Fast forward to present time.<\/p>\n
Everything is working fine.\u00a0 With one minor exception. When I requested an ADS-B performance report (it tells you if all the ADS-B data you’re transmitting is valid and accurate), it showed this one ridiculously small error.\u00a0 Basically, it was saying that for 3 to 5 seconds on any flight, I was not transmitting the GPS altitude.\u00a0 What’s really weird is that it showed this error on a 20 minute flight or 2 hour flight. I checked the flight data logs and it showed the correct GPS altitude for every second of the flights.<\/p>\n
Here’s a report from a 2 hour flight.<\/p>\n
ADS-B 1<\/a><\/p>\n Any parameters out of compliance are colored red.\u00a0 In this case, four seconds of missing altitude data.<\/p>\n I checked everything I could think of and kept coming up empty for a solution.<\/p>\n Then I contacted Trig.\u00a0 I figured that since the data seemed to be present and it was the transponder that sent it, that seemed the logical culprit.\u00a0 Because they’re based in Scotland, there’s a time difference that I had to work around.\u00a0 But their responses were very prompt. After just a couple of exchanges, I was told that the software on my transponder was version 2.4 and that they were currently at version 2.7 and that before chasing anything else it would be prudent to get my unit up to date.<\/p>\n I asked how to do the update and was told it would have to be done by an authorized Trig dealer.\u00a0 The cost would be whatever the dealer decided to charge. Or I could ship it to their US distributor and they would do the update for free. \ud83d\ude42<\/p>\n So in July I pulled the transponder and shipped it to Mid-Continent Instrument and Avionics in Kansas (they’re the Trig distributor for the US). It took one day to do the update and then it was on it’s way back to me.\u00a0 Did I mention there was no charge for the update?<\/p>\n I installed the updated transponder and took Ann up for her second flight in the Velocity. After I got back home I requested a report on the ADS-B data.\u00a0 There were a bunch of errors now! I sent an email to Trig and got a response back within an hour that explained I needed to change one of the configuration parameters on the GPS (that’s where the position data comes from).\u00a0 I made the change and did a quick flight. Because it was a weekday and my home field is in a very active MOA, I checked in with Tyndall Approach to get a squawk code so they could keep the F-22’s from running over me.\u00a0 After I entered the code, approach advised that they were receiving no replies and they only had a “faint primary return”.\u00a0 “Primary return” is what shows up on their screen when the only thing they receive is a return from the radar.\u00a0 No identifier or altitude.\u00a0 And the reason it was “faint” is because the airplane isn’t metal. So the return from the radar was mostly going through the plane and bouncing off any metal inside.\u00a0 I power cycled the transponder and tried a couple other things but nothing.<\/p>\n Now the only thing I did between the first and second flight with the new transponder was to change something on the GPS.\u00a0 It didn’t seem likely that would cause the transponder to stop transmitting.\u00a0 But because my profession involves troubleshooting, and what I teach is: “ALWAYS suspect the last thing that was done.”. So I changed the GPS configuration back and flew again.<\/p>\n Same thing.<\/p>\n Change the GPS back to the correct configuration and flew again (I know, I know.\u00a0 But you never know, right?).<\/p>\n So then I figured that it’s got to be the antenna lead. I disconnected the antenna lead at both ends and looped it (center conductor to the shield) and checked the continuity (I had to check it this way because I’m alone and the ends are pretty far apart).\u00a0 Showed good.\u00a0 Then I had a thought (always dangerous).\u00a0 I realized that I got an ADS-B report after the first flight that showed some valid data. Granted some of the data had errors, but there was data.\u00a0 Which means the transponder was transmitting. That means the antenna was functional. Just to be on the safe side, I requested another ADS-B report. I guess just to see what is looked like. it showed a perfect data capture.\u00a0 Zero errors.<\/p>\n So I stopped troubleshooting the antenna.<\/p>\n I contact Trig again and after a few exchanges, they had Mid-Continent overnight me a replacement transponder with an unreleased version 2.9 code. It arrived, I installed it and made a test flight. Approach still couldn’t see me.<\/p>\n Back to Trig.\u00a0 I suggested that maybe we should downgrade back to the last known good configuration.