ADS-B: The Future Is Now
ADS-B provides timely on-board weather and traffic
BY CHARLES H. STITES (From AOPA Pilot, November 2005.)
Almost every airplane owner has his Holy Grail, that one
piece of equipment he would install, then proclaim his flying world to be
complete. My Holy Grail is to have "real time" datalink weather on the Garmin
AT MX20 multifunction display (MFD) in my North American Navion.
To me, the MX20 is a wonder box, capable of a variety of
well-presented moving-map and terrain displays. But, even with those pixels
accurately mimicking the Earth passing below, when comparing that view to the
real world outside, I realize that I am getting only half the picture.
Something important is missing. The sky.
To see the sky in depth, beyond the next few miles, and to
confidently make a judgment call about weather or traffic that may lie in wait,
well, there's the rub. A rub that can only be satisfied with a substantial
investment. But recently, fortune smiled upon me, and I was asked if I wished
to participate in an ADS-B demonstration project.
ADS-B stands for automatic dependent surveillance-broadcast.
It is "automatic," in that it requires nothing of the pilot, and "dependent,"
in that it depends on a WAAS-capable GPS signal to precisely show where the
airplane is and provide it with only the information it needs for that area.
"Surveillance" means that air traffic control (ATC) can see ADS-B targets, even
when they are operating in areas without radar coverage. And the airplane is
not just receiving information, but also it is "broadcasting" it to other
ADS-B-equipped aircraft in the vicinity and ATC.
The other abbreviations of importance have to do with
traffic information service (TIS-B) and flight information service (FIS-B).
TIS-B deals with the display of traffic targets whether they are simply
squawking a conventional transponder code or broadcasting an ADS-B signal.
FIS-B is the weather information component, with displays of Nexrad graphics
and METAR and TAF text products. Traffic and weather information is uplinked to
ADS-B-equipped aircraft from ground base transmitters (GBTs).
My participation in the project began with a phone call from
Steve Merritt of the North Carolina Division of Aviation. North Carolina had
partnered with the FAA to install transmitters providing coverage for the
entire state, and Merritt was now on the hunt for 10 owners of MX20-equipped
aircraft who would agree to have a Garmin GDL 90 universal access transceiver
(UAT) installed. Under a grant, the state would pay for the units and their
installation. In exchange, for the period of the project, the owners would be
responsible for in-flight demonstrations to potential users, and for providing
monthly reports on the effectiveness of the services. The first of the North
Carolina demos began in June 2005.
"We think the project is a terrific way of showing the
flying public what the cockpit of the future looks like. We want people to
learn how it works, and encourage them to equip their own airplanes. We also
want to 'debug' the system, and we've already had some display issues on the
MX20 that were corrected as a result of us operating the system," Merritt says.
After signing on to the project, it wasn't long before my
Navion was at Sparkchasers Aircraft Services, an avionics facility in
Smithfield, North Carolina. According to Sparkchasers' co-owner Bill Betts, the
installation was very straightforward, and included mounting the transceiver in
the fuselage just aft of the baggage area, installing two very small blade-type
UHF antennas and a WAAS GPS antenna, and making connections with the MX20,
altitude encoder, and power supply. It's important to note that with an MX20
already in place, no changes were made to the panel.
With ADS-B, datalink weather is shown on a dedicated "page"
with familiar Nexrad graphics. In addition to the graphical display, a list of
available METARs and TAFs can be called up on a secondary text-only page, then
highlighted to display the full report. All of this is available to pilots for
free, with no monthly or annual subscription costs. Traffic can be displayed on
several of the moving-map screens on the MX20, but there's also a dedicated
traffic display, plus a traffic text page that lists all targets within a
Flying the system
A recent cross-country flight provided a good example of the
value of ADS-B services. On climbout from my home field, it was less than a
minute before I was within line of sight of two of North Carolina's eight
ground transmitters and began receiving both traffic and weather information.
En route, traffic was light, but once approaching the busy
Charlotte Class B airspace, and with a high volume of traffic inbound for a
Nascar race at nearby Concord, North Carolina,
Charlotte looked like it had been invaded by an organized swarm of
light-blue bees (light blue being the target display color).
ATC started calling a steady stream of traffic for me, all
of which my wife and I had already located both on the MX20 and then outside.
