SkyView shutdown timer restarts

[Terke]

The last few flights the SkyView shutdown countdown timer restarts. After all power has been removed from the system (it has a standby battery) we get the red bar warning that the system will shut down in 30 seconds. It starts counting down and at 21 seconds the red bar flickers and restarts the countdown timer at 30 seconds. It repeats this until the turn-off button is selected.

Any thoughts?

Thank you

 

[dynonsupport]

Is your airspeed reading above zero when that happens? It thinks it's in flight if you have airspeed and cancels the timer.

You may want to run a zero airspeed calibration if this is happening and check the pitot system for water.

 

[Terke]

Nope. This even happens when we are sitting in the hangar. No water in the system. We checked.

Thank you.

 

[dynonsupport]

But I mean are you LOOKING at the airspeed when this happens. It only takes 20 knots indicated (.005 PSI), and it might be flickering. Every time we've seen this before, that's what it's been.

Send us a video if you can.

 

[Terke]

Will do the test tomorrow, and make a video.

Thank you.

 

[Terke]

In the morning in the hangar I turned the SkyView on and back off. No flashes of speed and a normal countdown happened.

After the flight:
You are right, there are flashes of speed on the speed tape and the counter restarts. I covered the pitot tube, but a speed still flashed on the speed tape. Then I covered the static ports and speed flashes still occurred. Lastly I covered everything with pieces of tape, but speed flashes still occurred, so I had to force the SkyView to turn off.

While running around with tape I forgot to video the speed flashes.

Sorry and thank you

 

[Terke]

I don't know if it is related but I also have a post up under: Airspeed lag on takeoff and GPS mismatch due to unstable airspeed and airspeed/GPS lag.

Thank you

 

[Dynon]

So there is a zero pressure calibration that is designed to set the zero airspeed point and that would be our nominal advice assuming you're not sitting in a 20 knot wind. But given your other post and the other erratic IAS behaviors you're seeing, there might be something more fundamental going on here (see other thread).

 

[Terke]

If you mean the calibration described on page 5-22 and 5-23, then we did that calibration in a hangar with closed doors. The readings would vary rapidly +/-3 knots (roughly) making it difficult to read the speed tape. We had to use the 6 pack to get an idea of the average reading. I have uploaded a video of the shutdown timer behaviour while the static ports, pitot, and AOA ports were all covered by tape.
https://youtu.be/ibdD8fNd4ws

Thank you

 

[Dynon]

Well in particular, the ZERO PRESSURE IAS/AOA calibration portion. If you've done that we should have a look at your ADAHRS. Give our tech support team a call at 425-402-0433 or an email at support at dynonavionics dot com so that we can offer some more individual support.

 

[Terke]

Per your suggestion; I contacted the tech support team directly and we sent the ADAHARS in. It came back with the comment that it was an installation caused issue. We checked the pinouts at the ADAHARS. The two grounds tested clean to common ground. The two powers tested stable at 8.0 volts. The aux power tested at 11.4 volts. The data lines were pinned correctly and tested for continuity. Nothing on the airplane was turned on with exception of the SkyView, transponder, and autopilot. The airplane was powered by a battery charger at a stable 13.1 volts.
The zero pressure calibration was performed with a water manometer in the hangar with the doors closed. We even walked really carefully and slowly around the airplane to keep from disturbing the air around the static ports. The airplane was on jacks so no motion was possible. We had the same unstable readings at the low end of the calibration. I made a video of a number of the readings to illustrate the point.
https://youtu.be/lQPoKQe8wUk

As illustrated in the video we used the 6-pack display to get an average of the airspeeds to compare against the manometer. Agreement between the EFIS speeds and the manometer was very good, and generally within 1.3 knots or less. I'm willing to concede that my ability to read the manometer easily explains this discrepancy.  ;D

Any thoughts on what next to check to get the EFIS numbers to settle down? The speed tape is very difficult to read with these fluctuations.

 

[jakej]

FWIW - I see movement of the VSI & Altimeter at times during the video indicating a static system issue ? as well.  Just a thought, try the test without anything else turned on eg Txpdr & A/Pilot, then do the same test with only the a/pilot turned on - the results could be interesting :-/

 

[Terke]

I did do the test with nothing on at all except the SkyView. I even did the test with everything on to see if it got worse.

I also did the test with the static ports taped over, because I noticed the VS as well.

Same result each time. I'm really very confused why this would be.

 

[Dynon]

Yeah, that video is definitely not what we want to see. Do you have a SkyView backup battery? If so, if you power the system using just that, does that change anything?

 

[jakej]

I did do the test with nothing on at all except the SkyView. I even did the test with everything on to see if it got worse.

I also did the test with the static ports taped over, because I noticed the VS as welL
Same result each time. I'm really very confused why this would be.

Maybe I missed seeing that - wouldn't have made the suggestions otherwise. It's good to have ALL the data points before analysing an 'issue'.

 

[Terke]

Nope you did not miss it. I redid the calibration a number times with all sorts of different configurations to see if-, or what-, the 'installation induced failure' might be that the Dynon lab marked on the sheet they returned with the AHARS. I just can't figure out what the installation error might be. The only thing left is to unplug the bus and plugging the AHARS directly into the back of the EFIS panel. I just read the Dynon site again, and I'll go find the NET-TEST cable that should be in the hangar to do exactly that.
We flew the airplane in close formation with another. Our altimeter readings were within 50 feet of each other.
Still on opposing headings within minutes I get the following readings for GPS ground speed (in blue), TAS (in red), IAS (in green). Alt/10 is the brown trace and heading the orange trace. I know I should be happy that I never have a headwind.  ;D

 

[Terke]

To all;

I should have posted this much sooner, but I want to compliment the Dynon guys. I used the phone number given and had a chat with one of the techs. He reviewed the video and immediately saw that it might be an issue with the actual AHARS. Before the end of the call a replacement unit was on the way! These guys are awesome. Thank you.