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  #21  
Old 04-17-2017, 03:28 PM
YellowJacket RV9 YellowJacket RV9 is offline
 
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Great video, and inspired me to go do some practice today using AOA. I have the derived AOA on my GRT Sport, but have actual AOA plumbed to my Dynon D10. I haven't been using the AOA display from the D10 as it is not my primary instrument and I don't generally look at it on approach. This thread has convinced me to build and install the tone generator which should be a perfect solution for me.

What I re-learned while practicing today was that I have let my approach speeds get too high. The day I did my first flight, I found a full-flap stall speed of 44KIAS, so I flew my approach at 60 knots, and it worked great. I've flown as slow as 55KIAS for short field practice without incident, also. In the year since then, I am guilty of letting my approach speed creep upwards for various reasons (gusty, crosswinds, heavy, etc) until I found myself generally flying final at 65 KIAS. This is almost always too fast and results in too much float, which means more time for something to go wrong, too.

Flying with and paying attention to AOA today I found myself back at 58-60KIAS, and nailed some spot landings, even with a 5-7 knot x-wind. There was still plenty of energy left for a flare and gentle touchdown.

I obviously don't fly any crazy flight regimes in my 9A, but any tool I can use to make me a more precise, safer pilot, I am all for. The ultimate goal is to fly the same perfect, precise, stabilized approach to land, every time. The 9A is so forgiving, it let me get away from that perfection without really noticing.

Thanks

Chris
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  #22  
Old 04-17-2017, 03:47 PM
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rv8ch rv8ch is offline
 
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Default interesting document

Mike, Thanks for the link to the document. I found this amazing:

19. Schuck, 0. H., "Angle of Attack Indicating Device," U. S. Patent No. 2,948,149, Aug 9, 1960.

Almost 60 years and we still struggle to get this very useful safety feature in all aircraft.
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  #23  
Old 04-17-2017, 06:05 PM
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Mark Dickens Mark Dickens is offline
 
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Quote:
Originally Posted by Vac View Post
P.S. Mark--this logic does work with the SkyView and we've built a prototype that is compatible, but haven't tested it yet. I believe the SkyView uses an improved AoA algorithm, and likely produces more consistent calibration results than the earlier DY equipment does. In theory, it should be easier to program the tone generator for a SkyView system; but we'll have to complete testing to determine if that's the case.
Thanks. Can't wait to learn more!
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  #24  
Old 04-17-2017, 06:07 PM
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schristo@mac.com schristo@mac.com is offline
 
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Default should work already with a setting adjustment

Quote:
Originally Posted by Mark Dickens View Post
If someone could make these available commercially so that it worked with the Skyview, I'd buy one immediately!
The Skyview AOA system is based on the calibration that you fly... typically the target point is a specific configuration stall and the audio trigger points. From the Config file, there there are two settings that indicate the start of sounds and the start of the solid tone:

audio_sound_aoa_start_thld=50
audio_sound_aoa_solid_thld=95

I believe that you can simply adjust the start threshold from 50 to have the tones begin at the desired 'On Speed' target.
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  #25  
Old 04-18-2017, 08:53 AM
Vac Vac is offline
 
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Default Find 60% Lift

Stephen is correct that the progressive tone can be adapted to provide an approximation of ON SPEED.

Most basic technique:

Calibrate your AoA system in accordance with instructions. If you aren't sure about what the system is sensing for stall (i.e., you can down load data from an EFIS, but you can't from a stand-alone AoA sensor), just do some comparison flying--check your AoA indications against Vref at 1G in different flap configurations (or Vx or minimum sink glide, if you've got that information) and correlate any display or audio cues. That will provide a rough approximation of ON SPEED. This technique will work if you have steam gauges and an AoA sensor of some type.


More in-depth considerations:

Measuring actual AoA is a black art! All we are doing is using our differential pitot pressure sensor as a surrogate--that will get us close enough for every day life; but calibration still presents some challenges...

ON SPEED occurs at about 1.3-1.4 times the stall speed for an RV, so you know about what IAS to look for at 1G as you set up any system.

Calibration of differential pressure AoA systems "teaches" the software where 100% lift is, and the indication and progressive stall warning is based on what percentage of lift is being measured. Since ON SPEED occurs at approximately 60% lift, if your calibration has stall occur at 100% lift, then the 50% audio trigger point Stephen mentions would be just a bit faster than ON SPEED, but reasonably close. If the tone is progressive, and you slow from the point the tone starts (50%) to Vref, whatever the tone sounds like at Vref is about right.

The older DY Dynon systems have the option of starting audio at the bottom or middle of the yellow band--depending on calibration, likely one of those settings is going to be very close to ON SPEED if (big if), the stall is occurring at 100% lift as sensed by the EFIS.

On the other hand, if the calibration has stall occur at 85%, then the 50% start of the tone is roughly equivalent to ON SPEED. It's simply proportional.

