I think that if Flarm were installed with 2 antennae, one high in the
cockpit or on top of the fuselage, and the other below, there would be
no Flarm blind spot and it would be as near perfect as possible. We
don’t do that because it is too much trouble and/or too expensive. It
is hard enough to persuade many pilots to have Flarm even in its most
basic available form.

Similarly, if we all had blind spot mirrors, the chance of seeing a
potential collision as the Finland one would be improved – but not
perfect still, as the human eye and attention is not capable of
perfection. Downward and rearward facing CCTV would be a further
enhancement of visual collision avoidance. (The latter is coming in on
road vehicles, so not technically impossible, just expensive to
develop and install.) Have we done it? No – “it isn’t worth it”.

As for PCAS – I have one of those too. I have only an aerial on top of
the glare shield. AIUI, transponders in gliders with only one antenna,
usually underneath, will have weak or non-existent signals upwards,
and my PCAS will only see at very shallow angles down, so would not
help in the Finland type accident if the lower glider had only a
transponder and only the upper one a PCAS.

As I have said before, the best is the enemy of the good. If everyone
waits for the best/perfection, we will have too many fatalities that
meanwhile the good – Flarm + PCAS – can help avoid some, or most,
times.

Chris N.