Mike Schumann wrote:
On Tuesday, April 7, 2015 at 11:00:15 PM UTC-4, Darryl Ramm wrote:
On Tuesday, April 7, 2015 at 3:37:23 PM UTC-4, Darryl Ramm wrote:
On Tuesday, April 7, 2015 at 10:00:36 AM UTC-7, Andy Blackburn wrote:
On Tuesday, April 7, 2015 at 9:43:26 AM UTC-7, wrote:

Problem: The rest of the world isn't concerned about frequency
congestion and airlines are less than enthusiastic about having to
have both mod existing 1090 transponders and ALSO install a UAT ADS-B
box onboard. Solution: Keep 1090 for aircraft that fly above 18,000
since they are the ones that will encounter the overseas environment.

Isn't it true that most of the RF congestion comes from the
bandwidth-intensive interaction of TCAS with Mode C (and earlier)
transponders? I've been told that the reason Europe didn't have to go
down the UAT (or equivalent) path was because they mandated Mode S.
It's possible the US could have done the same, but apparently the FAA
didn't want to force a transponder upgrade (which seems silly given all
the other mandated equipment and duplicate antennae). And so we get the
mess we have that, as you pointed out, the FAA isn't so concerned about
because our concerns have little to do with the problems they were solving for.

I remain somewhat skeptical that GA will go en masse to UAT. If Trig
comes out with a Mode S/1090ES Out single box that hooks up to an
existing Mode C antenna I think it could be quite popular.

Andy

That would be my summary of much of this (and BTW TCAS only interrogates
Mode C or S, it won't ever interrogate Mode A and just won't see a Mode
A transponder at all). I think a significant part of the issue was the
FAA was under pressure from lobbyists like AOPA who wanted to keep Mode
C transponders in use. Doing that can cause significant radio frequency
congestion issues because of TCAS interrogation of those Mode C
transponders, and also makes SSR a little less wonderful than it could
be in a pure Mode-S environment. I was never impressed by the technical
depth of the arguments used that dual-link was required because of
1090MHz/1030MHz congestion. This at least in part relied on some
Monte-Carlo simulation of RF congestion in the LA Basin, but there just
never really seemed to be as much academic research and debate as I
would have hoped with this. I would have preferred to see wider
research, with more broad assumptions/scenarios allowed, all the other
mitigation options really well explored, and more academically
peer-reviewed studies made before all the cost of a complex dual-link
ADS-B system was inflicted on owner/pilots and the US taxpayer.

But anyhow layering complexity on complexity the FAA went dual-link over
109ES and UAT. Then you fold in other agendas like trying to sell UAT
to GA aircraft by providing FIS-B data over UAT. Although you only need
a cheap UAT-receiver to use FIS-B so it does not really encourage
adoption of ADS-Out on either UAT or 1090ES link-layer. And a cynical
view was some folks in the FAA just wanted to resurrect the failed FAA
FIS (airborne VHF weather data) service. Did we get dual-link becasue of
FIS-B or did we get FIS-B because of dual-link? The reality is maybe
parts of both. And WX Satellite weather is a better product with better
features and wider coverage, especially on the ground pre-flight). But
WX Weather requires a paid subscription unlike FIS-B (although you may
see paid parts of FIS-B in future from ITT/Excelis). Possible revenue
from commercial use of FIS-B is maybe another decision factor in the
whole dual-link mess.

The FAA's reasoning about inducements and expectations around using UAT
for GA aircraft never made sense to me. Newer aircraft have Mode-S
transponders that can be upgraded to 1090ES Out, older aircraft with
transponders may be due a transponder upgrade anyhow. So maybe that
leaves some in the middle, but that just never seemed like a reason to
prioritize "we must keep Mode C" like AOPA pushed for. And the FAA tried
to make UAT more widely used by initially allowing use up to FL 240, but
that just seemed long-term crazy for things like direct link
compatibility with all the big guys flying around in Class A. Once it
was clear you were going to needed 1090ES in Class A airspace, then the
high-performance singles/light turboprops etc. were all going to go that
way, and those owners were more likely to be ADS-B early adopters in the
GA space. And once you have some of those folks with 1090ES Out, more of
the GA community will follow, both becasue they have GA oriented product
available and for direct compatibility with 1090ES Out used by those early adopters.

What the GA lobby should have been pushing for IMNSHO was a usable
1090ES-Only system that would support a usable GA-oriented traffic
awareness system. Or at a minimum some more extensive academic research
to validate the claims for need of a dual-link system. End-of-life of
Mode-C could have been done over a decade+ time frame. Relying on ground
infrastructure to provide ADS-R link-layer translation makes the current
ADS-B system a mess for GA traffic awareness. There are too many places
of interest to GA where there is not ADS-R coverage, including close to
many GA airports and gliderport traffic patterns. And the system is just
too complex, still many pilot's don't see to understand they need ADS-B
Out to receive ADS-R or TIS-B traffic service.

