Is the ADS-B glass half full?

In the words of Richard Collins, it is “the most important airspace rulemaking proposal ever made: it will affect more pilots and carry a greater financial burden than any previous proposal.”

Mac McClellan argues that, “The FAA had a good idea when it planned transition… but is now screwing the whole thing up.”

ADS-B system diagram
ADS-B is complicated, but is there any good to it?

More concerns about the 2020 ADS-B mandate, you say? No. In this case, Collins was writing about the requirement to add Mode C transponders, in the May 1988 issue of Flying magazine. McClellan’s editorial, written three years later, was about the Mode S transponder proposal (which was eventually shelved).

Today, you could read a similar editorial in most aviation magazines, but of course the target is now ADS-B. The system may have been a good idea in principle, we read, but now it’s overdue, over budget and overly restrictive. As AOPA President Mark Baker recently wrote, it’s plagued by “technical glitches and hazards” and offers no clear benefit for pilots.

That means over the past 25 years, pilots have complained about three different transponder rules: Mode C, then Mode S and now ADS-B. Is the FAA really this incompetent, or do pilots just like to gripe? As usual, the answer is a little bit of both, but I say the ADS-B glass is half full.

Now before you reach for the pitchforks, let me assure you that I’m no Pollyanna (I didn’t say the glass was completely full!). The FAA’s handling of ADS-B, and their NextGen modernization program in general, has been absolutely dreadful. After 10 years and nearly $2 billion, the ADS-B ground station network is complete, but little else is. Necessary ATC upgrades are far behind schedule, and less than 10% of required airplanes have been upgraded to meet the mandate. One key reason is that the system is almost laughably complicated. Do you need ADS-B In or Out? 1090ES or 978 UAT? Want a WAAS GPS with that?

But while everyone loves to bash the FAA (including me), I think we’ve gotten a little carried away this time. It’s simply unfair to say that ADS-B is all bad and no good.

First, it’s worth remembering that not everyone will have to upgrade to ADS-B. If you fly a Cub off a grass strip to chase $100 hamburgers, you most likely won’t have to upgrade (airplanes certified without electrical systems are exempt). Likewise, if you don’t fly to busy airports (Class B, C or D airspace), your airplane never has to equip with ADS-B. These details have been public knowledge for years, but in my unscientific surveys shockingly few pilots know them.

Doomsday scenarios suggest thousands of airplanes will be parked on January 1, 2020, orphaned by an arbitrary FAA rule. The more likely scenario is a lot less dire: pilots who don’t equip with ADS-B will simply avoid busy airspace. Pilots have decades of experience at muddling through; that will come in handy once again.

ADS-B traffic
A full traffic picture? Why is that a bad thing?

Another reason for optimism is that ADS-B actually offers some benefits. While the Mode C mandate did almost nothing for pilots (hence Collins’ outrage), ADS-B offers both uplinked weather and traffic. Those are two valuable services, and neither one requires a subscription.

Also, in contrast to the Mode S debacle, the ADS-B ground station network is actually in place–so pilots can and are taking advantage of these benefits right now. Tens of thousands of pilots are flying with portable ADS-B In receivers, which have lowered the cost of avionics and led to safer flights.

Of course there’s a catch, and in this case the catch is that pilots have to equip with ADS-B Out transponders in order to receive those valuable traffic reports. That costs money, but some perspective is in order: if someone told you 15 years ago you could have a full traffic display and a new transponder in your cockpit for $4,000, many would have jumped on it. After all, the other option was to pay $20,000+ for an active traffic system. I know at least five aircraft owners who have added ADS-B Out to their airplanes after flying with ADS-B In, because they got a taste of the system but wanted a better traffic display.

So while ADS-B was definitely created to help Air Traffic Control, we should admit that there’s plenty for pilots to like, too.

Like most things in aviation, the real debate about ADS-B comes down to cost. Traffic and weather are nice, but at what cost? While no one can argue that ADS-B Out transponders are cheap, they’re a lot less expensive than early Mode C transponders, which cost well over $10,000 (in 2014 dollars). Even that $4000 price may come down further when some recently-announced products hit the market in 2015. Not a slam dunk by any stretch, but we’re far ahead of both the Mode C and Mode S schedule.

Some associations have their hearts set on a portable ADS-B Out transponder as a way to lower cost. It’s a very interesting idea, but I see almost no chance of it becoming a reality. It would be akin to shooting an LPV approach in actual IFR conditions with a portable GPS–something the FAA would never allow (and they’re right). I have trouble seeing ATC separating a Boeing from a Cirrus based on a portable device sitting on the back seat.

In the end, I think pilots don’t like to be told what to do. We like to plan our avionics upgrades, not have the FAA do it for us. I get that. And ADS-B is needlessly complicated, summing up so much of what is wrong with the FAA. But this system is coming, whether we want it or not. I think we might all be a little happier if we stopped talking about “the mandate” and started talking about “the benefits.”

After all, pilots were quite willing to spend money on panel-mount GPS units when it became obvious that they had real benefits. Might we get there with ADS-B?

Full disclosure: my company sells ADS-B products, including developing the Stratus ADS-B receiver. However, the opinions in this article are mine alone–certainly informed by my experience with ADS-B products, but not written to sell them to you.


  • ADS-B out may not be the most horrendously expensive FAA mandate in history, and lack of compliance with the mandate will still leave large portions of USA airspace open. There are some benefits to GA pilots from ADS-B In, but they’re not very impressive compared to what could have been, say, from a satellite based broadcast system rather than a ground based system.

