ADS-B has a Missing Link

The FAA’s ADS-B requirement moves the bulk of air traffic control hardware and technology from the ground and puts it into the airplane. Instead of using a radar network on the ground to locate the position of aircraft, ADS-B relies on equipment in each airplane to broadcast its location, altitude, and movements.

ADS-B will provide a more accurate picture of the location and velocity of aircraft than radar can because new position reports will be broadcast from every aircraft at least once each second. Radar antennas take many seconds to complete a sweep so aircraft position can only be updated as often as the radar beam scans each aircraft within range.

The ADS-B acronym stands for automatic dependent surveillance-broadcast. The reporting of aircraft position, altitude, and so on is automatic. The system is dependent on every aircraft reporting its location accurately based on a common grid, which will be supplied by GPS. The dependent part of ADS-B also means that each airplane must have equipment functioning properly or it will be invisible to controllers.

But the FAA has taken this concept of every airplane broadcasting its location to every other airplane and to the controllers and divided the sky in half. The ADS-B equipment in some airplanes can communicate with other cockpits, but other pilots will not be able to receive this information even though they have fully functioning certified ADS-B equipment installed.

The reason some ADS-B equipped airplanes will be invisible to other equipped airplanes is that the FAA has created a two-tier system. Actually, it’s a dual language system. Depending on what type of airplane you fly, your ADS-B won’t talk to other airplanes without an FAA-supplied ground station in between to translate the two languages.

Courtesy: itt. Top photo courtesy: NASA

The ADS-B languages are actually radio frequencies. The ADS-B in all higher performing airplanes – both airlines and GA – will broadcast on 1090 MHz, the frequency used by all transponders. Lower performing airplanes that do not fly above 18,000 feet can opt to install a universal access transceiver (UAT) that broadcasts on 978 MHz. If the UAT-equipped and 1090-equipped airplane are flying high enough so that the line-of-sight signals can reach an FAA ground station, be translated, and rebroadcast, the pilots in each airplane can see each other. If the airplanes are too low, or too far from a station, each is invisible to the other.

How did this dual ADS-B system develop? Obviously, the UAT is not really “universal” because it can’t receive the 1090ES (extended squitter) position broadcast that all higher-performing airplanes will make. The move to ADS-B will eliminate the need for ground-based radar, but replaces radar with a ground-based translating system so all airplanes and the controllers can see each other.

The long road to the current ADS-B rules and dual system go back decades to when the technology for TCAS, the airborne traffic warning system, was being developed. ADS-B was a contending technology to provide TCAS. But, as is still true, for ADS-B to provide useful collision warning every airplane must be equipped with compatible participating avionics.

But an alternate technology we used to call BCAS, for beacon collision avoidance system, was adopted as the traffic warning standard. BCAS operates on the transponder frequency – 1090 MHz – and it can interrogate any transponder-equipped airplane and calculate the relative position of that airplane from the BCAS-equipped airplane. The first airplane to install BCAS – since called TCAS – gained collision protection from every transponder-equipped airplane. That was an obvious and winning advantage for BCAS. All traffic awareness systems use this same basic technology.

Meanwhile, ADS-B technology remained in the background, hanging around waiting for an application. The FAA really didn’t want ADS-B messing around with the transponder frequency so it was assigned 978 MHz. That dedicated frequency also allowed bandwidth for ADS-B to receive useful information such as weather reports and other alerts. It was the 978 UAT version of ADS-B that the FAA deployed in Alaska for its reasonably successful Capstone Program to demonstrate that ADS-B could work in a non-radar environment. It is also UAT that the helicopters are using for traffic separation over the Gulf of Mexico, and that UPS is using in its fleet of freighters and that several major aviation flight academies have installed to keep track of their fleets.

Courtesy: FAA

But when the FAA and other national aviation authorities decided to convert to an ADS-B Nextgen world, it became clear that UAT was the wrong choice for many aircraft. The reason is that the traffic warning systems already installed in all jets and many propeller airplanes – TCAS – must remain as a final collision warning system in case the ADS-B system in an airplane fails. TCAS operates using a Mode S transponder on – you guessed it – 1090 MHZ. So it makes perfect sense to send out the ADS-B position and other information on 1090 MHz since the traffic warning systems are already using that frequency.