ADS-B is one of those things that is trying to serve many masters, and
as well described in the earlier post, it's really a aircraft
surveillance system for the FAA Nextgen project, everything else is
really a secondary add-on to try to make it more appealing to other
constituents. Hoping I expect from the FAA's view point that those other
constituents will then support the adoption of ADS-B, but the only real
significant reason the FAA want it is for NextGen surveillance. The poor
FAA is stretched thin between powerful constituents and masters, that is
largely the US Congress, Airlines, and the occasional whack of a stick
from the NTSB. GA gets a small mention every now and again, but the
lobbying from various owner/pilot organizations for things related to
ADS-B seems to have been pretty confused and/or ineffective. And some of
the folks lobbying for those organizations I've spoken to clearly did
not understand the technology at a useful level. And its arguable that
the FAA was in a tough situation, with NextGen very underfunded, but
either way, that is certainly what is really driving ADS-B.

Meanwhile Europe looked at the 1090MHz/1030MHz congestion issue, they
have airspace like over Paris where this was a concern (but yes still
less ongestion than some US locations). Europe went Mode-S only, which
largely solved the TCAS bandwidth problem as TCAS can do selective
interrogation of one transponder at a time. And TCAS-II can also save
bandwidth by reducing interrogation of a target aircraft if it can be
tracked via 1090ES.... but it still hammers away at it with transponder
interrogations if it thinks it is a real threat... (oh the irony that
that 1090/1030MHz bandwidth saving trick does not work against a target
with Mode C/UAT-Out). And their are other options for future like
tweaking TCAS power levels to trade off range/congestion. I certainly
don't think it is absolutely clear that the FAA *had* to go dual-link
with ADS-B becasue of bandwidth.

Heck, if lots of folks don't go Mode-S/1090ES out and stick instead with
Mode-C and TCAS use increases it might even be possible that at some
point in the future the FAA has to come back and end of life Mode C
anyhow. But maybe that possibility is so long off that natural aircraft
and Mode C transponder attrition/replacement will prevent that happening.

Head hurting yet? Go crack a beer and dream about your next glider flight....

A little bit of history is important to understand how we got into this
mess. ADS-B was originally developed by MITRE to improve situational
awareness for General Aviation and to provide an economical alternative
to traditional radar coverage in remote areas, like Alaska.

MITRE made the decision to start with a clean sheet design to address two
basic issues: 1. To come up with a low power low cost hardware
platform, and 2. To provide the bandwidth to support a wide variety of
services as the system evolved.

This resulted in the UAT design, which was extensively tested in Alaska
as part of the multi-year Capstone project. The FAA paid for equipping
about 100 aircraft with ADS-B IN and OUT hardware and moving map
displays. The initial product roll-out included Weather and TIS-B.
During the test period, there was a dramatic drop in the frequency of
fatal GA accidents in the test area, which got the attention of the FAA bureaucrats.

Instead of rolling out this low cost technology as a way to improve
situational awareness for the GA fleet, someone came up with the bright
idea that this would be a great way to provide high resolution position
reporting for IFR aircraft, which would permit the dismantling of a very
expensive conventional radar system, while simultaneously providing the
accuracy necessary to support simultaneous parallel approaches at major
airports in minimal visibility conditions.

That's when the whole program got perverted. The FAA insisted that all
ADS-B OUT systems need to have GPS position sources that were FAA
certified and provided integrity signals that are not part of any
commercial GPS chip sets. As a result, instead of having a $10 GPS
receiver, ADS-B OUT systems were required to incorporate $1,500
certified position sources.

The FAA's idiocy is clearly demonstrated by their unwillingness to relax
the specs for VFR aircraft who have no desire to enter Class B airspace.
The rules for gliders are even more bizarre. Under the rules, we don't
need anything to makes us visible (transponders or ADS-B OUT). However,
if we voluntarily equip with ADS-B we have to meet the gold plated IFR
specs. The bottom line, is that the FAA would rather have a glider
flying around invisible, than permit the installation of a low cost
non-certified piece of hardware that might not meet their big iron standards.

Mitre was involved with lots of ADS-B work but they did not "invent ADS-B".
Maybe you meant UAT. Which they did more drive. And ADS-B was not primarily
developed as a GA collision avoidance technology--maybe some engineers felt
it was but the FAA was paying for this development and back in the early
1990s they were clearly already pushing it primarily as a future
surveillance technology. And that is how the FAA sold it to Congress and it
got funded.

