AP losing NAV source

As Rich says, it's something that we've seen from a few customers, and are looking into the root cause to figure out how we can provide a better experience here.
 
Now that I have my 296 outputting the right data stream, I too see the 'nav source lost' message come up about once every 10 or so minutes.  Problem is, that without an AP74, I have a few extra buttons to hit to get back on NAV.  

Hope you can get something figured out.

Thanks,

DaveG
601XL/D180/roll servo
 
For all of you - when NAV fails down - does it fail down to HDG mode or TRK mode? Thanks!
 
Same here. It goes to TRK mode and I must manually re-select NAV.

DaveG
D180/296
 
Hi!

A small report primary for Dynon Support:

I made my first longer x-country today 2 times 3 hours, most of the time with the AP engaged. My equipment is AVMAP EKP IV and EFIS D-100 + AP74. On the first leg I think we got the NavSource log message about 11 times and some fewer on the return leg. Always able to reenable by pushing NAV btn within a few seconds.

But whats bothers me is that every time the TRK mode engaged the airplane tried to roll and turn quite violently to the side were heading bug was. Shouldn't she AP continue on present TRK from the GPS? Or does the AP lose track info momentarly from the GPS as well?

Trying to realigning the heading bug with the TRK indication lessened those rolls/turns.

But every few times even this didn't helped as I realized that when the Nav Source lost message appeared the heading bug was moved to some other heading way off. I wasn't able to see if it was by 180 degrees or some other value.

Any ideas?

Thanks for a impressive product otherwise.

Best Regards,
Andreas Glöckner
 
So yours is failing to HDG instead of TRK?

More of a question for Dynon is why would a loss of GPS nav data cause the hdg bug to move??????
 
No, it is failing to TRK according to the AP-74 but it behaves strange though.

/Andreas
 
Guess the problem is not limited to Garmin X96 models hu?

Strange that it appears to be following the Hdg Bug when it is rolling over to Trk...

Strange the hdg bug is moving when it does this.

Seems I read somewhere where Dynon stated that if the AP lost one frame of data from the GPS, it would kick out of nav mode. I would bet that they will need to add some logic to shore this up... The error handling routine needs a little work!
 
Andreas,

If the AP loses GPS NAV data only, it falls back to TRK, resetting the purple TRK bug to the currently reported ground track.

If the AP loses the GPS entirely (in either TRK or NAV mode), it falls back to HDG, resetting the yellow HDG bug to the current heading reported by the EDC (compass).

In neither case should the AP initiate a turn.

Please get in touch with our support via email:
support@dynonavionics.com

or give us a call at:
425-402-0433

Hi!

A small report primary for Dynon Support:

I made my first longer x-country today 2 times 3 hours, most of the time with the AP engaged. My equipment is AVMAP EKP IV and EFIS D-100 + AP74. On the first leg I think we got the NavSource log message about 11 times and some fewer on the return leg. Always able to reenable by pushing NAV btn within a few seconds.

But whats bothers me is that every time the TRK mode engaged the airplane tried to roll and turn quite violently to the side were heading bug was. Shouldn't she AP continue on present TRK from the GPS? Or does the AP lose track info momentarly from the GPS as well?

Trying to realigning the heading bug with the TRK indication lessened those rolls/turns.

But every few times even this didn't helped as I realized that when the Nav Source lost message appeared the heading bug was moved to some other heading way off. I wasn't able to see if it was by 180 degrees or some other value.

Any ideas?

Thanks for a impressive product otherwise.

Best Regards,
Andreas Glöckner
Click to expand...
 
Andreas,

I've not seen the heading bug chase happen like you are describing, but here's one possible technique for your bag of tricks, as this Nav Source loss issue gets worked out. When the AP begins to chase the heading bug, press the HDG button on the AP-74. That should sync the heading bug to your current heading, and the rolling/turning should stop. Then when the NAV signal is good (which so far seems to be immediately for most), you can re-engage the NAV mode.

I've actually been sync-ing my heading bug while in NAV mode (as a regular practice) by pressing the HDG button then going back to NAV immediately, even when everything is working and tracking fine. Just an old habit pattern that I also use at work...I like to have my heading bug sync-ed whenever I'm tracking a NAV source, so that if the NAV mode starts doing something wacky, I can just hit HDG hold while I figure out what "Hal" is doing. This can also be done with the AP-74 adjust knob (I have that set to adjust heading without pressing it), but the HDG mode press is a quick way to do the same thing.

Just one technique. Hopefully this NAV Source issue will just take a little algorithm work to remedy. Once the AP-76 is available and folks are coupling to approaches, this will become a more critical issue, so it's good we're seeing it and getting the bug worked out now!