That left the FAA in a pickle because it has been promising GA that a change to ADS-B would provide free weather and traffic warning display, but that is only possible on UAT because of bandwidth crowding on 1090 MHz. At the time of the original “free weather”
promotion there was no XM Weather or Sirius satellite weather, so it sounded like magic to us in GA. The “free” part of weather in the cockpit still sounds good, but any pilot who flies much at all for transportation already has at least a handheld device that can receive satellite weather. Heck, even an iPhone gets a good Nexrad radar picture in the cockpit.

We’re all required to install an approved ADS-B “out” system to broadcast our location and velocity in order to fly in regulated airspace after January 1, 2020. GA pilots have the choice of selecting a UAT system, or a transponder type of system operating on 1090 MHz. If you go with a 1090 system you play with the big boys and all higher-performance airplanes can see you without need to be within range of a ground station. If you go with UAT you will be able to receive weather and other information from those same FAA ground stations.

I can’t predict how the cost of UAT versus a 1090 system will play out over the next eight years. The 1090 system has some advantages because all airplanes will need to keep the same transponder capability required now and have it tested for accuracy and performance every two years as we do now. But there will almost certainly be some clever UAT designs that meet the basic requirements while minimizing costs.

But the bottom line is that I find it to be frustrating that a system – ADS-B – that is supposed to show every pilot the location of all aircraft around him ends up being divided into an A system and a B system that needs ground-based intervention to link us together. This system is a little better than the current radar system, but not nearly as good as it should be.

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42 Responses to ADS-B has a Missing Link

  1. But what about back up? When, not if, there is an interruption to GPS, transponders may send out a signal, but do they know where they are. We are just moving into the beginning of what may be an active sunspot cycle and it’d only take one major Coronal Mass Ejection (CME) to hit earth and GPS might need some new satellites let alone the chaos from a few hours to a day or so of interruption. Of course it appears we’ve done away, or are doing away with any ground based back up systems.

  2. Mac says:

    Hi Roger,

    The ultimate backup for ADS-B will be the TCAS traffic warning system that all jets must carry, and many smaller airplanes also have installed. That’s why we must all continue to have functioning transponders after 2020 when ADS-B becomes a requirement. An airborne traffic warning system won’t help controllers, but it can provide a final line of collision prevention should the ADS-B equipment on an airplane fail, or as you say, if something disrupts GPS reception.

    Is this good enough? The FAA and international aviation regulators think so.

    Mac Mc

  3. Pete Zaitcev says:

    Why not have a system instsalled that receives in both bands, and broadcasts in one? It would display and warn about aircraft of both types. What are cost, weight, and bulk penalties for it? The main reason I’m asking is because 3-modal cellphones were not prohibitively expensive (we are talking $300 to $500 on unlocked market).

  4. Mac says:

    Hi Peter,

    It is legal and possible to install equipment to receive both frequencies, but only one transmitter is allowed for obvious reasons. The bulk is not much of an issue because the electronics are quite compact. In many cases, the UAT can use an existing transponder antenna, and, of course, the 1090 will use the existing transponder antenna.

    Cost is an uncertain issue. Either the UAT or the 1090 solutions will almost certainly be in the thousands of dollars, not the hundreds of dollars, so installing both systems may be too costly for many.

    Mac Mc

  5. Bill Berson says:

    Good article Mac.
    I think ADS-B has several missing links.
    For example:
    How does the FAA propose to detect criminal or other airspace incursions without radar? Radar detects all aircraft, not just law abiding pilots using ADS-B.
    Terrorists, airplane thieves and drug runners might not install or use ADS-B.


  6. Mac says:

    Hi Bill,

    I have heard, but not had confirmed, that there is a plan for the security types–TSA, CBP or some agency like that–to take over the operation and maintenance of some FAA radars once ADS-B is mandatory. As you correctly point out, without ADS-B any airplane is invisible to Nextgen. However, if the law breaker decides to keep his transponder turned on, then detection might be possible. Not likely.


    Mac Mc

  7. Jeff says:

    Excellent article, I just wonder by the time it forced on us if the prices will have become reasonable for those of us on the low end?
    Hopefully so.

