AOA calibration warning

[bruceh]

I updated my Skyview Classic and Touch screens to 16.6. After reviewing the release notes I decided to go recalibrate the AOA now that it supports multiple flap positions. I go up, do stalls at 0, 10, 20 and 30 degrees of flaps (RV-9A). All seems to be set up fine.

The next day I went flying and as I was taxiing out to take off, I get spurious and repeating "Caution" announcements. The EFIS screen is basically blinking yellow CAUTION, then back to normal MESSAGES. I hit the Caution button, but nothing comes up, just "no message". Finally, I was able to see it briefly flash "AOA Calibration needed". I took off and the repeated pestering of the Caution went away. I landed at another airport, and the same thing happened taxiing out for take off there. So, back up in the air I got back into the AOA Calibration menu, and for some reason, I only had AOA settings for 0, 10 and 30 degrees. For some reason the 20 degree setting was gone. I don't know if maybe I didn't SAVE it correctly? Anyway, I repeated the process of calibration for all of the settings and the Caution pestering seems to have gone away.

I assuming that hitting a fast taxi turns on the AOA readings, and if the calibration is incomplete it can start this intermittent CAUTION audio warnings.

Anyone else experience this?

 

[airguy]

There is a setting to inhibit the AOA alerts below a certain airspeed to avoid this - I have mine set for 40 knots.

 

[bruceh]

I flew the airplane again today, and the problem is still happening. The AOA calibrations have been done. I did slow flight with every flap position and confirmed that the AOA begins alerting at different airspeeds corresponding to the flap setting. The AOA display on the EFIS shows that I'm just getting into the yellow as the audio alerting begins. This means that the AOA is calibrated and seems to be working just fine when flying.

On the ground, sitting still (no airspeed) as I did my run up to 1700 RPM, I started getting the repeating "caution" audio alert, and the EFIS was displaying the message "caution" on and off rapidly.

The inhibit AOA below airspeed is set to 40 knots.

Here's a quick video of the on/off rapid caution alerts.

https://photos.smugmug.com/RV-9A-Project/Phase-2/i-hZRSmR4/0/22f2fd72/1920/IMG_6267-1920.mp4

The only change has been to update to the 16.6 firmware.

 

[Rhino]

The caution is a calibration warning. The inhibit setting for airspeed probably will not turn that off. It appears the system intermittently thinks you don't have the calibration done when you advance the throttle. In situations like this, I tend to suspect a loose connection being triggered by vibration from the engine. Where that might be I have no clue.

 

[bruceh]

The caution is a calibration warning. The inhibit setting for airspeed probably will not turn that off. It appears the system intermittently thinks you don't have the calibration done when you advance the throttle. In situations like this, I tend to suspect a loose connection being triggered by vibration from the engine. Where that might be I have no clue.

I was just responding to the other post asking about the inhibit speed being set.
It does seem very random, so vibration might be a consideration, but it only happens on the ground. The ADAHRS is secure, and I have both the primary and secondary ADAHRS in the system. Other than the SV network, OAT and Pitot/static/AOA lines, I can't think of any other loose connection that would be causing this.

Possible next step is to do the Zero pressure IAS calibration again, then redo the AOA calibration. Stalls are fun!

 

[Rhino]

I can't think of what could be causing it either. That's a definite head scratcher. But there have been numerous instances of vibration on the ground causing issues that don't occur inflight, so that doesn't necessarily rule it out. Must be a different flavor of vibration. It's weird. Hope your next step works.

 

[Dynon]

There's a chance that settings aren't syncing between displays, and behind the scenes one is the leader/master, but you don't know (or care) which from a pilot perspective. Try turning on each display by themselves. Does it always display on one of them? If so, perform a network configuration from the "good" display, which will push its settings over to the other. And actually, before you do that, make sure the tail numbers are set the same on each display. That's the "key" that the displays use to allow themselves to share settings at all. So if they're off, you can end up with inconsistent settings, which can manifest with intermittent odd behaviors like this.

Of course, it could be something else completely, which I'm scratching my head trying to think of what it might be.

 

[RV14_TD]

same problem over here

 

[bruceh]

Following up after the holidays. I did the zero pressure calibration in my hangar. I did not warm up the electronics for 30 minutes, but I did fly the airplane earlier that day. The installation manual says to warm up it up for at least 5 minutes.

Here is a screen capture of the menu.

After this was done, the repeated "caution" announcements ALMOST are entirely gone. I still get one "caution" as I roll onto the runway during take off. I've done three flights after the calibration and it happens once every time I take off.

I'll do some more testing as suggested with the other screen and make sure they are in sync.

I'm also going to add this to my annual condition inspection routine for continued airworthiness as suggested in the manual. Obviously, it had never been done!

 

[airguy]

Where is your pitot tube installed? Is it close enough inboard to catch some occasional gust of wind from the prop during the 1700 rpm runup? If it does, then the system is doing exactly what it is supposed to do - if it sees a pressure pulse on the pitot that registers as 40+ knots, it thinks you are flying and activates the AOA system, then that pulse disappears and so does the AOA alert.

