back to article US in move towards GPS-based air traffic control

The US aviation regulator has selected ITT Corp to provide a new generation of GPS satnav-based air traffic control equipment, awarding a $207m, three-year initial contract. Current air traffic control systems worldwide use radar to detect and track aircraft: either "primary," in which radio pulses from the radar reflect back …


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  1. Anonymous Coward
    Anonymous Coward

    Another waste of Taxpayer money!

    Does anybody believe that ITT and 15 sub-contractors will be able accomplish the task of producing an air traffic control system without the prerequisite finger pointing, "milking the cow", etc, etc? Forget about "Ontime delivery" or "Within Budget", I can't even guess if such a system would ever WORK with so many cooks in the kitchen.

    And what is this crap about getting rid of the existing radar system...anyone ever hear the platitude "Don't put all your eggs in one basket"? (Especially when the basket is being provided by government contractors?) Never mind Chinese antisatellite missles, ever hear of sunspot interference or have you tried to get satellite TV working in a blinding rainstorm, let alone a Buffalo, NY snowstorm!!!!

    I assume the system will be running on M$ Windoze... "Excuse me ladies and gentlemen, there will be a slight decrease in altitude while I try to re-boot the guidance system server...looks like one of you brought in a virus when you connected your laptop to our new in-flight wireless internet service." (In the background you hear, "What do you mean you can't remember the user name and password!!")

    My suggestion: completely parallel systems, no rollover to new GPS systems until they have been in place, operating for 5 years with 99.99999% uptime and equal or better accuracy. Require 20% retention bond, satisfied only when uptime and accuracy goals are accomplished.

    Fix the existing radar system FIRST, all it needs are new electronics that aren't based on Vacuum Tubes and new computers that use post 2000 A.D. technology. Put in a contract clause that says that all microprocessor based electronic parts MUST be readiliy available for a minimum of 50 years.

    Oh and order a few dozen spare GPS satellites (and boosters) so the system can be fixed in the future. Never know when you might find a few "chinks in the armor".

    And one last thing, buy stock in the Railroads and Ocean liners.

  2. Orv

    Other security issues with the old system

    There are other security issues with the old system besides setting the wrong code. For example, one criticism I've seen leveled at ADS-B is the idea that someone could spoof the location data to make an aircraft appear to be somewhere it isn't. But the current system trusts the altitude reported by the aircraft's on-board altimeter, which in most light aircraft can be set to any value at the twist of a knob.

    I'm sure radar will be retained as a backup system for the foreseeable future. It could still be vital in some emergency situations -- for example, in the event of a on-board electrical system failure.

  3. foof

    What about small aircraft?

    Try telling the owner of a old Piper Cub with no radio that he has to outfit his antique with full GPS so a tower can see him.

    @ Orv

    The altitude reported buy the transponder is usually taken from an altitude encoder, not the altimeter. An encoder isn't adjustable and has a fixed pressure setting ensuring all aircraft operate with the same inaccuracy.

  4. Robert Baskerville

    Which centuary is this?

    Get with the programme.... Go take a look at Fylingdales, where the golfballs (which contained the yee olde anciente spinning radar technology) are being removed. For many years there, a large and impressive static pyramid has replaced these functions using phased array radar technology. No moving parts, electronically "steered". You can track and scan at the same time, scan fast, scan slow, track multiple targets at once.

    Far more accurate than GPS...

  5. Anonymous Coward
    Anonymous Coward

    It's a long road to progress and it has speed bumps and pot holes..

    This idea has potential as it could see the end of the ludicrous bottlenecks from airways, STARS and SIDS.

    The long overdue depature from 1940's phase comparison analogue systems of ILS and VOR could free aircraft movements and improve safety.

    It is true that airports are overworked and aircraft are squeezed into too little sky but the problem is due to a lack of available land to build runways.

    In reply to the earlier post from Orv, Mode C altitude reporting is based on a 1013.2 millibar reference pressure and cannot be influenced by turning any knobs.

    Forgetting to put the transponder to standby before changing code could indeed lead to the spoiling of one's day.