    But the defenders of the ADS-B mandate are minimizing the very delicate state of private, non-commercial aviation today that is subject to, I fear, the “straw that broke the camel’s back” syndrome.

    The cost of new aircraft is simply unattainable for most current pilots, other than a handful of the rich and certain businesses. The cost of maintaining old legacy aircraft is getting higher and higher, along with fuel prices that are likely to climb even faster once the EPA-mandated 100LL replacement takes over. There a hundreds of thousands of pilots who are simply not flying as much as they used to, if at all – due to cost … and due to the aging pilot population because so few young people are choosing to fly due to the expense.

    We know that most of today’s private non-commercial aircraft are relatively low value airframes. Suddenly adding a $7 thousand marginal cost onto owners of aircraft worth only 20, 30, 40, or 50 thousand bucks could very well prove to be that proverbial straw that broke the back of personal aviation … the marginal cost that many of today’s pilots say they simply cannot and will not absorb.

    The ADS apologists also say (as John does here) that “there is lots of airspace that won’t require the ADS-B Out equipment.” But that argument again ignores the marginal effect on the pilot population and where it lives and flies. Most of today’s pilots live in populated areas because, well, that’s where the people live in America. So saying that 70% of the airspace is not affected misses the point that 70+% of the pilots, living and flying where they normally fly today, most certainly ARE impacted. The busiest GA airports aren’t the ones in the middle of nowhere – the busiest GA airports are those in urban and suburban areas of the country where most people live today. And no matter where you live, if you want to fly IFR or use VFR flight following, or occasionally, you know, fly somewhere different, then you must equip.

    One chucklehead writing over at Flying Magazine’s website even made the stupid statement that the ADS-B mandate will be GOOD because it will force people to move their aviating to small towns where they really need the business? Really? So now you not only have to pay to equip, but you have to sell your house and move to a small town where you also have to give up your job and your family and business connections? Great .. that really makes the equation go fully in favor of ADS-B!!! Where do people come up with such absurd totalitarian ideas anyway, other than in government bureaucracies that like to force health care reforms that most of us don’t want (“You can keep your doctor if …”).

    Finally, the notion that we can’t safely utilize portable equipment for air traffic separation, as John has said here … that’s simply preposterous. There is nothing inherently safer about panel mounted equipment than portable equipment. There is everything inherently more expensive about panel mounts than portable units, though. The GPS signal could care less about whether it was sent or received by a TSO’d panel mount system or a cheap portable system. It is all exactly the same.

    If the FAA ever were forced by Congress to overcome its bureaucratic inertia and stupidity, and pulled its head out of its hindquarters, they would have approved portable GPS nav units for IFR flight years ago. The other obvious solution to safety innovation is to simply adopt ASTM industry standards for avionics … just as the construction, automobile, and medical products industries – all of which deal with life or death consequences in their design and manufacturing of consumer products have been doing for decades. Get the Federal government entirely out of the safety product certification business altogether. That alone would be the greatest safety innovation in the history of American aviation, bar none.

  • The elephant in the room is this: equipping with the lowest-cost-available ADS-B out device produces ZERO benefits in the cockpit. Zero. All of the bennies come from ADS-B in, which is unavailable in the low-cost hardware, but ironically is available via consumer-grade portable devices! Of course, if you equip with $30k worth of glass, you can share in all of those benefits, too.

    Six grand plus installation, for a device that is the ADS-B equivalent of a blind encoder and a transponder. And I have to keep and maintain my existing blind encoder and transponder. And I get zero benefits in the cockpit. Such a deal!!!

    “Doom-and-gloom” sometimes is congruent with reality. Based on conversations with lots of owner-pilots, my best estimate is that, come January 1, 2020, half of the light-GA fleet will be parked – permanently. This is the half of the fleet that GAMA and other alphabet groups estimate is comprised of vehicles that are worth $50k or less.

    What is the likelihood that I would spend 8 or 9 grand “upgrading” my $25k Tomahawk or Cherokee – just to stay legal? 35% of my hull value is one helluva tax. Anybody else remember what they did to our expensive Loran navigators? And that was the same guy who told me that I could keep my doctor, and save $2,500 a year while doing so.

    I may have been born yesterday, but I stayed up late last night, studying……

    • Tom, I agree with a lot of what you say here. As I wrote, the glass is half full at best. So the question is, when does the price become tolerable? $6000 is a lot for a $30,000 airplane. Is $3000? $2000? It may still be a bitter pill, but is there a price that makes it able to be swallowable?

      The other thing we have to admit is that our industry groups helped write a decent chunk of this law, and we will have had a 10 year advanced warning. Not like it was dumped on us overnight.

      • While it was not “dumped on us overnight”, the cost and adoption rate is abysmal. One would expect that normal avionics attrition alone would forward the cause over this long of a period. Unfortunately, the mandate was planned without a clear accountability to price vs performance of the system as a whole, or how it would affect the vast majority of users of the system that do not need to add precision IFR to their panel.

        The real question is- if a non-WAAS Nextgen system install could cost an average user $3k end to end with a normal IFR-approved GPS source, and the WAAS system costs increase to $7k to $8k for many for a basic compliant system, who benefits from the extra $4k-$5k of the costs? It doesn’t seem likely that the reason is collision avoidance. It doesn’t appear to be likely to benefit a controller or nearby aircraft to have that precision in the outbound signal. It is a great idea for an aircraft on a precision IFR approach, and to meet the mandate for direct GPS RNAV (which is a small slice of users). But a J-3 inside a mode C veil will provide equivalent actionable information with a non-WAAS system to nearby aircraft as with a WAAS system.

