AOA System - Calibration and Use

[Terry Lutz]

After speaking with DR about this post, here is a survey regarding the calibration and use of AOA in your daily flying. EAA has an active AOA working group to see if the use of AOA can reduce the risk of loss of control accidents. We would like to know the experience of the RV community in the calibration and use of AOA, and your comments about the use of AOA as a stall warning and in the traffic pattern. Here goes:

1. What AOA system are you using?
Dynon/AFS
Garmin
Alpha Systems
Bendix/King
Uavionics
Safe Flight
General Technics
Lift Reserve
Other

2. Did you find the calibration to be straightforward or difficult?

3. Are you comfortable with the accuracy of the calibration?

4. Do you find the AOA system to be an effective stall warning?

5. Do you use the AOA system regularly, particularly in the traffic pattern?

Many thanks!

 

[Amadeus]

1. What AOA system are you using?
---Garmin G3X

2. Did you find the calibration to be straightforward or difficult?
---Straight forward. Best to have a co-pilot with eyes out the canopy as you will be busy bringing the aircraft into a slow flight nose up attitude while staring at your screen.

3. Are you comfortable with the accuracy of the calibration?
---Very.

4. Do you find the AOA system to be an effective stall warning?
---Very much so. It hits the extreme warning red bar just as my flare becomes a stall to land.

5. Do you use the AOA system regularly, particularly in the traffic pattern?
---It is on all the time but in the landing pattern is where it is most active.

 

[mburch]

I calibrated several times for specific airspeeds but for some reason the actual usage experience does not match those speeds.

FYI, I have most often seen this when when the aircraft is not flown level when required during calibration.

The Garmin system needs to have the option of being audible for the increasing green chevrons not just the yellow and red.

It does: https://vansairforce.net/community/showthread.php?t=219935

• This provides the ability to modify the AOA audible alerts, and can be toggled in the Sound configuration menu.
• When set to Stall Awareness, the system will audibly alert the pilot when the AOA indicator enters the caution range and will beep progressively faster as AOA is increased towards a stall. A constant tone indicates a stall. When set to Approach + Stall Awareness, the pilot is audibly alerted in the same manner, however the alerts begin when at or above the approach target calibration point and increase progressively faster until a constant tone is reached at the point of stall.

 

[MacCool]

.....

1. What AOA system are you using?
Advanced Flight (note that calibration procedure is different than Dynon)
2. Did you find the calibration to be straightforward or difficult?
not so much difficult as very cumbersome

3. Are you comfortable with the accuracy of the calibration?
yes

4. Do you find the AOA system to be an effective stall warning?
yes. very accurate and repeatable

5. Do you use the AOA system regularly, particularly in the traffic pattern?
yes, I fly the AoA

 

[M McGraw]

After speaking with DR about this post, here is a survey regarding the calibration and use of AOA in your daily flying. EAA has an active AOA working group to see if the use of AOA can reduce the risk of loss of control accidents. We would like to know the experience of the RV community in the calibration and use of AOA, and your comments about the use of AOA as a stall warning and in the traffic pattern. Here goes:

1. What AOA system are you using?
Garmin G3X Version 9.31

2. Did you find the calibration to be straightforward or difficult?
Straight forward. 3 points are required 1.5, 1.1, and stall. 1.3 is optional.

3. Are you comfortable with the accuracy of the calibration?
Very comfortable both flaps up and flaps down. I verify the calibration on a regular basis.

4. Do you find the AOA system to be an effective stall warning?
Yes

5. Do you use the AOA system regularly, particularly in the traffic pattern?
I use AOA for takeoff, initial climb, aerobatics, glide, approach and landing.

Many thanks!

On final note, I am very interested in the OnSpeed.org system. I simply have not been able to purchase the required parts.

 

[Mikeyb]

1. What AOA system are you using?
MGL IEFIS lite with extender
2. Did you find the calibration to be straightforward or difficult?
Straightforward

3. Are you comfortable with the accuracy of the calibration?
Yes

4. Do you find the AOA system to be an effective stall warning?
Yes

5. Do you use the AOA system regularly, particularly in the traffic pattern?
Yes
On the MGL the tone threshold is adjustable. It’s set to beep slowly at normal approach speed. It’s also useful on initial climb.

 

[Lkitson]

1. What AOA system are you using?

Dynon

2. Did you find the calibration to be straightforward or difficult?

Straightforward. The menus on the Dynon screen walk you through the procedure

3. Are you comfortable with the accuracy of the calibration?

Yes

4. Do you find the AOA system to be an effective stall warning?

Yes.

