Robert Ehrlich wrote:

Eric Greenwell wrote:

...
I'm guessing the relatively slow speeds (compared to the airliner) and
low G turns of a glider (compared to a fighter, for example) would still
allow the TCAS to sort things out to the benefit of all concerned. At
the least, the TCAS is providing bearing, and altitude to the
glider, a big improvement over a pair of eyeballs looking out a window
going 300 knots.


I understand clearly how the TCAS can determine range and altitude (by
timing the return and decoding the encoded altitude), but how can it
determine the bearing? directional antennas coupled with compass information?

I'm not sure, either. Here's a quote from "Introduction to TCAS II
version 7":

"TCAS interrogates
ICAO-compliant transponders of all aircraft
in the vicinity and based on the replies
received, tracks the slant range, altitude
(when it is included in the reply message),
and bearing of surrounding traffic."

It also uses the term "relative bearing" about half the time, so it's
not clear to me which they mean. I suspect it's actually relative
bearing. In any case, the bearing info appears to be determined by using
two or more antennas.
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Eric Greenwell
Washington State
USA