        I say get rid of the WAAS mandate, and we will see ADS-B move much faster.

        • I wouldn’t assume an ADS-B Out with WAAS has to be $7K. L3, for one, is coming out with some new products that may be much mor aggressive.

          • Nobody should assume anything…all they need to do is look at what things actually do cost.

            L3’s avionics offerings are focused on breathtakingly expensive offerings to government and larger biz jet clients. They claim to have a solution “…for every budget…”, yet no pricing is even hinted at. I am inclined that their use of the word “budget” is more oriented to wading down to slum with the King Air drivers than to lie down with Aeronca drivers.

            I fully expect costs will come down. But the WAAS mandate is holding that trend hostage. For most users of the airspace, the WAAS requirement is no more helpful than a $3000-$4000 lucky rabbit’s foot.

          • You may be right on L3. But a lot of people are working on the cost side of things – I say stay tuned.

      • “When does the price become tolerable?” An excellent question. John, I think that this ADS-B pill is made as bitter by its lack of benefits, as it is by its onerous cost. In other words, if we got as much value out of a “low-cost” solution as is available in a $30k solution, more of us would be able to justify the expense. The pill would cost as much, but it wouldn’t taste as bitter. This train of thought supports my “$10k magic box” fantasy, as I’ve written about earlier.

        Back to “When does the price become tolerable?”. If it’s a blind “compliance-only” box, my guess is that it would have to cost not more than $2k – including installation and paperwork. Which still is more than the cost of a pretty decent portable solution.

        What does the FAA hate most about portables? They can’t reliably determine the identity of the aircraft in which they’re being operated. Please note, that’s equally true for existing Mode A-C radar-based solutions (Mode S includes a vehicle-specific code). Insistence on a firmware ID isn’t about safety. It’s about surveillance, accompanied by indirect accountability (who’s actually flying N12345?).

        And sadly, John, a lot of the bitterness of this pill comes from widespread and deep distrust of just about anything the FAA says or does. That distrust is independent of the financial cost of their initiatives.

        To your valid point about the “10-year warning,” I would say this: a long-lead bad idea is no better than a surprise bad idea – it’s still a bad idea.

        My own objections to this entire scheme are technical in nature, as I’ve written about before in this space. I cut no slack to the pinheads in the GA alphabet groups, who conspired with the FAA to approve this deeply flawed scheme. In the end, we’re going to have to maintain the existing radar infrastructure (or an expensive replacement for it) in perpetuity – ON TOP OF the new stuff. That’s because the “S” in ADS-B (Surveillance) is by definition unreliable. So what will we get for our money?

        As an engineer, I don’t see things in terms of the glass being half-full OR half-empty. To me, it’s just half a glass… And to think – I coulda had a V-8!

    • Tom,

      ADS-B out has to use your current mode C encoder. You do not install a second one. ADS-B uses pressure altitude for ATC separation. You can’t have an encoder for your transponder and a encoder for ADS-B out and possibly have two different altitudes displayed to ATC. This is also why there is no recertification of the equipment every couple of years like there is for your mode C equipment today because you use the same encoder that is already being checked every two years. ADS-B out also reports geometric altitude (GPS Altitude) but it is not used by the FAA for separation of aircraft or for TIS-B traffic information. Only pressure altitude from your current encoder is used. See AC20-165A.

      • Tod:

        Yeah, I understand all of that. But it’s a bug – not a feature.

        It’s preposterous for the FAA to require the accuracy (and cost) of WAAS, only to ignore the provided accuracy in the Z-axis (altitude). Seriously. If the device already knows your geo altitude within a half a meter, why would you disregard that information in favor of a plus-or-minus 100-foot data-point, as provided by a pressure-altitude detector? It’s NUTS. And it’s typical FAA-think. Oh, sorry – I’m being redundant.

        And thus, we’re stuck with the cost of maintaining TWO position-reporting systems on board our vehicles. Fantastic! Give them a Collier!

        • Tom,

          Geometric altitude does not have the accuracy that you stated it is not simple a Z axis calculation. It varies greatly depending on what study you read, however most reports from MIT will show a calculation error from 20 meters to 120 meters. Just go searching on the WEB for “accuracy of geometric altitude” most of the articles can explain it much better than I can. There is one report I read that shows a 500ft error at 10,000 ft at 30 degrees Celsius. Not really the point of all this but people should understand why the requirements are what they are. Another good study to read is:


          • Tod – if GPS WAAS altitude data were as imprecise as you suggest (up to 120 meters, or even 500 ft errors), then how the heck does the FAA get away with approving precision GPS WAAS approaches? Obviously, if altitude errors were in the range of up to 120 meters, there would be a heckuva lot of crashes going on by pilots relying on such faulty and imprecise data. Not to mention that such poor altitude accuracy would render GPS navigators as practically worthless for general terrain and obstacle avoidance.

            The reality is that GPS WAAS is actually used for legal land surveys with accuracies down to as little as hundredths of a foot. Land survey WAAS GPS’s have additional equipment not included on portable GPS receivers, but even in portable receivers, WAAS precision is far better than you suggest from your research of various studies.