5. Do you use the AOA system regularly, particularly in the traffic pattern

Yes but mainly on short final. The tones don't start until I slow down to near touchdown speeds. This might change now that Dynon has updated the software to allow calibration based on flap position although I haven't had a chance to update my software. Note - I mainly use the aural tones. The AOA indicator on the Dynon screen is a bit too small and not in easy field of view. I want to be eyes outside when in the pattern.

 

[airguy]

1. What AOA system are you using?
Dynon Skyview

2. Did you find the calibration to be straightforward or difficult?
Very easy

3. Are you comfortable with the accuracy of the calibration?
Yes, and I test it frequently. It gives consistent alerts during a full-stall landing right where it should.

4. Do you find the AOA system to be an effective stall warning?
Audible - yes. I never look at the AOA indicator on the panel.

5. Do you use the AOA system regularly, particularly in the traffic pattern?
Eyes outside - like they should be - with the AOA chirping in my ear. Best of both worlds.

Many thanks!

I don't have any use for the on-screen display, but I REALLY like the audible tones.

 

[rleffler]

1. What AOA system are you using?

I have both installed. I had the AFS installed with the wing ports long before the Dynon offering. I eventually replaced a Gretz pitot with a Dynon. I’m still using the AFS wing ports since the are more accurate than the pitot version.

2. Did you find the calibration to be straightforward or difficult?

Straight forward

3. Are you comfortable with the accuracy of the calibration?

Yes

4. Do you find the AOA system to be an effective stall warning?

Yes

5. Do you use the AOA system regularly, particularly in the traffic pattern?

Not normally, the exception of flyins like OSH which you never know who you will be following. I’ve got the aural warnings enabled if something needs my attention.

 

[rockwoodrv9]

G3X AOA video

I just watched this yesterday. Dome by Paul Dye for the G3x. Im not sure it answers all the questions but was worth watching.

https://www.kitplanes.com/how-to-calibrate-angle-of-attack-on-garmins-g3x-touch-system/

1. What AOA system are you using?

I have the G3x touch System

2. Did you find the calibration to be straightforward or difficult?

Straight forward - video helped

3. Are you comfortable with the accuracy of

Yes

4. Do you find the AOA system to be an effective stall warning?

Yes

5. Do you use the AOA system regularly, particularly in the traffic pattern?

Yes

 

[rv8ch]

After speaking with DR about this post, here is a survey regarding the calibration and use of AOA in your daily flying. EAA has an active AOA working group to see if the use of AOA can reduce the risk of loss of control accidents. We would like to know the experience of the RV community in the calibration and use of AOA, and your comments about the use of AOA as a stall warning and in the traffic pattern. Here goes:

1. What AOA system are you using?
Dynon/AFS
Garmin
Alpha Systems
Bendix/King
Uavionics
Safe Flight
General Technics
Lift Reserve
Other

2. Did you find the calibration to be straightforward or difficult?

3. Are you comfortable with the accuracy of the calibration?

4. Do you find the AOA system to be an effective stall warning?

5. Do you use the AOA system regularly, particularly in the traffic pattern?

Many thanks!

Hi Terry, you might want to consider using a Google Form to capture this data.

https://support.google.com/docs/answer/6281888?hl=en&co=GENIE.Platform=Desktop

In any case, here's my answers:

1. GRT
2. Easy
3. Yes
4. Yes
5. Yes

 

[BobTurner]

Terry, for completeness, you may want to add two systems to your list:
Old GRT, circa 2012. This system is purely computed from efis data, no extra air sensor needed.
Newer GRT. Works off a spit sensor pitot tube like the Dynon.
I have both the Dynon D6 and the old GRT.
My answers
1. Dynon D6 and old GRT
2. D6, yes, as long as I followed the instructions. Old GRT, no calibration needed, it directly computes AOA from efis data.
3. Yes for both
4. Yes for both
5 yes for both. Both are on all the time, but I have never inadvertently activated them, and only hear them during deliberate stall practice, and during the landing flare. Note, I have not tested them for any accelerated stalls or other rapidly changing maneuvers. I think the computed grt system may have some lag for these (probably the reason they now use dual air sensors like everyone else.)

