iFly GPS Forum

I had a wingman in a 172 who has a VERY OLD ANALOG transponder....oddly, it would show and then NOT SHOW on the ADSB, aka "fish finder" in flight.  I would have him for a bit, then nothing...

Strangely, he was able to see me almost continuously during the FIVE hours of flight.  Thinking through it with other wingmen who had digital transponders, we are thinking the issue was in his non-ADSB equipped ancient analog transponder...what you yinz all think of this problem?

Mike, it might have something to do with the "out" frequencies, 978 and 1090 mHz, or altitude, or both. Or magic. I've had several odd experiences like yours in the half-dozen flights I've made in the vicinity of other aircraft since (finally!) installing the uAvionix UAT 978 mHz gizmo that I bought here about 15 months ago. (It passed the FAA's test in all categories, by the way.)

In one case I flew in trail in a two-ship with another Searey, but a factory-built SLSA version that came with ADS-B 1090 installed. My Experimental Searey has a 13 year old Becker Mode C transponder and an iFly 740.  The other pilot said he could see me constantly in his display--but I saw him only intermittently in my iFly. We were flying low--below 200 feet most of the time--over the James River and the wooded areas along it. His Searey is painted mostly green, and it blended in with the local foliage in SE Virginia, so a good ADS-B indication would have been really helpful. Eventually I just gave up worrying about running into him and veered off until he landed at KJGG, where we had lunch. (Great lunches there, and inexpensive.) But as I was climbing from about 500 feet to enter the pattern, a clear target showed up 600 feet above me--a different airplane altogether.

In another case, however, I was flying down the James in the same area a few days ago and noticed a clear indication of traffic about 7 miles ahead of me. I was then descending through 1200 feet and the target was 1100 feet lower. So it was low. I descended to 300 feet and watched his progress directly toward me, until we passed each other. At that point I rocked my wings and he rocked his in return. We were separated by about 500 feet horizontally and 150 vertically, and that was easy to see on the iFly 740. So that time it worked beautifully. But I'm not confident that it's going to work in every case. Eyes out!