With each traffic call, I was able to immediately respond that I had the
traffic. I have little doubt that had I not been able to visually identify the
traffic so quickly, one of us would have received vectors for avoidance. In
that congested airspace, even with only one ADS-B-equipped airplane, the case
can be made that ADS-B increased efficiency for a number of aircraft, and
lightened the controller's workload.
This is a good time to address one concern I've heard from
those who have yet to fly with ADS-B, and that's the potential for pilots to
keep their heads in the cockpit looking at the display instead of looking
outside for other aircraft. I can now echo what I've heard other ADS-B users
say: With the accuracy of the traffic displays, my time looking outside is now better
spent because I know much more precisely where to look and can locate traffic
The outbound portion of the trip was made under severe clear
conditions, a forecast that was supposed to hold throughout our late-afternoon
return flight. But just prior to our departure, the FBO's computer showed that
weather to the southwest had moved in much faster than forecast.
Though we flew for almost an hour through an area displayed
as light green on the ADS-B weather display, I was easily able to stay well
away from the dark-green, yellow, and red precipitation returns appearing on
the MX20. During the flight we never saw a drop of rain on the airplane. In the
past, faced with the pessimistic display on the FBO computer, I would have
likely delayed the flight. But this time I was confident that I could use the
timely on-board information to provide a safe, wide berth around the weather,
and that confidence was rewarded with a smooth and uneventful flight home.
Several weeks later, for our long cross-country to EAA
AirVenture in Oshkosh, I was aware that we would only have weather information
for a portion of the trip over the Appalachian Mountains. With a broad and deep
line of thunderstorms along the ridges on the morning of our departure, and
knowing that because the network of ground transmitters is not nearly complete
we would run out of ADS-B weather information before we ran out of weather, we
elected to lengthen our trip and skirt the storms by heading to the southwest
for an overnight visit with friends.
The next morning we departed for Wisconsin, but soon faced
another powerful and very fast-moving line of storms in western Tennessee. With
no ADS-B services yet available in that area, once again we were forced to land
and wait out the squall line before turning north to complete the trip.
The return flight home dramatically proved the value of
ADS-B weather information both in terms of safety and economics. Departing the
Lexington, Kentucky, area for the last leg, I correctly anticipated the usual
"heat of the day" convective activity over the mountains, and just as we were
beginning to face an area of quickly building cells, we picked up the East
Coast-area ADS-B service. Using Nexrad images to safely pick our way around the
cells, we had a smooth ride all the way. In the past, without timely on-board
weather information, we would not have attempted the flight and would have
rented a room and spent the night. Instead, well before dark, the airplane was
in the hangar, and we were soon relaxing at home.
I do have a wish list for future enhancements such as the
real-time display of temporary flight restrictions, and from what I hear, that
capability is on the way later this year. Next on my list is a tweaking of the
display possibilities on the MX20. At present, the weather information is
displayed only on its dedicated page, instead of being overlaid on the regular
moving maps of the MX20. According to Garmin, that's a result of color
conflicts with the Nexrad weather depiction.
Garmin has addressed this with a split-screen function that
divides the display in half, with the moving map on one side and the weather
display on the other. It works pretty well, but since it takes some of the
functionality out of the MFD, it's what I would call the "kissing your sister"
approach. Based on feedback from the demo-project pilots, Garmin will consider
a software change to modify the "weather" display so that it can also show
critical airspace and navigation information typical of that on the moving
Although my original wish was only for weather information,
I am surprised at how often I use and benefit from the traffic display. There
are a number of offerings available from private companies that provide either
traffic or in-flight weather information, but ADS-B does both with only one
installation, and does so without a subscription fee. Now, after a few months
of flying with datalink weather and traffic services, my only real complaint is
that I can't wait for more ground stations to be installed and come online.
Charles H. Stites is an aviation photographer and writer,
and an instrument-rated private pilot who flies his restored 1949 North
Links to additional information about ADS-B may be found on
AOPA Online (www.aopa.org/pilot/links.shtml).
If We Build It, They Will Come
Although ADS-B is not yet widely known in the aviation
community, the technology actually has been in use for some time, especially in
Alaska, where there are more than 300 aircraft equipped with the ADS-B
datalink, a multifunction display, and an IFR GPS (see "Datalink Roundup:
Weather to Go," March 2004 Pilot).
