.vansaircraft.com/cgi-b...337343-128-6&browse=airframe&product=ss-pitot
2. AN-832-4D coupler
3. AN-934-4D nut
4. 25' of 1/4" OD pneumatic tube
5. 1/4" tube to 1/8" male NPT adapter (for connecting tube to Dynon)

pitot option 1.jpg

Option 1A -
6. Screw a 1/4" Female Pipe to 1/4" tube fitting to the AN-832-4D to join a pneumatic tube directly with the pitot tube. Gently run the pneumatic tube through my wing and directly to the Dynon. Could be an issue if I ever have to take my wing off.

Option 1A seems the easiest to me.

Option 1B -
Per plans, join a flared aluminum pipe to the interior side of the AN-832-4D and run the pipe along the wing to the wing root. I guess this would be sturdier than running just a pneumatic tube the whole way?

Requires aluminum pipe, AN-819-4D sleeve, An-818-4D nut, snap brushings.

I suppose the aluminum pipe can later be joined with the pneumatic tube using an adapter. I couldn't quite tell by the plans how that happened.

Option 2 - Replace with Dynon -
Purchase a Dynon heated pitot kit, run a new pneumatic tube using the Dynon tubing kit, and sell my old pitot tube / heater.

https://www.dynonavionics.com/aoa-pitot-probes.php

Pros: Don't have to drill any holes.
Cons: Would probably require recalibration of my pitotstatic system. Slightly more expensive in parts.

I am now leading towards Option 2 as it seems the least destructive, although recalibrating the pitot system seems a bit daunting to me.

Option 3 - Mimic Advanced Systems AOA Sport -

Rather than installing a probe, make a small hole on the underside of the wing and join the pneumatic tube directly with that hole, like in rv8ch's kit.

I am not sure if the Dynon AOA is sensitive enough to register this, or if there is some aerodynamic property that would warrant bringing the AOA probe away from the wing skin. If it doesn't work, then I would have a rather useless hole on the bottom of my wing.

I have the advanced systems aoa sport which came with some delrin blocks, threaded into a hose connector. Photo here. Glued on with proseal. It also came with some hyper long rivets which I also glued in, but didn't squeeze or buck - too chicken, and seriously not needed. The tubing is very flexible rubbery material - not 100% sure what.

View attachment 4701

Option 4 - Adapt RV-12 AOA installation N 16-12-14

https://www.vansaircraft.com/service-information-and-revisions/n-2016-12-14/

This is for the RV-12 so the exact placement on the -6A is not known.

Option 5 - Plump an AOA probe through the tie-down hole

Editing to gather all the options in one place.

Nothing that fancy.

I basically connected the D-10A AOA input to the 3/8" threaded tie-down hole in the wing. I drilled a 1/16" hole near the end (bottom) of the 3/8" hole in the tie-down square rod in the wing. Pressed/glued in a 1/16" tube and ran a plastic line to the D-10A AOA input.

For the actual probe, any piece of 3/8" OD stock can be used. Even part of a 3/8" bolt. Simply drill a small hole through it and cut the end at an angle. I think you'll find that the angle is not critical, but this makes it real easy to experiment with length and angle. Screw in the probe before flying. Remove and install tie-down ring when needed. My plane is hangared, so rarely tied down. (Because I didn't have a 3/8" wood or plastic dowel on hand, I used progressively smaller tubes inside a 3/8" pex tube.)

Sorry, I don't remember the thread size of the tie-down hole, but you can easily get that from the tie-down ring. 3/8-16?

But, yes, you could design a fancy (streamlined) tie-down ring with a channel and hole in it. Strength would be an issue though.

Finn

I may try this out. This was my Aircraft Spruce order. Used 1/4" ID polyurethane hose. Seems a little thick but that's the best thing Spruce had. I am planning on just putting a little hole in the tie down square rod, and making a little Delrin block to attach the tube. I have never been inside the wing so I am not sure exactly what to expect.

Code:
	Ship	B/O	Item	Unit Price	Total Price
1	1	0	02-52001 DELRIN ROD 1" (NATURAL)	5.500	5.50
8	8	0	6504 6504 MINI BREEZE CLAMP .250" THRU .625"	0.990	7.92
3	3	0	0705-015 0705-015 POLY TUBE CONNECTOR	0.910	2.73
17	17	0	0585-071 POLYURETHANE TUBE 0585-071	2.040	34.68
4	4	0	0700-153 0700-153 PLYETH HOSE ADAPTER	1.100	4.40
Subtotal: USD	55.23

Oh, another thing. You'll need an angle drill to drill the hole in the tie-down square rod in the wing. (Square in the RV-3B factory built wings. Was a round tube in my old RV-3.) Even with a small drill motor I don't think there's room to drill the hole.

