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Gfeldman

skyview transponder during in-air engine re-start

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Gfeldman

Hi All,

I was doing some soaring last week under dark bottomed cumulus clouds in southeastern PA under moderate/ weak lift conditions. Upon engine re-start I found that the transponder took several minutes to become active. This happened 4 times. I am wondering if the Skyview shouldn't be shut down and restarted each time the engine is shut down. My checklist for on ground engine starts calls for the Skyview EFIS to remain on during engine starts- this makes sense because there is no other way to check oil pressure after engine starting.

So I assume that the Skyview can handle the power surge that accompanies engine starts.

Any thoughts?

George Feldman N33GF

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mikeschumann

What were the indications that you saw on Skyview that the transponder was not active?  Did you save a diagnostic dump and take a photo of the Skyview screen when this happened?  I would forward this to the Dynon tech support people.  They are very responsive to investigating these types of issues.

The one thing that I have run into is when flying near Orlando and West Palm Beach, without warning, Skyview will no longer display ADS-B traffic, but will instead show only TIS traffic that it is receiving from the FAA's Mode S radar systems.  This is a subtle problem that you will only notice if you are watching ADS-B equipped aircraft that are flying at low altitudes that are not visible on ATC radar.  Note:  TIS is being phased out, so this only occurs in those areas where the radar systems have not been upgraded.  Dynon has verified this as a known problem, and will fix this in the next Skyview firmware release.

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Jim Lee

The Skyview is designed to be on during engine starts.  Obviously, we need to check the engine oil pressure right away after an engine start and this dictates that the Skyview already be turned on to see this.  There is no difference between an in-air start and a ground start.  The only equipment that needs to be off during an engine start or stop is the Becker radio, which can blow an internal fuse.  The only fix for that is to send the radio back to Becker.  The Dynon radio is designed to be on during engine starts or stops.

I had a nice 5 hour wave flight yesterday in the Phoenix.  The Skyview (and transponder!) were on the entire flight.

https://www.onlinecontest.org/olc-3.0/gliding/daily.html?st=olc&rt=olc&df=&sp=2021&c=US&sc=

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Gfeldman

Hi Mike and Jim,

I just talked to Dynon about the problem and I think they nailed the solution. A weak or nearly dead backup battery for the Skyview would explain what I am seeing happen. Apparently during startup the Dynon is isolated from the current surge going to the starter by the backup battery. Without this protection the Dynon startup goes through a number of useless cycles.

Any thoughts?

George

 

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mikeschumann

Have you run a backup battery test?  Under normal conditions, the Skyview backup battery would only be discharged if you ran out of power in your main battery.  In this case, a fully charged backup battery should still power the EFIS for about an hour.

The Dynon backup battery does not power the transponder.  The transponder is wired thru the radio circuit breaker.

Again, my question is what was the indication you had that the transponder was not active?  My standard procedure when I run into a Skyview issue, is to take a photo of the screen and then immediately take a diagnostic data dump to a USB stick (you can do this in flight), so that Dynon has a complete picture of what the problem is.

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Gfeldman

Mike,

the indication that I got that the transponder was not working was a large X through it in the upper left corner of the screen. As I mentioned

the transponder came back on after about 5 minutes.

upon shutdown the skyview no longer gives me the option to test the backup battery. That clue

and the erratic behavior of the screen when the power was left on during engine startup led the Dynon representative to suggest a weak and dying backup battery. My backup battery is more than 5 yrs old and I understand that that is

about it’s expected life.

best

George

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mikeschumann

You can easily test the backup battery by pressing the Stay On button after you shut down power to the Skyview system.  If your backup battery is OK, the Skyview display should run for at least 45 minutes after you shutdown the main power.  The Dynon system will only show you the Test Battery option when you power down, if you are due for a battery test (I assume that it is on a one year schedule).

Back in 2018 I had a problem with my Skyview display not powering up.  It turned out that the EFIS circuit breaker was partially tripping while under load.  This was a subtle problem that took a little sleuthing to figure out.  See this post for the details:  https://www.motorgliders.org/forums/topic/674-dynon-skyview-powerup-problem/?tab=comments#comment-3493

You might be having a similar power problem with your transponder.  However, assuming that your aircraft is wired the same as mine, if that was the issue, you would also notice problems with your radio, since they are on the same breaker.

Good luck.

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Gfeldman

Thanks Mike

appreciate your help

g

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