 

[bruceh]

Pitot tube is outside of the last inspection port on the wing. Always been there and never had any issues.

 

[djones]

I was just responding to the other post asking about the inhibit speed being set.
It does seem very random, so vibration might be a consideration, but it only happens on the ground. The ADAHRS is secure, and I have both the primary and secondary ADAHRS in the system. Other than the SV network, OAT and Pitot/static/AOA lines, I can't think of any other loose connection that would be causing this.

Possible next step is to do the Zero pressure IAS calibration again, then redo the AOA calibration. Stalls are fun!

Bruce,
I have engineering looking into this and they would like to get diagnostic files from your system.

 

[Janekom]

I have updated to the latest but did not yet do the AOA. in my case I do not have a position sensor connected to the flaps. Will the AOA calibration work? I cannot see how if there is no flap position.

 

[PaulSS]

AoA warning works on the Critical Angle of Attack. It doesn't give two hoots where your flaps are. Flaps up, stall at X degrees Critical Angle of Attack, flaps down, stall at the same X degrees Critical Angle of Attack......which just so happens to be a lower IAS. The AoA works on differential pressure and establishes the Critical Angle of Attack and, therefore, is unaffected by configuration. That just changes the speed, not the angle.

 

[Rhino]

The new calibration procedure allows you to enter flap positions if you choose. No, you do not need a position sensor.

 

[swatson999]

Flap deflection does not increase the critical (stall) angle of attack (AOA). In some
cases, flap deflection actually decreases the critical AOA.

Airplane Flying Handbook (FAA-H-8083-3C)

 

[RV8JD]

Three pictures are worth 3,000 words:

Page 36 of "Aerodynamics for Naval Aviators" shows the effect of a typical high lift device as shown by the airplane's lift curves. The angle of attack (AoA) at CLmax is roughly the critical (stall) AoA. Note the lower AoA at CLmax with flaps down ("Flaps") compared to flaps up ("Clean").

Note that the type of flap makes a difference also. From Page 40:

Effect of leading edge slats (No reference for this):

 

[Hummel]

I updated my Skyview Classic and Touch screens to 16.6. After reviewing the release notes I decided to go recalibrate the AOA now that it supports multiple flap positions. I go up, do stalls at 0, 10, 20 and 30 degrees of flaps (RV-9A). All seems to be set up fine.

The next day I went flying and as I was taxiing out to take off, I get spurious and repeating "Caution" announcements. The EFIS screen is basically blinking yellow CAUTION, then back to normal MESSAGES. I hit the Caution button, but nothing comes up, just "no message". Finally, I was able to see it briefly flash "AOA Calibration needed". I took off and the repeated pestering of the Caution went away. I landed at another airport, and the same thing happened taxiing out for take off there. So, back up in the air I got back into the AOA Calibration menu, and for some reason, I only had AOA settings for 0, 10 and 30 degrees. For some reason the 20 degree setting was gone. I don't know if maybe I didn't SAVE it correctly? Anyway, I repeated the process of calibration for all of the settings and the Caution pestering seems to have gone away.

I assuming that hitting a fast taxi turns on the AOA readings, and if the calibration is incomplete it can start this intermittent CAUTION audio warnings.

Anyone else experience this?

I have exactly the same issue. Random Caution warnings on the ground (especially “around the runway“, before departure and also after landing… I checked with both screens on battery power and they both show the newly calibrated settings for the different flap settings.

Furthermore my AoA seems to be incorrect for the settings with flaps. The AoA sound doesn‘t come up during approach as before and also the visual indicator is still way in the green. I did some stalls and was barely able to come to the red zone, especiall with flaps down. Also in Savvy, when I check the data, I never get above 60-70% AoA clean and 40-ish with full flaps, even after doing the calibration again.

I think there is a bug in the calibration routine after the update!

so to anyone who has done the update but not yet the new calibration, I suggest to wait for a patch.

Has anyone done the new calibration and it turned out good?

Fabian
RV14, HB-YAF
Zurich, Switzerland

 

[pmerwood]

The new calibration procedure allows you to enter flap positions if you choose. No, you do not need a position sensor.

Are you sure about that? If so, how do you enter your aircraft's flap positions?

I started another thread for AoA calibration issues (https://forum.flydynon.com/threads/aoa-calibration.15099/) and have also been in touch with Dynon support for the problem I'm having. They told me you have to have a flap position sensor for the AoA Calibration wizard to get to the new multi flap position calibration. I have manual flaps on my RV-6 and no flap position sensor. That explained why I don't see the calibration screen shown in Figure 57 in the latest version of the SkyView System Installation Manual. However, it doesn't explain why I can't calibrate my AoA at all. It seems this AoA calibration process is a bit buggy.

 

[Janekom]

Thank you - that is what I thought. Cannot see any way it could work without a flap sensor.