    • Mac says:

      Hi Jeff,

      It’s impossible to know what will develop between now and Jan. 1, 2020 when the ADS-B rule requires all of us who fly in regulated airspace to have ADS-B out. A UAT system that also contains a WASS GPS sensor could be the low cost solution because you will not need to have a WAAS GPS navigator in the panel to meet the rule. However, there is another issue in the rules and that is the requirement that you enter a transponder code in only one device and it sets the code in both the normal transponder, and the ADS-B system. The most common transponders such as the Bendix/King KT76 or the Narco 150 units cannot have an external unit select the code. On the other hand, they do not have a “smart” system that allows them to export the code to a UAT device. I don’t know how that is going to work out. More than you wanted to know, I’m sure, but the whole ADS-B plan is a work in progress.


      Mac Mc

  8. Bill Berson says:

    I thought the primary push for ADS-B from the FAA was to save money now spent on old inefficient and expensive radar. But if TSA will keep the radar anyway with more people, how is taxpayer money saved?
    A better way, in my opinion, would be to take a fresh look at a system invented in the 1940′s by RCA called Teleran*. With this system, a radar picture was transmitted to local airplanes for use in the cockpit so pilots could view other targets and also see “highways” guiding them to the runway in use. Teleran would still use radar of course, but modern radar will work with very low power (such as used by the military for portable surveillance). I think a local terminal radar for each airport would be ideal. Sort of like the automated unicom my airport has (0s9) for assisting arrivals but with cockpit video included of current traffic. It would only need low power ground based radar and cheap receivers in the airplane.

    But I suppose the ADS-B plan is locked in, by now.
    *google “Teleran” for info

    • Mac says:

      Hi Bill,

      The big cost savings that we all hope for from ADS-B and Nextgen will come from a reduction in traffic delays and miles flown because airplanes will be able to fly closer together due to the more precise position reporting. The FAA will save money because much of the cost of the equipment for its ground based radar system now moves into our cockpits and onto our tab. If an agency other than the FAA keeps the radar system running, the FAA still saved money. Remember, it’s not about total spending, but about what a government agency spends, or receives. Total cost is a different issue.


      Mac Mc

      • William Leonard says:

        Also, we currently have a tiered radar system. With 3 or more layers of radar in many places. The DOD has always maintained control over the radar to look for the rule breakers and national defense. Those were never the same radars as those used by ATC. So ATC will eventually reduce costs by only having to maintain relatively simple transmitters rather than troublesome radars. They are passing along the costs, but it is not the end of the world. I just installed my for less than $3k (experimental aircraft and self installed) and the weather features alone (compared to subscription weather) will pay for the system in about 3 years. And that does not take into acount the vastly improved traffic awareness that I now have.

  9. Raymond Tolhurst says:

    It matters little if you get run over by a high performance frequency aircraft or a low performance frequency aircraft, it is still going to hurt!
    There are plenty of gliders flying around with their own collision avoidance system (Flarm) that neither of these frequencies can see. Still might pay to keep the eyes out of the cockpit!

  10. Mac says:

    Hi Raymond,

    Looking out the window is always a good idea if there is something to see. But ADS-B and Nextgen are really IFR systems. ADS-B will keep airplanes apart while flying in the clouds. The ability to warn of traffic in visual conditions is a nice side benefit just like the traffic warning systems we have now. But in the ADS-B world VFR will still be the rule when weather conditions allow.


    Mac Mc

  11. Thomas Boyle says:

    Hi Mac,

    VFR, “See and avoid” using the human eye doesn’t work very well. The basic reason it works at all is the “big sky” theory, not because pilots actually see each other.

    Gliders are more sensitive to this issue, perhaps, because the 2nd leading cause of fatal accidents in gliders (after stall/spin) is the midair collision (gliders tend to congregate in areas of lift). They all happen in VFR. “See and avoid” works much better if you can automate/tech-assist the “see” part – and that’s why Flarm has been a success among glider pilots!

    As anyone who flies gliders will tell you, VFR not only doesn’t work all that well, but it double-doesn’t work when the sky is full of instrument jockeys who never look out the window to begin with. You only have to watch a business jet fly through a glider-packed thermal, to get the idea (think about filing 18 or 20 near-miss reports at once!). Glider pilots would love to have a solution that works with business jets, Bonanzas, SR-22s and other GA aircraft whose operators don’t look out the window. Unfortunately, the power requirements of ADS-B are based on the need to reach a ground station, not the need to communicate just a few miles to conflicting traffic, and are no more suited to gliders than the current transponder standard is. We can only hope that, at some point, there will be a low-power ADS-B standard, and/or that Flarm receivers will be built into the TCAS/ADS-B receivers.