 

[GatorsR1]

here's my answers:

Dynon
Easy
Yes
Yes
Yes, but wish the screen display was larger so I could easily recognize status with a glance during maneuvers. I asked the Dynon guys at SNF & OSH if it could be made larger or add a separate display like Garmin GI-260 ... answers were basically negative Ghost Rider, screen is full.

 

[Ed_Wischmeyer]

1. What AOA system are you using?

Garmin G3X Touch


2. Did you find the calibration to be straightforward or difficult?

3. Are you comfortable with the accuracy of the calibration? yes

4. Do you find the AOA system to be an effective stall warning? yes. Especially appreciate the progressive beep rate, indicating closeness to stall.

5. Do you use the AOA system regularly, particularly in the traffic pattern?

No, I don't use AOA guidance at all in normal flying. Airspeed does everything I need, including many things that guidance AOA does not. And the theoretical advantages of AOA guidance for general aviation really don't make any difference. NASA documented that 60 years or so ago.

Stall warning, yes. Guidance, no.

I've documented fundamental and aerodynamic limitations of AOA that EAA and other organizations refuse to address, sort of like the emperor's new clothes. For example, here's what AOA looks like in gusts:
https://www.youtube.com/watch?v=bWSzptdQyFk.

It's as if everybody is so intent on finding a magic bullet that they don't do their homework. There have been no factual challenges to the results I've documented, and everything I've published is repeatable. Nobody has bothered to duplicate or to try to disprove my results. And I've paid lots of dues that others haven't, including MIT Ph.D. and decades of aviation safety research.

I've received many comments like "that's not how I do it" or about the Navy or the airlines but no comments based on fact. And it's a sad commentary on several organizations that posts contrary to their party line or pet ideas have been deleted and letters not published.

 

[marchudson]

1. What AOA system are you using?
Garmin

2. Did you find the calibration to be straightforward or difficult?
Not as easy as the Dynon but not too bad

3. Are you comfortable with the accuracy of the calibration?
Yes

4. Do you find the AOA system to be an effective stall warning?
Very much so

5. Do you use the AOA system regularly, particularly in the traffic pattern?
I use it as my primary approach instrument

 

[marchudson]

1. What AOA system are you using?

Garmin G3X Touch


2. Did you find the calibration to be straightforward or difficult?

3. Are you comfortable with the accuracy of the calibration? yes

4. Do you find the AOA system to be an effective stall warning? yes. Especially appreciate the progressive beep rate, indicating closeness to stall.

5. Do you use the AOA system regularly, particularly in the traffic pattern?

No, I don't use AOA guidance at all in normal flying. Airspeed does everything I need, including many things that guidance AOA does not. And the theoretical advantages of AOA guidance for general aviation really don't make any difference. NASA documented that 60 years or so ago.

Stall warning, yes. Guidance, no.

I've documented fundamental and aerodynamic limitations of AOA that EAA and other organizations refuse to address, sort of like the emperor's new clothes. For example, here's what AOA looks like in gusts:
https://www.youtube.com/watch?v=bWSzptdQyFk.

It's as if everybody is so intent on finding a magic bullet that they don't do their homework. There have been no factual challenges to the results I've documented, and everything I've published is repeatable. Nobody has bothered to duplicate or to try to disprove my results. And I've paid lots of dues that others haven't, including MIT Ph.D. and decades of aviation safety research.

I've received many comments like "that's not how I do it" or about the Navy or the airlines but no comments based on fact. And it's a sad commentary on several organizations that posts contrary to their party line or pet ideas have been deleted and letters not published.

Wow Ed. The OP didn't say anything about using AOA as guidance or a "magic bullet" for that matter. Simply saying "EAA has an active AOA working group to see if the use of AOA can reduce the risk of loss of control accidents". Just my opinion, but I believe it does. Especially when coupled with a tone in the headset. Distractions happen in the cockpit and another tool to assist in preventing approach turn stalls I think is a good thing. I don't have an MIT Ph.D studies to back up my observations, only a few dark nights behind a grey ship. YMMV.

 

[jeffk]

1. What AOA system are you using?
Garmin G3X Touch with GI-260 in my former RV-7 N771KM (sold to a friend)

2. Did you find the calibration to be straightforward or difficult?
Yes, my friend flew with me and we completed the process in one flight (thanks Jeremy!)

3. Are you comfortable with the accuracy of the calibration?
Yes

4. Do you find the AOA system to be an effective stall warning?
Yes, it gives a good indication of alpha.

5. Do you use the AOA system regularly, particularly in the traffic pattern?
All the time. I found if I kept the GI-260 on the green dot everything worked out well. I could venture into the yellow (audio tones helped as well). It became my primary approach instrument and I really liked having it in my peripheral vision.

