On Aug 15, 1:16 pm, Mark Berger wrote:
sisu1a wrote:
When people in the FAA, AOPA, etc... read these kind of comments, what
do you think happens to our sport's credibility?

Running the risk of being accused of having a sense of humor *can* be
pretty damaging, please censor yourself accordingly.

Kinda reminds me of a story I heard a few years back (forgot by who,
but it was out east...). A few syndicate owners of a glider found
themselves with an empty hole in the panel to fill so for kicks, one
of them took an instrument carcass and made a new Fun-meter
(Funometer?), with a nicely made scale and pointer to measure how much
fun was being had at any given moment, with "Fun" written on the scale
to indicate such. After rigging the ship one day, another club member
came up and was quietly studying the panel in the ship for a awhile,
puzzling over this new gadget. Eventually he pipes up and asks one of
the guys: "What does F.U.N.stand for"?

-Paul

What does UAT stand for?

Mark

Short answer...UAT stands for Universal Access Transceiver.

Long answer...

UAT is one of the two physical link layers used for ADS-B in the USA.
The other is 1090ES.

UAT stands for Universal Access Transceiver. Even though "transceiver"
is part of the name not all "UAT" boxes are transceivers, some are
receivers only and some might be transmitters (but by the time a
manufacturer goes to all the effort of building and certifying a
transmitter I expect them to include a receiver).

Ultimately UAT is specified by RTCA standard DO282B and 1090ES is
specified by RTCA standard DO260B and these specs are what roll up
into the FAA 2020 carriage mandates (for powered aircraft not gliders)
and TSO approval specs for the devices.

For powered aircraft 1090ES is required in the 2020 mandate for flight
above FL180.

1090ES layers on top of the data transmission and reception capability
in Mode S transponders. 1090ES operate on 1090MHz, the current
transponder reply frequency, hence their name. The "ES" part is for
"extended squitter", "extended" = larger data packet, squitter =
automatic broadcast without begin interrogated.

UATs operate on 978 MHz.

UAT are mostly a USA thing, Europe in particular has standardized on
Mode S transponders as a step towards 1090ES based ADS-B. That has
some implications on the glider community for products coming from of
Europe. Specifically this likely the reason the PowerFLARM contains a
1090ES receiver and not a UAT receiver. It is also the reason we have
interesting Mode S/1090ES capable products usable in gliders like the
Trig TT21.

Part of the original desire for UAT in the USA was to avoid congestion
on 1090MHz but I am far from convinced on that. The Europeans don't
necessarily agree with the USA analysis. TCAS, TCAD etc. hammering on
Mode C transponders especially consumes a lot of bandwidth. And one of
the ways to free up a lot of that bandwidth is to require Mode C
transponders to be replaced with Mode S. Sounds scary but much less if
we had started early to allow this to be done over 5-10 years. Now
ironically it looks at least to me that many GA aircraft are going to
equip with 1090ES data out it does not matter since they will be
transmitting on 1090MHz only - but at least that upgrade gets rid of
that aircraft's bandwidth wasteful Mode C transponder.

And Raytheon actually bid on the FAA ADS-B deployment contract as
1090ES only - kind of calling bull**** on many dual-link assumptions.
Ironically had their bid been accepted we might actually ended up with
a more usable ADS-B system.

A benefit of UATs over 1090ES is they will receive FIS-B data (e.g.
weather, TFR, NOTAM etc.) once the USA ADS-B ground infrastructure is
in place. This requires you have a display able to display the data
and line of sight to a GBT ground station (ie. you may not be able
receive on the ground at some locations, e.g. before flight).

The main benefit of 1090ES is it is layered on top of Mode S and that
capability is already in or can be added to current Mode S
transponders. Since carriage mandates in the USA for power aircraft
for transponders and ADS-B data-out equipment overlap I expect many GA
aircraft to equip with Mode S/1090ES data-out. UATs that meet the
carriage requirements once avaible at low cost might be compelling for
many lower end GA and sports airceaft with Mode C transpodners who do
not want to upgrade to a Mode S 1090ES capable transponder. For
gliders the interest there is a single box like a Trig TT21 can
provide transponder capability with airline and fast-jet TCAS *and*
provide ADS-B data out via 1090ES.

One of the desires of UAT is that maybe lower cost devices that
transponders could be produced. I am somewhat pessimistic of that
happening, especially not down to the sub $1,000 price point for a
transceiver which I suspect is completely unrealistic. Even if current
UAT specs are simplified the relatively small USA market for UAT
devices (large parts of the GA market I expect to go 1090ES anyhow)
will keep UAT pricing high.

UAT receivers may also be popular with all GA aircraft (and gliders?)
for receiving FIS-B (unlike with traffic you do not need any ASD-B
transmitter capability for FIS-B to work). The competition there is
for-fee XM Weather which may already has significant penetration
amongst people who want in-flight weather services. We'll have to see
how all this shakes out, including if widespread reception on the
ground is an issue, a free products vs. XM weather, etc. UAT FIS-B is
also expected to add commercial charge-for service data products in
future - I expect that to be hard to pull off against XM Weather.

The dual-link ADS-B scheme in the USA has some pretty unfortuante
implications on use of ADS-B in gliders, including like not being
usable with mixed UAT and 1090ES equipment when running ridges etc.
outside of GBT (ground station) coverage. I see no way around that at
the ADS-B level except the availability of dual-link receivers that
receive on both 1090ES and UAT links.

Traffic display and warning requirements, Flarm with ADS-B and Flarm
vs. ADS-B technologies has been talked about in other threads
recently.

Hope that helps. :-)

Darryl