On Oct 11, 6:50*pm, jcarlyle wrote:
Darryl,

I found your fourth paragraph very confusing:

ADS-B data-out in gliders will not provide an airliner with an RA from
its TCAS II system - something many *pilots are not aware of. TCAS
needs a transponder to interrogate to issue an RA. The whole topic
does not get talked about much because it is implicitly assumed that
threat aircraft have transponders or transponders *and* ADS-B data-
out. If your airline has fitted a modern TCAS II that includes ADS-B
data-in and CDTI then you will get traffic display of ADS-B data-out
equipped aircraft but no RA. And you may even have have TCAS II with
ADS-B data-in for TCAS "enhanced surveillance" but still no CDTI/ADS-B
data-in display of traffic at all.

Are you making an assumption here that the glider in the first
sentence is flying in the US and has a UAT setup to yield ADS-B data-
out? Because in Europe I'm almost positive that ADS-B out can only
achieved with 1090ES, which of course will indeed provide a RA from a
TCAS system.

-John

John thanks sorry if I confused things. Yes I was taking about the
USA, this thread flopped geographies several times, I had assumed that
Russell was also talking about the USA where ADS-B over UAT is a link
layer option, I'm not sure how else to understand Russell's comment
"our salvation as glider pilots lies in the low cost development of
ADS-B" [presumably as opposed to transponders which was the topic up
tot that point]. I also point out later in my post that Mode S with
1090ES data-out will indeed interoperate fully with TCAS II. But to be
really clear...

In Europe and most other places ADS-B will be over 1090ES only
(thankfully the European based work on VDL never ended up being
supported as a link layer for ADS-B). And as John points out since
those ADS-B data-out systems are also Mode S transponders they will be
fully compatible with TCAS II. And technically its possible to build a
1090ES data-out transmitter that does not implement transponder
functions, but nobody is doing that or announced any plans to do so,
but once you go to all that effort to do 1090ES data-out it might as
well be a full Mode S transponder.

Darryl