          • Tod – if you’re really interested in the details of the GPS WAAS system and the required performance specification in terms of vertical precision, you can find it at

            To summarize, LNV/VNAV and LPV performance specifications are that to pass RAIM performance specs, the vertical precision anywhere within the continental USA up to 100,000 feet at two times 10 to the minus seventh availability is within plus or minus 20 meters, and that performance is available effectively 100% of the time within CONUS up to 100,000 ft. That’s actually greater precision than that required of precision air data computers that are required for use in RVSM flight levels (FL290-410), which is a maximum altitude error of plus or minus 41 M. The high flying jets use the precise ADCs rather than GPS WAAS, but it’s clear that GPS WAAS altitude signal is actually more accurate in most cases than standard non-RVSM baro altimeters.

    • @Tom, I don’t understand your comment about $8-9K for ADSB-out only. We just replaced the KT76 that went T/U with a KT-74. Now it is a slide-in replacement so all-up out 182 is now 2020 compliant. Total cost $3,700 including the hookup to the 430W for an STC approved GPS source.

      • Tim:

        The key to your lower all-up cost is your previously-installed 430W. A lot of “full-IFR” planes lack ANY GPS, let alone a WAAS-certified one.


  • I totally understand both sides of the argument and I think this article is one of the best written on this subject.

    I also think duane’s reply makes some great points.

    I’m on both sides of the fence as well. On one side, ADS-B adds safety and traffic info. If you’ve ever had a near miss with a a/c flying without contact with atc you can surely see this is a major help if everyone in the sky is on your and ATC’s screen. Also if you got into flying thinking there wouldn’t be any costs, you were basically a fool. Even on a cheap plane your annuals are at least 1 to 2 thousand dollars. I’m sorry your airframe is only worth $40k but you can either pay to play or sell at this point, complaining isn’t helping anyone. It would be like someone complaining about haveing to remove lead paint from their house. Houses have costs and so do airplanes, and when it comes to safety it is worth it. Its also much cheaper and worthwhile to get an avionic upgrade than sell and take a hit on hull depreciation as well as give up your licenses and hangar.

    On the other side of the fence, the ENTRY cost into general aviation is ridiculous. This certainly doesn’t help because someone looking to buy a 100k plane now has an extra cost which just makes it completely not worth it. Note, yes, I am saying if you already own a plane just man up and upgrade, but if you dont own and dont have licenses or an a/c this is just one more reason to stay away. This may be the straw that breaks GA’s back but a better/cheaper form of transportation in the future (ie cars that self drive) will the the dagger in the heart that kills GA once and for all.

    • Duane,

      It is a hard one to understand and I am not sure if this will make sense but I will attempt an answer. When exciting an approach the glide slope is calculated between an altitude at a known fix to an altitude to the next known fix at a specific angle, this is a geometric equation. If you had a 100 meter error from GPS altitude at the first fix you would supposedly have the 100 meter error at the second fix so the indication of the glide slope should remain constant. In the LPV approach the GPS altitude is not displayed as point that you would base your missed approach on you based your missed approach on your altimeter which is pressure altitude corrected for ISA pressure.

      • Tod – GPS altitudes are not calculated on the basis of approach geometry – they are calculated by altitudes yielded from time differences from multiple GPS satellites as corrected by signals generated by ground based WAAS signals as calculated by the GPS WAAS receiver. 100% of this process is entirely independent of a GPS navigator’s determination of GPS altitude and its relationship to a given planned flight path. I don’t know where you get your info from, but your understanding is incorrect.

        As I said above, with the appropriate correction factors as provided by ground based correction signals, WAAS GPS can determine elevations (or altitudes) to within hundredths of a foot. It is all a matter of having the available ground based correction signals as well as required receiver circuitry.

        • One key piece of this is the installation, isn’t it? Yes, WAAS is incredible technology, but one of the things the FAA tries to ensure with TSO’d/STC’d avionics is that they’re installed in such a way that they are reliable, not just accurate. I think that may be the bigger heartburn – what if somebody throws the portable under a seat and the GPS can only get 50m accuracy? That’s due to installation error, not the technology.

          • Actually, John, GPS WAAS accuracy and precision is independent of the quality of the installation (panel or portable), because it’s based upon the functioning of the GPS/WAAS satellite and the ground based correction transmitting system, and the proper electronic functioning of the GPS receiver itself, which is based virtually only on its design and manufacture.

            Even a simple portable aviation (or even non-aviation) WAAS system will deliver the same precision performance, even with just a portable antenna, as a panel mount system … that is, plus or minus 20 meters on altitude and 3-5 meters lateral position.

            The only thing that is omitted from an aviation (or non-aviation) GPS WAAS receiver that is found on all panel mounted IFR approach certified GPS navigators is the RAIM (“receiver autonomous integrity monitoring) circuitry. But that is simply another add-on circuitry item in a GPS chip, very cheap to add (literally just a few bucks).

            The reason that portable aviation GPS WAAS units (like one that I fly with, as a backup to my panel mount Garmin approach-certified GPS WAAS navigator) don’t include RAIM is because RAIM is only required for approach certified IFR navigators. It would be very easy and cheap to include RAIM in a portable unit, if it were allowed by FAA for IFR approaches.

          • John – I think that many people who aren’t familiar with the inner workings of GPS navigators mistakenly believe that some things that mattered in the setup and operation of analog electronics nav systems, like VORs – i.e., “calibration” – is still a factor with digital navigation. “Calibration”, which is an important factor with the old VOR receivers, doesn’t apply to GPS navigators. With digital nav boxes, there is literally nothing to calibrate or adjust or even test for. It either is working fine, or it isn’t. There is nothing to tune or adjust or set up or install with these devises (the only installation tasks are to connect the unit to power, to the antenna, and if coupled, to additional avionics and flight control devices)

            FAA does require that IFR approach certified GPS navigators (which are also required to be WAAS equipped) be continuously monitored by a built in RAIM system. RAIM effectively monitors the signals with test signals which look for defaults (which might be caused by a receiver malfunction, or a malfunction in the GPS broadcasting system, such as a malfunctioning satellite). RAIM also has the ability to exclude defective signal inputs if sufficient functioning sat signal inputs are still available to deliver precise results.

