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DAC GPSS out of synch on startup

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flybikeski View Drop Down
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    Posted: 01 May 2016 at 5:38pm
I installed a DAC GPSS unit which works which is really cool, but not right away.  On startup the GPS annunciator light blinks which means something is wrong, in this case likely it is not receiving the ARINC 429 data correctly from the 540, no matter how long I wait.  If I power it down and back up, the GPS light is steady and the unit works as advertised.  Unfortunately rebooting it in flight right now is not easy because it is on a non-pullable breaker shared with the MLB100 (each fused separately).  I could get a pullable breaker and pull it each flight to get the thing running, but that isn't very elegant. 

I know others have the DAC unit.  Anyone run into this? Any ideas?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gring Quote  Post ReplyReply Direct Link To This Post Posted: 01 May 2016 at 7:15pm
I would check with Avidyne tech support on this one.  I know that there was a problem in the previous release where the LIO board booted out of sequence.  This affects the IO of the unit and you can tell if your unit has the issue because while on the legal screen you'll see your HSI/CDI full left, full down deflected.  When this happens, the unit will not cross sync (if you have 2) properly.  Rebooting usually clears the issue.  I'm wondering if you are experiencing this issue. since the ARINC429 would be the same type of IO that falis on the crosssync.  It has been corrected with the current release.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote paulr Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2016 at 11:48am
I have a similar issue, with the same config-- new GDC31 and new IFD540. The GPSS light consistently blinks until I start my takeoff roll, even after the IFD540 has a GPS fix and I've entered a route in the FMS. The light goes solid at around 30kts. GPSS has worked flawlessly in flight, however.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote flybikeski Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2016 at 12:11pm
Originally posted by paulr paulr wrote:

I have a similar issue, with the same config-- new GDC31 and new IFD540. The GPSS light consistently blinks until I start my takeoff roll, even after the IFD540 has a GPS fix and I've entered a route in the FMS. The light goes solid at around 30kts. GPSS has worked flawlessly in flight, however.

That does make sense - somewhere I saw reference that the GDC31 also looks at the ground speed label and not just the bank angle label in the data stream. 

However mine will stay blinking until I get comfortable in cruise and can deal with it.  For right now it isn't bolted down, so I can reach it, pull the connector off and put it back on, and the light immediately comes on steady.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote edanford Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2016 at 12:31pm
My IFD540 / GDC31 performs exactly like Pauls
Ed
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Post Options Post Options   Thanks (0) Thanks(0)   Quote oskrypuch Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2016 at 2:02pm
Originally posted by paulr paulr wrote:

I have a similar issue, with the same config-- new GDC31 and new IFD540. The GPSS light consistently blinks until I start my takeoff roll, even after the IFD540 has a GPS fix and I've entered a route in the FMS. The light goes solid at around 30kts. GPSS has worked flawlessly in flight, however.

I have the same thing happening with an STEC 55x, well, sort of.

If I try to engage the STEC 55x GPSS on the ground, it will indicate FAIL. However, if I try to activate it while on the IFD540 legal screen, it WILL activate fine.

For me it is not an issue, as I don't need GPSS "on" until in the air, and would not activate it on the ground -- except for testing purposes (that is how I discovered this). But it does seem to indicate that data that is needed by GPSS is not available on the bus until the IFD540 senses that it is flight mode.

But, as long as it always starts working on the takeoff roll, it shouldn't be an issue. If it won't, then it would be messy, you need a power switch for it.

* Orest


Edited by oskrypuch - 02 May 2016 at 2:03pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mfb Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2016 at 2:10pm
I have an Aspen PFD with Internal GPSS. It worked fine when it was installed last spring. We just installed the latest Aspen software and 10.1.1 on the IFD540. Now the GPSS won't engage at all.

Any ideas?

Mike
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Post Options Post Options   Thanks (0) Thanks(0)   Quote oskrypuch Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2016 at 3:55pm
Originally posted by mfb mfb wrote:

I have an Aspen PFD with Internal GPSS. It worked fine when it was installed last spring. We just installed the latest Aspen software and 10.1.1 on the IFD540. Now the GPSS won't engage at all.

Any ideas?

Mike

If it won't engage AT ALL, it is likely an install error.

The ASPEN GPSS works just fine with an IFD. I used it for every trip, before I got the STEC 55x installed.