\u00a0 Once again, Trig had Mid-Continent overnight me another transponder this time with an out of date version of software.\u00a0 Good old 2.4 code.<\/p>\n Installed it and had to wait for Hurricane Hermine to pass before I could fly. When I did, same problem. So now I’m sitting here with THREE TRANSPONDERS<\/strong> with three different version of code on them and every single one had the same problem.<\/p>\n I’m really frustrated at this point and I’m sure Trig is frustrated and<\/strong> concerned. I would bet that if I asked, Trig would have put an engineer on a plane and flew them to Panama City, FL to help me get this figured out.<\/p>\n But I decided that they had already performed above and beyond the call of duty. I mean, I was sitting here with three transponders and only one was mine!\u00a0 And they hadn’t asked for so much as a credit card number.\u00a0 And besides, at this point there was no way that this could be the transponder.<\/p>\n So I called Carl at Monarch Aviation<\/a>.\u00a0 He did my transponder certification a few months back.\u00a0 I was very impressed with his knowledge and willingness to work on experimental aircraft built by rank amateurs.\u00a0 He said that if I could get over there today at 1pm, he could take look at it.<\/p>\n I run out to the airport and takeoff headed to Defuniak Springs airport. I pull up as Carl is finishing up a transponder check on an trike.\u00a0 One of those hang gliders with a Rotax engine on the back.\u00a0 Carl is willing to work on anything!<\/p>\n I had already given him the rundown on the situation. The first thing he wants to do is see if the transponder is transmitting. So I power up the avionics and he fires up his test rig which will send out the interrogation signal the read the reply. “Nothing” he says. Then we disconnect the antenna lead at both ends. I climb underneath where the antenna is and he hands me one of the test leads and has me put in on the center conductor of the antenna wire. “Looks good” he says. “Now on the shield, please.” once again he says “Looks good”.\u00a0 None of this is any surprise to me (because I already check this, remember?). Then he asks for the test lead I was using. As I’m getting up, he says “There’s your problem.” I get a sinking feeling because I know what he’s found.\u00a0 I say “center conductor is shorted to the shield, right?”\u00a0 “Right you are.” is his response.<\/p>\n Normally I would have checked that.\u00a0 Honestly, I would!\u00a0 But the antenna was working!\u00a0 I know this because I’ve got the ADS-B reports which say so.\u00a0 But I should have checked it.<\/p>\n He then says that it’s going to be shorted at one of the two ends and that no matter which one we pick to re-terminate, it will end up being the other. I tell him that ain’t going to happen. “Why is that?” he asks.\u00a0 Because the short is on the connector that attaches to the transponder. When he asks how could I know that, I tell him because it’s the only connector that was touched before the problems started.\u00a0 So he puts on a new TNC connector at the transponder end of the antenna lead.\u00a0 Then I power up the avionics while he powers up his test unit.<\/p>\n Good signal!!!<\/p>\n There are a some of lessons here:<\/p>\n 1) Don’t shortcut troubleshooting procedures because of what you “think” that you know. Whenever you have the slightest suspicion of a cable, troubleshoot it completely. It only takes a second to do a complete check.\u00a0 If I had done this in the first place, I would have saved a bunch of people a bunch of time.<\/p>\n 2) If you are stuck, don’t hesitate calling in a fresh set of eyes. It took Carl all of five minutes to nail this one down.\u00a0 Partly because he wasn’t influenced by outside information.\u00a0 Basically, he was unbiased and assumed nothing.<\/p>\n 3) If you need a transponder, radio, GPS or audio panel, consider Trig Avionics<\/a>!\u00a0 I can not say enough good things about their support. If I ever get back to the homeland of my Great Grandfather, I will be certain to look up Lindsey at Trig support.<\/p>\n The thing that nobody can explain was how ADS-B data was being transmitted out of an antenna that had a lead with a dead short in it.<\/p>\n <\/p>\n","protected":false},"excerpt":{"rendered":" One of the things that I’ve been chasing for about six months is an ADS-B anomaly. A bit of background for the non-avionics types (skip ahead if you already know this:-) ) ATC (Air Traffic Control) knows where we are … Continue reading ![\"aliens\"](\"https:\/\/www.velocity-xl.com\/blog\/wp-content\/uploads\/2016\/09\/aliens1-300x300.jpg\")
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