Parowan midair?

Darryl,

A question arising from your reply to Walt, specifically concerning
TIS-B. From your reply and PowerFLARM's literatu

A. It appears that this unit will give accurate direction, range and
relative altitude info to FLARM equipped planes, and it also will
broadcast FLARM signals to other aircraft.

B. It also appears that it will give you estimated range, relative
altitude, but no direction to Mode C and Mode S transponders that are
being interrogated.

C. If your aircraft does not have a Mode S with ADS-B out
transponder, you will still get accurate direction, range and relative
altitude info to ADS-B data-out equipped planes once a second around
other aircraft.

D. If your aircraft does have a Mode S with ADS-B out transponder,
you will get accurate direction, range and relative altitude info to
nearby aircraft with ADS-B data-out transponders once a second around
your aircraft.

We'd like point D2 to also include getting TIS-B data, meaning "SSR
radar (or multilateration) traffic information retransmitted on ADS-
B", but I can't find anywhere that PowerFLARM claims to do this. I
have an e-mail from Dr. Thomas Wittig, the developer of a competing
product (Funkwerk TM250 Traffic Monitor), that says his system
supports "ADS-B IN via Mode S 1090, but not TIS-B or TIS".

Does PowerFLARM really do TIS-B?

-John






On Jul 13, 3:23 am, Darryl Ramm wrote:
PowerFLARM to the extent it has PCAS capabilities can see other
transponders being interrogated by ground (SSR Radar and in some
places multilateration systems) and airborne interrogators (TCAS, TCAD
etc). This would give you no direction information for that traffic.

PowerFLARM has a 1090ES receiver so can "see" with high accuracy
aircraft with 1090ES ADS-B data-out. That will over time include all
the airliners, fast jets, any traffic flying over FL 180, and I expect
it to include many GA aircraft who I expect will go with 1090ES data
out and not UAT to meet the ADS-B carriage requirement. Since there is
nothing else involved the line of sight range on this may be quite
significant, well beyond PCAS and FLARM (and ADS-R and TIS-B).

PowerFLARM has a 1090ES receiver so *if* you also have an ADS-B
transmitter properly configured to transmit your GPS position and ADS-
B receiver capability codes (i.e. set to show your aircraft receives
1090ES) then the ADS-B ground infrastructure will rebroadcast UAT data-
out equipped traffic over 1090ES that it is aware of within a cylinder
around your aircraft. The size of this cylinder is significantly less
than the ultimate range of UAT or 1090ES direct transmissions so this
one damper on anybody thinking they can track their glider buddies
over very long ranges in the air if there is mixed UAT and 1090ES
involved. The ADS-B data-out/transmitter you need for this would
typically be something like the Trig TT21 Mode S/1090ES transponder
but could be a UAT transmitter (or transceiver).

For the PowerFLARM or any other ADS-B receiver to see SSR radar
targets via TIS-B again the ADS-B ground infrastructure needs to know
where you are so it can broadcast possible threats in a cylinder
around you. But it will only broadcast traffic that the SSR radar
system (or multilateration in some areas - like the newly announced
Alaska deployment) can "see". There seems to be a common misconception
that ADS-B TIS-B will show transponder equipped threats over vast
areas, but it cannot show any TIS-B threats near you if you are flying
outside of traditional SSR radar (or multilateration) coverage. Again
the ADS-B data-out needed to tell the ground infrastructure where you
are would today normally be a Mode S /1090ES transponder.

One point of confusion with ADS-B traffic is some people talk about
TIS-B as if it means any traffic you see on ADS-B, it specifically
means just the SSR radar (or multilateration) traffic information
retransmitted on ADS-B. Traffic information via UAT or 1090ES data-out
direct and ADS-R is not "TIS-B" traffic.