            Effectively, a GPS system works or it doesn’t work, like an on-off switch. And/or it may work but may not provide sufficient signal integrity to allow precision approaches – and the navigator will tell the user whenever that is the case.

          • John,

            Yes the ADS-B message has GPS altitude contained in the message but the FAA uses the pressure altitude from the mode C encoder that is also required in the ADS-B message for altitude separation from other aircraft. The pressure altitude is also used in the ADS-B IN to show you the difference of altitude from other aircraft. This is part of the problem with the portable solution. You would have to get the mode C from your aircraft into the portable so that message can be used. I don’t know if or for what for the FAA uses the GPS altitude at all. See AC20-165A to help understand this requirement. We separate all aircraft from the one, same reported altitude source.

    • Sorry PScott but I am very happy to report that not everyone see things the way you do! I fly for a living yet do not have the $$ to as you say it “man up and upgrade.”

      My annuals do not cost $1-2 thousand like you post because I do most of the work myself then the IA inspects then signs the airplane off. If I had to pay someone to do them for me then I would probably stop flying as the costs for maintenance eat into my 100LL fund.

      “Just man up and upgrade?” Which part of the FAA or GPS company do you work for? Sorry but I just had lunch with four other friends who fly antique tail-draggers for fun. Every one of them are retired professional aviators and when I brought this subject up with them not one of them acted like you do, instead all feeling sorry that this WILL kill gemeral aviation as we know it in America. This may keep the FAA and a lot of GPS companies in business but in 2030 American will be begging for pilots to fly the airplanes because there are none coming up the ranks…

      • I don’t like ADS-B very much, but why is it that every time we don’t like an issue it’s “the end of general aviation as we know it?” Maybe it’s a bad idea, but I doubt that ADS-B will be the death blow.

        I think we’re our own worst enemy sometimes–talking about the end of GA. Not very encouraging for a new person.

        • Chad, you must have a better bank account than I do. My health insurance went up 300%, deductable went from $2500 to $6500 and my taxes have steadily increased the last 5-6 years. Then there is the cost of everything in our daily lives going up not to mention 100LL now costing almost $6.00/gallon.

          How pray tell do you see pilots being able to afford to fly in the next 5-10 years? The $100 hamburger just became the $250 hamburger and its only going higher.

          If you know a way around this please let us know. Costs like this ADS-B that are simply not needed for the average General Aviation pilot are “not very encouraging for a new person” either…

  • The article claims it is only a $4000 investment to have 1090es or UAT to be ADS-B compliant. What the article didn’t cover was that this is only half the equipment cost for most of GA to comply. This is because you will also need a WAAS compliant GPS, which roughly doubles the cost of an installation.

    If you do not already have a WAAS GPS source, and over 85% of us in GA do not, you will have to pony up 3000-4000 extra for a blind receiver plus install. The blind units have yet to obtain a TSO and are a 337 install as far as I can tell. Alternately, a person could pony up the same amount or more to install a WAAS panel mount nav system. This will change and costs will come down somewhat.

    However, the fact remains that the requirement for a WAAS GPS source doubles the cost of an install for most of us.

    These costs come with no benefits to either the pilot or the airspace system for the vast majority of VFR flights or enroute IFR flights. It just does not help anyone to know their position to 18 feet rather than 40 feet for these flights, including for collision avoidance.

    Writing off a hefty chunk of the lower cost GA fleet for ops in mode C veils is an unacceptable mandate when there are no discernible benefits from half of the costs of the mandate for either the FAA or the pilots themselves.

    Dropping the WAAS mandate would go a long ways towards getting the Nextgen mandate into the most cockpits at the lowest cost and highest useful performance. I like the weather and traffic features it offers, even as they will be obsolete by the time the mandate comes to pass.

    • Not true. Garmin recently announced the GDL-84 which is ADS-B out with built in WAAS GPS for $4000. Others including L3, Appareo, and Bendix/King have announced similarly competitive products and the prices are surely to drop. These will also allow you to receive ADS-B In on a portable device.

    • Lee – WAAS is not actually a big cost driver. An independent chip set and a WAAS-cable antenna are all that is necessary to deliver WAAS performance. In non-FAA certified applications, you can even buy a WAAS GPS system with antenna that simply plugs into a laptop or tablet and costs under $40.

      The cost issue is driven by FAA’s continuing refusal to accept portable equipment and the requirement that panel mounted equipment be TSOd. If both of those requirements were relaxed – as is supposed to be the outcome of the FAR Part 23 reform that the FAA is currently stonewalling in violation of Federal law – the cost issue for ADS-B Out compliance would virtually disappear. There is no good reason why a capable installation would consist of nothing but an approved antenna installation, plus a power connection and antenna connection to a portable ADS B Out or Out/In combo device for under $1,000 installed. End of argument.

      But as always the FAA is recalcitrant and in this instance is actually breaking the law by refusing to comply with the Part 23 reform by October 2015.