Actually I think I used a 3/32" or #40 drill, or perhaps 1/8" or #30 in my angle drill attachment and 1/8" OD metal tube of some kind in the hole to connect the 7/64" ID plastic tubing.

Alternatively it may be possible to remove the square rod to work on it on the bench -- if you can get to the nuts and bolts holding it to the wing.

Definitely take off the wing inspection cover near the tie-down hole and have a look at what you have to deal with. Measure the depth of the 3/8" hole so you know where to drill the small hole.

Finn
 
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...
Option 3 - Mimic Advanced Systems AOA Sport -

Rather than installing a probe, make a small hole on the underside of the wing and join the pneumatic tube directly with that hole, like in rv8ch's kit.

I am not sure if the Dynon AOA is sensitive enough to register this, or if there is some aerodynamic property that would warrant bringing the AOA probe away from the wing skin. If it doesn't work, then I would have a rather useless hole on the bottom of my wing.


...
More information/clarification about this method, I have not yet made it work with my GRT AOA, mainly because the "computed" AOA seems to be good enough, and I have not yet taken the time to calibrate it.
 
.... If it doesn't work, then I would have a rather useless hole on the bottom of my wing....

https://vansairforce.net/community/showthread.php?t=186185 post #10.

However, I would have to remove the wing tank to replace the pop rivet with a oops rivet if it doesn't work well :(

But still not flying :(

BTW, I did install a AOA "probe" in the tie-down hole in my RV-3B (as suggested in post #23 this tread). Works fine with the Dynon D-10A. Unfortunately the factory-built wings on my RV-3B do not have lightening holes in the main spar so can't get to the leading edge to install a pop-rivet (unless I remove a tank or wing tip).

Finn
 
I used the 12 style rivet in the leading edge of my 10. Worked well, though some thought and possible testing goes into the location/placement of the rivet. Not an aero engineer, but would think there is too much turbulence near the wing root. Mine is out near the tip, where it was easy to run the plubing to the backside of the rivet.

So I'm getting ready to start building this, as my plane will be in the shop for February as my mechanic builds some new wheel pants and performs the conditional. Currently juggling a few options.

Option 1 - Joe's Solution - Fab a new tube

I am consulting my RV-6A plans for building the pitot tube. It looks like an AN-832-4D union protrudes from the wing and is coupled to a flared aluminum tube on both ends.

My parts list:

1. Vans pitot tube kit. Includes flared aluminum pipe, AN-819-4D sleeve, An-818-4D nut. I would probably bend this downwards and maybe cut it a little bit. Or just get some aluminum tubing. Vans part # VENT-P-100 https://shop.vansaircraft.com/cgi-b...337343-128-6&browse=airframe&product=ss-pitot
2. AN-832-4D coupler
3. AN-934-4D nut
4. 25' of 1/4" OD pneumatic tube
5. 1/4" tube to 1/8" male NPT adapter (for connecting tube to Dynon)

View attachment 6998

Option 1A -
6. Screw a 1/4" Female Pipe to 1/4" tube fitting to the AN-832-4D to join a pneumatic tube directly with the pitot tube. Gently run the pneumatic tube through my wing and directly to the Dynon. Could be an issue if I ever have to take my wing off.

Option 1A seems the easiest to me.

Option 1B -
Per plans, join a flared aluminum pipe to the interior side of the AN-832-4D and run the pipe along the wing to the wing root. I guess this would be sturdier than running just a pneumatic tube the whole way?

Requires aluminum pipe, AN-819-4D sleeve, An-818-4D nut, snap brushings.

I suppose the aluminum pipe can later be joined with the pneumatic tube using an adapter. I couldn't quite tell by the plans how that happened.

Option 2 - Replace with Dynon -
Purchase a Dynon heated pitot kit, run a new pneumatic tube using the Dynon tubing kit, and sell my old pitot tube / heater.

https://www.dynonavionics.com/aoa-pitot-probes.php

Pros: Don't have to drill any holes.
Cons: Would probably require recalibration of my pitotstatic system. Slightly more expensive in parts.

I am now leading towards Option 2 as it seems the least destructive, although recalibrating the pitot system seems a bit daunting to me.

Option 3 - Mimic Advanced Systems AOA Sport -

Rather than installing a probe, make a small hole on the underside of the wing and join the pneumatic tube directly with that hole, like in rv8ch's kit.

I am not sure if the Dynon AOA is sensitive enough to register this, or if there is some aerodynamic property that would warrant bringing the AOA probe away from the wing skin. If it doesn't work, then I would have a rather useless hole on the bottom of my wing.



Option 4 - Adapt RV-12 AOA installation N 16-12-14

https://www.vansaircraft.com/service-information-and-revisions/n-2016-12-14/

This is for the RV-12 so the exact placement on the -6A is not known.

