danlj wrote:
Aviation Consumer's current issue has an article on traffic-detection
systems. It points out that mode S is already going away and ADS-B in
only just beginning to be installed. and that a defect of ADS-B is
that several seconds may elapse between the time aircraft A replies to
the radar facility, the facility processes the signal and calculates
vector information, and then broadcasts this. So this isn't going to
help as much as we'd like in gaggles, never mind that it won't be
available everywhere for a long time.

I haven't read the article, but the above is only partially correct.
This only refers to the case of an ADS-B equipped aircraft detecting a
nearby Mode C or S equipped aircraft. When two ADS-B (more correctly,
UAT) equipped aircraft are in proximity, they communicate directly with
minimal delay, the ground network and radar facilities are not involved.

It sounds as though FLARM is available and functional. It might be
possible for pilots to cooperatively use it without an FAA
imprimateur, though the FTC will have jurisdiction over the use of
frequency.

If a FLARM-like device using an FCC approved frequency was available, we
could use it without FAA approval. But, our glider population density
is much lower than Europe, except in a few areas, and other aircraft are
a hazard these days in many areas. ADS-B UAT is a FLARM-like device
with regulatory issues that make it difficult to develop a low cost
device. It seems to me that the best thing to do is attack the
regulatory problem, so that gliders, balloons, light sport aircraft,
etc. can all participate in the system at a lower cost...

Marc