  6. Greem


    "Under ADS-B, each plane is fitted with GPS satellite navigation, and thus knows its own location precisely."

    *Thinks* it knows its own location. Just like they do now, in fact. Those darned altimeters are too easy to baffle - look at how many airprox reports and actual crashes have happened because some technician or other forgot to remove a piece of gaffer tape from the static port on a pitot assembly.

    So it'll be OK, we can pinpoint the aircraft to five metres of lat/long, but we won't have a damned clue how high they are unless someone's made GPS work *really* accurately in that third dimension...

  7. Mike Stephens


    I think you'll find transponders use their own altimeters set to 1013Mb. ATC see a corrected figure.

  8. b shubin

    System failure

    whether located by GPS or radar, an onboard electrical systems failure that takes out the fly-by-wire mechanisms in Airbus birds (Boeing is probably much the same) will quickly result in a crater and giblets.

    when the hydraulic control systems for altitude go, the plane is going down.

    maybe if they make the GPS durable like the black box, and put a communicator in it (maybe male it buoyant, too), the rescue operation would be able to find survivors more easily and quickly.

  9. Charles Manning

    What about UFOs?

    Will the message be sent out to the whole universe?

  10. Anonymous Coward
    Anonymous Coward

    Not a complete waste

    To the first poster: Chill out - it's not that bad. There's enough valid criticism that can be leveled against ADS-B without need for ranting like that. ADS-B also has a lot going for it (such as real-time weather data uplinks) . The article was a little weak on details, but you can find all you want here:

    ADS-B itself doesn't rely on GPS per se, it merely receives position and velocity data from airplanes. A lot of small aircraft will get that data solely from GPS, but most airliners have a very complex navigation system that takes input from a variety of sources: internal inertial sensors, ground-based radio beacons and GPS. In that case, complete loss of GPS would degrade the accuracy a bit, but probably wouldn't be that noticeable.

    I don't think anyone is discussing getting rid of the existing radar system. ADS-B is supposed to supplement it. Its main purpose is to transmit data directly to aircraft. For example, right now, a pilot has to listen to the radio for verbal warnings from a controller. With ADS-B, that same pilot can have a graphical display showing all the nearby traffic.

    As for your other concerns: Don't worry about Windows; it can't be used on safety-critical computers (in flight or on the ground). Look up the DO-178 spec sometime to see what you have to go through to get software approved by the FAA. (Compliance with that spec is, in fact, one of the reasons aerospace software is so expensive.)

    On the issue of snowstorms: First, half your problem with satellite TV is the cheap mount for the dish that is flexing in the wind. The other half is signal degradation. Secondly if you're in a storm bad enough to degrade a ground-based signal (which ADS-B is), you're already screwed. Very few airplanes are certified for flight into known icing conditions. (Airliners are, but even they require the services of a de-ice truck before takeoff into a snowstorm.) In a bad snowstorm, you're going to be accumulating ice on your wings and control surfaces fast enough that you've probably got less than a minute before you transition from "pilot of an airplane" to "passenger in a ballistic object heading down fast".

    I have some concerns about the cost and the possibility of rouge transmitters spewing all kinds of garbage, but mostly I dislike how long it will take to build out enough of the system to make it really useful.

    BTW Orv: The knob on altimeters compensates for changes in air pressure due to weather (an altimeter is just a very sensitive barometer that's been calibrated in feet above mean sea level). The altitude data that is sent to transponders is pressure altitude and doesn't have this compensation. ie: twiddling the knob on the altimeter doesn't affect the data sent to the transponder. That said, it is trivially easy to spoof your altitude: the data is a 9 bit Gray code and you can use the parallel port on a PC to send it.

  11. Anonymous Coward
    Anonymous Coward

    @ Foof

    If you want to take a Piper Cub (or any other airplane) into controlled airspace, it currently must have a radio and transponder. A GPS receiver isn't particularly expensive, though an ADS-B capable transponder probably will be for the foreseeable future. It's true that adding to the list of required equipment will result in grumbling from some pilots, but our hypothetical Cub is already pretty restricted in where it can fly. Now, if the FAA decides to make ADS-B transponders mandatory for any flight anywhere in the country (my understanding is that most of Europe is covered by a similar rule), then there certainly will be an uproar from a lot of folks.

