by Michael J. “Mick” Kaufman
It has been more than five years since we first started hearing about Automatic Dependent Surveillance – Broadcast (ADS–B) and I published my first article on the topic for Midwest Flyer Magazine. Since then I have had the opportunity to look at many of the new innovations and products that have entered the market and write numerous articles on the subject, and ADS-B remains a concern of aircraft owners expected to comply with FAA’s 2020 mandate.
As aircraft owners, we need to decide what the most cost-effective system is best for us, and while we hold out for a less expensive option than is presently available and approved by the FAA, the clock is ticking! A clock destined to become FAA’s greatest fiasco since the agency’s founding in 1958. Our hope is the FAA will consider some reasonable/less expensive means of compliance, which I will describe here.
At the Wisconsin Aviation Conference in La Crosse in May, FAA and state aeronautics officials addressed the ADS-B 2020 mandate, which is not going as well as the FAA had hoped. A recent FAA survey on ADS-B, conducted by Emery Riddle University, intended to sample our thoughts, revealed that if everyone who is not yet equipped decided to schedule an installation today, it would not be physically possible given the number of aircraft and the limited number of avionics facilities and technicians. (This brings up another topic: what is the FAA doing to attract talented people to our industry? Answer: Not much! Promoting the industry is no longer an FAA mandate, but implementing unrealistic policy is.)
So what is the FAA going to do to speed things up?
It is necessary for some history lessons to better understand how this whole program came into being, but first, a bit of information about myself for those who are new to my column.
I have been a bit of an electronics geek all of my life, owned and operated a public safety radio sales and repair service for a number of years, and I am an avid amateur radio operator, as well as an airline transport pilot, flight instructor, lecturer and author.
Shortly after the implementation of the GPS navigation system, an amateur radio operator (Bob Bruninga, WB4APR) conceived the concept of taking GPS coordinates received from satellites and retransmitting these position reports and supporting data on amateur radio frequencies. This marked the birth of the “Automatic Position Reporting System” (APRS) some 21 years ago. The APRS concept has been used in all of the tracking devices in use today and the forerunner of the CAPSTONE PROJECT ADS-B, ON-STAR and many others. So why has such a simple equipment costing $100.00 or less to purchase for cars, trucks, boats and portables, end up costing as much as $7,000.00 or more to implement in aviation? The only answer lies in the hands of the bureaucrats running the FAA – not the avionics shops or the equipment manufacturers.
For two decades, I have been using APRS in my truck, car, boat, airplane, and even in a bicycle handheld, as have many other pilots/amateur radio operators. I am currently using a handheld, self-contained APRS tracking device (FIG 1) in my airplane costing $100.00 on amateur radio frequencies and under amateur radio rules, as are many other pilots flying worldwide. This APRS movement has been going on in aircraft for two decades and seems to have started with a Van’s Aircraft homebuilt group. The Civil Air Patrol was also an early adapter of APRS in their search and rescue missions.
Today, aircraft APRS stations can be seen live on the web by searching http://www.mail2600.com/cgi-bin/everyone.cgi for aircraft only or http://aprs.fi/moving/ for ships, autos, trucks and other APRS stations. Using my tablet connected to my APRS tracker via Bluetooth, I can display all other APRS stations on a map or filter for any specific type of station I want to see. I can receive weather broadcasts from other amateur radio weather stations and bulletins from the National Weather Service. How about sending a short message (SMS) to another amateur radio operator on the ground or in his/her aircraft half way around the world by typing it on my tablet, and all for $100.00.
So why did the FAA want ADS-B and how did the CAPSTONE PROJECT come into existence?
The cost of implementing and maintaining radar sites for air traffic control is a number with so many zeros I could not even give a wild guess. ADS-B costs a fraction of what radar costs, but has far greater accuracy and future potential.
For example, ADS-B enables air traffic controllers to see aircraft taxiing on the ground during foggy conditions with an accuracy of 10 feet. Also with ADS-B, ATC will be able to send us our IFR clearance digitally, allowing us to transfer the clearance to our navigator with no errors, once we accept it.
The CAPSTONE PROJECT began in Alaska almost two decades ago trying to find a solution to cover this vast state with some sort of traffic and weather information. The project was deemed a success, and FAA’s promise to provide Alaska pilots equipment free of charge to use this system, never materialized.
