On Monday, 2 October 2017 11:50:48 UTC-6, Darryl Ramm wrote:
The 14 CFR Appendix F to Part 43, ATC Transponder Tests and Inspections required by 14 CFR 91.413(c) only test RF properties of the transponder. There are unlikely to be undetected problems with modern transponders that causes errors in operation or impact other airspace users. And a call to Reno Approach for a transponder check would have been good assurance that the basic transponder operations are working, a good idea on any new install. In some ways Appendix F seems to address concerns of older generation less reliable transponder technology, and specifically to look for know faults that do could impact operation and other users, so still useful to know that stuff is working, and still a 14CFR requirement and should be done.


My story - I bought a Ventus 2CX that is registered experimental with a installed transponder and appropriate log book entries and bi-annual checks. I checked the antenna and it was a L2 antenna, http://wingsandwheels.com/l2-aae.html, that was mounted behind the pilot seat on the floor of the fuselage. Seemed a bit odd to me as the fuselage is carbon but with all the signoffs, and I know the A&P that installed it, I assumed I was uninformed. I flew for a couple of months, including a number of wave flights around the Salt Lake Class B and over, through multiple arrival and departure lanes, and then put it away for the winter.

Next spring before flying I did the transponder bi-annual check, different company than one used previously, and the guy went about his business. Measured output inside the cockpit, measured output at the wingtip and measured output 100 yards away. He then asked for the log book, went through it and then placed his sticker in the book and signed it.

He called me over to the cockpit and asked me to show him the antenna setup which I did and he just shook his head and smiled. He then gave me the logbook and asked 'Do your testicles tingle or glow after a long flight?'

He went to explain that he measured 250 watts in the cockpit, ~125 watts at the wingtip and 50 watts at 100 yards. Basically I was just bombarding my body.

He *did* signoff on the bi-annual test as the transponder was operating correctly!

Yes I quickly got a external shark fin antenna installed and verified it was operating correctly with SLC ATC during the next flight.

Yes we all must understand how our equipment works and use common sense when needed.

Ron Gleason