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04-06-2012, 07:38 AM
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Join Date: Dec 2010
Location: Alpharetta, GA
Posts: 88
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Will the G3X calculate (or at least display) AOA?
Regarding the Garmin G3X product line, does the Garmin G3X ADAHRS support the second pitot input necessary to calculate AOA? If not, will the GDU 370/375 accept AOA data from an external instrument over one of its input interfaces? If so, which external instruments are compatible?
Thanks in advance.
- John
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04-09-2012, 05:57 PM
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Join Date: Sep 2010
Location: Olathe, KS
Posts: 2,885
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John,
Thank you for considering the Garmin G3X.
Garmin hasn?t ruled out providing an AOA readout on the G3X, but does not yet offer this capability.
As others have pointed out on this site, the value of displaying AOA on the EFIS may be low compared to having a dedicated AOA readout up high where you are looking when landing, but we appreciate that not everyone wants to mount an AOA readout in the primary field of view for landing.
We appreciate the question and carefully consider all input such as this when prioritizing future G3X features.
Thanks,
Steve
__________________
Garmin G3X Support
g3xpert@garmin.com
1-866-854-8433 - 7 to 7 Central Time M to F
Please email us for support instead of using Private Messaging due to the limitations of the latter.
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04-09-2012, 06:45 PM
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Join Date: Mar 2006
Location: Newport, TN
Posts: 7,496
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Would Garmin consider putting an AOA variable in a serial stream so that it could be used by those of us that have built inexpensive remote AOA displays?
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04-09-2012, 09:18 PM
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Join Date: Mar 2006
Location: Evansville, Indiana
Posts: 661
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Quote:
Originally Posted by Brantel
Would Garmin consider putting an AOA variable in a serial stream so that it could be used by those of us that have built inexpensive remote AOA displays?
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I second Brian's request. I like the simplicity of his AOA display and would love to add one on top of my panel; in the field of view as you suggest.
Brian, would you add a link to your AOA display and controller?
__________________
______________________
Steve Eberhart, W9JUQ
3EV - Evansville, IN
Where is Steve and the Sky Terrier?
RV-7A Slider, O-360 A1A, Catto 3 blade, 2 screen Garmin G3X Classic, GTN 650, Bionics APRS. FLYING since June 24, 2009
EAA Chapter 21
Last edited by newtech : 04-09-2012 at 09:50 PM.
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04-10-2012, 09:34 AM
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Join Date: Sep 2010
Location: Olathe, KS
Posts: 2,885
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Calculated AOA
Quote:
Originally Posted by Brantel
Would Garmin consider putting an AOA variable in a serial stream so that it could be used by those of us that have built inexpensive remote AOA displays?
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Brantel,
Please correct me if I am wrong, but I think you are asking that G3X calculate AOA (without measuring it with an AOA probe) using available data and include this calculated value in the RS-232 text output data stream that G3X supports (and is described in Appendix K of the installation manual).
We have spent quite a bit of time investigating this "calculated AOA" method of providing AOA information, but we haven't yet become comfortable with implementing this approach for our customers. A spot is reserved in one of our output streams to add the AOA value should we engineer a measured or calculated solution for this.
We have read the posts that others have contributed regarding the adequacy of this method of determining AOA, and appreciate that it may be "good enough" for most conditions.
All of the measured GPS, attitude, and air data you might need to perform this calculation should already be present in the data stream that G3X outputs should you wish to perform this calculation and display it on a remote display.
Thanks,
Steve
__________________
Garmin G3X Support
g3xpert@garmin.com
1-866-854-8433 - 7 to 7 Central Time M to F
Please email us for support instead of using Private Messaging due to the limitations of the latter.
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04-10-2012, 11:40 AM
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Join Date: Mar 2006
Location: Newport, TN
Posts: 7,496
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The perfect world is that you would provide us a AOA value in the data stream. You guys will have to decide for yourself if the calculated method will meet your standards instead of a real AOA sensor method.
Now if GRT will just publish their algorithm for calculating AOA, we might get a head start on that..... 
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04-11-2012, 09:51 AM
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Join Date: May 2007
Location: Somerset West
Posts: 1,033
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Quote:
Originally Posted by Brantel
Now if GRT will just publish their algorithm for calculating AOA, we might get a head start on that..... 
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It is quite simple and based on pitch attitude, vertical speed and true airspeed.
Using vertical speed and true airspeed gives you an angle of decent. AHRS gives you pitch attitude.
Combine both and use a normal calibration flight to find differences in pitch angle and flight path angle for various airspeeds (i.e. fly close to a stall and also get a "neutral" point - usualy straight and level, high power setting). Assume the stall point is 15 degrees (or therabouts) and everything else kinda falls into place.
This works very well for the stabilized approach but is pretty useless for everything else (which is perhaps fine). It suffers a bit from lag issues if the input data doesn not change fast enough so dynamic performance is not as good as a real AOA.
Real AOA works in any attitude so you can use it in a steep, slow bank to tell you how you are doing. Granted, this can be faked as well using bank angle from the AHRS and well known changes in loading and stall speeds. It gets close - but perhaps not close enough.
Good to use as a gadget and fun to play with (we have a calculated mode as option in our EFIS's in addition to normal differential or relative AOA measurement modes).
I agree with Garmin's opinion that perhaps calculated AOA is not the best of ideas. Suppose it depends on how its used.
Rainier
CEO MGL Avionics
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04-11-2012, 10:15 AM
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Join Date: Oct 2007
Location: Norwich England
Posts: 155
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AOA
Steve G3expert
More to the point..
If a serial output from a AOA transducer was available, could you display it on the G3, and if it could what form of data would you need.
Ive have been eagerly waiting the outcome of this discussion.
p.s. an alarm to the audio panel would be good as you approach the stall.
Thanks
Rob
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04-11-2012, 02:25 PM
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Join Date: Mar 2012
Location: Houston, TX
Posts: 4
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Tell them you want it
Garmin has a place on their website to provide ideas/feedback regarding their products. I would assume that if they hear AOA enough, it will move up their priority list.
Jim
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