On one occasion, it alerted me to a 'soon to be' departure stall as I turned cross wind on a max performance climb out.

In the attached photo, note the GI-260 on the glare shield mounted just to the right of the left seat pilot's view. I plan to go this route again...

 

[rv8ch]

...

I've documented fundamental and aerodynamic limitations of AOA that EAA and other organizations refuse to address, sort of like the emperor's new clothes. For example, here's what AOA looks like in gusts:
https://www.youtube.com/watch?v=bWSzptdQyFk.
...

Hi Ed, any idea why the AoA indicator in your video is so wild and frisky? I have not seen anything like this on my GRT AoA, which uses a tiny air pressure port on my right wing. Perhaps the GRT is dampening a bit more than the one you showed in the video.

I have very little AoA experience outside of my RV-8, so outside of watching Vac's many excellent videos with AoA and OnSpeed, I don't have a huge database to sample from. Perhaps Terry's poll will shed some light on if this kind of variation on AoA is a wider problem.

 

[M McGraw]

Hi Ed, any idea why the AoA indicator in your video is so wild and frisky? I have not seen anything like this on my GRT AoA, which uses a tiny air pressure port on my right wing. Perhaps the GRT is dampening a bit more than the one you showed in the video.

I have very little AoA experience outside of my RV-8, so outside of watching Vac's many excellent videos with AoA and OnSpeed, I don't have a huge database to sample from. Perhaps Terry's poll will shed some light on if this kind of variation on AoA is a wider problem.

I have the same AOA system as does Ed. I went to Ed’s presentation at AirVenture. I also attended the EAA presentation on AOA. I do have experience as an aerospace engineer and 15 to 18,000 flight hours. I use AOA A LOT! 1,000 of those hours are with the same system Ed dislikes and yet we disagree.

AOA is a tool, use it as such and cross reference just like EVERY instrument in your aircraft. When you see low oil pressure a good idea would be to look at oil quantity and temperature. When you look at climb rate a good cross check would be airspeed/AOA. There is not a single instrument that tells the whole story all the time.

Be safe and learn as much as you can about your entire panel.

 

[BillL]

1. What AOA system are you using?
Garmin AoA pitot and G3X display

2. Did you find the calibration to be straightforward or difficult?
Process was simple, but unclear as to resulting accuracy with various flap settings.

3. Are you comfortable with the accuracy of the calibration?

Overall, no - but seems to be within 2 kts at 20deg flap setting, the calibration point.

4. Do you find the AOA system to be an effective stall warning?

It seems to be effective- it has always alerted, but not much aural feedback below on-speed - green dot.

5. Do you use the AOA system regularly, particularly in the traffic pattern?
In most of 250 hrs, no. But - -lately have been attempting to use it on final. The issue is aura beep is hard to use to maintain on-speed and heads/eyes up on final.

Many thanks!

It was calibrated in Ph I and have greatly refined my handling of the RV since then. My general lack of confidence could be calibration or lack of experience in precisely how the G3X implementation should be used.

Maybe I would be better if the tones were more like VAC's on speed system. Or maybe I just need more experience is it's use. Fuzzy response - - - sorry.

 

[Ironflight]

It was calibrated in Ph I and have greatly refined my handling of the RV since then. My general lack of confidence could be calibration or lack of experience in precisely how the G3X implementation should be used.

Maybe I would be better if the tones were more like VAC's on speed system. Or maybe I just need more experience is it's use. Fuzzy response - - - sorry.

Hey Bill - now that you have more experince with the airplane, go back and do the Cal again (very simple), and if you have the latest software, you can get the tones to come on at a lower alpha (approach guidance instead of just stall warning) and I would wager you’ll like it a lot better. Sounds like you’re almost there….

 

[dmattmul]

AOA, wouldn’t leave home without it.

After speaking with DR about this post, here is a survey regarding the calibration and use of AOA in your daily flying. EAA has an active AOA working group to see if the use of AOA can reduce the risk of loss of control accidents. We would like to know the experience of the RV community in the calibration and use of AOA, and your comments about the use of AOA as a stall warning and in the traffic pattern. Here goes:

1. What AOA system are you using? Garmin

2. Did you find the calibration to be straightforward or difficult? Straightforward

3. Are you comfortable with the accuracy of the calibration? Yes

4. Do you find the AOA system to be an effective stall warning? Yes, very much so.

5. Do you use the AOA system regularly, particularly in the traffic pattern? Always. The tones are great to have and easy to interpret.

