On 12/9/2010 6:16 PM, Darryl Ramm wrote:
On Dec 9, 2:10 pm, "Tim wrote:
Actually the data on their brochure is actually pessimistic. In speaking
with the company directly this is all based on test data and in worst case
scenarios during warm up, transmitting on the 7777 frequency and at full
power...what they confirm as an estimate of current consumption at 12 VDC is
likely much closer to500 mA .very doable in almost any glider application
and will operate down to11 Volts.
There are several relevant arguments for both Mode C and also for UAT
including lower power requirements than Mode S (at similar power output) and
the possibility of simple and lower cost displays for all traffic, not
simply aircraft equipped with FLARM in that UAT will show all transponder
equipped aircraft. The cost appears higher but at an estimated price
possibility of about $3500 +/- that would not only include the UTA but the
transponder as well..We easily see prices in the same range for transponder
and FLARM / PowerFLARM equipment and the UAT can also provide a TCAS type
warning and display in a glider size package.
tim

As has been covered in this thread. Yes a Mode S individual
interrogation rely may use more power than a Mode C reply (one that is
mostly no/null pulses) but a mode S transponder may well use less
power in practical situations that a Mode C due to the reduced number
of interrogations that the Mode S transponder will reply to. We see
that in practice, the Trig TT21 is flying in gliders with power
consumption 300mA including encoder. Spectaculary low power
consumption - proving you can do this with a Mode S transponder.

A UAT based traffic system can provide a TCAS I like warning - every
traffic systems with direction information can provide a TCAS I like
traffic alert (TA). None, including Flarm or anything Sandia develop
based on a UAT can provide a TCAS II like RA. There is nothing unique
in that claim.

The "see all transponders" you mention is TIS-B. PowerFLARM does that
just just as well (and as bad) as a UAT receiver will well when the
PowewrFLARM equipped aircraft with 1090ES data-out. It has nothing to
do with using Mode C per-se.

To see that you need ADS-B data out either UAT or 1090ES and a
receiver (on the same link layer is preferred).

And you need to be within coverage of a GBT and the TIS-B service
needs to be deployed where you are flying (and the deployments differ
for en-route or terminal volumes). And even then the resolution of TIS-
B won't allow things like close flying of gliders etc.

The practical danger is that in many situations a PowerFLARM equipped
glider would see a glider equipped with Mode C becuase of the PCAS in
the PowerFLARM but this Sandia Mode C + UAT won't see a PowerFLARM
equipped glider at all because it won't be within GBT coverage, even
if the glider is transponder equipped.

So you really want to push Mode C + UAT as an alternative to
PowerFLARM? I hope people really get that the several hundred and
growing early orders for PowerFLARM in the USA means that thinking
about UAT technology and gliders in the USA is not a good idea. That
was last decade's dream that did not happen. It is a real concern that
we have critical traffic areas (like the white mountains and ridges
back east) where we need to think about technology to help avoid
glider on glider collisions and where mixed PowerFLARM and UAT
technology should not be expected to work. I hope potential purchasers
and dealers really understand the issues here. And where the primary
concern is glider on glider traffic all owners need to purchase is a
PowerFLARM (and they'll still get PCAS alerts for GA traffic as long
as that transponder equipped traffic is being interrogated).

Any though process for doing ADS-B via Mode C plus UAT ought to have
some *huge* benefit vs. PowerFLARM + 1090ES data-out. About the same
price and about the same power consumption (or more) but having
serious compatibility issues with a large number of PowerFLARM
equipped gliders seems a pretty dangerous direction to advocate.

Darryl

I can't let this post go unanswered. Saying that PowerFlarm is the
answer for the glider community and UAT was last decade's dream is
pushing the limits. PowerFlarm doesn't even exist yet. UAT is the
FAA's recommended solution for GA, so I wouldn't be writing that off so
easily.

I'm not going to predict how this all falls out. There will undoubtedly
be lots of ADS-B solutions coming out in the next few years, both 1090ES
and UAT based. I'm not going to predict which way the market is going
to go, which will likely be heavily influenced by pricing.

If GARMIN decides to make a major push in this space for the single
engine VFR GA market, things could change in a very big way. Given the
size of this market, it's hard to imagine that GARMIN isn't going to
pursue this aggressively. If their mass market product is UAT based,
and you have 50-80% of the GA market equip, having gliders standardizing
on 1090ES is going to be a pretty bad move if you are flying low or in
remote areas, where you don't have ground station coverage to translate
between systems.

If you have the money and want to buy something right now, a 1090ES
capable Mode S transponder sounds like a reasonable investment.
PowerFlarm might also fall into that category IF you are an active
contest pilot, or are flying in an area where there are a critical mass
of glider pilots making the same investment in the near term.
Otherwise, at this point anything else is betting on untested marketing
spec sheets and speculating on a somewhat unpredictable market.

--
Mike Schumann