  12. Anonymous Coward
    Anonymous Coward

    Rogue vs. Rouge

    Correction: That should have been *ROGUE* transmitters. We'll save the cosmetics discussion for a later time...:)

  13. Orv

    @foof - Thanks

    Thanks for the correction. My ignorance probably stems from the fact that I never flew anything with an electrical system or a radio, much less a transponder. ;)

  14. Eugene Goodrich

    99.99999% uptime for 5 years is 26 minutes allowable downtime.

    Unless my math is wrong, that's a bit strong of a requirement, isn't it?

  15. John Stag


    Could this be spoofed by "terrorists"? What if I send out a signal saying I'm somewhere else?

  16. Paul R

    re: 99.99999% uptime for 5 years is 26 minutes allowable downtime

    Actually, it's more like 15 seconds.

    365 * 5 * 24 * 60 = 2,628,000 minutes

    2,628,000 * 0.0000001 = 0.2628 i.e. just over a 1/4 of a minute.

    That's one hell of a requirement.

  17. fixit_f

    I don't like the sound of it.

    In the maritime world it's best practice that in addition to GPS you plot your position on a chart using old fashioned navigation techniques, and tools such as a protractor and ruler. This is so that if your GPS fails you still have a fair idea of where you are and can continue to monitor your own position. In the aviation world (where you add the extra dimension of altitude) it seems a bit daft for air traffic control to deliberately phase out their backup system. Anyone that has owned a GPS knows that sometimes they are occasionally downright wrong to the point where people like polar explorers or cartographers carry three - two are permanently switched on, and when they give a differing result the third is switched on to establish which one is right!

  18. Joe Harrison

    Rouge transponders

    I've often wondered about the brain mechanism that tricks otherwise stellar spellers into words like rouge and flourescent. There is something here that goes well beyond a mere typo opportunity.

  19. Dave Driver


    Well we've already got mandatory Mode-S transponders coming very soon for all aircraft (incl. gliders and balloons) in controlled and uncontrolled airspace, despite the fact that there's hardly a radar station in the UK that can read them. What difference does one more bit of mandatory kit make?

    Private flying will very soon be beyond all but the very rich.

  20. Karl Lattimer

    does this mean...

    That planes will start going the wrong way down one way streets, and ending up in rivers where there used to be bridges?

  21. Ken Hagan Gold badge

    A great idea

    If every civil aircraft becomes dependent on the availability of GPS, then the US would be committed to spending whatever it takes to keep their system available to all concerned. The last remaining justification for Galileo just went out of the window and the European taxpayer just saved a few squillion euros. (Perhaps they could toss a few across the pond as a thank you to the US taxpayers.)

  22. SImon Hobson Silver badge

    Just for the record ...

    Mode-S is already a requirement over here in the UK - either as in "had to have several years ago" or "will have to have very soon" depending on what the aircratf is used for and where it is flown. The difference is ...

    ... in the US they actually use the capabilities of Mode-S to provide a benefit for pilots - someone has already mentioned weather data uploads etc. As a result, I gather that even though it's not a requirement there is a queue at teh avionics shops to have it installed. Over here they aren't going to do any of that, so it's a big outlay to equip a plane, for next to no benefit to anyone. Light aircraft aren't going to get anything useful like weather data, or even data on other aircraft - just nothing.

    <rant>Basically it's all to make the controlled (and in many cases effectively closed) airspace more efficient for the big commercial stuff whos operators then complain that they are subsidising GA (General Aviation).

    Interesting concept of "subsidy" isn't it - get lots of other people to spend money on equipment from which they will gain little or no benefit so that you can enjoy better use of the airspace that the little guys are kept out of anyway !</rant>

  23. Anonymous Coward
    Anonymous Coward

    ATC roulette.

    As a now voluntarily inactive commercial pilot with over 16,500 hours part 121 & part 135 turbine aircraft time, I gave up dodging the Cessna flack.

    My suggestion! time take the Train!

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