  • Well! First let me say that a am advocate for ADS-B and disagree with many of the items that are in print today. ADS-B offers a big benefit to ATC but for GA the benefit is huge. In Michigan where I live once you get mid way north of the center of the state the majority of the state is controlled by Minneapolis center and RADAR coverage is only good to about 5000ft MSL and some places only to 7000ft MSL. ADS-B will allow these aircraft to be seen at a significant lower altitude depending on the ground stations. Altitudes as low as 2500ft will display target on the controllers scope. This is a huge benefit for traffic and when flying IFR and waiting to shoot an approach into an airport. Instead of holding at 7000ft waiting for a cancellation from non-RADAR procedures the holding pattern can get down to 3000ft MSL. There are so many examples of this type, once ADS-B is fully implemented.

    There is no place in the FARs that require you to have ADS-B to fly IFR or for flight following. The regulations as written today will just prohibit you from certain airspace if you don’t equip.

    When I checked pricing for an active traffic system to be installed in my aircraft (P32R) the quote was $11,000.00. Well above what I wanted to invest in a 36 year old airplane. I did install a GTX330 at the time for mode S (TIS) traffic however. Then the upgrade was just $2000.00 to be ADS-B compliant, with $800.00 more for a STRATUS II for TIS-B and free weather. I cancelled my XM subscription and it’s paid for itself.

    Yes it is going to cost, and for some it won’t be affordable but that is what sometimes happens to maintain the safest and most efficient system in the world.

    As far as handhelds and precision of accuracy, we must maintain the same accuracy for separation in IFR conditions for all aircraft. Do you want to be flying in the clouds separated by 1000ft with another aircraft that his precision might be +/- 300 ft or more? I don’t.

    As far as staying stayed tuned for L3, they are behind the game and this is causing to many people to delay assuming there will be some significant breakthrough in pricing. I don’t think it will be that much different and waiting won’t help in the long run. Avionics shops are raising there labor rates each year. L3 made there announcement in July at OSH and said they would have more information by September. September as come and gone and no significant information has been announced.

    • Tod – you don’t fly in the clouds based on your ADS-B transmitter output, which you can’t even read inside the cockpit. You fly in the clouds based on altitude readout from a precision barometric altimeter (or multiple altimeters in the high flight levels). The ADS B Out only tells the FAA controllers where the aircraft are.

  • The Garmin solution looks great…but is still at 4500 for in and out capability, plus install. The Bendix solution is the same. Neither solution has an STC. Neither solution will ship until next year. But it is good to see at least some brand new price reductions. Aspen is still hovering around 5500 for in and out.

    The prices are still driven by the WAAS requirement. The differences between the integral WAAS units and the unequipped units are still thousands of dollars apart.

    Bring the costs down to 3k on average, and watch the adoption rate soar in GA.

  • A good article John. I am in agreement with all of your points. The primary ones being; there are benefits for all (not just GA pilots) to be had and the price is not unreasonable.

    I don’t think everyone will be equipped by 2020 and,despite all the scare stories by the FAA and industry, there will not be mass chaos as a result. Eventually though, ADS-B will become completely accepted same as Mode C is today. I could forsee that the Mode C requirement (if you’re UAT out) will eventually go away. Seems to me that it’s primary purpose is to allow current airline “fish finders” to work and provide potential radar backup as the new system proves itself.

    • Stephen

      UAT and 1090ES transmitt the same ADS-B message as defined by FAR 91-227 sec D. All altitude separation is based on the same source, pressure altitude from mode C. FAA only uses pressure altitude for ATC purposes.

      • Yes,but Mode C is just a dumb 1090 transponder hooked to an absolute pressure encoder. That encoder could just as easily feed only a UAT transmitter. I think the problem is that there is still a need for a transponder type device to be triggered by the existing radar system and transmit a radar signature and altitude to TCAS systems and ground scopes. However, if the radar system is eventually decommissioned then the need for a transponder goes away. I don’t know if there is a plan to ever decommission radar completely though; maybe not.

        • Stephen,

          Sorry didn’t mean to post an Anonymous post I used a different computer and it wasn’t filled out. But anyway, the mode C is wired into the UAT transmitter to meet the requirement of the ADS-B message which is to include pressure altitude. If you have a very sophisticated aircraft that has two different mode C encoders and two different transponders than whatever encoder is transmitting your pressure altitude via the transponder then that same encoder has to be transmitting the same pressure altitude via the UAT transmitter. This is so the ATC ADS-B and the RADAR mode C messages are the same. We can’t afford to have two different altitude reports. RADAR will never go away. The FAA had hoped for this until 9/11 happened, now the plan is you will have ADS-B targets and RADAR target fed from multiple sources. The target displayed on the controllers scope will always be the most updated target. That should be a minimum of one second updates, but it could be even less than that. This is sorted of explained in AC20-165A. about the same source of mode C information.

    • Unfortunately, there isn’t even close to enough bandwidth on the 1090es system to handle current traffic needs in existing airspace. This was THE prime motivator to bring the UAT solution online for NextGen so that more targets could move information around.

      In fact, in order to make a bit more room in the 1090es bandwidth, the 1090es specification got rid of even basic error checking. This means the system can suffer a denial of service attack by anyone with some relatively inexpensive equipment, some open source software, and a bad mood. In addition, false targets can be generated and will be presented to a pilot as part of the air-to-air element of the collision avoidance component. The FAA can largely filter out these false targets in the terrestrial broadcast, but the air to air is entirely vulnerable.

  • We need a tax credit for the purchase and installation. Period. If the government needs this so badly they can afford to subsidize our acquisition and installation of it.