Last year at OSH turn to final at 200 ft (pretty task saturated (first time flying in)) I heard the tone and looked down at my airspeed and was too slow. Added power and pitched down slightly. (The 14’s performance is amazing).

One issue I’m not completely sure is when the full flap setting for AOA kicks in. I’ve read needs to be more than 50%. I’ve adjusted half flaps to a slightly lower degree setting to insure I’m not at full flap AOA calibration with half flaps. Figured better to be a little on the fast side than slow for that particular flap configuration. I’ve really like the system and looking at the history log can tell exactly what my airspeed is at point of touchdown. (Max AOA reading) I’m getting almost 500 hours per set of mains. Landing at the slowest speed possible I believe helps.

Many thanks!

Added words to get the min in.

 

[Steve]

Do this first

For those of us using a G3X for the last few years but not the AOA function, you must first enable that function by:
Entering Configuration mode on the G3X (Hold MENU while powering up).
Touch the LRU button.
Touch the AOA tab.
Select ENABLE. The factory setting is DISABLE.
Press BACK.
Press SAVE and REBOOT.

Then go fly and calibrate the AOA per PD's video.

 

[BillL]

Hey Bill - now that you have more experince with the airplane, go back and do the Cal again (very simple), and if you have the latest software, you can get the tones to come on at a lower alpha (approach guidance instead of just stall warning) and I would wager you’ll like it a lot better. Sounds like you’re almost there….

Thanks, Paul, just watched your video (5/5) - -and looked up the latest instructions for my G3X non-touch - - - I am betting you are right , a recalibration, + many SW updates, should improve the experience.

 

[Vac]

After speaking with DR about this post, here is a survey regarding the calibration and use of AOA in your daily flying. EAA has an active AOA working group to see if the use of AOA can reduce the risk of loss of control accidents. We would like to know the experience of the RV community in the calibration and use of AOA, and your comments about the use of AOA as a stall warning and in the traffic pattern. Here goes:

1. What AOA system are you using?
Dynon/AFS
Garmin
Alpha Systems
Bendix/King
Uavionics
Safe Flight
General Technics
Lift Reserve
Other

2. Did you find the calibration to be straightforward or difficult?

3. Are you comfortable with the accuracy of the calibration?

4. Do you find the AOA system to be an effective stall warning?

5. Do you use the AOA system regularly, particularly in the traffic pattern?

Many thanks!

1. Other

2. Straightforward. Calibration is automated, resulting in standard cues from airplane to airplane, regardless of type. A single deceleration run from Vmax to Vstall is flown at each flap setting (up to 5) and the system calibrates maneuvering angle (AOA associated with maneuvering speed), L/Dmax, on speed (Vapp and a 0 Ps [used as a maneuvering reference]), and stall. Calibration is optimized to increase dynamic accuracy of the system (i.e., better AOA during maneuvering flight or flight under turbulent conditions). An on speed band of +/- 1 deg is calculated, which results in a speed band of +/- 2 kts from a precise on speed condition at 1 G that correlates with 1.25 to 1.35 Vs. 2 degrees of stall warning is provided, which results in 5 kts of warning at 1.4 G's in a sustained 45 degree bank.

3. Yes. Instrumented flight test shows an accuracy of ½ degree or less error from actual AOA and a transient response accuracy of 1 degree or less up to six Gs at 20 degrees of yaw or less. The physics used to achieve this level of performance are described in this paper https://www.tc.faa.gov/its/worldpac/techrpt/tc18-7.pdf.

4. Yes. Here is a series of low G (less than 2) accelerated stalls that could occur in a normal traffic pattern, including some skidding and slipping departures from controlled flight. My airplane lacks buffet cues at 2Gs or less, so I'm dependent upon the progressive stall warning at low G. Note how airspeed is essentially constant during the accelerated stalls. The last test is interesting, it's a sustained series of oscillating stalls with yaw present--a relatively demanding scenario for any AOA system: https://youtu.be/ymQqkHbHEPE. Listen to the tone and watch the conventional military indexer (AOA visual display) as the airplane momentarily looses then regains stability during the series. "Perch" is a USAF expression for the point in the traffic pattern where you start the base turn. Since the flight envelope is defined by aerodynamic, structural and airspeed limits, it is also handy to know when approaching ANY of those limits including G limits adjusted for asymmetric maneuvering (rolling G). In addition to stall, it’s handy to know when the airplane is at maximum structural cruising speed, at or below corner velocity (maneuvering speed adjusted for gross weight), at L/Dmax (best range glide, approximate best rate of climb, maximum range), on speed (approach and landing, maximum endurance glide, maximum sustained turn rate for a given power setting and best angle of climb) and "fast" or “slow” relative to that optimum condition.

