On Aug 17, 8:10*pm, Mike Schumann
wrote:

When you get a PCAS alarm, the aircraft could easily be coming from
behind you or another blind spot. *Or you could have two aircraft at the
same range coming from opposite directions. *All PCAS (and PowerFLARM)
gives you is an alert to start looking. *It doesn't come close to giving
you all the information you need to avoid disaster in certain situations.

A classic example of this was a couple of years ago when I was flying a
K-8 south of Mpls. *Earlier in the day, we saw a couple of C-130s
heading south. *About an hour later, I heard them coming up behind me
(low tech audio PCAS+). *What do I do? *If they saw me and were avoiding
me, a sudden turn could put me in their path.

With ADS-B, I could have seen exactly where they were and reacted
accordingly. *With PCAS, I wouldn't be any better off than with my basic
hearing.

--
Mike Schumann- Hide quoted text -

- Show quoted text -

I still have to disagree. Using your example, with PCAS you would
have been warned well prior to hearing the C-130s. If the warning
continued to show decreasing range, and possible altitude conflict,
and you could not see the threat aircraft in front, then a turn to
check 6 would put you in a position to see them (hard to miss two
Herks). As far as the concern that a turn will put you in their path,
think of the relative speeds and distances involved. Unless the other
plane is right on top of you, your turn is not going to move you in
space very much, but on the other hand may make you visible to the
other plane and allow normal rules of the road to apply.

Mike, I don't disagree that ADS-B, when fully implemented, will be a
wonderful thing - for GA. I've been using the military version
(JTIDS) for years and love it, but unless the hardware requirements
come down to something reasonable it will take a while to get into
gliders. Flarm, OTOH, is here now, and solves some nasty, glider
specific problems (which ADS-B will probably never do, given the
market). Unlike you, I am comfortable with the level of warning that
PCAS gives me for transponder - equipped threats (especially VFR
traffic that won't see your transponder or be talking to Center). I
also am comfortable staying away from airliners - but I'm not flying
near Minden/Reno. Around Phoenix, I know pretty well where the
heavies are and scan accordingly.

I also think the nature of glider flight makes the chance of a midair
with another glider much higher than that of getting hit by an
airliner or GA plane. My experience in 2500 hours of gliding, all
over the US, supports that view.

Kirk