  • So the FAA has spent nearly 2 billion? How about the FAA subsidize the transponders. Maybe pay half? What’s another few million dollars. I think everyone would be happy,

  • I have been looking at this for my Cherokee. I think the FAA will eventually have to moderate its position on ADS-B out requirements. As the rules stand in 2020 permantent mounted ADS-B out equipment will be reqiured at class B, C, and D airports, but other than a controller, there is little similarity between a class B and a Class D airport. The FAA should loosen the requirements for Class D and also allow portable ADS-B out equipment for VFR use in class C and Class D airspace. Why? Cost is one point, but versatility is another. VFR operations by nature my tend to avoid the larger Class B airports, but it is unlikely all VFR operations will omit all flights to Class C or Class D airports. Portable ADS-B out equipment for VFR operations means the same unit could be used in different aircraft, so for someone who owns two aircraft, like a small taildragger and a larger plane for XC the cost would be MUCH less, prompting more people to buy ADS-B out equipment sooner. The idea is to get everyone to use it so the traffic information will be of more use. Doesn’t it make sense to do that by making it easier for non power users to get it?

    • William,
      I don’t believe you will see any change in requirements. Traffic is only a benefit of ADS-B, the reason is for “separation of aircraft” through surveillance. This is the reason for the stringent standards. The data from the aircraft must have the same precision tolerance weather it is VFR or IFR to be legally separated. While some portables can be just as precise as a hard wired unit there is data from the aircraft that is needed for the ADS-B message. I don’t think you will see what you are asking for.


        • While the FAA definition states no separations services are provided between VFR aircraft in class D airspace, in reality separation services are provided between IFR aircraft in D airspace. There are times that separation services are provided between an IFR aircraft and a Special VFR, or between two SVFR aircraft in class D airspace. ADS-B can benefit these places that RADAR coverage is not to the ground today. I believe that not enough of the positive benefit has been explained to the public.

          • The way that “separation services” are provided in D airspace is by restricting the airspace to use by one aircraft at a time. You don’t need ADS-B – or even radar – to do that.

            The ADS-B pooch first got screwed when the FAA admitted that it had to maintain radar in parallel with ADS-B. The pooch really got it when MH-370 turned off its transponders. Poof! No target.

            “Surveillance” that relies upon self-reportage is not surveillance at all. It’s self-deceptive wishful thinking. In this case, billions of dollars’ worth.

            The very best implementation of a flawed concept is, by definition, flawed. ADS-B is a crappy implementation of a fatally-flawed concept.

            As I believe that it’s never too late to make a good decision, I recommend that we junk the entire thing, and instead design and build something that will work. That would require three things that don’t exist in abundance in OKC – courage, competence, and leadership.

  • The FAA certainly won’t move if we as pilots and owners don’t ask for it… and we should! Portable equipment can be just as precise if properly designed, but I understand the need for permanent equipment when flying in the soup. The FAA should be open to a softened position especially if it helps equip the overall fleet sooner.

    • William – as I described to the author John n comments above, there is no difference in the precision or accuracy of portable vs. panel mounted equipment. A GPS WAAS position either is available or it isn’t – to either type of device – it is not a signal or output that can be calibrated in any way.

      The end point of the current death spiral in avionics pricing as well as airframe and engine pricing is that eventually, general aviation will simply bifurcate into the worlds of commercial aviation and experimental aviation – certified non-commercial general aviation equipment as we know it now is unsustainable, and must eventually disappear. And safety will, and rather perversely so, be hurt as a result of FAA’s insistence on rigid concepts of “safe flying” no matter the cost.

  • So if I install ADS-B Out & In, why do I have to retain the Mode A/C transponder?

    Shouldn’t the FAA allow ADS-B Out as a substitute for the transponder, allowing me to replace my aging transponder with an ADS-B?

    • Because the FAA still needs to be able to use its existing radar network to interrogate your transponder. It needs that old reliable belt because its expensive new suspenders are completely unreliable.

  • Tom Yarsley, Separation in class D can be provided by the one in and one out method but that is the inefficient method and costly to the aircraft owner in respect to wait time and fuel burn. With a surveillance system RADAR or ADS-B ( yes ADS-B is not required in D airspace) than we can separate arrival aircraft by 3 miles laterally on final (sometimes 2 /12 under certain circumstances). The one in one out would require the arrival to be spaced 5 miles between arrivals.

    With an arrival and a departure the one in one out method would require the departure to wait for arrival to land and turn off before he could depart, which would require a two to three minute delay, that is based on 120kt final, and assuming that there is not another arrival 5 miles in trail, which means the aircraft waiting for departure would have to wait longer. With surveillance we can launch that departure with 2 miles of separation as long as it will increase 3 miles within one minute after departure. This is a much more efficient way then one in one out.

    As far as your comment about MH-370 this not the reason for the dual system this is more because of 9/11. The dual system was designed and proposed before MH-370 even happened.

    • They sold us ADS-B with assurances that it would be paid for partly with the retirement of ATC radar. Their excuse for the belt-and-suspenders system that we’re being saddled with was 9-11. Truth is, there’s simply no surveillance in ADS-B, or any other self-reporting system. If you absolutely need to know where the targets are, you need to have a military-defense-grade radar system that is not dependent upon in-vehicle hardware. Post 9-11, we could have – and should have – gone in that direction. I highlighted MH-370 because that’s the event that made it obvious to the average Joe that the entire paradigm was undermined by one little switch.

      Any field with enough traffic to warrant all-day 2- 1/2 -mile separation of IFR traffic already gets class C treatment. That’s a 48-count level-of-activity. At that field, taxiway issues are more challenging.