5. Yes. I find the audio trend information helpful for aircraft handling, including approach and landing. The system is sufficiently accurate and responsive that it is practical to fly the airplane without airspeed or G references.

v/r,

Vac

 

[Pilot135pd]

1. Other

2. Straightforward. Calibration is automated, resulting in standard cues from airplane to airplane, regardless of type. A single deceleration run from Vmax to Vstall is flown at each flap setting (up to 5) and the system calibrates maneuvering angle (AOA associated with maneuvering speed), L/Dmax, on speed (Vapp and a 0 Ps [used as a maneuvering reference]), and stall. Calibration is optimized to increase dynamic accuracy of the system (i.e., better AOA during maneuvering flight or flight under turbulent conditions). An on speed band of +/- 1 deg is calculated, which results in a speed band of +/- 2 kts from a precise on speed condition at 1 G that correlates with 1.25 to 1.35 Vs. 2 degrees of stall warning is provided, which results in 5 kts of warning at 1.4 G's in a sustained 45 degree bank.

3. Yes. Instrumented flight test shows an accuracy of ½ degree or less error from actual AOA and a transient response accuracy of 1 degree or less up to six Gs at 20 degrees of yaw or less (with a spherical sensor) or 6 degrees or less (non-spherical sensor). The physics used to achieve this level of performance are described in this paper https://www.tc.faa.gov/its/worldpac/techrpt/tc18-7.pdf.

4. Yes. Here is a series of low G (less than 2) accelerated stalls that could occur in a normal traffic pattern, including some skidding and slipping departures from controlled flight. My airplane lacks buffet cues at 2Gs or less, so I'm dependent upon the progressive stall warning at low G. Note how airspeed is essentially constant during the accelerated stalls. The last test is interesting, it's a sustained series of oscillating stalls with yaw present--a relatively demanding scenario for any AOA system: https://youtu.be/ymQqkHbHEPE. Listen to the tone and watch the conventional military indexer (AOA visual display) as the airplane momentarily looses then regains stability during the series. "Perch" is a USAF expression for the point in the traffic pattern where you start the base turn. Since the flight envelope is defined by aerodynamic, structural and airspeed limits, it is also handy to know when approaching ANY of those limits including G limits adjusted for asymmetric maneuvering (rolling G). In addition to stall, it’s handy to know when the airplane is at maximum structural cruising speed, at or below corner velocity (maneuvering speed adjusted for gross weight), at L/Dmax (best range glide, approximate best rate of climb, maximum range), on speed (approach and landing, maximum endurance glide, maximum sustained turn rate for a given power setting) and "fast" or “slow” relative to that optimum condition.

5. Yes. I find the audio trend information helpful for aircraft handling, including approach and landing. The system is sufficiently accurate and responsive that it is practical to fly the airplane without airspeed or G references.

v/r,

Vac

Other : OnSpeed system. Everything Vac said !

 

[BillL]

3. Yes. Instrumented flight test shows an accuracy of ½ degree or less error from actual AOA and a transient response accuracy of 1 degree or less up to six Gs at 20 degrees of yaw or less. The physics used to achieve this level of performance are described in this paper https://www.tc.faa.gov/its/worldpac/techrpt/tc18-7.pdf.

<snip> The last test is interesting, it's a sustained series of oscillating stalls with yaw present--a relatively demanding scenario for any AOA system: https://youtu.be/ymQqkHbHEPE.
Vac

Huge thanks Mike! The question of slip for landing in crosswind came to me in my slumber. I think this fully addressed that situation. I'll recalibrate (Thanks Paul!) my G3X and do some slip testing for fun. {Edit - I have garmin pitot}

Your website has a listing for all the electronic components to assemble a control module, it seems that may be around $400 to build. Would there be a possibility of creating group buy for an economical batch of fully assembled units? Call it a field test. Just asking . . .Thanks

 

[rockwoodrv9]

I went to check my AOA calibration and noticed there is a clean and flaps configuration. I don’t remember it having both when I calibrated the first time. I will re do both if we ever get a good flying day here in Michigan! I did the first calibration with flaps so it will be incorrect clean. Thanks for the prompting.

