How do you get a GOOD AOA Calibration with RV-12is and G3X

[jackking123]

So I helped this Gent when he first got his RV-12iS flying. I assisted in Phase 1 and never could get the AOA to calibrate. I told him, do some research and calibrate it later. I cut him lose to finish up Phase 1. He never got back to the AOA.

Coming up to his 2nd condition inspection, gave him a flight review and could see many things that needed attention. One being he never got the AOA set up. So we went up today to do the AOA Cal. Ahhhhhhhhh. No joy.

I read and watched videos one being "How to Calibrate Angle-of-Attack on Garmin's G3X Touch System - KITPLANES" by Paul Dye (This does flaps up only and uses a somewhat reverse order, not top to bottom to do Calabrations)

AOA Cal menu from TOP to BOTTOM as it shows on G3X AOA Cal Page. (Note what I think speeds should be, correct me if I am wrong)
> Stall Warning AOA Calibration (Start, slow to full stall, break, recover, calibrate, done)
> Caution Alert AOA Calibration (Min Control Speed, Pre Stall 45–50 knots)
> Minimum Visible AOA Calibration (User preference 85 knots)
> Approach Target (65 kts)

Another video did do flaps up and down, and calibrated top to bottom. G3X in the RV-12is has separate pages, FLAPS UP and FLAPS DOWN.

I am not going to get into every permutations of calibration, orders, techniques, did calibrate everything. Cleared and started over x3. AOA Cal Error window was showing. No AOA appeared on approach.

A descending-order of AOA correction values for Stall, Caution, Approach, and Minimum Visible AOA is expected. Failure to achieve this order results in an error. I recall we did have issues with these values.

If you have ideas, troubleshooting, checks, step by step, button by button, airspeed / config appreciate it.

RV-12iS leading edge AOA port (and spinner pitot) has issues being calibrated? Original aluminum pitot was replaced with the SS one. Since it is due for transponder check I am going to suggest he has Pitot / Static / AOA check for leaks. The AOA rivet was installed per plans.

 

[mburch]

The order that you perform the calibration steps doesn't actually matter; the important thing is the relationship between the recorded readings for minimum, caution, and stall AOA points. These need to increase from one to the next, in that order - otherwise the system will tell you that your calibration is invalid.

The stall AOA calibration is typically foolproof, just start the procedure and go do a stall. The biggest error I usually see with the minimum and caution AOA calibration steps is when people don't follow the instructions to maintain straight and level flight. Holding X knots while maintaining a constant altitude will produce a much different AOA versus flying that same airspeed but allowing the airplane to descend.

The Approach Target AOA calibration step is optional; I'd wait to address this until you have the rest of your calibration set up properly.

Also, consider double-checking that your plumbing is correct, I've seen more than one airplane where the airspeed and AOA lines were swapped...

 

[jackking123]

Also, consider double-checking that your plumbing is correct, I've seen more than one airplane where the airspeed and AOA lines were swapped...

Bingo, I suspect this. Since he is VFR he did not need get a Pitot-Static test done, nor does he need one. Does need a transponder check. I am recommending he get full pitot static test done and his transponder at the same time.

That AOA probe with a POP rivet and janky or dubious tube connection is highly suspect. Avionics technician is not going to test the AOA port. My plan is get the G3X out of panel, disconnect the AOA tube at back of EFIS. Block AOA with tape or thumb, pull a light vacuum, see if it holds. I would not be shocked of it's leaking. That set up is sketchy, not only the pop rivet to tube connection but the location. Just my opinion.

Also the who Pitot in spinner is another odd ball.

Today was really rough down low. Had to get out of Class B airspace and climb to 4500 ft for smooth air. ill pick a smooth day and try again. I will be looking at those factors making sense.

 

[N8DAV8R]

That AOA probe with a POP rivet and janky or dubious tube connection is highly suspect. Avionics technician is not going to test the AOA port. My plan is get the G3X out of panel, disconnect the AOA tube at back of EFIS. Block AOA with tape or thumb, pull a light vacuum, see if it holds. I would not be shocked of it's leaking. That set up is sketchy, not only the pop rivet to tube connection but the location. Just my opinion.

I have been waiting on pins and needles to hear the report on how it went when you removed the G3X and disconnected the AOA tube from the back of the EFIS. Your posts illustrate that you are much more knowledgable and experienced than the people who designed and kitted these "janky and dubious" systems. You obviously know these systems much better than Van's. So...how did this test go?

 

[jackking123]

I have been waiting on pins and needles to hear the report on how it went when you removed the G3X and disconnected the AOA tube from the back of the EFIS. Your posts illustrate that you are much more knowledgable and experienced than the people who designed and kitted these "janky and dubious" systems. You obviously know these systems much better than Van's. So...how did this test go?

Thanks for your interest. The wind has been... well too windy. Easter is happening. Next week we'll give it a go. I will be sure to give a PIREP. Happy Easter.

 

[jackking123]

UPDATE UPDATE!!! Breaking News.... Success and Sadness....
Before takeoff, preflight, made sure LRU, AOA, Sound Settings were all enabled. They were. Turned ESP off to use the autopilot at slow speeds (pitch and bank protection)

After doing three of the 4 calibrations, Stall, Caution, Visible.... AOA showed up and was getting aural warnings. Yeah, did the fourth and last calibration "Target" the green ball.

Although we could have stopped there, went on to do flaps down page to started over. The system does know if flaps are up or down. Can not even do the flap down calibration unless they are full down. Again Stall, Caution, Visible.... but the numbers were not descending. Target calibration was greyed out. Re-did all of the calibrations, sometimes 2 times. Did get descending factors, barely, however target calibration was still greyed out. Had the AOA error message. Cleared the calibrations (I think), went back to flaps up. AOA was still "Working".

Did an approach and landing. PROBLEM - Everything was too high by +10 kts or more. The AOA was showing at +90 kits or higher, but was set for 80 kts. The warning beeping was going off at a higher airspeed than it should have been. Departed airport, climbed up and went after the flap up calibrations again, going for lower numbers. Did get a small improvement, but again in AOA became visible at too high of an airspeed, all the warnings were at too high airspeed. It was a little bouncy down low, so it may have affect it? Calibration was done in smooth air at altitude).

More research. I found a leak in the pitot/static/aoa system could cause this issue of airspeed. Is it possible we still are not doing the process to calibrate properly? I might have said yes the first or second time. However now after three times I think we have it. We did make headway and get the AOA to calibrate with flaps up.

Leading edge AOA rivet in leading edge is not my favorite, not to mention the pitot in spinner. The builder said he did it per plans. There is an access cover near the AOA port. During condition the AOA will be checked for leaks and proper position. Static and transponder will be tested and certified for the (24 mo) required certification. The pitot will also be checked (optional for a VFR plane).

Right now we are done with AOA, it is "working". The Sound is OFF. Will not revisit until after condition inspection in May and all connections are checked.