Help with AOA calibration G3X

[Flyyak]

Need help calibrating AOA. Have an RV7 with G3X. Stall speed full flaps is 47kts. I normally fly instrument approach at 100kts, if in pattern 90kts base, cross end of Rwy at 70kts.

Have tried to set AOA calibration using minimum visible at 90; caution at 60; stall warning by doing power off stall full flaps. Seems to calibrate successful at end of each but when setting target AOA, reports AOA calibration is invalid.

Have tried several times in smooth air but single pilot. Any help will be appreciated. Any suggested speeds will be appreciated. Garmin support suggested minimum visible at 1.5 stall which is approximately 75; caution at 1.1 stall - 53; target at 1.3 stall or 72.

[Flyyak]

Sorry - garmin sugest target at 1.3 or 63kts

[Flyyak]

Watched your YouTube and it is neat but way over my head. I somewhat follow but if I am having difficulty calibrating the G3X AOA, the likelihood of me adapting to OnSpeed system is nonexistent.

I am sure if I can get the AOA operational, it will greatly add to the safety of operation of the RV. Thanks for the info. I have emailed your prior post and YouTube to a fellow RV owner with a dynon

[Ed_Wischmeyer]

One of the Garmin folks will give you a definitive answer, but the procedure in the book (IIRC) is to do a full stall and the software does the rest. There's no procedure for what you want. The approach speeds it gives me in the -9A, flaps up and flaps down, are reasonable, but not necessarily what I want all the time.

If you do the math, AOA is proportional to 1/V**2 at a constant 1 G. That, and the fact that you want AOA to come on at arbitrary speeds may be working against you. And you don't know how linear the Garmin system is, internally, and that may mean that you're asking for something physically impossible.

When I plotted the airspeeds at which the AOA bars came on in my RV-9A with G3X, I found that the "width" of the bars, measured in knots, ranged from 3 - 9 knots. In other word, AOA is not precise. And it gets less useful the farther you are away from the stall. If your plane stalls at 47, AOA ain't gonna do squat for you at 100 knots in terms of guidance.

I've done a whole bunch of additional work on AOA dynamic response, filter characteristics, etc., and have submitted an article to a major publication. The bottom line is that AOA is the emperor's new clothes of aviation safety.

Use airspeed, fly attitude. It's more useful, it's easy to adjust for weight if you really need to, it's more readable in turbulence.

And if you're interested, look up NASA TN D-6210. They tried real hard to see what AOA would do in a light twin, and they clearly express their disappointment. Lotsa good quotes in there.

[Ed_Wischmeyer]

One possibility is to connect to the serial data output of the display screen with your own computer and AOA display. The air data is sent out (don't recall exactly) somewhere between 5 and 10 times per second. It has both AOA and AOAcp, I believe, along with airspeed, G, pitch, all kinds of things. You could do your own AOA display calculations from that, but based on the work I've done, the filtering algorithms would be extremely challenging.

I've not messed with that serial output and have been content to look at the after the flight SD card data, which is recorded at 1 Hz.

Good luck!