Trig TT21 Transponder Thoughts?

On Jun 21, 11:28*am, Darryl Ramm wrote:
On Jun 21, 10:23*am, "Mike Schumann" mike-nos...@traditions-

nospam.com wrote:
One note of caution about relying too much on TCAS for collision avoidance.
TCAS was designed as the last line of defense against collisions when all
else fails. *It is NOT designed for use as the primary way to avoid
collisions. *Unfortunately, given current FAA ATC procedures, this is the
way it is currently being used.

One of the problems with TCAS and gliders is that the TCAS logic is designed
for typical aircraft. *As a result, TCAS is assuming that targets are
traveling in a relatively straight trajectory. *Gliders don't do this, so
the TCAS RA may generate advice that actually creates a collision.

If you are really serious about minimizing the threat of collisions, you
also need a device that will show you where the other traffic is. *If you
are in an area where there are ADS-B ground stations, an ADS-B UAT
transceiver is definitely the way to go. *If you look at the FAA web site,
you will see that there currently is ground station coverage on the entire
east coast, in southern Florida, and in other isolated other areas of the
US. *By next summer, there should be a major expansion of the ground station
coverage, with most of the US covered by 2011.

If you are not in an area with ADS-B coverage, a PCAS type of device is an
alternative.

Mike Schumann

[snip]

If all you want is TIS-B traffic information then a Mode-S transponder
can get you traffic data, provide TCAS compatibiiey, and also
compatibility with PCAS systems used in some gliders and GA aircraft.
I know Mike knows all this, that comment is to make it clear to
others.

TCAS is the absolute last defence and for high-traffic jet/airline
areas I just hope people will not think a glider would be better off
with ADS-B TIS-B traffic data *instead* of a transponder that provides
visibility to TCAS equipped jets.

While there are arguments about TCAS RA predictions, the RA are based
on altitude and jet traffic can climb or descend rapidly when needed
and the TCAS will monitor what is happening as the threat target
converge. This is not a satisfactory answer but I just worry that many
readers might thing that TCAS is doing some sophisticated track
avoidance and therefore a glider maneuvering might cause far more
complexity than the altitude based avoidance that actually happens.
Being primarily altitude based makes the resolution determination a
lot simpler. Gliders are also relatively slow moving, so even if
maneuvering their relative location to a fast jet does not move
rapidly. Gliders might change climb rates at +/- thousands of feet per
minute but with altitude margins in TCAS and the continuous monitoring
of altitude as targets converge probably make this less of an issue
than it could be. I am not aware of any technical study that shows
serious problems with gliders (or other slow traffic) and TCAS. I'd
love to see any if they exist.

With TCAS on TCAS targets the Mode-S transponders are communicating RA
data to ensure that both aircraft are not instructed to climb etc.
Since a glider won't have TCAS that won't happen, but the real issue
with that is avoiding TCAS *directing both the jet aircraft with high
climb/descent performance to do the same thing, and the ultimate fall
back here is the ability of a jet to normally out-climb or out-descent
a glider even if the glider pilot decides to change altitude abruptly
to avoid a collision.

So again, the problem if people just relied on ADS-B UAT devices and a
TIS-B traffic display is that the glider would be entirely invisible
to TCAS. I would much rather have the TCAS help the fast jet avoid me
than me avoid the fast jet. But ideally have both. And ADS-B TIS-B
(either over UAT or 1090ES) offers more range than PCAS - one of the
issues with PCAS (I fly with a Zaon MRX) is it may not have sufficient
range to be useful for fast jet traffic. And even if you have a fancy
TIS-B display you may still decide to make an avoidance manouvre that
conflicts with what TCAS is telling the other aircraft to do. Again
this would rely on the jet typically being able to out climb or out
descend a glider.

Had the ASG-29 flying near Reno a few years ago had a simple
transponder the Hawker jet very likely would not have collided with
with it. ATC hopefully would have given the Hawker a traffic advisory
(but as Mike points out there is no guarantee that currently they
would have since both aircraft collided outside controlled airspace),
failing that the TCAS should have done its job. Likewise with another
incident near Reno more recently a transponder would likely have
avoided the jet pilots and ATC being "surprised" by a glider while on
approach to Reno, and the subsequent hassles for all involved.

