"Scott Moore" wrote in message
news:yjstc.9901$Ly.7087@attbi_s01...

I cleaned up my language a bit, then sent my tirade off to Phil Boyer :-)

He gave me a short note, then promised me an "in depth" note from their
staff expert on the subject. I believe the gist of it is that the AOPA
has fought tooth and nail to keep the mode-s requirement out of light
airplanes due to individual airplane ids and their potential for for
fees and misuse (imagine the "stop the noise" zelots having the ability
to get an N number automatically).

True. Cost is also an issue.

I don't mind adding a UAT, if that is what it takes. I mind the apparent,
from reading the FAA material, dogma that light airplanes shall have
UAT and big airplanes shall have mode-s, and the FAA shall act as the
bridge between the two (ha !).

It's not FAA dogma. It's a reasonable compromise to gain concensus from two
diverse groups, each of which has its own needs within the airspace. The
FAA actually hasn't mandated either one for any specific group. The
statement that GA will have UAT and airliners have 1090ES, is merely a
generalization of expected market response. There is nothing that requires
anyone to select one over the other. Nor is there anything that prevents
you from equipping with both.

All kinds of "what to do" things occur to me, but each seems to be
centered around a group with an interest who does not want to move.

o Allow "anonymous mode-s", and so remove the light pilot/AOPA objection
to mode-s ? This has been proposed many times in many places. Apparently
the FAA would rather die than this, but why are they (apparently) going
to allow UAT to so do, but not mode-s ?

Mode-Select (Mode-S) was designed twenty years ago for a very specific set
of needs. It does that very well. It is an addressed communication system.
Trying to make it do something for which it wasn't designed could compromise
the system or at best add a lot of expense and complexity.

UAT was created about 8 years ago specifically to support ADS-B, TIS-B, and
FIS-B. Note the "-B" in all the systems -- that stands for broadcast. UAT
is a non-addressed broadcast system. Basically it's a half-duplex radio
modem. When you transmit, you have no ability to determine who is
receiving. Likewise, in receive, you'll receive anybody within range.

o Require UAT on airlines, so that everyone speaks the same language, and
UAT eventually replaces mode-s as a more advanced method ? I could hardly
blame the airlines for fighting that one. The FAA just got through
requiring
them to buy into mode-s. It would put the airlines into the position
of buying the "black box of the month" as the FAA changes with the wind.

Airlines have Mode-S because it's a required part of a TCAS system, which is
mandated. TCAS will not be going away. ADS-B may augment TCAS, but it
won't replace it. Adding ADS-B to the Mode-S system is the most
cost-efficient route if you already have the Mode-S/TCAS equipment.

o Require light airplanes to have both ? Time for us to scream, I guess,
but
that is where I am headed anyways, since I was stupid enough to buy mode-s
(for TIS).

As I said before, you're not required to have either one. And I wouldn't
say you are stupid for buying into Mode-S for TIS. TIS is a very good
service. While it is limited to areas of Mode-S radar coverage, it allows
you to see any aircraft the radar is capable of tracking. While ADS-B
doesn't need radar, if the other guy isn't equipped, he's invisible.

In any case, it appears that the FAA, the AOPA and the airlines have all
already come to the solution:

o Airlines have mode-s, we have UAT, and the friendly FAA will translate
between the two, but only under radar control (neatly severing the
non-radar
reliant feature off ADS-B). The theory is, I guess, that airlines allways
travel under radar so it won't matter in any cass.

Major point here. The ADS-B repeater/translator is NOT radar based. It is
a 1090MHz receiver and a UAT receiver to "collect" ADS-B broadcsts from
aircraft in the vicinity. The data is then broadcast out on both 1090 MHz
and UAT (this broadcast is called TIS-B -- this is not the TIS you currently
have.) These are relatively cheap (a couple orders of magnitude cheaper
than a radar) autonomous ground stations that can be stuck pretty much
anywhere, including places where there is no radar coverage. This is
exactly what they did in Alaska for Capstone.

o Light airplanes unlucky enough to have high altitude capability would
need both mode-s and UAT. This would also apply to a huge number of
jets and even heavy aircraft, since there are a lot of light jets and
passenger aircraft servicing smaller, non-radar fields.

No. You can pick one, or neither, or both. While you may need a basic
Mode-S transponder for some high altitude airspace (RVSM), that does not
mean you have to have a 1090ES ADS-B system.

A fine point here. Your GTX330 is a long way from a 1090ES ADS-B system.
It currently provides only elementary surveillance support. It would
require an upgrade to support full ADS-B broadcast. Once you did that, you
could provide ADS-B broadcasts, but you'd still have to get a 1090 MHz
receiver to be able to receive ADS-B or TIB-B over 1090. (Your TIS data
comes up from the ground radar on 1030 MHz using the Mode-S comm-b
protocol.) Adding that receiver will not be cheap. The receiver and
transponder upgrade will likely cost as much or more than a UAT.

Gerry