ADS-B is a broad industry wide technology development with by far the
largest interest in it being for ATC surveillance.

You and Bernald Smith seem to be the US Soaring sales reps for Mitre and
their UAT technology. All that has resulted from all the talk over many
years is... exactly nothing. Not one single useful thing. Except time
wasted, potential users confused and in some cases a decrease in safety as
some people put off adopting other technology.

The Capstone project heavily involved ATC ADS-B based surveillance in an
area that had no SSR coverage, it was funded and managed by the FAA as a
*surveillance project*. the FAA attributed the increase in safety due to
improved *surveillance* and used that to justify ADS-B and NextGen funding.
Good luck finding much mention of cockpit traffic systems buried well below
the FAAs focus on Capstone surveillance. e.g.
http://www.faa.gov/news/fact_sheets/....cfm?newsIdy57

UAT was a mistake that should have been shot through the head by the FAA.
And the glaring problems of lack of TCAS compatibility should have made it
a non-starter for any use in gliders. Instead the US Soaring community has
had years of folks hyping this crap, and making people think there is
likely to be some new UAT box around the corner. And in some locations that
may have had an impact on safety by discouraging glider owners to install
transponders. We had some pilots who put off installing transponders in the
Reno area thinking UAT technology was coming and would be very low-cost.
Now maybe they were never actually going to install anything and UAT
futureware was just a convenient excuse. Luckily many more pilots in that
area behaved more responsibly.

Your constant labeling of UAT as "crap" is pretty insulting to a lot of
very bright people in MITRE and to our fellow glider pilot Bernald Smith,
who had the vision to try to introduce a state of the art technology to
replace the antiquated World War II vintage architecture that provides
the basis for current Mode C and Mode S transponders.

It is unfortunate that these folks couldn't get the FAA to see the long
term advantages of this approach and provide a clear migration plan to
incorporate ADS-B into the TCAS architecture, so that conventional
transponders could eventually be retired. Because the FAA couldn't get
their act together on a long term migration plan, we are now stuck with
an overly complicated dual frequency system which will still require
aircraft to be transponder equipped into the indefinite future.

Your assertion that the development of UAT has resulted in "not one
single useful thing" is complete BS. There are thousands of pilots who
are currently buying low cost UAT based ADS-B receivers. While the
traffic data provided by these receivers is only useful if the A/C is
ADS-B OUT equipped, these units provide free weather and notam data. I
would be willing to wager that Sporty's has sold at least 10x as many
Stratus ADS-B receivers over the last couple of years than the number of
POWERFLARM systems sold in the US.

The frustrations that you espouse have their roots, not in misinformation
that I and others are providing to the pilot community, but rather the
result of people recognizing POWERFLARM's limitations on displaying
non-glider traffic. There are a lot of people who don't want to waste
their money on a product that has a half baked ADS-B IN implementation
that is not going to be able to identify ADS-B UAT equipped aircraft.

If the POWERFLARM folks want to stay in the game, they need to
incorporate a dual frequency ADS-B receiver and/or support TIS-B. If
that happens, people like me will shut up, and maybe even buy the product.

What I said was all the Mitre salesmanship and pro UAT-hype from folks like
Bernald and you have not resulted in anything at all of use/benefit to the
soaring community. Is that clear enough? And yes I know, the reasons why
that is will be entirely somebody else's fault...

And I am certainly not pushing FLARM, for the apparently serious glider-GA
traffic midair collision risks like you have described with the Minnesota
Soaring Club operating under a Mode C veil it might be that transponder
carriage would be more useful, maybe in collaboration with FAA ATC
procedures/awareness. Maybe PCAS and 1090 ES in in PowerFLARM would help. I
would hope that if safety issues there are as serious as you make out that
pragmatic people would have long since been looking at what is actually
usable/doable to minimize mid-air collision risks, wether that is
awareness, training, procedures, reaching out to the FAA or GA community,
use of practical technology etc. So what has the club done?

All I think we ever hear about is you raising concerns, over many years
about the mid-air collision risk there, and how there is apparently nothing
technically available that would be a practical help with these safety
concerns--although lots of other owners, clubs etc. seem to somehow find
that Zaon and other PCAS, PowerFLARM and/or transponders were very
effective practical aids for their environments. Hopefully the Minnesota
Soaring Club has not just spent years waiting and hoping for some mythical
low cost UAT based solution and/or used that as an excuse not to adopt
*any* technology to help with as you describe it a serious glider-GA
mid-air collision risk.