BTW people wanting to see what TIS-B traffic on a UAT device might
look like in a real product -- the NavWorx PADS600 receives TIS-B (and
FIS-B) data, it does not do ADS-B out. Seehttp://www.navworx.com. The
receiver is currently ~$1,500 and can display traffic data on a Garmin
496 or several other types of popular GA displays. As Mike points out,
this technology is quite interesting for the future.

Darryl

Sorry my first para was supposed to say

If all you want is TIS-B traffic information then a Mode-S transponder
**with ADS-B in** can get you traffic data, provide TCAS
compatibility, and also compatibility with PCAS systems used in some
gliders and GA aircraft.

As mentioned in my first post in this thread the Becker Mode-S claim
to support ADS-B in for TIS-B. If I had a Becker Mode-S and lived near
ADS-B coverage I'd be playing with that now (done on the ground, a few
wires to a the transponder data out pins and see what is is sending
out...).

Darryl

A question regarding ADS-B out capability on a Mode S transponder. Can
you feed the output of a glider GPS, say a Volkslogger, and into the
Mode S transponder?

Since the transponder and the encoder both require TSOs for use in the
USA airspace, I assume the answer to this question is an emphatic
"no".

A similar question for ADS-B in - are you required to display the TIS-
B and/or FIS-B data on a TSOed display?

-John

On Jun 21, 1:10*pm, jcarlyle wrote:
A question regarding ADS-B out capability on a Mode S transponder. Can
you feed the output of a glider GPS, say a Volkslogger, and into the
Mode S transponder?

Since the transponder and the encoder both require TSOs for use in the
USA airspace, I assume the answer to this question is an emphatic
"no".

A similar question for ADS-B in *- are you required to display the TIS-
B and/or FIS-B data on a TSOed display?

-John

John

Correct. All ADS-B out requires an expensive certified GPS. That is an
issue for UAT and Mode-S/1090ES. There are people trying to change
this but it is a complex issue.

There is no requirement per-se to display the traffic on a TSO display
if the equipment is not permenently installed. IFR at the other
extreme is entirely another can of worms.

The Garmin 496 display for example that some vendors connect to just
use the legacy input defined for TIS-A on those devices. Most of that
TIS data should be easy to decode to display on PDA devices etc. We
will need soaring software vendors to support this. Since we don't
really want to be looking at the display we will also need those
vendors to impliment audible traffic alerts. That is not something
that a TIS-B receiver will normally do for you. Which is why I am
curious if somebody has got a Becker Mode-S hooked up in a glider to
do this.

BTW even ADS-B in only TIS-B receivers can have a GPS since they use
that to know where they are to output display data. Somewhere in the
reciever-display chain a GPS is needed.

Darryl

Darryl

Thanks, Darryl - I'm much more educated now on ADS-B, TCAS, TIS-B and
FIS-B than I was this morning!

All I need now is input from anyone who has a Trig TT21, especially
with regard to ease of use and reliability.

-John

On Jun 21, 4:55 pm, Darryl Ramm wrote:
John

Correct. All ADS-B out requires an expensive certified GPS. That is an
issue for UAT and Mode-S/1090ES. There are people trying to change
this but it is a complex issue.

There is no requirement per-se to display the traffic on a TSO display
if the equipment is not permenently installed. IFR at the other
extreme is entirely another can of worms.

The Garmin 496 display for example that some vendors connect to just
use the legacy input defined for TIS-A on those devices. Most of that
TIS data should be easy to decode to display on PDA devices etc. We
will need soaring software vendors to support this. Since we don't
really want to be looking at the display we will also need those
vendors to impliment audible traffic alerts. That is not something
that a TIS-B receiver will normally do for you. Which is why I am
curious if somebody has got a Becker Mode-S hooked up in a glider to
do this.

BTW even ADS-B in only TIS-B receivers can have a GPS since they use
that to know where they are to output display data. Somewhere in the
reciever-display chain a GPS is needed.

Darryl

Darryl

The TT21 has only just received its European approval, so there is very
little experience yet.