* Orest



Edited by oskrypuch - 02 May 2016 at 3:56pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote flybikeski Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2016 at 9:48pm
Originally posted by edanford edanford wrote:

My IFD540 / GDC31 performs exactly like Pauls

Paul and Edanford: Do you guys know if you use a IFD540 ARINC 429 data port, or a RS232 port?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote edanford Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2016 at 10:33pm
I have ARINC 429 communication
Ed
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Post Options Post Options   Thanks (0) Thanks(0)   Quote paulr Quote  Post ReplyReply Direct Link To This Post Posted: 03 May 2016 at 8:58am
I don't know, and the plane's in the shop for annual so I can't check the 540 configuration, but I suspect it was probably ARINC 429.

Edited by paulr - 03 May 2016 at 9:03am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote M20Kid Quote  Post ReplyReply Direct Link To This Post Posted: 03 May 2016 at 11:09am
For they people indicating the GPSS light doesn't light up until on the takeoff roll, I'm wondering if you have activated the flight plan on the ground?  I have the same GPSS switch and mine will flash until there's an activated leg to follow.  I understand the IFD540 will sequence to activate a flight plan after reaching a certain speed on the takeoff roll, which would in turn lock the GPSS.

My sequence is to activate the flight plan and make sure the GPSS and other settings are correct before taking the runway.  I don't want to get airborne and then find I have a connection problem.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote paulr Quote  Post ReplyReply Direct Link To This Post Posted: 03 May 2016 at 11:11am
That's a good point-- I haven't been explicitly activating the flight plan. I think that's an old (bad) habit from my KLN94, which treated the flight plan as active if you were starting from the first fix on the plan.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote oskrypuch Quote  Post ReplyReply Direct Link To This Post Posted: 03 May 2016 at 11:34am
Originally posted by paulr paulr wrote:

That's a good point-- I haven't been explicitly activating the flight plan.

Well, with no active flightplan, there can be no active leg.

* Orest

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Post Options Post Options   Thanks (0) Thanks(0)   Quote flybikeski Quote  Post ReplyReply Direct Link To This Post Posted: 04 May 2016 at 6:28pm
Originally posted by Gring Gring wrote:

I would check with Avidyne tech support on this one.  I know that there was a problem in the previous release where the LIO board booted out of sequence.  This affects the IO of the unit and you can tell if your unit has the issue because while on the legal screen you'll see your HSI/CDI full left, full down deflected.  When this happens, the unit will not cross sync (if you have 2) properly.  Rebooting usually clears the issue.  I'm wondering if you are experiencing this issue. since the ARINC429 would be the same type of IO that falis on the crosssync.  It has been corrected with the current release.

I upgraded my IFD540 unit to the latest and was very hopeful that would do it, but not to be.  The GPS annunciator does go steady for about 5 seconds during the 540 self-test legal screen, but then the DAC unit seems to get confused and requires a reboot. 

Dang.  I guess I'll get a pullable breaker and handle it that way.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote paulr Quote  Post ReplyReply Direct Link To This Post Posted: 08 May 2016 at 9:44am
Wrong again. My RS232 config screen on the 540 shows channel 2 as "Icarus-Alt/Aviation" so they must have used RS232.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote flybikeski Quote  Post ReplyReply Direct Link To This Post Posted: 08 May 2016 at 11:58am
Avidyne tech support has been helpful and their current thinking is this: The DAC unit is auto-baud detect and when the IFD540 self test screen comes up, the ARINC 429 data stream is output at low speed, and there I get a steady GPS lamp, and there the DAC unit locks on to that baud rate.

Later the IFD540 comes alive with ARINC 429 high speed, but now that confuses the DAC unit which has already experienced and locked onto low-speed (unless it is rebooted).  The solution may be to set the 540 429 port to low speed and next week I'll test that.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote oskrypuch Quote  Post ReplyReply Direct Link To This Post Posted: 08 May 2016 at 1:46pm
I have the exact same parallel issue with my Stec 55x autopilot. I just leave it off until the 540 finishes boot up. Prefer to leave the 429 on high speed.

* Orest
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Post Options Post Options   Thanks (0) Thanks(0)   Quote flybikeski Quote  Post ReplyReply Direct Link To This Post Posted: 09 May 2016 at 5:57pm
I did test the solution suggested by Avidyne, setting the ARINC 429 port to low speed, and that worked. 

It sounds like STEC does the same thing as the DAC GDC31 GPSS.  There may be other avionics that would also auto-baud-detect and lock on to the low speed output during the 540 self-test and then be unable to reset to the high speed port later. 
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