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> Air traffic controllers have primary radar and secondary radar in addition to ADS-B information. No they don't. Most secondary (surveillance) radar in the U

> Air traffic controllers have primary radar and secondary radar in addition to ADS-B information. No they don't. Most secondary (surveillance) radar in the US has been shut down already. The FAA has been busy shutting down basically anything that requires maintenance, and LORAN is gone too. I believe the whole point of ADS-B out was to shut down basically the rest. Source: commercially-rated pilot.

korethr 7y ago
So then if everything goes to ADS-B and GPS, doesn't that create a potential single-point-of-failure scenario, as isn't the data that ADS-B sends out itself derived from GPS? Having all navigation information come from a single source strikes me as about a good idea as the single AoA sensor on the 737MAX. I'd like to be wrong about this, but I'm not sure how I am. How am I potentially wrong about this?
- redis_mlc 7y ago
  You're correct. That's the direction the FAA is headed. It doesn't have to make sense.
wrycoder 7y ago
If you shut it all down and something catastrophic somehow goes wrong with GPS, it will be very difficult to get the thousands of planes in the air back onto runways.
- cbanek 7y ago
  Are they also getting rid of VOR for navigation? https://en.wikipedia.org/wiki/VHF_omnidirectional_range https://en.wikipedia.org/wiki/VHF_omnidirectional_range (Sorry, paywall is blocking me)
  - boarnoah 7y ago
    Not too familiar with aviation or IFR. Isn't VOR primarily a beacon that you use to orient yourself, doesn't seem like it helps the ATC maintain separation etc..
    - sokoloff 7y ago
      IFR separation does not have to depend on radar. Though radar procedures are the norm, there are non-radar procedures wherein ATC can issue instructions (clearances) that provide separation for airplanes who are all navigating themselves with respect to ground-based or satellite fixes. In that regard, VORs help ATC maintain separation.
    - redis_mlc 7y ago
      VOR is used for many things, including navigation, holding and locator beacons. I suspect VORs will be kept for airport locations and en route instructions, but most others will be shut down in favor of GPS.
  - tjohns 7y ago
    VOR navigation is very much still a thing. They've been reducing the number of redundant ground stations lately as part of a project called "Minimum Operational Network", or "MON". (Mostly on affecting the east coast.) But they're explicitly making sure there's enough coverage that you can get a VOR signal anywhere above 5,000 feet AGL. More info: https://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/transition_programs/vormon/ https://www.faa.gov/about/office_org/headquarters_offices/at...
tjohns 7y ago
Do you have any citations from the FAA for that? Given that then ADS-B mandate was just a couple weeks ago, it seems logistically odd that secondary radar would already be turned off. More generally, my understanding was that the FAA was keeping primary+secondary radar around to augment ADS-B via sensor fusion. I know the "reply" light on my plane's radar transponder still lights up regularly, so at least out here on the west coast the secondary radar is still active. :) I've also heard there's a longer-term plan to consolidate ATC radar into the NOAA weather radar stations, once they upgrade weather radar to phased-arrays at some unknown point in the future. The marginal cost to keep secondary radar running in that environment is basically zero. That said, they have certainly been turning down many of the redundant VOR stations as part of MON, and they just turned HIWAS off last week. I don't think anyone really misses LORAN, though. ;)
sokoloff 7y ago
Secondary radar is very much alive in the US. Forget to turn on your transponder (whether or not you are ADS-B out equipped) and how long until ATC notices? For me, it's usually been before I'm through 400' AGL. Or, as tjohns mentions, just look at how often your reply light flashes. From the FAA itself: "The Mode S SLEP Phase 2 program will implement modifications to the Mode S system to sustain secondary surveillance service through 2028." 0 - https://www.faa.gov/air_traffic/publications/cip/files/FY16-20/FY16-20_CIP_Intro_Jan_2016.pdf https://www.faa.gov/air_traffic/publications/cip/files/FY16-...
touisteur 7y ago
Err... The FAA is replacing all their secondary Mode S radars with... secondary Mode S radars with ADS-B capability. That's probably gonna last at least 20 years, once installed. Maybe you're thinking of old-school SSR radars ?