Playing with one on the bench, and making up a cable harness for an
installation, it looks good both for the installation and ease of use.
The documentation is clear, concise and comprehensive - a highly unusual
combination.

The two box solution means that the panel fit is easy, and the box that
does the real work can be positioned for a short co-ax run to the antenna
for minimum RF loss.

From my dealings with the company, I am impressed so far.

Peter

At 21:12 21 June 2009, jcarlyle wrote:
Thanks, Darryl - I'm much more educated now on ADS-B, TCAS, TIS-B and
FIS-B than I was this morning!

All I need now is input from anyone who has a Trig TT21, especially
with regard to ease of use and reliability.

-John

The Zaon PCAS unit which is the size of a cigarette pack contains an
accurate pressure encoder plus almost all the electronics needed for a
transponder at a street price less than $500. What it does not have is
the high power transmitter. So I called the Zaon technical people and
suggested had they ever considered making an inexpensive, low power,
single unit tiny in size transponder. Their response was not seriously
because of the certification process but they would consider what I
suggested.
The bottom line to this is that the technology is available to make
a tiny inexpensive fully featured transponder and sell it for less
than a $1,000. Will it happen? Probably not. A couple more people from
the glider community talking to Zaon might be useful.
Zaon has almost the total market for PCAS deservedly because of
their 2 excellent products. They must be thinking of an encore.
How about a transponder?
Dave

PS There is not technical reason for a 2 piece transponder and the new
one discussed in this thread, in my opinion, still has not got it
right.

On Jun 22, 7:32*am, kd6veb wrote:
* The Zaon PCAS unit which is the size of a cigarette pack contains an
accurate pressure encoder plus almost all the electronics needed for a
transponder at a street price less than $500. What it does not have is
the high power transmitter. So I called the Zaon technical people and
suggested had they ever considered making an inexpensive, low power,
single unit tiny in size transponder. Their response was not seriously
because of the certification process but they would consider what I
suggested.
* The bottom line to this is that the technology is available to make
a tiny inexpensive fully featured transponder and sell it for less
than a $1,000. Will it happen? Probably not. A couple more people from
the glider community talking to Zaon might be useful.
* Zaon has almost the total market for PCAS deservedly because of
their 2 excellent products. They must be thinking of an encore.
How about a transponder?
Dave

PS There is not technical reason for a 2 piece transponder and the new
one discussed in this thread, in my opinion, still has not got it
right.

I'll bite.

There are RF engineering reasons why it will be harder to put a PCAS
and Transponder in the same box. Zaon would an uphill battle already
enterign the transponder market for light aircraft with Becker and
others and now Trig with some pretty nice transponders. Zaon does low-
end traffic avoidance, they need to be focused on keeping there
leadership there. with ADS-B (Both UAT and 1090ES) is the future of
traffic avoidance in the GA fleet and that is where Zaon should be
spending there time. I'd hope they are working on a combined PCAS+UAT
(data in only) device. Otherwise devices like the NavWorx PADS600 will
take that market away from Zaon as ADS-B starts being adopted.

There are often great reasons for a two box transponder. Including
being able to mount the RF box nearer the antenna and simplify cabling
and save RF power loss as the previous owner mentioned. However with
the need to plumb the transponder to a static line there may be
tradeoffs between static line and coaxial cable routing. You also get
to avoid RF coax cable flex and damage with gliders with front hinged
panels. The compact control head allows mounting in shallow panels,
takes weight off the panel mount screws etc.

The Trig TT21 RF box is also significantly smaller than other two box
or single box transponders. e.g. the TT21 RF box is 5.6" x 2.4" x
1.8". A normal Becker Mode-S panel mount is 8.0" x 2.4" x 2.4" and a
remote mount box is 8.5" x 2.4" x 2.4". That makes it easier to mount
in many remote locations.

The only nits I have to pick withe TT21 is it does not appear to allow
tandem installation (dual control heads), and as mentioned easier it
supports ADS-B 1090ES out but not in. But (I forgot to mention this
earlier) there is a tantalizing RS-232 port for "future upgrades". Mmm
I wonder if that could be for ADS-B TIS-B out. Either way, given its
price and size and other things if it works as claimed and is reliable
it looks to me like a winner.

Darryl