If your system is calibrated, and the manufacturer provides data about how the graphic display works, you can determine where ON SPEED is. For example, if it's an AFS pro, then ON SPEED is the green doughnut (the doughnut is the classic military standardized solution for displaying ON SPEED). Other systems use a similar logic. On the other hand, if it's a progressive display (chevrons, LEDs, etc), then you may have data about how that display works in terms of % lift; so if you've calibrated so that stall is occurring at 100% lift, then whatever portion of the progressive display corresponds to 60% is what you are looking for to approximate ON SPEED.

For experimenters that have an EFIS:

The first step is to calibrate the AoA system in accordance with the manufacturer's instructions, and then fly a stall series and record the data. Set your EFIS data recording system to 1 second intervals--that's sufficient.

It is sufficient to fly stalls in three configurations: flaps up, half flaps and full flaps. Set the altimeter to 29.92 and fly a representative pressure altitude. The simplest technique is to select idle power and maintain altitude precisely. Trim as the airplane decelerates, but stop trimming at about 80-90. After the stall, use AoA to recover (i.e., pitch down) and let the airplane recover at idle power and accelerate to about 100 MPH/90 KTS indicated (just a bit faster than trim speed)--you'll lose a few hundred feet of altitude (which is fine, since our objective is to generate an easy to read graph, not pass a check ride). Once you've accelerated to about Vfe ish (that's where the 100 MPH/90 KTS ROT comes from), add power, climb up and get set up for the next iteration. This isn't a speed drill--about 45-60 seconds per stall should work out about right.

After you land, download the flight data. Find the stall series in the data (use a data marking function if your system allows or a time hack to help find the information). Plot % AoA and IAS vs elapsed time--look at what the AoA/pitot is sensing vs stall and figure out what the peak AoA % value is for various configurations. In an RV, it's sufficient to look at flaps up, half flaps and full flaps. The data from this test drill will allow you to program the various tone trigger points if you are building a tone generator.

If you don't provide a flap position sensor that tells the computer which data curve to generate tone from, you can still approximate ON SPEED in a landing configuration (where you obviously want the most accuracy) and accept some error during maneuvering flight (where all it's costing you slightly reduced accuracy in sustained turn performance feedback).

Fly safe,

Vac
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  #26  
Old 04-18-2017, 11:59 AM
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Thank you for your work in this area. This device has the potential to vastly improve the safety record for GA. I hope you will consider applying for the 2017 EAA Founder’s Innovation Prize. You would be a shoe-in!

https://www.eaa.org/en/eaa/eaa-news-...novation_prize
The 2017 EAA Founder’s Innovation Prize is a contest to solve the problem of fatal loss of control accidents in amateur-built aircraft through innovation. The contest is intentionally open-ended, with the only stated goal to reduce fatalities from this type of accident in amateur-built aircraft dramatically over the next decade - 25% in the next five years, 50% in the next ten. Submissions are due June 15th, 2017.

Goals and Criteria

Loss of control (LOC) in flight is the leading cause of fatal accidents in general aviation, particularly in amateur-built aircraft. Fatal LOC events include base-to-final stalls, departure stalls, loss of control while maneuvering, spatial disorientation, and more. The 2017 contest seeks ways to solve this problem. The solution could be technical in nature or otherwise.

The judging criteria include:
•Effectiveness in reducing LOC occurrence, including wide applicability to the experimental amateur-built fleet and maturity of the solution
•Low Cost
•Ease of installation/implementation

Prizes

The winning individual or team will receive a prize of $25,000, with $10,000 awarded for second place, and $5,000 for third. The five finalists will also be featured in EAA media leading up to the final award.
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  #27  
Old 04-18-2017, 02:06 PM
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RV6_flyer RV6_flyer is offline
 
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Quote:
Originally Posted by Noah View Post
Thank you for your work in this area. This device has the potential to vastly improve the safety record for GA. I hope you will consider applying for the 2017 EAA Founder’s Innovation Prize. You would be a shoe-in!

https://www.eaa.org/en/eaa/eaa-news-...novation_prize
The 2017 EAA Founder’s Innovation Prize is a contest to solve the problem of fatal loss of control accidents in amateur-built aircraft through innovation. The contest is intentionally open-ended, with the only stated goal to reduce fatalities from this type of accident in amateur-built aircraft dramatically over the next decade - 25% in the next five years, 50% in the next ten. Submissions are due June 15th, 2017.

Goals and Criteria

Loss of control (LOC) in flight is the leading cause of fatal accidents in general aviation, particularly in amateur-built aircraft. Fatal LOC events include base-to-final stalls, departure stalls, loss of control while maneuvering, spatial disorientation, and more. The 2017 contest seeks ways to solve this problem. The solution could be technical in nature or otherwise.