  12. Mac says:

    You’re right about how difficult it is to see other aircraft. All you need to do is fly with a TCAS or TAS system to realize that you only see a few percent of all airplanes around you. Even with the traffic system showing the location it can sometimes be almost impossible to see a light airplane at very close range if it is flying either in the same direction or at you. Our eyes work a little better when another airplane crosses our field of view, but see and avoid really relies on the big sky more than anything else.

    As for pilots flying IFR not looking out the window, that’s a fundamental problem. Every IFR pilot must maintain an assigned course and altitude and nothing outside the window tells you that you are on your assigned altitude, or course. So you have to monitor the instruments all of the time. The only partial solution is for IFR pilots to have the autopilot do the job of holding heading and altitude so the human pilot can look at other things, such as for traffic.


    Mac Mc

  13. Thomas Boyle says:


    Human behavior being what it is, I don’t expect IFR pilots will change and start looking out the window even if they are on autopilot. As we agree, it might not help a whole lot even if they did.

    We need technology to implement “see” in “see and avoid.” Indeed, if we had it, the controller’s role for most GA flights could largely be limited to sequencing in and out of airports – and that could be handled by the tower! (If you can “see” every airplane out there, there’s little real need for separation services – after all, GA pilots consider self-separation entirely normal when they can actually see each other.)

    ADS-B appears to be a wreck, from a technology architecture point of view. It’s a shame. The best way to make it work properly, at this point, will be to open it up (make receivers that handle multiple signal formats, allow lower-power transmitters for GA that doesn’t require IFR services, and allow them to be built to consumer product standards to manage the cost) rather than tighten it down (the regulatory impulse to impose excessive performance and certification requirements, making the perfect the enemy of the good).

  14. Pingback: Issues Persist with ADS-B | High Altitude Flying Club

  15. I guess I have a little different take on the see and avoid. It’s generally not the guys who fly a lot and particularly IFR. I doubt it’s more than a small percent who don’t fly on autopilot. When flying on AP you have much more time to look outside when not in the soup and most of us are paranoid when below a four or five thousand foot ceiling. Now admittedly even when flying a coupled approach it gets busy in there and there’s not much time to look at the scenery or for other airplanes, BUT you have a lot more time than the pilot who is hand flying an ILS . Even non precision approaches take a lot of attention away from outside.

    Also when ever near an airport, even small ones that have approaches VFR pilots *should* become acquainted with the instrument procedures at those airports. ..Yah, I know…why would a VFT pilot care, or should they care, but the top reason is you are likely end up flying *through* one of their instrument approaches. The Final Approach Fix or FAF is *usually* about 5 KM from the airport and not necessarily in line with any runway. Procedures *may* take the airplane close to another 5 miles (more in some cases) out. Depending on terrain portions of these approaches may vary from *about* 500 AGL to 2000 AGL and *UP*

    ALL VFR pilots should expect IFR pilots in these areas to have very little time to look outside. We do as much as possible but on top of flying the airplane ATC is likely to
    talk to us more in this small area than they do in a the rest of a 1000 mile trip. So the IFR pilot is going to have the heaviest workload, flying the airplane, flying procedures, talking to ATC, writing down clearances in the bumpiest part of the trip, AND then trying to read those clearances back to ATC AND look outside for other airplanes in an area containing more airplanes than they might have seen in the whole trip. This is not to mention the FAF or ILS intercept where ATC is likely to start…giving clearance instructions while sounding like an auctioneer. That is not an exaggeration, we had one at a large airport South of here who did that. We have to write that down (hopefully a copilot can do that but not always) those clearances and then read them back while approaching the airport at speeds faster than most other small planes fly.