The rest of the world, except the U.S., developed its own version of ADS-B based entirely on a system called 1090 Extended Squitter Technology (1090 ES).* The U.S. needed to be in sync with the rest of the world, so we decided to offer a two-frequency system, using the international format and a derivative of the CAPSTONE PROJECT called Universal Access Transceiver (UAT).
With the idea that the FAA wanted to get all U.S. pilots and aircraft owners on board with this new technology, the agency decided to offer free in-flight weather to those equipping their aircraft with ADS-B, and free traffic as well. When we hear the word “free” – especially from the government, we take note. This backfired as many pilots decided to purchase a Stratus WX receiver, receive the free weather, and go no farther. This receiver could be purchased at a reasonable price from Sporty’s Pilot Shop. The free weather, in my opinion, is lacking a lot compared with satellite XM, which has a pricey subscription cost, but worth it to pilots who fly in weather a lot. The other carrot the FAA offered was free traffic, but set up the system so that it is not available unless you have ADS-B out. When pilots had a chance to see how this all worked, most of them decided it was not worth an additional 7 AMUs (Aviation Monetary Units/ $7K) for traffic information. Remember, the only sure way of collision avoidance is to look outside the cockpit windows.
I would like to present some basic theory to help everyone understand the reasoning behind the two-frequency system and how all of this magic works.
Let us present an example using water and frequency to show this point. Let’s say you have a 100-gallon tank of water, and you want to empty it with gravity feed and you have a block of data, say 100K that needs to be moved. The bigger the hose, the less time it takes to move the water, and the larger the radio frequency allocation, the less time it takes to move the data. With all of the weather and traffic data that needed to be moved, the hose/frequency range was not big enough to move all of that data. If the available frequency allocation at 1090 Mhz had been available, this whole ADS-B situation would have been a lot simpler. The way the system is conceived to work at this time is to use the ADS-B ground station and collect traffic data from both frequencies, combine it, and resend it on both frequencies.
Let’s concentrate on traffic only and forget the weather to simplify our understanding.
When the FAA compliance plan told pilots that to be ADS-B “out” compliant, we had a choice of two options: 1) Update or replace our 1090 Mode C transponder to 1090ES (Extended Squitter) equipment (required if you fly above 18,000 feet MSL or internationally), or 2) Install a UAT ADS-B transceiver, which operates on 978 Mhz – the same frequency that provides ADS-B weather and traffic. One note on option #2 is that you must keep your old Mode C transponder and keep it on to make your position known to aircraft using Traffic Collision Avoidance System (TCAS) advisory equipment used by the airlines and some GA aircraft. Having both UAT and the mode C transponder operating at the same time, creates a problem with all of the portable UATs on the market today by creating a ghost image on the traffic display. I hope this can be solved as I think this could open the market for low-cost portable ADS-B transceivers.
To better understand the entire concept of ADS-B and how it works, we need to explain some of the problems that needed to be overcome.
For us to understand radio, we need to note that if two radios are transmitting at the same time on the same frequency, the receiving station gets a corrupted, unusable signal. The one exception to this rule is called “simulcasting,” which does not apply or used in ADS-B.
There is a system called “smart beaconing,” which is used in both APRS and ADS-B. In amateur radio (APRS), a beacon is sent if there is a change in speed, direction or altitude or a specific time. If by chance two conflicting beacons are sent at the same time, an error correction protocol requests a resend of the information. Smart beaconing in ADS-B is a bit more complicated as we are not only handling an aircraft’s position, but a large amount of weather data as well.
I would like to add one more radio theory to the ADS-B concept – the characteristic of the frequency used is “line of site.”
Setting the limit of 18,000 feet MSL to UAT subscribers, a frequency can be reused several hundred miles away. Using the atomic clock as a standard of time, the transmit time used by ground stations and aircraft can be assigned so no two stations send data at the same time.
Each ground station is given a precise time to broadcast the weather data to aircraft within receiving range. I was told that each ground station broadcasts the weather for airports within about 150 miles of the transmitter, thus as we travel, we are constantly picking up the weather ahead of us as the ground stations within range of our aircraft continue to change. A segment of time is given to aircraft, as well using position and altitude to calculate the precise time of transmission. As I understand. there is no error correction on ADS-B should something not work properly and there is corrupt data.
