AXP340/322 ADS-B Transponder - APX 340 Intermittent

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APX 340 Intermittent

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=973
Printed Date: 26 Mar 2026 at 1:01pm
Software Version: Web Wiz Forums 12.07 - https://www.webwizforums.com

Topic: APX 340 Intermittent

Posted By: aweltman
Subject: APX 340 Intermittent
Date Posted: 21 Feb 2016 at 4:01pm

Since we installed our APX 340 it work normally most trips. Altitude transmitted to center is accurate. Then out of the blue, new trip the altitude transmitted to center is off by 400 feet. Some times below sea level. Altimeter and encoder check normal.

Avidyne Replaces APX 340. Everything works fine, Then same as above happens again. Turn the APX 340 off, and back on altitude is correct.

Ok....spend another $1,000 and replace the encoder. That would be the logical thing to do.. Except that we have the same problem with the IFD 540. Most of the time works find. Then i'm on climb out and the screen goes blank, then on , then off, then on then off 4 times, then dumps all programing. Re enter everything and works fine for the next couple of trips. Then a failure on an approach. Take the unit back to Gulfcoast, after many upgrades, same thing again.

I'm a real jerk, I spend $3,000 more and install an MLB 100. Works find on the inital trip. Guess what, next trip the IFD 540 goes off , the the APX 340 shows me below sea level.

I'm at my wits end. Avidyne has turned our aircraft into an expermental toy. Fly at your own risk. Someone is going to get hurt, this is not safe.

Help

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ajw

Replies:

Posted By: AviSimpson
Date Posted: 22 Feb 2016 at 3:51am

Pm Sent.

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Simpson Bennett
Avidyne Corporation
Product Manager