  • I think the solution to accept uncertified equipment for WAAS or ADS-B Out is problematic to say the least. However what must be done is to radically simplify FAA certification rules for equipment that has nothing to do with VOR/NDB/ILS/COMM frequencies.
    The FAA has been given free reign to increase regulatory certification complexity in a knee jerk reaction mode to every accident and perceived problem with Aviation. The rules must be redesigned to force the FAA to limit certification costs that force certified equipment to be so damn expensive. If FAA cert costs were US$ 50k instead of several million and handheld equipment could be design to have a semi permanent install option, this could drive Garmin and gang to certify all of their aviation handhelds allowing for all of that to be used for WAAS/ADS-B Out.
    But then there is the big problem to that, the same Garmin that makes handhelds also have hundreds of millions invested on current certified equipment, and a major overhaul of certified equipment costs would create major competition from new low certification cost entrants. It would cannibalize many of its product lines.
    It is a complex subject.
    I believe this is what the Tea Party should really be about. Not destroying govt but forcing every branch of govt to reform itself. I have been a study of the nuclear industry for a while and I see that the NRC is doing everything the FAA did to the aviation industry to the nuclear industry TIMES 10. So has the EPA, and the FDA, the list goes on.
    Let’s stop attacking the consequence, but rather the cause.
    The reality is most of us don’t want to admit the importance of govt, don’t want to get involved, don’t want to spend time on this. The reality is we all must.
    Sorry for the harsh words.

    • Another relevant comments…
      WAAS accuracy is very different from altimeter accuracy.
      WAAS/GPS accuracy comes with a percentage of certainty.
      98% of time WAAS will be accurate to 0.5 meter lateral and vertical.
      99.9% of time WAAS will be accurate to 10 meter vertical and 5 meter lateral.
      WAAS has been measure to err over 10 meter vertical in some extreme cases.
      But this will improve radically when the FAA unveils dual frequency WAAS receivers. Today the largest error source for WAAS is iono errors, because those must be calculated using data received from WAAS signal. With L5 capable receivers iono errors will be calculated directly by WAAS receivers using L1 and L5.
      This could make LPV CAT II possible for light aircraft.
      This would make LPV approaches possible a thousands of miles away from a reference station (central america and south america).
      I just hope the FAA doesn’t find a reason for force users to upgrade to those dual frequency receivers. As higher end users upgrade to dual frequency receivers a market for cheap single frequency used WAAS FMS should open up.

  • My problem is not with ads-b out, it is with in. I recently flew with a guy that was equipped and vowed never to own or fly any plane with ADS-b in ever again. It is a total cockpit distraction, not to mention the PIC felt that the technology made it possible to never look for trafic again. I am building a home built and am forced by location to only have access to controled airspace, so I do feel like the mandate is overkill. But like all government programs (I work as a contraction in DOD) there is no rime or reason for it other than we need to spend the funds.

  • I bought a Trig TT22 Mode S transponder and consequently spent some time perusing the Installation Manual

    The chapter on Configuration has parameters for stuff such as wingspan, fuselage length and location of antenna on the Airframe. WAAS accuracy can eventually ensure wingtips will not crunch on adjacent taxiways or aprons at major airports. Note that 1: GA aircraft are rarely present on the taxiways and aprons where the big guys are 2: they’re so small that WAAS accuracy doesn’t matter on the ground.

    Your average airline passenger’s big concern is not colliding in the air. 50m accuracy is absolutely plenty for airline equipment to detect an ADS-B target in the air from miles away and take avoiding action.

    As a glider pilot with PowerFLARM, I regularly pick up ADS-B airline traffic from several miles away.

    If the FAA allowed, I could cable my PowerFLARM GPS (good enough to separate gliders in the same thermal) to my Trig transponder and make myself visible to the airliners from several miles away for under $5 in parts and maybe $20 for the DSUB insertion tool.

    Beginning January, UK NATS is running a GA ADS-B trial in Southern England with non-WAAS GPS units.

  • The most common complaint about the ADS-B OUT mandate seems to be that it provides ZERO benefits to the aircraft owner. This overlooks the enormous benefit of having ATC and other aircraft know your precise position, speed, track, and altitude so THEY can avoid you or vector other aircraft around you. That seems similar to driving an automobile in reduced visibility daylight conditions with your headlights on. It doesn’t help YOU to see any better, but makes you more visible to other traffic and thereby provides an increased margin of safety for everyone.

    • Lindsey,

      I totally agree with you but there is even more, there is a misconception that we have complete RADAR coverage though out the US all the way to the ground, we don’t. In my state of Michigan when you fly in the northern part RADAR coverage is only good to about 5000msl and a few areas to 7000msl. This causes holding when you have cloud decks at 2000agl. The holding for the approach can be eliminated once ADS-B is fully implemented and ATC will be able to vector aircraft down to about 2500msl well below the cloud decks. There are other benefits that will help ATC eliminate delays but the general aviation just hasn’t been educated on how this can save time and fuel for the average pilot.

  • I am a retired pilot that flies a vintage aircraft that does not have an engine driven electric system. Therefore I am not required to have ADS-B out for my typical flying outside of ABC airspace. I fly with my iPad and can monitor ADS-B in information. If ADS-B out equipment were to become affordable for me, I would like to have it as a safety feature for others to be able to see me. Recently I have seen a number of different relatively inexpensive systems being offered for experimental aircraft but not permitted for certificated aircraft such as mine. I would like to better understand the logic behind why these systems are considered suitable for experimental aircraft but not for certificated aircraft.

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