I see the RV had a Skyecho, but seemingly didn't 'see' the Phenom with that!
Was the Phenom outputting ADS-B or Flarm as it it wasn’t then SE2 would not see it and this shouldn’t be a surprise.
I see the RC had a Skyecho, but seemingly the Phenom didn’t ‘see’ it but then does the Phenom have ADS-B in?
In the Recorded Section above Reported it is alleged that the Phenom was putting out Modes A, C & S. The RV9 was Mode A/C. Now, Sky Echo 2 had bearingless turned off in software a few revisions back, so it wouldn't have seen the Phenom. The Phenom was running TCAS II, so depending on the current SIL/SDA value output the by the SE2, the Phenom might have seen it, but without knowing what they trigger on, and if they ignore CAP1391, I can't say.
However, TCAS II should be able to interrogate a transponder?
My own very brief experience with the SE2 on the dash is that the range isn't great and is not uniform 360 degrees round. However, it should be good enough for close up stuff.
ATOM would have seen the Phenom via 3D mode-S, or MLAT, or whatever you want to call it.
As for the Flyer forums... shrugs... awaits homogeneous echo from the chamber tainted with self righteous indignation...
Now a PAW in the aircraft would have started audio warnings with "Traffic, six o'clock, level, 3km" and got keener as time passed.
The audio is so under rated for dealing with aircraft with a location...