 

[Pilot135pd]

Huge thanks Mike! The question of slip for landing in crosswind came to me in my slumber. I think this fully addressed that situation. I'll recalibrate (Thanks Paul!) my G3X and do some slip testing for fun.

Your website has a listing for all the electronic components to assemble a control module, it seems that may be around $400 to build. Would there be a possibility of creating group buy for an economical batch of fully assembled units? Call it a field test. Just asking . . .Thanks

A couple of things. The part about 6 and 20 degree slip is based on the pitot tube you have. Also as I understand it using the off-the-shelf AOA pitot tubes would give the 6 degrees of yaw and using the 3D printed spherical pitot tube would give the best AOA 20 degrees of yaw.

Regarding the box itself, the current issue with building it is that some parts are not available so the guru in the group is in the process of finishing up the Version 4 design with currently available parts.

The fully assembled units is what's expected for the future. Vac addressed that on this forum on another thread some time ago. I think he mentioned having it eventually sold through Van's or something like that but don't quote me, plus that's still down the road a bit.

I went to check my AOA calibration and noticed there is a clean and flaps configuration. I don’t remember it having both when I calibrated the first time. I will re do both if we ever get a good flying day here in Michigan! I did the first calibration with flaps so it will be incorrect clean. Thanks for the prompting.

So happy that the Onspeed testing has rubbed off on the big guys. Hopefully all of them eventually add this to their systems if they haven't already lately.




Edited my post to add this info below from where I based my comment on pitot tubes, since I'm not a test pilot or a computer whiz:

We've tested Dynon, Garmin, Alpha Systems as well dual tube and custom spherical sensors....

...The offset (alpha) port on the Dynon and Garmin sensors are a bit of an afterthought, and the commercial sensors have about 5-6 degree beta (sideslip) limit before you run into problems. The Dynon is notable for the lipped, conical pitot port. We've found this configuration performs well at high alpha. Ultimately a spherical head will likely give best overall performance, mitigating sideslip effects. This configuration could have between two and five ports, depending on number of pressure sensors fitted to the computer.

After experimenting with a home made "L tube" configuration, we found it was necessary to damp the offset pressure to mitigate noise effects. A small machined "bullet nose" with a tiny aperture did the trick:

Overall, this sensor proved to be slightly noiser than the Dynon or Garmin probes, but usable. It has the tactical advantage of being easy to fabricate and inexpensive. We've also found that printing a sensor is a neat way to experiment. We use a common mounting configuration (Alpha Systems) to make it easy to swap probes for testing:

Vac

FlyONSPEED.org

 

[Pilot135pd]

If you're still on the fence about AOA, read Vac's link. To me the best summary was the last line in this section:



2.5 WHY IS FLYING ANGLE OF ATTACK IMPORTANT?
Why is it important to understand that V L/Dmax varies with weight, but αL/Dmax does not?

Look at the speed for L/Dmax (best range speed) for a typical 3300 lb. single-engine retractable-gear aircraft.

With a single pilot and some equipment aboard, that aircraft might typically depart with full fuel
at 2900 lbs. The pilot operating handbook gives the equivalent airspeed (EAS) in knots equivalent
airspeed (KEAS) at full gross weight as 105 KEAS. That aircraft might carry 74 gallons of useable
fuel.

The KEAS for VL/Dmax decreases with decreasing weight as the square root of the weight ratio. For
full fuel at 2900 lb., the EAS for VL/Dmax is approximately 98 KEAS. At half fuel, it is approximately
95 KEAS. With empty tanks, it is approximately 90 KEAS. However, the AoA, αL/Dmax, remains
constant.

Flying AoA might make the mission possible whether it is to the mission destination or,
in an emergency, a glide to an on-airport landing rather than an off-airport landing.

Furthermore, no calculations are required; the AoA must simply be flown.

 

[dmattmul]

Garmin applicable

I went to check my AOA calibration and noticed there is a clean and flaps configuration. I don’t remember it having both when I calibrated the first time. I will re do both if we ever get a good flying day here in Michigan! I did the first calibration with flaps so it will be incorrect clean. Thanks for the prompting.

Garmin with the 9.31 update added the second flap position for the AOA.

