Tuesday, January 14, 2020


It was mandated. All airplanes flying in controlled airspace* must be equipped with "NextGen" ADSB-out equipment. *the ADS-B mandated airspace defined in 14 CFR 91.225 (above 10kft MSL in Class E or within the boundaries of Class B and Class C airspace) including the 30-mile veil. 
An ADS-B Out transmitter alone is not sufficient to meet the requirements of 14 CFR 91.225 and 91.227. Aircraft must be equipped with a Version 2 ADS-B Out transmitter and a compatible GPS position source. There are two types of ADS-B systems available:
  • Mode S transponder with Extended Squitter, referred to as 1090ES that meets the performance requirements of Technical Standard Order TSO-C166b
  • Universal Access Transceiver (UAT) that meets the performance requirements of TSO-C154c. UAT has the additional capability to receive weather data provided by the FAA ADS-B network and operates on 978 MHz.
Due to the S-LSA restrictions previously discussed, my new mode S transponder with Extended Squitter,  (1090ES), is a Garmin GTX 335. Since the new transponder has the same dimensions as the old, I ASSUMED  it would be a simple "plug and play". Nope.

  1. The new mounting box screws did not align with the avionics tray. New holes had to be drilled in the tray. Not trivial if you don't have a right angle drill.
  2. The mounting mechanism has moved from the center of the old transponder to the right on the new. The instrument panel had to be trimmed to accommodate this change.
  3. The old connector (from the Dynon D100 EFIS) would not fit the new transponder. We did a deep analysis of the old versus new pinout to determine what pins had to be added to the new connector. (This would provide the RS232 altitude information.) New pins were soldered and inserted into the new connector.
  4. A new GPS antenna is required which meant a new custom cable had to be built. Holes were drilled through the skin in front of the canopy and the cable was connected to the new transponder.
Thank you CERTUS!

Ready to fly? Nope. It also has to be programmed. This is done by holding the ENTER key while turning the unit on. This brings up a series of configuration menus.  Most are fairly straight forward but some require knowledge greater than mine. Fortunately, there is YouTube, right? That didn't get the job done. Test flights showed that it wasn't working properly (Thank you Tampa Approach for being so patient.) I needed an expert and found Mike. Call Garmin G3X support at 866-854-8433. The last problem was a SIL failure (Source Integrity Level). Mike took me through all of the configuration options and found that I needed to change my "UNK" to IE-7. (Yeah, that doesn't mean anything to me either.)

But it works.  I am 2020 compliant!