Cheers,
Bob
 
Dynon, this might be of some help? I have documented the following-
The good: no nav source lost with the lower 7 sentences (yet)
$GPGLL,4725.7503,N,09223.3261,W,224254,A,A
$GPBOD,,T,,M,,
$GPVTG,11.7,T,11.6,M,0.0,N,0.0,K,A
$HCHDG,137.8,,,0.1,E
$GPRMC,224256,A,4725.7504,N,09223.3260,W,0.0,11.7,170109,0.1,E,A
$GPRMB,A,,,,,,,,,,,,V,A
$GPGGA,224256,4725.7504,N,09223.3260,W,1,10,0.8,420.2,M,-31.9,M,,

The bad: nav source lost with the lower 12 sentences
$GPRMC....
$GPRMB....
$GPGGA...
$GPGSA,A,3,03,06,08,09,15,18,21,22,,26,,29,0.0,0.8,0.8
$GPGSV,3,1,12,03,19,310,31,06,27,301,32,08,02,017,00,09,17,137,30
$GPGSV,3,2,12,15,54,064,40,18,62,275,34,21,83,214,38,22,28,265,38
$GPGSV,3,3,12,24,40,130,28,26,34,047,37,27,09,028,20,29,11,185,34
$GPGLL,4725.7474,N,09223.3264,W,224008,A,A
$GPBOD,,T,,M,,
$GPVTG,11.7,T,11.6,M,0.0,N,0.0,K,A
$HCHDG,134.4,,,0.1,E
$GPRTE,1,1,c,

Using a Garmin GPSmap 60CSx
Frank Karasti Dynon AP user RV-9A
 
Are those two different modes that have different groups of sentences? In any case, the second group doesn't have the required sentences in it, period. See http://wiki.dynonavionics.com/GPS_Serial_Compatibility_and_Configuration_Settings for what we need for basic GPS data and GPS NAV.
 
Are those two different modes that have different groups of sentences? In any case, the second group doesn't have the required sentences in it, period. See http://wiki.dynonavionics.com/GPS_Serial_Compatibility_and_Configuration_Settings for what we need for basic GPS data and GPS NAV.
Click to expand...
Sorry, lost a few lines on my copy/paste. fixed. Yes this Garmin has about 5 mode combos to choose from. I'll try to fly tomorrow and see what I can document, what MNEA group holds the nav source.
 
Hello,
Any fix for this yet? Reseting is getting old.


I'm using a Garmin 496 to drive my Dynon AP.  Occasionally I will see an error saying something like "NAV source lost".  

Is this normal behavior?  I'm told by one of the beta testers that this is because the 496 is prone to dropping packets.  
Click to expand...
 
Hi,

You had previously posted a setting that semeed to be working; is it not working after all?

A NAVSRC LOST message indicates that the HSI did not get an update from the GPS for up to three seconds or that the GPS reported that it did not have a fix on satellites.

We don't have much experience with the GPSMAP 60CSx, but the data you post raises a couple of questions:
  • What settings did you use for each set of data?
  • Neither set of data includes the checksum that allows the HSI to verify that the data was transmitted correctly; did they get omitted from the post, or are they really not there? (The checksum always starts with a '*' followed by two letters or numbers)
One thing we have seen with some GPSses is that in WAAS mode, the GPS will give up completely if they lose just the WAAS satellite - even if 10 regular GPS satellites are there. In these cases turning off WAAS fixes the problem.

If the 'good' setting you posted before isn't working, we'd like to look more closely at your GPS output, preferably a minute or two of data in its raw form; you can send it to support@dynonavionics.com
 
I just installed a roll servo in my RV8 and it seems to work great except that I too am getting a NAV source lost message about once every 5-10 minutes. I have an EFIS-D100 connected via RS-232 to a GNS-430. I am pretty sure I have both configured as per your instructions and your wiki. I do not have an HS34 or an AP74. I am sure an HS34 would solve this but I don't have the panel space. I would appreciate any suggestion you might have.

-Luis Luciani
 
I have tried turning off altitude reporting from the 430 and tried different UART bit rates.

Is Dynon investigating this?
 
It is something we're looking into, but we haven't found any silver bullets yet. We think that some of the issue is that occasionally some GPSs do output invalid data for a few seconds.
 
Originally the thought was that this only happens with the handheld x96's but it seems this can also happen with the panel mount TSO'd gps's as well.

Easy to place the blame on a lowly handheld but a TSO'd gps???

This should be high on the list to resolve... Never seen a complaint from any users of competitive products so it must be solvable.

Please keep up the hard work until this one is gone!!!!
 
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