    The entire system seems to conspire to make sure the IFR pilot has little time to look outside and particularly so when near an airport where there are likely to be many more planes. OH! and just to keep things interesting and they do not do it often, but ATC does make the occasional mistake and YOU are expected to catch it. <:-))

    *BUT* it's been my experience when flying with others at how few VFR pilots seem to pay attention to the outside world. They fly by the AI (look out the windshield at the real horizon) and hold altitude by watching the VSI (don't do that! it's a trend instrument and will get you in trouble flying high performance). Out of the many hundreds I've let fly the Deb all but a few have it in a PIO in less than a minute. I just reach over and cover the VSI, point outside at the horizon going up and down. When it gets where I think it should be I tell them to keep it there and quite watching the VSI. Just glance at the altimeter and then back outside. If the altimeter shows we are losing altitude I tell them to lower the horizon a bit and then check the altimeter again. If we are gaining altitude I tell them the raise the horizon in the windshield.

    And then there are those who fly by a GPS without ever matching the scenery to the chart.

    But back to see and avoid. We were some where over Southern Kentucky at about 10,500. (VFR) We were on our way home after spending Christmas with my son and his family near Gainsvill GA and loaded to gross. I was flying a Cherokee 180 Northbound into a head wind that had cars passing us. There wasn't a smooth spot from as low as I was willing to go to as high as I could get, so I settled on 10,500 as the best compromise between speed, comfort and endurance at economy cruise.

    ATC advised me I had a King Air approaching from 5:00 O'clock at my altitude.He passed behind me and on by on the port side. According to ATC were were fairly close and it was severe clear. I never did see him even with all those strobes.

    NOTE If you travel with passengers *always* make sure things are where you left them after a gas or pit stop. Voice of experience.

  16. John Smith says:

    There are certainly weak links in ADS-B, but if the system is implemented as planned, unfortunately the one you picked is non-existent. ADS-R (Automatic Dependent Surveillance – Rebroadcast) is the service that re-transmits on both bands so all ADS-B equipped aircraft will see each other. ADS-B and ADS-R both make up “surveillance services” and are categorized as “critical services” for ATC. In short, anywhere ATC will be able to see ADS-B equipped aircraft, so can every other airplane.

    Which brings us to the real weak link. ADS-B *is* a ground-based surveillance system. Yes, position vectors are calculated aboard the aircraft using satellite GPS, but *surveillance*, the ability for ATC to see ADS-B aircraft, is dependent on ground-based transmitters (GBTs). Furthermore, this infrastructure for the first time is not owned by the FAA but owned, and maintained, by ITT. The FAA only contracts for the data feed which it receives at the service delivery point, and which as it stands now, they can only monitor for status. If it fails, all the FAA can do is call ITT.

    That all being said, I don’t doubt the technology works. It’s in limited use now and for the most part fulfilling the mission. But there’s still something rotten in Denmark (no offense to Danes who might read this, it’s just an American colloquialism).

    When the contract was awarded to ITT for ADS-B they were advised by Michael J. Dyment, an investment banker, consultant, self-professed “senior advisor to several FAA administrators” and managing partner of Nexa General Partnership Capital.

    With airlines balking at NextGen equipage costs, an amendment was made to the FAA Reauthorization bill that passed the House in April of this year creating a public-private partnership called the NextGen Equipage Fund. This fund, financed with private capital, would give the airlines enough money to equip 75% of their fleet with deferred payment loans guaranteed by the federal government. If the FAA fails to provide the promised NextGen services to utilize the equipment? The airlines don’t have to pay. Who does do you think? Well of course, we the taxpayers. And someone has to manage that money right? For a fee I’m sure. How about Nexa General Partnership Capital, now with an additional managing partner, Russ Chew, former COO of the FAA ATO (Air Traffic Organization)? Principal investor in the fund? ITT of course. And who testified before Congress in favor of the NextGen Equipage Fund? Why Marion Blakey, CEO of Aerospace Industries Association and Russ Chew’s former boss as FAA Administrator. I’m sure all of this is just people passionate about air transport having a common interest in developing improved infrastructure for the common good, but forgive me if I feel a compulsion do give a *wink* *wink* *nudge* *nudge* here.

    Reauthorization has yet to pass, and maybe it never will at this rate, so this fund isn’t actually funded…yet. Sometimes when Congress does nothing, we’re better off…

  17. Eliacim Cortes says:

    How can the FAA continue implementing ADS-B, if the 40,000 LightSquared ground stations which the FCC approved will cause the GPS signal to be unreliable throughout many areas in the country?

