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AOPA Pilot Magazine

ADS-B: The Future Is Now

ADS-B provides timely on-board weather and traffic information

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 certain range.

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 faster.

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 maps.

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 American Navion.

Links to additional information about ADS-B may be found on AOPA Online (

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 the same hardware in both aircraft flown by AOPA staff, a Piper Archer and a Beechcraft A36 Bonanza. Randy Kenagy, AOPA's senior director of advanced technology, 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 datalink uses 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 competition emerges."

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

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