CDI momentary source glitch

[swatson999]

I know Dynon is on holiday, so I don't expect a response to this right away, but wanted to capture the info and relay it while it's still fresh.

Short flight today. While leaning out in level cruise and watching the EGTs and lean status, I saw the CDI momentarily (less than a second) flash green course indication lines. The CDI is currently set to source from the GNS-430W, and nothing was selected for GPS navigation. The radio was tuned to some random local VOR. When it flashed, I saw the green CDI bar and the green course lines. It was obvious that for a split second, it was being driven by the 430 NAV radio.

This seems to be either a fault of the EFIS (for whatever reason, selecting the radio source instead of the GPS for a moment), or the ARINC box (less likely, but you never know).

If Dynon wishes, I can still get a diagnostic log and upload it. The flight was < 1 hour.

 

[Dynon]

Are you using the auto-switching CDI option? If so, I wonder if we got an erroneous "switch over" message for a second.

 

[swatson999]

Yes, the system is set to auto-switch to radio nav for ILS approaches...it works great, by the way .

I screwed up, though, and forgot to get the diagnostic file before flying again .

Recall that there is an occasional issue I (and others IIRC) have noticed with very brief drop-outs of GPS nav data...either the 430 is dropping a packet or three, or the ARINC box is getting out of synch, or something.

But this is the first time I've seen it randomly go from no active nav source (i.e., no FP in the 430) to the VOR for nav, just for a split second.

 

[krw5927]

Recall that there is an occasional issue I (and others IIRC) have noticed with very brief drop-outs of GPS nav data...either the 430 is dropping a packet or three, or the ARINC box is getting out of synch, or something.

I've had this ongoing issue ever since I can remember as well.  Never have seen the HSI completely switch sources momentarily (and my GNS480 is set up to auto-switch), but course guidance on the HSI disappears for a quick second or two all the time - notice it on almost every flight, sometimes multiple instances on a single flight, and I'm sure I don't catch 100% of the drop-outs.  Hasn't been a issue operationally, but pretty annoying.

When it happens, the GNS480 is still happily humming along giving course guidance on its nav page, so it's not losing position lock or anything like that.

 

[Jrskygod]

I get an occasional drop out of the GPS signal as well. It is always momentary, usually just a blink of the HSI, however every once in a while it lasts long enough to cause the autopilot to kick off. It is disconcerting when on an approach but it is rare. I have never had the HSI switch sources momentarily. I have my skyview connected to a Garmin 430W. The course and aircraft position are displayed on the map correctly when this happens so it seems like a communication issue between the two systems. I have not experienced an integrity message at these times as well.

 

[swatson999]

I get an occasional drop out of the GPS signal as well. It is always momentary, usually just a blink of the HSI, however every once in a while it lasts long enough to cause the autopilot to kick off. It is disconcerting when on an approach but it is rare. I have never had the HSI switch sources momentarily. I have my skyview connected to a Garmin 430W. The course and aircraft position are displayed on the map correctly when this happens so it seems like a communication issue between the two systems. I have not experienced an integrity message at these times as well.

Course and position on my map are from the GPS-2020, so I wouldn't see that.  I, too, suspect a comm issue of some kind first, followed by an error on the GNS430W side, but you'd probably have to grab the data stream between the ARINC and the Garmin boxes and analyze them.

BTW, thns is the first time I've *seen* it "switch" sources...usually (I say usually, but it's a very rare event), the purple CDI and the 430-driven data fields on the screen just go away for a split second.

This time, it went from *no* GPS source driving a CDI (no FP or Direct-to selected on the 430) to displaying the green (Radio NAV) CDI for a split second.

 

[krw5927]

Dynon, should we start a new thread for the CDI drop-outs, so that we don't clutter up Steve's original issue (uncommanded source switching)?

Sounds like this may be a more systemic concern than a one-off installation issue.

 

[swatson999]

I'm not so sure they aren't the same thing...