korethr 7y ago

So then if everything goes to ADS-B and GPS, doesn't that create a potential single-point-of-failure scenario, as isn't the data that ADS-B sends out itself derived from GPS? Having all navigation information come from a single source strikes me as about a good idea as the single AoA sensor on the 737MAX. I'd like to be wrong about this, but I'm not sure how I am. How am I potentially wrong about this?

redis_mlc 7y ago
You're correct. That's the direction the FAA is headed. It doesn't have to make sense.

wrycoder 7y ago

If you shut it all down and something catastrophic somehow goes wrong with GPS, it will be very difficult to get the thousands of planes in the air back onto runways.

cbanek 7y ago
Are they also getting rid of VOR for navigation? https://en.wikipedia.org/wiki/VHF_omnidirectional_range https://en.wikipedia.org/wiki/VHF_omnidirectional_range (Sorry, paywall is blocking me)
- boarnoah 7y ago
  Not too familiar with aviation or IFR. Isn't VOR primarily a beacon that you use to orient yourself, doesn't seem like it helps the ATC maintain separation etc..
  - sokoloff 7y ago
    IFR separation does not have to depend on radar. Though radar procedures are the norm, there are non-radar procedures wherein ATC can issue instructions (clearances) that provide separation for airplanes who are all navigating themselves with respect to ground-based or satellite fixes. In that regard, VORs help ATC maintain separation.
  - redis_mlc 7y ago
    VOR is used for many things, including navigation, holding and locator beacons. I suspect VORs will be kept for airport locations and en route instructions, but most others will be shut down in favor of GPS.
- tjohns 7y ago
  VOR navigation is very much still a thing. They've been reducing the number of redundant ground stations lately as part of a project called "Minimum Operational Network", or "MON". (Mostly on affecting the east coast.) But they're explicitly making sure there's enough coverage that you can get a VOR signal anywhere above 5,000 feet AGL. More info: https://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/transition_programs/vormon/ https://www.faa.gov/about/office_org/headquarters_offices/at...

tjohns 7y ago

Do you have any citations from the FAA for that? Given that then ADS-B mandate was just a couple weeks ago, it seems logistically odd that secondary radar would already be turned off. More generally, my understanding was that the FAA was keeping primary+secondary radar around to augment ADS-B via sensor fusion. I know the "reply" light on my plane's radar transponder still lights up regularly, so at least out here on the west coast the secondary radar is still active. :) I've also heard there's a longer-term plan to consolidate ATC radar into the NOAA weather radar stations, once they upgrade weather radar to phased-arrays at some unknown point in the future. The marginal cost to keep secondary radar running in that environment is basically zero. That said, they have certainly been turning down many of the redundant VOR stations as part of MON, and they just turned HIWAS off last week. I don't think anyone really misses LORAN, though. ;)

sokoloff 7y ago

Secondary radar is very much alive in the US. Forget to turn on your transponder (whether or not you are ADS-B out equipped) and how long until ATC notices? For me, it's usually been before I'm through 400' AGL. Or, as tjohns mentions, just look at how often your reply light flashes. From the FAA itself: "The Mode S SLEP Phase 2 program will implement modifications to the Mode S system to sustain secondary surveillance service through 2028." 0 - https://www.faa.gov/air_traffic/publications/cip/files/FY16-20/FY16-20_CIP_Intro_Jan_2016.pdf https://www.faa.gov/air_traffic/publications/cip/files/FY16-...

touisteur 7y ago

Err... The FAA is replacing all their secondary Mode S radars with... secondary Mode S radars with ADS-B capability. That's probably gonna last at least 20 years, once installed. Maybe you're thinking of old-school SSR radars ?