Parowan midair?

Butterfly has very good customer support friendly and prompt!

They told me that PowerFLARM does not yet display TIS-B information.
The hardware supports it, but their target for displaying TIS-B is
Summer 2011, via a software update.

Reinforcing what Darryl has said, to get TIS-B data sent to your
plane you need a proper GPS connected to a Mode S transponder, with
the transponder configured to (1) send ADS-B Out with position data
and (2) send the ADS-B In capability bit.

-John

On Jul 13, 4:35 pm, jcarlyle wrote:
Darryl,

The item C and D corrections were exactly what I had in mind - thank
you! The extra comments are much appreciated, too. The situation is
truly a confusing mess; thanks for trying to make sense of it all for
us.

Regarding the ability of PowerFLARM to display TIS-B, I'll follow your
advice and send an e-mail to Butterfly. The previous message in this
thread from Urs of FLARM strongly hints that PowerFLARM is intended
mainly for the US market, so presumably PowerFLARM either does (or
will shortly) support TIS-B.

Regards,
John

On Jul 13, 2:29 pm, Darryl Ramm wrote:

John

I'm not sure I corrected C and D to what you meant, but here goes.

On Jul 13, 6:55 am, jcarlyle wrote:

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.

CORRECTED 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 *FROM* all 1090ES data-out eqipped aircraft once per
second.
You *MAY ALSO IF LUCKY* see *UAT* data-out equipped planes once a
second
but only around other *SUITABLY EQUIPPED* aircraft.

I'd hope people look at that scenario as completely unreliable since
the proximity/threat cylinder used by the ground infrastucture while
reasonably large in radius is likely relatively limited in altitude so
you could easily not "see" traffic via ADS-R and TIS-B even if you
might otherwise think it is relatively close. I am not sure there is a
hard commitment for this "threat cylinder" or service volume size but
typical numbers are around 15 nautical mile radius but only +/- 3,500'
around an suitable equipped aircraft. So the other nearby ADS-B data-
out equipped aircraft has to be relatively close to your altitude for
this to work. Think of it working "by accident" at times but not
something we should not every think about relying on.

It also will only work if the aircraft you are "close" enough to
either has 1090ES or UAT data-out and is transmitting the 1090ES
capability code bit -- that will cause the ground infrastructure to
transmit TIS-B around that aircraft. The ground infrastructure would
also transmit ADS-R data for UAT equipped target aircraft around that
other receiver equipped aircraft -- unless that other receiving
aircraft also happens to have a UAT receiver and is properly
transmitting the UAT capability code bit. In which case the ground
infrastructure should suppress the ADS-R data because the other
aircraft would receive the UAT data directly. Confused yet? :-) Repeat
after me... for ADS-B receivers to work properly in the USA your
aircraft must also have an ADS-B transmitter sending your GPS location
and have properly configured capability class bits (to describe your
aircraft's ADS-B receiver link type).

BTW it is also maybe worth noting that above FL180 all aircraft will
be assumed to have 1090ES (not UAT) data-out as required in the ADS-B
mandate and therefore I expect the ground infrastructure won't do ADS-
R for UAT or TIS-B to UAT receivers at these altitudes. That seems to
be backed up by some documentation I've seen. That may make UAT
devices in gliders useless in wave windows for traffic awareness/
avoidance (and the issue there may really be glider traffic staying
outside the wave window).

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.

Yes that is correct but technically an over-requirement. If you have a
PowerFLARM with a 1090ES receiver you will directly see other 1090ES
transmitting aircraft and in that specific scenario you do not need a
local 1090ES transponder to receive that other traffic since it comes
via ADS-B direct not ADS-R. However clearly the the other aircraft
have no chance of seeing you via 1090ES, and having a 1090ES receiver
while not transmitting any ADS-B data-out signals is a huge problem
for ADS-R and TIS-B as I've hopefully flogged to death already.

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?

I cannot speak for PowerFLARM specifically but any device that has a
1090ES receiver essentially gets TIS-B and ADS-R for "free" if the
aircraft also has the proper ADS-B data-out equipment - which yes, is
not "free" to you since you gave to buy that ADS-B data-out device.
The receiver can tell from the data if a traffic message is ADS-B
direct, ADS-R or TIS-B. The SSR radar (or multilateration) derived
positional accuracy of TIS-B is much worse that the GPS derived ADS-B
direct or ADS-R positional data and I have no idea how specific
traffic awareness/collision avoidance products will handle display and
warning for TIS-B traffic. Remember the portable avionics market is
the wild-west there is no strict standard how any of this traffic data
is handled or displayed. One option would be to ignore all TIS-B
traffic but I would be very surprised by a vendor doing this. This
problem is similar to and a bit more complex than the same problem
with the positional accuracy of Mode S TIS where the TIS system is
careful to display a threat "on top of you" when it is gets close to
you within a reasonable margin of error.

To the Funkwerk comment...

"TIS" means the Mode S TIS used in the USA where *some* terminal/
approach radars communicate SSR radar traffic to aircraft equipped
with Mode S transponders that have TIS capabilities. I never would
expect an add-on receiver box to do Mode S TIS. That capability
requires the Mode S transponder to broadcast it has TIS receive
capability and then the TIS ground infrastructure sends directed
messages to that transponder about the relative position of nearby
Mode C or Mode S equipped traffic. Because of how this works it
happens within the Mode S transponder. Most modern Mode S transponders
will support TIS. Likely of most interest in the USA is the Trig
TT21/22 transponders that do support Mode S TIS, and there are some
glider pilots in the USA starting to play with TIS traffic data from
their TT21 transponders. Clearly this is only of interest around busy
terminal/approach radar coverage areas and getting that traffic
displayed is an issue since it not the glider defacto-standard Flarm
serial port data protocol.

"Does no support TIS-B" could mean several things and it may be worth
clarifying the vendor's statement...

0. The information from the vendor could be wrong (I've managed to get
clearly wrong capability claims/misinformation from vendors in this
early market). But presumably given the source of this claim it is
accurate that the device does not support TIS-B.
1. The vendor does not want to claim TIS-B support becasue they do not
know for sure your aircraft has the proper ADS-B data-out capability
to support this.
2. The vendor has decided to suppress all TIS-B traffic data because
they do not want to handle the relative imprecise or otherwise
problematic TIS-B position reports (that would surprise me). For
European manufactures that TIS-B is not important in Europe may be a
factor here.
3. The vendor has decided to suppresses all TIS-B traffic data because
they have not yet developed the capability to handle the relatively
imprecise TIS-B position reports (and maybe other technical issues
like target ghosting/deduplication) and/or since TIS-B is not
important in a device in Europe and they have chosen to delay
implementing TIS-B support. (The question would then be when is this
support coming?).

It would not be good for an ADS-B receiver devices for sale in the USA
to not support TIS-B. It's already a confusing enough mess out there
(have I proven that yet?? :-)) without having devices selectively not
implement this. However given that we don't have ADS-B ground
infrastructure widely deployed at the moment, if this device
limitation was clearly explained by the vendor with a "coming in a
firmware update in future" promise then that would be a different
matter.

Again please get specific answers from Butterfly/PowerFLARM or
Funkwerks etc. I have never used either vendors ADS-B products.

Regards

Darryl