  18. Jeremy Brady says:

    here are companies hard at work on giving pilots the full view of ADS-B IN. The fact that ADS-B is divided to two frequencies does not limit its ability to give more information in the cockpit than ever before. In fact, the simplest solution that UAT manufacturers will be implementing at some point, is to add a 1090MHz receiver into the UAT alongside the 978MHz transceiver. This will allow UAT equipped aircraft to see every other ADS-B equipped aircraft. Also, there are already some clever UAT designs that minimize cost as well as fully functional ADS-B displays: NavWorx, FreeFlight, SkyVision Xtreme, and others.

    Regardless of the future improvements, ADS-B is a system that deserves serious consideration from all GA Pilots. It’s available, accurate, and affordable NOW!

    As a very experienced pilot once told me when making a decision about purchasing a traffic avoidance system: “You can’t write the check on the way down!”

  19. Mac says:

    Hi Jeremy,

    You’re right. It’s smart to buy the best traffic warning system that you can afford. Right now the ADS-B “in” standards are not fully formed. The ADS-B “out” which is the required part has standards that set requirements, but there is still uncertainty on exactly what combination of sensors, transmitters and so on–plus pilot interface–will be approved for actual installation in a specific type of airplane.

    If you want good traffic warning now there are several systems available for a range of airplanes. Will some of that equipment adapt to the ADS-B world after 2020? I hope so.


    Mac Mc

  20. Tim Taylor says:

    The UAT link has huge capacity – today it carries traffic and weather information (high quality, graphical, subscription free) and int the future is going to carry a lot more. The ground stations are cheap and therefore plentiful – lots of coverage and better than radar in terms of resolution, accuracy and integrity. Chances of a failed ADS-B system on an aircraft without the world knowing are better that 1 in 10 to-the-minus 5 per flight hour – and the ground system builds a bubble around any failed airplane – plus you have a transponder back up (seen by TCAS) so you are not going to bump into an airliner because of ADS-B. It is true that a UAT equipped aircraft, outside of ADS-B coverage will not see a transponder equipped aircraft – but we are talking about a very limited volume of airspace (mostly very close to the ground away from busy areas) so its not huge problem. The rest of the time you get the FAA feed of ADS-B traffic that is not on your frequency plus (for now) all radar traffic that the FAA can see. Hugely better that just looking out the window. Add the subscription free WSI based graphical weather an enhanced search and rescue capability and you are going to have a lot of tools that can make your flight safer.

    On the weight of equipment issue – you can get a TSO UAT that weighs less than the Wendy’s double I just had for lunch, and it will definitely be better for you.

  21. John Bouyea says:

    ADS-B = “A Dumb Solution – Botched” 2 incompatible frequencies, gee whiz!

    It sounds sketchy even for pilots operating equipment with new or -even- somewhat current avionics. I know a fair number of people who do not have deep pockets or the desire to keep their aircraft avionics up-to-date, just operational. My Cardinal has 2 NavComms, DME & a KT-76A transponder. I have no desire or need for IFR-rated GPS and I operate through Class B & C airspace all the time. The ADS-B “solution” takes away a fair amount of airspace from owners/ pilots like me. My KR2 only has a hand-held Comm & a transponder. Ouch.

    I see this new requirement as yet another method to “out spend” the little guys’ ability to pay for upgrades. Does anyone even fly for fun anymore?

    How does the EAA lobby represent the grass roots pilot on this issue?
    Is AOPA speaking up for pilot members who own and operate an airplane in the “pleasure” class; you know, just to take a “joy ride?”

  22. Tim Taylor says:

    Aircraft like yours are easy and (in aircraft terms) inexpensive to add ADS-B. Leave the panel alone – except for a 21/2 inch on off / good bad / squawk panel. Under the floorboards goes a small radio and a cheap -but-certified WAAS receiver.- combined weight around 2 lbs Two antennas – one on top for the GPS and one underneath for the ADS-B radio. Add a little coupler to read the mode 3A code that your KT is sending so the radio can automatically send the same code and thats about it. Operationally, ADS-B Out just does its thing, ADS-B In traffic and weather will show up on your cool knee mounted iPad or similar. All the benefits, no workload, your panel stays the same as it is today.

    • George P. Burdell says:


      No offense, but If I had to guess, you work either for the organization that developed UAT or for a company that sells UAT transceivers. I’d *love* to see a UAT transceiver with a TSO *issued* that’s as cheap and available as you claim.

