Intermittent X-Ponder Altitude Issues :-(
Printed From: Avidyne
Category: Avidyne General
Forum Name: AXP340/322 ADS-B Transponder
Forum Description: Topics on the Avidyne AXP340/322 ADS-B Transponder
URL: https://avidynelive.com/forum_posts.asp?TID=1017
Printed Date: 26 Mar 2026 at 10:18pm
Software Version: Web Wiz Forums 12.07 - https://www.webwizforums.com
Topic: Intermittent X-Ponder Altitude Issues :-(
Posted By: cajungene
Subject: Intermittent X-Ponder Altitude Issues :-(
Date Posted: 26 Mar 2016 at 12:11pm
|
I’m frustrated as hell with Avidyne and feel like I’m a Beta
tester for them. I installed an
IFD-540/AXP-340 combo in May 2015. I a few minor glitches, but no issues. Felt I was home free. In November 2015 I took the plunge and installed an
MLB-100. The day I picked it up when I took off ATC
reported that I was showing an altitude of 64,000’. After landing back at my avionics shop
Avidyne tech support determined that it was an MLB-100 SW issue. The shop disabled the MLB-100, but on the
way back to my home base ATC (Washington TRACON) reported that I had no Mode C
altitude. Recycled and got back
home. Flew a few times with one incident
of no Mode C altitude that was fixed by recycling the transponder. In February I had the MLB-100 patch installed
along with the newest patch for the IFD-540.
Flew back home without incident.
On March 10th was trying to get back to my home base and
again ATC told me that I had no Mode C, but again I recycled and fixed the
issue. Today, March 26th had the same issue, and
recycling didn’t help. ATC said that my
altitude was going in and out. Now I’m
stuck inside the Washington, DC SFRA and have to coordinate with both ATC and
Homeland Security in order to get it back to the shop. I’m not a happy camper. Don’t expect to spend big, big $$ to have an
experimental product. Couple of questions: 1. Anyone else having this issue? 2.
Any ideas of what it could be? 3.
Why do I think this is an MLB-100 related issue? 4.
How do I fix it? I’m so frustrated that I’m about to chuck my whole stack and
go with Garmin and let everyone in the world know that Avidyne is not ready for
prime time. |
Replies:
Posted By: oskrypuch
Date Posted: 26 Mar 2016 at 12:33pm
|
Well, you could certainly have a failing transponder. Haven't read about anyone posting of that yet, but it is just electronics. Note that recycling solid state transponders doesn't usually accomplish anything, though that is usually ATC's first request. I would bet on either a sick encoder, or perhaps an install issue with an intermittent connection somewhere. If the problem is constant, should be easy to track down now, once you get out of the SFRA jail! * Orest |
Posted By: cajungene
Date Posted: 27 Mar 2016 at 8:39am
| Guess the question is where does the AXP get its squawk info? Directly from the encoder or thru the MLB-100 and then to the encoder. Is this an install option so I can have the shop bypass the MLB-100? All the problems started when the MLP-100 was installed. |
Posted By: oskrypuch
Date Posted: 27 Mar 2016 at 12:49pm
|
Well, if you pull the breaker on the MLB100, do you still have Mode C? The MLB100 does need a PA. I have no idea if the input is/can be paralleled and/or daisychained. The forums are not an official tech support area, so if you don't get an answer here, give Tech Support a call yourself. I've generally found them to be quite helpful.
* Orest |
Posted By: chflyer
Date Posted: 27 Mar 2016 at 1:28pm
|
I think you're doing Avidyne a disservice with your comments about them not being ready for prime time, given the experience you relate. Avidyne is doing everyone a huge favour with this forum, and Garmin sure as heck isn't taking a risk with something similar allowing everyone to spread their similar Garmin experiences for all the world to hear. Sure, there were quite a few squawks that arose in the first year after the 540 came out, but that has really quieted down in the last 9 months. You said yourself that you had no issues with the 540/340 combo and it sounds like the current ones are MLB100-related. So throwing out all Avidyne and replacing with Garmin sounds like an over-reaction to me. A large number of the issues that come up in this forum are installation-related. I'm not familiar with the MLB100, but other threads suggest to me that there are various ways to interconnect MLB100/AXP340/encoder/IFD540. Have you checked the installation manual and the schematics of your installation that were provided by your avionics shop? Your shop did provide you the schematics, didn't they? Did you notice if GPS reception remained ok? The AXP340 will lose mode C if the GPS feed from the IFD540 drops. It has happened once to me. If that were to happen, it might have come back by the time you were finished recycling the xpdr causing you to think that the recycle fixed the issue. I suggest you take Orest's advice about contacting tech support directly via phone. ------------- Vince |
Posted By: AviSimpson
Date Posted: 28 Mar 2016 at 4:21am
Sent you a PM. ------------- Simpson Bennett Avidyne Corporation Product Manager |
cajungene wrote:Posted By: PeterC
Date Posted: 24 Apr 2016 at 10:24am
|
I'm also having a problem with my mode-c. Got plane back from annual Wednesday and initial contact with atc they said they were not getting my mode c -altitude I guess. Next atc had me recycle the xponder and did not question me after that. Today leaving home airport atc said my altitude was showing ground altitude. I recycled and they said it was still off so I switched to mode a. I have ifd 540, axp322, Tas605 and mlb100. I am at 10.1.2 and mlb 4.10. Any ideas. ------------- Peter - 1977 Cardinal RG C-FJPC - IFD550/540/240/322/605A/Skytrax100, Aspen MAX 2000, Trio A/P |
Posted By: cajungene
Date Posted: 24 Apr 2016 at 2:10pm
| Finially appear t have gotten at the root of the problem. Hats off to Avidyne Tech Support. Went out to the airport and went thru some buttonology. One of the key things was to check the air data compute page to see if the altitude shown agreed with the PA on the ground and check the configuration settings. They didn't. When I took it back to the shop that installed it found that the original wiring diagrams for the install were not entirely correct and introduced a loop to the AXP. So sometime it would get the right data and sometimes not. After that they reconfigured it and that appeared to fix the problem. The shop will have to do the work. As an added precaution I also had them put in a new cable to my Xponder antenna since the old cable was 30 years old. Will be testing a lot this week. Check the air data computer page to see if you have this issue. Still sort of bummed that the install Doc's were sort of fuzzy. Have a hanger neighbor who is having similar loop issues since he installed the MLB-100. Not sure why, but the MLB seems to introduce new issues. Never had a problem till it was installed. Hopefully it is fixed for good. |
Posted By: PeterC
Date Posted: 24 Apr 2016 at 3:38pm
|
Thanks, Cajungene. I'll check the air data page. ------------- Peter - 1977 Cardinal RG C-FJPC - IFD550/540/240/322/605A/Skytrax100, Aspen MAX 2000, Trio A/P |
Posted By: DavidBunin
Date Posted: 25 Apr 2016 at 11:23am
| Glad you got yours working, Gene. I fly with an MLB, and I fly with a number of other pilots with the same equipment, so I absolutely know that it CAN work properly. Sorry you had trouble with your installation. |