(Posting as a new post so I can upload the drawing)
 
BTW, I did install a AOA "probe" in the tie-down hole in my RV-3B (as suggested in post #23 this tread). Works fine with the Dynon D-10A. Unfortunately the factory-built wings on my RV-3B do not have lightening holes in the main spar so can't get to the leading edge to install a pop-rivet (unless I remove a tank or wing tip).

Finn

Hey Finn, this sounds like a pretty good solution too. I decent at CAD so I may try to fab a new part to serve as both a tie down and an AOA probe. I saw in your previous post (#23) you had speculated on how you might build this - drilling a hole in a tie down ring and adding a bent aluminum tube. Is that what you ended up doing?
 
Hey Finn, this sounds like a pretty good solution too. I decent at CAD so I may try to fab a new part to serve as both a tie down and an AOA probe. I saw in your previous post (#23) you had speculated on how you might build this - drilling a hole in a tie down ring and adding a bent aluminum tube. Is that what you ended up doing?

Nothing that fancy.

I basically connected the D-10A AOA input to the 3/8" threaded tie-down hole in the wing. I drilled a 1/16" hole near the end (bottom) of the 3/8" hole in the tie-down square rod in the wing. Pressed/glued in a 1/16" tube and ran a plastic line to the D-10A AOA input.

For the actual probe, any piece of 3/8" OD stock can be used. Even part of a 3/8" bolt. Simply drill a small hole through it and cut the end at an angle. I think you'll find that the angle is not critical, but this makes it real easy to experiment with length and angle. Screw in the probe before flying. Remove and install tie-down ring when needed. My plane is hangared, so rarely tied down. (Because I didn't have a 3/8" wood or plastic dowel on hand, I used progressively smaller tubes inside a 3/8" pex tube.)

Sorry, I don't remember the thread size of the tie-down hole, but you can easily get that from the tie-down ring. 3/8-16?

But, yes, you could design a fancy (streamlined) tie-down ring with a channel and hole in it. Strength would be an issue though.

Finn
 
Nothing that fancy.

I basically connected the D-10A AOA input to the 3/8" threaded tie-down hole in the wing. I drilled a 1/16" hole near the end (bottom) of the 3/8" hole in the tie-down square rod in the wing. Pressed/glued in a 1/16" tube and ran a plastic line to the D-10A AOA input.

For the actual probe, any piece of 3/8" OD stock can be used. Even part of a 3/8" bolt. Simply drill a small hole through it and cut the end at an angle. I think you'll find that the angle is not critical, but this makes it real easy to experiment with length and angle. Screw in the probe before flying. Remove and install tie-down ring when needed. My plane is hangared, so rarely tied down. (Because I didn't have a 3/8" wood or plastic dowel on hand, I used progressively smaller tubes inside a 3/8" pex tube.)

Sorry, I don't remember the thread size of the tie-down hole, but you can easily get that from the tie-down ring. 3/8-16?

But, yes, you could design a fancy (streamlined) tie-down ring with a channel and hole in it. Strength would be an issue though.

Finn

I'm going to try this out. This was my Aircraft Spruce order. Used 1/4" ID polyurethane hose. Seems a little thick but that's the best thing Spruce had. I am planning on just putting a little hole in the tie down square rod, and making a little Delrin block to attach the tube. I have never been inside the wing so I am not sure exactly what to expect.

Code:
	Ship	B/O	Item	Unit Price	Total Price
1	1	0	02-52001 DELRIN ROD 1" (NATURAL)	5.500	5.50
8	8	0	6504 6504 MINI BREEZE CLAMP .250" THRU .625"	0.990	7.92
3	3	0	0705-015 0705-015 POLY TUBE CONNECTOR	0.910	2.73
17	17	0	0585-071 POLYURETHANE TUBE 0585-071	2.040	34.68
4	4	0	0700-153 0700-153 PLYETH HOSE ADAPTER	1.100	4.40
Subtotal: USD	55.23
 
Oh, another thing. You'll need an angle drill to drill the hole in the tie-down square rod in the wing. (Square in the RV-3B factory built wings. Was a round tube in my old RV-3.) Even with a small drill motor I don't think there's room to drill the hole.

Actually I think I used a 3/32" or #40 drill, or perhaps 1/8" or #30 in my angle drill attachment and 1/8" OD metal tube of some kind in the hole to connect the 7/64" ID plastic tubing.

Alternatively it may be possible to remove the square rod to work on it on the bench -- if you can get to the nuts and bolts holding it to the wing.

Definitely take off the wing inspection cover near the tie-down hole and have a look at what you have to deal with. Measure the depth of the 3/8" hole so you know where to drill the small hole.

Finn
 
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AOA

With the audible tones in the Dynon HDX, I monitor airspeed on final down to crossing the threshold and never put eyes on the panel after that. The increasing audible tone rate becomes second nature.
 