      I hope you’re right…


  23. Mac says:

    Hi Tim,

    I hope your prediction of a simple ADS-B out UAT unit comes true. It is possible because the regulations are performance based–describing what the equipment must do, not how it must do it–but there will be issues. As always the devil is in the details but there are several years to go before the requirement is here.


    Mac Mc

  24. Shortcomings aside, ADS B is probably one of the most sensible systems to come down the pike for GA and commercial aviation alike. Yes I can see some problems with *possible* cost and also the definition of “controlled air space. In the lower 48 that includes almost all airspace except a few spots in Upper Michigan and Out West in the mountainous areas. However those are areas where ADS B could really make a difference.

    There are bound to be some glitches and much will depend on just how the FAA decides to implement it. Like other agencies with forethought they can make the implementation as painful or painless as they decide. Even with the potential problems from LightSquared which is likely to be implemented regardless of input as it is a pet project of the administration. BUT if it shows up as a true hazard to commercial aviation I think they will yield. *Technically* LightSquared was only given permission for a test trial, BUT (unless things have changed) with tacit approval to start installing equipment which adds a new element to the credibility of the testing, particularly when LightSquared was put in charge of the evaluation and in charge of the input to the FAA. They have also started parterning with other utilities so they may find less need for the 40,000 stations running as much as 45 KW each. Even the best receives costing many thousands of dollars, require substantial space from adjacent channel signals that strong. So we’ll have to see how that plays out. But about all it’ll take is one verified interference problem with an airliner and I’d bet dollars to donuts that lightSquared would lose all that expensive investment, so I would assume (which is never safe) they will proceed with caution. Expensive mistakes are not at all popular with stockholders.

  25. Tim Taylor says:

    Dave, none taken and you are right – I am in the business but definitely not with the original UAT company. Everything I posted is true and is happening right now. I would be happy to give you the details off – line (don’t want to use this forum for selling). You can get in touch with me through the above link.

  26. Dick Siano says:

    Hi Mac,
    As always your words are always worth taking the time to read them. I notice that neither you or any of the other commentators mentioned the concept of “self separation” that is fueling the FAA’s move to ADS. Moving the Air Traffic Controllers workload to the cockpit and to the pilots is a concern that I have. I believe we should not permit this to happen. Adding the work load of self separation to the pilots already high workload is only going to make safety suffer again.
    As far as collision avoidance goes, I also noticed that no one has offered the concept of “randomness” as being our last defense against a mistake that either the pilot makes or the air traffic controller makes that causes two aircraft to be at the same altitude. The accuracy of the Wide Area Augmentation System of plus or minus one meter, never worse than two meters will guarantee a mid air collision. The Embraer Legacy 600 and GOL Airlines 737 that collided in Brazil is one example of that already happening. If either pilot had created some randomness in their aircrafts track, the collision would not have happened. I would recommend reading an article in Wikipedia entitled Navigation Paradox at:
    This article written more than 40 years ago makes a strong case for each of us adding a little randomness to our flight track.
    Dick Siano

  27. Mac says:

    Hi Dick,

    I think the concept you are questioning is often called “free flight” where pilots would use electronic devices to fly as though it was always VFR. Under visual conditions pilots can space themselves to a runway and it works good. If we had the technology to “see” every other airplane in the area, the theory is we could space ourselves in the clouds or low visibility just like we do when flying visual approaches.

    As a pilot I like the idea because it puts control back in the cockpit. I feel comfortable flying a visual approach under IFR because I can see the airplane ahead and space myself to allow enough time for the guy ahead to land and clear the runway. Would this same type of system work if we are “seeing” only an ADS-B picture of the airplanes ahead, I can’t say for sure. But I do like the idea. One issue is how to space airplanes to the final approach. Would we race each other to get there first, or would a “cop” be needed to select an order of approach. Those are big questions, like yours, that intrude on the great idea of all of us just working out traffic control on our own.


    Mac Mc

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  35. Austin Vialoux says:

    If you look at the Next gen equipment they are working on surely they should have just waited for the VDL-2 or higher satelight data links that use the iridum or imarsat networks. Skipping the need for either the UART or Transponder Upgrades. This would also allow two way ADS-B and the use CPDLC (Texting to and from Control tower). We would all install one datalink Trasceiver and one antennae. There are many benefits to this system. ei world wide coverage. No ground stations……

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