On Oct 29, 2:53*pm, "vaughn" wrote:
"Mike Schumann" wrote in message

... What evidence do you have that there are plans to turn off TIS-B after 2020?

Some TIS stations are already gone. See this AOPA blurb:http://www.aopa.org/whatsnew/newsite...is.html*Google for more.

Vaughn

Vaughn

Actual this is talking about Mode S TIS (sometimes incorrectly called
TIS-S). Which is not related to ADS-B TIS-B although some of the
concepts are similar. ("concepts" is my favorite work at the
moment...)

Mode S TIS is (or was if your local service has been decommissioned) a
great service used in the USA that uplinks terminal/approach radar
traffic information to a Mode S transponder capable of receiving TIS
data. (Yes Mode S transponders are fancy enough the can receive uplink
data as well as downlink data, but the uplink is not the same as
1090ES data-in).

Mode S TIS transponder advertise to the approach radar that is has TIS
capability then the approach radar TIS processor calculates threats
within an ~8nm radius cylinder +/- 3k' or so (its actually more
complex than that but I'll spare you the pain) around the client
aircraft and uplinks that data to the client transponder (using
relative distance and direction). This requires you are within
coverage of a TIS equipped SSR terminal (not enroute) radar and you
have a Mode S transponder that supports TIS and it is connected to a
compatible display. Enroute radar can't provide TIS for multiple
reasons including the slow scan/update rates, traffic volumes, etc.

The Mode S TIS decommissioning issue was as the FAA upgraded some
terminal SSR systems they did not want to pay to add the TIS support
to those systems, even if the SSR radar they were upgrading had
previously had it. To me this was a very poor decision since Mode S
TIS was encouraging many GA aircraft to equip with traffic displays
and encouraging pilots to use traffic awareness systems - which would
have been a good segway into ADS-B. To rub salt into this the are some
realtively low-cost add-on Mode S TIS processor systems that use
omnidirectional antennas (the Mode S TIS data-uplink does not has to
go though the SSR radar directional antenna) that companies proposed
to the FAA and were turned down on. But in the FAA's defense here is
they are just a funding starved organization trying to do a lot. Maybe
too much, but that is debatable.

Around the places like the San Francisco Bay Area where I live Mode S
TIS still provides very useful traffic information to many GA
aircraft. The other advantage of Mode S TIS is is is relatively a low-
cost feature to add to any Mode S transponder. For example the pretty
standard Garmin GTX 33 and GTX 330 transponders come with it included.
The Trig TT21 that is being used in gliders also comes with Mode S TIS
-- but you need to connect it to display that support the "TIS serial
protocol" -- e.g. something like my Gamin 496 -- and that's the same
whole issue that the UAT and 1090ES receivers not designed for glider
cockpits have with not supporting the Flarm serial dataport protocol
that is widely supported by display products in our cockpits.

Darryl