AOA

I use my AFS AOA as primary on my 9A
(900 hrs)
It allows me to use a slower approach and landing speed with confidence & consistency
Unlike airspeed it’s instantaneous and adjusts to DA, weight and temperature
For me, airspeed is a secondary reference.
The AFS system is easy to install and calibrate
I consider it to be the best safety feature available for GA
 
With the audible tones in the Dynon HDX, I monitor airspeed on final down to crossing the threshold and never put eyes on the panel after that. The increasing audible tone rate becomes second nature.
I use the same technique for landing and yes the audible tone quickly becomes second nature.

My landings are now "acceptable" rather than "Holy Cow"! :D
 
AOA very useful

I have an AFS "Sport" AoA. It's a stand-alone unit with a small .040" port on the top of the outboard wing and another on the underside. I mounted the LED bar graph display immediately to the left of my ASI so it's in my peripheral vision while landing. In a Lancair, it's a must-have safety device:

VrxWRN.jpg

I have the same unit, with the multiple light readout mounted center of the RV4 tip up canopy rail, almost as good as a HUD. Lights come on from bottom up first. Did some extensive flight testing:
1. Best Glide, MaxEndurance and Best climb angle - all green and first of three yellow lights on (like Snopercod picture)
2. Best App No Flap - all green, first and Second of three yellow lights on
3. Best turn rate (hack it, rack it, track it) - all green, all yellow and occasionally first red.
Unit has audio, but I don't use it - too annoying

Always know approximately what mph lights indicate. (little plastic tubes fell off the sensor once) For instance for my RV4 at low fuel and FLAPS DOWN:
1.One green always On
2. two green = 71mph
3. two green and three yellow = 59mph
4. two green, three yellow, two red = stalled (49mph)
FLAPS UP:
1.One green always On
2. two green = 99mph
3. two green and three yellow = 74mph
4. two green, three yellow, two red = 62 mph
5. two green, three yellow, three red = 60 mph
Didn't stall until ~ 55 mph

ALL ABOVE ONLY CORRECT FOR MY AIRCRAFT!
 
Testing

So I was thinking of rigging a bent probe as a new AOA probe and attaching that to my existing Dynon AHARS unit, as discussed earlier in this thread.

My mechanic convinced me that it would be easier to replace my heated pitot probe with a Dynon heated pitot/AOA probe instead, and the installation was actually pretty easy. It’s all hooked up, and I’m about ready to fly it once this very long conditional inspection is over.

I’ve read about the AOA calibration procedure: you put the Dynon in AOa calibration mode and stall a few times. This makes sense.

I’m curious though, since I’ve also replaced the pitot tube, should I expect my indicated airspeeds to change? Should I recalibrate these?

I was thinking of flying in a triangle or rectangle with a safety pilot, noting the indicated airspeeds, and matching these with the GPS speeds. I would fly in a triangle or rectangle to account for wind and average these out.

Is this a normal procedure or should I try to do something on the ground?
 
I’m curious though, since I’ve also replaced the pitot tube, should I expect my indicated airspeeds to change? Should I recalibrate these?

I was thinking of flying in a triangle or rectangle with a safety pilot, noting the indicated airspeeds, and matching these with the GPS speeds. I would fly in a triangle or rectangle to account for wind and average these out.

Is this a normal procedure or should I try to do something on the ground?

As long as both pitot tubes point in the same direction there is no reason your IAS should change (assuming you don’t introduce a leak!)
As to checking against gps, I’m sure you meant to say ‘note TRUE airspeed (or pressure altitude and temperature for later conversion of IAS to TAS)’. As to a triangle or square, I’ve found I get just as good results by flying directly into the wind, then a 180, and average the two gps ground speeds. I let the gps find the wind direction. In principle a triangle is best, but I think the winds change a bit during the time and distance it takes to do the triangle, negating the advantage. YMMV.
 
As long as both pitot tubes point in the same direction there is no reason your IAS should change (assuming you don’t introduce a leak!)
As to checking against gps, I’m sure you meant to say ‘note TRUE airspeed (or pressure altitude and temperature for later conversion of IAS to TAS)’. As to a triangle or square, I’ve found I get just as good results by flying directly into the wind, then a 180, and average the two gps ground speeds. I let the gps find the wind direction. In principle a triangle is best, but I think the winds change a bit during the time and distance it takes to do the triangle, negating the advantage. YMMV.

Thanks so much!! I was a bit worried about changing IAS values because the new pitot is just a bit more narrow, so I thought the forward pressure would be less which would lead to indicated speeds being lower than actual. But I suppose it’s not that big of a difference.
 
Thanks so much!! I was a bit worried about changing IAS values because the new pitot is just a bit more narrow, so I thought the forward pressure would be less which would lead to indicated speeds being lower than actual. But I suppose it’s not that big of a difference.
I know it's not obvious, but the pressure does not change with the diameter of the hole.
 
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