 

[BobTurner]

…..
Flying AoA might make the mission possible whether it is to the mission destination or,
in an emergency, a glide to an on-airport landing rather than an off-airport landing. ……

But keep in mind, that in the real world, you also need to take wind into account. e.g., if gliding into the wind towards an airport, max range will require a speed higher than what your AOA is telling you.

 

[DeltaRomeo]

1. AFS AOA Pro https://www.advancedflightsystems.com/advanced-aoa.php
2. Straightforward and not difficult.
3. Yes
4. Yes
5. Yes. It is my primary instrument on final. (airspeed second).

 

[Vac]

Gentlemen, respectfully request we don't hijack this thread (too bad) with a deep dive discussion, let's revive an old thread if you want to go there--It's important for Terry, Paul and team to gather data and help folks calibrate their systems. Thanks!

Having said that, I do want to close the loop on a couple of topics you brought up

Bob is correct. Appears to be a habit with him. Never buy a math engagement with a physicist Actual glide range is wind dependent. The glory of AOA references (say on speed for approach/landing) are generally always the same, no math, which is good for history majors like me...as folks have already pointed out AOA is only part of the performance equation, it's just a really good hack for an average stick monkey like me.

Yaw effects are a tricky topic because we don’t have a truth source that performs well under demanding conditions like the oscillatory slipping stalls I demonstrate in the video. For AOA measurement, the historic reference has been an air data boom and more recently, AOA derived from GNSS/INS (pitch – flight path angle corrected for earth-referenced G). Both sources are not capable of accurate AOA measurement under the conditions of this test. The best we can do is plot pressure-derived AOA and compare it to critical AOA for the two probes tested. That is shown in these two plots. What’s critical (pun intended) is that stall is detected, and warning is provided before longitudinal stability is lost (you can see this in the video). Critical AOA is 18.69 degrees relative to the fuselage reference line used for calibration for the test airplane in the video.

The 6-degree limit is for a blade type probe and was determined during wind-tunnel testing. The 20-degree limit is emperically derived from flight test for the two common pitot/AOA probes mounted at 26% chord, 6 inches below the left wing of the test airplane. The probes are approximately 8 inches apart and are in the same flow field. Keep in mind when we talk about yaw effects, we are talking about the accuracy of the computed AOA solution, not the ability to detect stall properly, which can be verified by flight test. This observation supersedes my quote above: "...the commercial sensors have about 5-6 degree beta (sideslip) limit before you run into problems..." It's been a steep learning curve. No excuse. More flight testing to be done. A properly calibrated system should (hopefully) detect stall within the normal yaw limits of the airplane. This can be verified by stalling in a slip in both directions (if you are comfortable performing that maneuver at altitude) with the system you have installed. That is the case for the two probes in the plots above.

There is zero point zero doubt yaw impacts pressure-derived AOA (and IAS for that matter). I can hear it when I slip the airplane. The important point is that stall is detected and the system performs well post-stall and during recovery. Cues are sufficient to maintain (or regain) aircraft control to the control travel limits in the test airplane. What’s important is that our logic does not use static pressure for normalization. Dr. Rogers discusses this in depth.

Bill, The processor we are currently using succumbed to COVID, so we are re-designing the hardware. The key to accurate AOA measurement is the differential pressure sensors. Dr. Rogers discusses the resolution required in the paper I attached above. These are relatively expensive components (about 60 bones each and three are required--two for AOA and one to facilitate automatic calibration).

Fly safe,

Vac

 

[Jeff Vaughan]

Onspeed user
Ditto Vac and Pilot135PD

 

[Terry Lutz]

AOA Calibration

1. G3X Touch
2. Mostly straightforward. Requires slow flight, particularly with flaps down, which can cause high CHTs if you are working too slowly in high OATs. There is also the risk of overspeeding the flaps if not careful during recovery.
3. Yes
4. Yes
5. Yes. To be head's out and use just the tone requires some practice, but you can use the threshold when the tone comes on to your advantage in the pattern. I found the tone to be irritatingly too high, so I placed it a little lower in volume than I would like.

 

[Terry Lutz]

AOA Calibration

1. Other - FlyOnSpeed
2. Straightforward. Requires a level decel from Vmax to Vs with a smooth reduction in power over 8 seconds. Can be done with flaps up and flaps down. Can be done with various flap settings if you have a flap position sensor.
3. Yes
4. Yes
5. Yes, completely. The tones are not intrusive and tell you just what you need to know when flying eyes out, particularly in the pattern.