Should I equip now for ADS-B out, wait, or forget it entirely?
If we are fortunate to have a Garmin 330 transponder or an upgradable unit, we should add the ADS-B equipment now, as costs have been in the two AMU average price range. If, however, we have any of the non-upgradable transponders, I would wait or forget it entirely. Remember, the 2020 ADS-B out mandate only applies to aircraft flying within Class A, B or C airspace or above 10,000 feet MSL. Many pilots never fly in those airspaces by habit or choice.
Remember, once you choose ADS-B out, your anonymity in the airspace system is gone forever, as big brother will always know who you are. If you currently have a Mode S transponder, don’t worry, as they already know.
AOPA and many pilot groups are working on alternate solutions to the ridiculous high price for many owners to equip their aircraft with ADS-B out to meet the 2020 deadline.
Many years ago, the FAA implemented a similar requirement for Mode C (altitude reporting on transponders), and encoding altimeters were in the $900 to $1,200 range. As the deadline for compliance was approaching, blind encoders hit the market for around $200.00, at which time I bought in. Many manufacturers and avionics shops took a big hit when this happened, as the price of the encoding altimeters dropped.
I can only speculate the FAA relaxing requirements for ADS-B out and will allow low-cost portable transceivers. The SkyGuard TWX (http://ADS-B.skyguardtwx.com/uat-transceivers/) that I tested and evaluated in the June/July 2013 issue of Midwest Flyer Magazine (http://midwestflyer.com/?p=6177) would be my choice if it would meet the 2020 compliance mandate. It provided weather, traffic and ADS-B out as a portable unit, and did a good job once the antennas were properly positioned.
I give much credit to the Aircraft Owners & Pilots Association (AOPA) as our voice in making our thoughts as pilots known to the FAA (see Mark Baker’s column in the June/July 2015 issue of Midwest Flyer Magazine).
There are a few downsides to the ADS-B program beside the high cost of compliance as the program stands as per regulation. Keep in mind as previously noted that once you chose ADS-B out, you would loose your anonymity when you fly. Also, an important, but apparently overlooked consideration on behalf of FAA planning personnel, is the venerability of putting so much dependence on the GPS satellite system with no viable back-up system. Many scientists and engineers agree that a solar flare (SOLAR MAX) equivalent to the one recorded in 1958 could render the entire GPS satellite network out of business. Pilots, on the other hand, may become so complacent that they fail to make visual scans for traffic out of the window.
We will revisit the topic of ADS-B if some major change occurs, and as we get closer to the compliance date. There is no doubt this system can work and lives will be saved by avoiding collisions and having more usable data to move our aircraft safer through the skies.
Until the next issue, fly safe and stay vigilant for that traffic that can only be seen out the window.
* If you’ve ever flown with a Mode S transponder, you’ve already done your fair share of “squittering.” By definition, the word “squitter” refers to a periodic burst or broadcast of aircraft-tracking data that is transmitted periodically by a Mode S transponder without interrogation from controller’s radar. Mode S (which stands for mode “select”) technology was first developed in the mid-1970s as a way of using existing ground-based secondary surveillance radar (or SSR) to track onboard transponders more precisely and more efficiently — while reducing the number of interrogations required to identify and follow aircraft on the controller’s radar scope.
To greatly oversimplify the terminology, a “squawk” is a response a transponder makes to an ATC interrogation, while a “squit” is a transmission format that routinely sends aircraft ID and positional information without being interrogated. By reducing the need for back-and-forth interrogation/response over the air, the Mode S squitter works to minimize transmitted “chatter” in the system – and, thus, increase its target-handling capacity. GARMIN
EDITOR’S NOTE: Michael J. “Mick” Kaufman is a Certified Instrument Flight Instructor (CFII) and the program manager of flight operations with the “Bonanza/Baron Pilot Training” organization. Kaufman conducts pilot clinics and specialized instruction throughout the U.S. in a variety of aircraft, which are equipped with a variety of avionics, although he is based in Lone Rock (KLNR) and Eagle River (KEGV), Wisconsin. Kaufman was named “FAA’s Safety Team Representative of the Year for Wisconsin” in 2008. Email questions to firstname.lastname@example.org or call 817-988-0174.