At the same time that aircraft in Alaska
received their equipment, AOPA signed on to the concept by installing
hardware in both aircraft flown by AOPA staff, a Piper Archer and a
A36 Bonanza. Randy Kenagy, AOPA's senior director of advanced
says, "AOPA has long been concerned that the FAA will implement
new technologies that do not benefit general aviation. We wanted to see
for ourselves just how good or bad this system would
be for the typical AOPA member, and we were evaluating the very
that the members told us they wanted, traffic and free graphic weather."
AOPA's review generated positive feedback from staff, noting
that once the pilot was accustomed to proper use of the on-board display, the
benefits were tremendous. But when decision time came, the FAA faced the usual
dilemma. How could it commit to spending scarce resources on a new technology when
there was no one out there equipped to use it? What emerged was a remarkable
development. Following a live demonstration flight by AOPA President Phil
Boyer, Embry-Riddle Aeronautical University volunteered to install ADS-B in its
fleet of more than 100 aircraft if the FAA provided the ground stations and
up-linked the weather and traffic. Within a year, the equipment was installed
in aircraft, and on the ground.
Then individual states sought out demonstration flights too,
exploring the possibility of ADS-B ground stations. AOPA demonstrated ADS-B to
the state of North Carolina, which was successfully partnering with NASA on
various projects like the Small Aircraft Transportation System (SATS).
Officials from North Carolina approached the FAA about a similar partnership.
Paul Fontaine, the manager of the FAA's Safe Flight 21 office, coordinated an
FAA go-ahead, and put the hardware and software into place, a process now
realized with a fully functioning ADS-B coverage area along much of the heavily
traveled East Coast.
Jim McDaniel, the FAA manager responsible to execute
Fontaine's strategy, says, "We put in the first pocket along the East Coast
from New Jersey down to Florida, when really there were no airplanes equipped.
We've got transmitters out there broadcasting the information, with very few
pilots able to take advantage of that right now. We recognized that, and we did
it on purpose. It's almost an 'if you build it, they will come' idea. If there
is no traffic and weather uplink to the aircraft, why would you want to be the
first person to have ADS-B? The FAA broke that stalemate by putting in the East
Coast ground stations."
Bill Williams, the director of aviation for North Carolina,
says he immediately saw the advantages of an early commitment to ADS-B. "We
wanted to provide as much of a safety net as possible for all the folks who use
our airspace, and since this is cutting-edge technology, and relatively
inexpensive, it will provide those benefits well into the future," he says.
With the success of the North Carolina project, the FAA is
now looking to partner with other states, especially in the Midwest, to build
the system out from the East Coast. Ground stations are already installed in
selected locations in Ohio, North Dakota, and Arizona, and there's now one in
Oshkosh. In fact, AOPA staff pilots used the ADS-B ground stations to check
weather and traffic as they flew through Ohio, and landed in Wisconsin for the
2005 EAA AirVenture.
Currently, the only manufacturer of a certified transceiver
is Garmin AT, so it's no coincidence that as of summer 2005, the output of that
box can only be displayed on Garmin's MX20 multifunction display. Sam Seery,
marketing manager for Garmin AT, says that's soon to change. "We're looking at
making the GDL 90 transceiver compatible with all of the Garmin display
products. We're pretty far down the trail in terms of development and
integration." When Garmin completes the updates, in addition to being available
on the MX20, ADS-B information will then be available on the Garmin 530, 430,
and the G1000. And AOPA is tracking these developments closely. Without
affordable avionics, the ADS-B system is likely to be met with resistance by
AOPA members. AOPA's Kenagy says that he reminds the FAA and manufacturers of
this important fact frequently: "The benefits are there, but the price is not.
We expect that to change if the FAA commits to nationwide deployment, and other
But now that the system is operating and growing, other
manufacturers are beginning to show serious interest, with several confident
that they can soon display ADS-B traffic and weather information on a variety
of handheld devices. Using the output of the Garmin transceiver (or those
manufactured by other companies in the future), they are investigating offering
ADS-B traffic and weather displays on portable GPS units and personal digital
assistants, a lower-cost alternative that should fuel increased interest in a
once-dreamed-of technology that's now in service. — CHS