The judging criteria include:
•Effectiveness in reducing LOC occurrence, including wide applicability to the experimental amateur-built fleet and maturity of the solution
•Low Cost
•Ease of installation/implementation

Prizes

The winning individual or team will receive a prize of $25,000, with $10,000 awarded for second place, and $5,000 for third. The five finalists will also be featured in EAA media leading up to the final award.
Noah that is a GREAT Idea. I agree with your assessment and thank you for suggesting it.
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  #28  
Old 04-23-2017, 09:01 AM
Vac Vac is offline
 
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Default Thank You

Folks,

I appreciate all of the replies, discussion and interest in our work!

We are happy to share everything that we've learned with ANYONE interested in building a tone generator, adapting this logic or just interested in discussing the concept. We have only been working on this project for a year, and still have some legwork to do to improve utility and accessibility for folks that may want to experiment or use a similar system. We aren't a commercial concern--just some of RV'ers that like to experiment.

What's nice about the concept is that it's just an aural logic--it can be "ported" to any AOA system if a manufacturer chooses to adapt it. Furthermore, it is really a "CAWS:" Caution and Warning System...there may be a better, more ergonomic method of conveying ON SPEED information to the pilot; or the logic could be integrated with other envelope protection. It's completely feasible to provide distinct, ergonomic aural warning for the entire flight envelope (aerodynamic, G and airspeed limits). Providing ON SPEED cues simply enhances the the system by providing an optimum performance cues as well. Pieces and parts of this already exist in currently available hardware; so it's a matter of adapting and integrating, as well as ensuring simple, effective calibration and education of pilots. Similar systems have proven effective in high-performance trainers and fighters, and if we are trying to mitigate loss-of-control, it's worth looking at what has worked in other flying communities faced with a similar challenge.

Any and all comments or questions are welcome. Please feel free to post, e-mail or PM. And please consider commenting regardless of your experience! One of our primary objectives is to help inexperienced folks safely transition to RV's and learn how to safely operate the airplanes throughout the flight envelope, and those folks have an outstanding perspective to offer valuable feedback.

The objective of this project is similar to the objective of preparing high-quality training resources: a community-based "self-help" project. In that spirit, I appreciate the point out the EAA Founder's Innovation competition. We did, in fact, apply last year without success; but have had several months to continue test and evaluation of the concept and will be re-entering this year. Competition aside (this isn't football or combat), hopefully participation will at least engender continued discussion and introduce more folks to the potential benefit of this of this type of "non-automatic" solution to mitigate loss-of-control mishaps.

Thank you!

Vac
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Last edited by Vac : 04-23-2017 at 09:13 AM.
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  #29  
Old 05-12-2017, 08:47 AM
Vac Vac is offline
 
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Default Short Video

For those folks not interested in enduring 17 minutes of instructor commentary, I've edited a shortened version of the video with some new footage. It provides a good 30,000 foot overview of the ON SPEED concept, and also includes "botched pattern" demonstrations where the tone assists with proper energy management when correcting pattern errors.

Please note, that in a couple of the demonstrations, I'm max performing the airplane in close proximity to the ground (under controlled conditions) to demonstrate how the tone logic assists with energy management. I don't advocate ever trying to salvage a bad pattern--it's far safer to go around. When I teach, in my personal and professional flying, I use a simple decision matrix: "if there is a doubt, there is no doubt..."

The purpose of the demonstrations is only to show how the tone logic assists the pilot with maintaining aircraft control under demanding pattern conditions, including "worst case" low energy conditions. Keep in mind that any departure from controlled flight below pattern altitude is likely to be unrecoverable.

Here's a link to the short video: https://youtu.be/BCQF8B49tgw

As always, any comments or critiques are welcome and hopefully the information may be helpful for some of the folks in our community.

Fly safe!

Vac
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Last edited by Vac : 05-12-2017 at 09:40 AM.
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  #30  
Old 05-12-2017, 10:43 AM
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snopercod snopercod is offline
 
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Quote:
Originally Posted by Vac View Post
Any and all comments or questions are welcome.
I have an AFS Sport AoA system in my Lancair 235, and would be nervous flying without it. I have to admit that the AoA has saved my bacon a couple of times. The Lancair is not known for its gentle stall characteristics. That said, I think the constant beeping on final approach would be very annoying, although I suppose one could get used to it. As I'm sure you know, the AFS Sport unit has an LED bar graph which indicates the same things that the various "fast" tones do in your system. I mounted mine just to the left of the ASI so it's in my peripheral vision when checking my airspeed. They also have displays that can be mounted on the glareshield. The only time I get an audible stall warning is when I get within 5% of a stall. The Sport unit also alerts me when I get below 95 Kts with my gear up - a real bonus in a retractable. The CPU also has two "tables" used to compute the stall speed - one in the clean configuration and another in the landing configuration. Short video:

https://www.dropbox.com/s/yx1kabddx9...81%29.mp4?dl=0
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