Dual ADAHRS calibration for AOA and Compass

B

BalsaBat

New Member
Joined
Sep 22, 2020
Messages
28
I have a Skyview HDX system with dual ADAHRS (200/201), about 5 years old. Recently, I had an intermittent OAT probe wire issue that caused me to look at the backup ADAHRS (OAT is solid on the backup). But when I to went to swap the primary and standby status of the 200/201 ADAHRS's, the system says that the backup ADAHRS has neither a compass calibration nor AOA calibration. Of course, comparing the two shows a significantly different compass heading. I did the compass calibration and AOA calibration a long time ago, with the primary ADAHRS providing output. I did not see anything in the manual that says both are done simultaneously, but there are a few posts herein (circa 2011-2015) that seem to say both are calibrated simultaneously. That does not seem to match my case.

So which is it, simultaneous or separate?

Before you say it, I know -- I should have compared primary and backup a long time ago, but so far only used for local VFR, and I've been chasing gremlins in other systems that kept me busy.
 
There is more wrong with this than needing a compass calibration. You should have been getting ADAHRS mis-comparison faults long before now. Even with the intermittent temperature wiring should have flagged a fault.
 
kurtfly said:
There is more wrong with this than needing a compass calibration. You should have been getting ADAHRS mis-comparison faults long before now. Even with the intermittent temperature wiring should have flagged a fault.
Click to expand...
Well, the primary ADAHRS (SV-ADAHRS-200) was working fine except for the new OAT issue. No faults related to mismatch from the OAT pop up, nor anything else related to mismatch. For what it's worth, AI says that a bad OAT input won't cause the ADAHRS to set a fault condition, and we know AI is never wrong. (snicker) But then, I don't think I've ever seen exactly what it takes to trigger the system to flag a malfunction. The defective OAT input bounces down as far as -38F, which I think is the open circuit value, and of course all the dependent calculated values act up with it.



One thing is that I'd like it to be easier to toggle between ADAHRS. I don't think I could reliably remember the menu navigation steps needed in the air. I do have diverse backups for AS and altitude, and glad I do.
 
Last edited:
You still have some kinda configuration or software problem. Magnetic heading is one of the parameters it compares. You should call Dynon with your software version and setup.
IMG_1617.png
 
Thanks for finding noting that section. All the parameters except compass heading are essentially the same. As for compass heading, perhaps the key is what does "significant difference" mean? 5 degrees? 20 degrees? I'll give Dynon a call on Monday as you suggested after I go back and record some values from both ADAHRS. However, if the calibration for compass and AOA does need to be performed separately for both the active and standby ADAHRS, that would explain the difference.
 
maartenversteeg said:
I went through a single ground calibration for the compass and both prime and redundant ADAHRS were set at that point
Click to expand...
Same here, but i question if the Skyview is actually compairing the two ADAHRS compass headings. It should have squawked a mis-compare. If it flagged a mis-compare you would need to see the two headings to determine which is wrong?
I would like Dynon to explain this.
You can see below from User Guide once you switch to the compare page to display side by side ADAHRS the heading is above the g-meter reading.



Kurt
 

Attachments

  • IMG_1621.png
    IMG_1621.png
    1.8 MB · Views: 20
Last edited:
On Monday it was beautiful and I really wanted to fly. OAT indication was bad (as before). I had about 45 minutes to spare so I pulled the OAT wires out and put back. Also, disconnected/reconnected the main Dsub connectors because I could not see the OAT temp connections due to installation interferences with Dsubs in place. OAT was good (for about 5 minutes) but at least I now know what end of the wire that trouble is on. I switched OATs so the good OAT was on the primary (calibrated) ADAHRS. I checked versions and status of both ADAHRS (both matched, though the serial number of the backup was quite a bit lower). On compare, the headings were off about 20 degrees. From the programming menu, I selected the "201" as primary, just for fun, and switched back to the normal "200" as primary (active) and went to fly. However, I am now getting a persistent message that the backup needs calibration. I know I never got that before. I'm a little confused with that, but to me, its almost like the backup somehow "woke up". The only conclusion I can make is that my my brain must be fubar; time to see a psychologist or worse.

Thanks for confirming that the compass and AOA calibrations do both ADAHRS at once. That's really the only way that makes sense, although I would think that the manual would say so or there would be some telltale on the screen upon completion of the calibration -- perhaps values or scoring for both ADAHRS. I don't know why the calibrations didn't take for my backup, because both have always been hooked up from the beginning. But I am pretty sure I had not gone into the programming menu to look at which ADAHRS was active before this week, and when I finally did, it clearly showed the "201" was present, but not calibrated. (Which it now does all the time, along with other reminders)
 
Last edited:
You must log in or register to reply here.
Back
Top