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AXP322 not working with IFD540

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Dominic View Drop Down
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    Posted: 29 Mar 2024 at 5:51pm
For 3 weeks an authorised Avidyne dealer has been trying to get our IFD 540 (only 9 months old and barely used) working with a new AXP322. They still haven’t succeeded and our plane is stuck hundreds of miles away from home in Guernsey. If anyone can help I would be very, very grateful. So far we have spent thousands of pounds on two amazing Avidyne products that just won’t work with each other.

I am certainly no avionics expert but people who are have tried the following to resolve the problem:

Warning “No Comm With Xpdr” alert flashing up and staying for about 4 seconds then clearing for about 2 seconds before reappearing. 

• All configuration settings have been checked and approved by Avidyne.
• It is sometimes possible to be quick enough to switch it to Altitude but then it goes off again and when it comes back it is again in Ground Mode. 
• In configuration mode there is a continuous clocking up of the data of RS232 channel 2 in chunks of 5 bytes.  This is quicker than every 2 seconds.  This would suggest that the IFD is receiving data from the AXP but is still flagging the “No Comm With Xpdr” message.
• A second AXP322 was flown from the USA in case the first was faulty. No luck.
• Three different antennas have been tried.
• The problem is independent of GPS lock.
• A second IFD (a 440) was slaved in with the same results. 
• All wiring has been checked and replaced. Continuity and insulation resistance of the RS232 lines and power and ground are ok. Tests indicate there is 13+V at the plug even with load on.
• Tried powering the AXP from a 24v supply in case it was not liking the aircrafts 12V to no effect
• Current draw has been monitored and is a consistent 0.12-0.14A and seemed to jump up very briefly to 0.2+A when I managed to get it to ALT mode before it lost communication.
• Data can be seen on the RS232 Data line coming from the transponder continuously counting up without stuttering.
• Checked the Altitude and heading input from the G5 on EFIS/Air Data and that is good.
• The problem is independent of whether the IFD has GPS WAAS lock or not.  (The transponder occasionally reports No ADS-B when the GPS is lost suggesting it is receiving the GPS data at least some of the time.)

Is there a problem with the software level in the AXP of 2.1 (and 2.14) talking to the IFD which is on v10.3.1.2?

If we can’t get to the bottom of this soon I will have to ask Avidyne to replace both the IFD 540 and AXP322 under warranty, with the setup tested before shipping. Thanks in advance for any suggestions we haven’t tried.
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AviSteve View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AviSteve Quote  Post ReplyReply Direct Link To This Post Posted: 01 Apr 2024 at 9:59am
You've swapped IFDs and swapped AXP322s, so it's exceedingly unlikely that getting another new IFD and another new transponder will produce a different result.

Since you're getting "No Comm With Xpdr", I'd start by looking at the RS-232 wiring again since that's the communication mechanism between the IFD and the AXP322.


Steve Lindsley
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dominic Quote  Post ReplyReply Direct Link To This Post Posted: 01 Apr 2024 at 3:56pm
Thanks for your reply Steve, it makes a lot of sense. Unfortunately our Avidyne dealer's engineer tested the wiring and then replaced the RS232 wires. He is convinced that isn’t where the problem lies.

The POH indicates a 'No Comm With Xpdr' message is generated when 'No data has been received from the remote transponder for greater than 2 seconds'. That’s why he tested it in maintenance mode – getting a continuous clocking up of the data of RS232 channel 2 in chunks of 5 bytes. As he explained to me, ’This is quicker than every 2 seconds, suggesting that the IFD is receiving data from the AXP but is still flagging the No Comm With Xpdr message'.

Could this be a software issue? And if so would rolling back versions be an option for the engineer or something only Avidyne can do if they have our IFD/AXP back?

new IFD and AXP, tested together prior to shipping (using any software version), should function immediately upon installation in my plane – or demonstrate irrefutably that the new wiring is at fault. 

I just need a route forward as soon as possible. My plane can’t take-off without a transponder that works and I don’t want to think about the cost of what has been tried so far.

As it stands Avidyne and their authorised dealer can’t agree on what is causing the problem or how to fix it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AviSteve Quote  Post ReplyReply Direct Link To This Post Posted: 01 Apr 2024 at 10:10pm
It would be great to have your wiring harness here, but I'm certain that can't happen.  Alternatively, you could have your dealer send a wiring diagram to tech support.  Tech support would be able to evaluate its correctness. If required, we could replicate it here in our facility to prove whether it works or not.

The weird behavior makes me wonder if there might be a grounding issue.

Could it be a software issue?  Never say never, but I seriously doubt it.  We've tested the interface many times and there are many airplanes out there with this exact configuration.
Steve Lindsley
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dominic Quote  Post ReplyReply Direct Link To This Post Posted: 02 Apr 2024 at 4:46am
Thanks again Steve. 

I have just received an email confirming the spare RS232 wire with units have been sent to Avidyne. At this point I wish I was with them... I could do with a holiday in Florida!

There is an ongoing discussion between our engineer and Avidyne Tech Support directly. I imagine they are able to send anything required (logs, video, wiring diagram). I am told the wiring is in accordance with the installation manual. Apparently the replacement wire was bonded to the back shell of the plug P1001 which is permissible.

Hopefully we will get to the bottom of the problem soon.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dominic Quote  Post ReplyReply Direct Link To This Post Posted: 03 Apr 2024 at 5:37am
Hi Steve,

For completeness I have added a link below so the following can be downloaded:

• The AXP322 wiring diagram (installed wires are highlighted yellow). I am told the external standby is used in dual installations, the external ident is optional and the suppression is for connection to the DME and Traffic systems if fitted.
• The Event Log.
• Video of the error message.

https://www.dropbox.com/scl/fo/fkyjg6j2lb74zx31rjt9s/h?rlkey=ow0cjniny76u6oq5up7dv6rb4&dl=0

I am sure the Avidyne Field Service Representative will have been sent a copy of everything and more.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote oskrypuch Quote  Post ReplyReply Direct Link To This Post Posted: 03 Apr 2024 at 2:25pm
Do let us know what happens!

It is going to be something usual I'm sure, so good to know about it.

* Orest


Edited by oskrypuch - 03 Apr 2024 at 2:26pm
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