How do class D tower controller separate VFR traffic without radar?

Discussion in 'Change to my Frequency...' started by aeronav, Aug 1, 2020.

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  1. aeronav

    aeronav Pre-Flight

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    I've been trying to understand how this works, I know that some class D airports have radar, others don't, for those who don't have it, the only thing I can think of is looking through binoculars but that sounds like a long shot.
    In some D airports I land at (VFR) which I am fairly sure don't have radar, they usually are able to tell how far I am on final, as well as reporting position of other traffic in the pattern, how is that possible without radar?
     
  2. Brad Z

    Brad Z Final Approach

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    Eyeballs and situational awareness, mostly. Even towers that have a Brite radar feed only use it for situational awareness, not actual vectoring or separation.
     
  3. aeronav

    aeronav Pre-Flight

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    I remember one day me and the instructor were maybe more than 10 miles out and the tower asked us to do a 360 to avoid other traffic, I was thinking how is that possible with just binoculars, but, I haven't looked through one or been in a control tower before, I don't know.
     
  4. iamtheari

    iamtheari Pattern Altitude

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    Q: How do class D tower controllers separate VFR traffic?
    A: They don't. AIM 3-2-5(e): "Separation for VFR Aircraft. No separation services are provided to VFR aircraft."

    That said, they do try to help pilots avoid mid-air collisions using any tools they have available, including eyeballs, binoculars, radio calls, and sometimes radar. But whatever they are doing at any particular airport on any particular day, don't assume it is separation.
     
  5. dmspilot

    dmspilot En-Route

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    3-2-5. Class D Airspace.
    e. No separation services are provided to VFR aircraft.
     
  6. aeronav

    aeronav Pre-Flight

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    Yes, obviously separation is not provided for VFR (unless on flight following), but the traffic flow in the pattern, actually in the entire class D airspace is controlled by the tower, I guess that is some kind of separation, maybe not in the sense providing vectors, but still.
     
  7. kath

    kath Cleared for Takeoff

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    Binoculars.
    Asking pilots where they are.
    (Both time-honored techniques!)

    I once came into a Tower without radar, where there wasn't any traffic. The controller said, "I don't have you in sight. Cleared to land."

    I once visited a Tower where not only did the Tower controller not have radar, but the Approach controller was there too and didn't have radar either! Twin Falls, ID. One of only two Approach's in the country that work that way, they told me. They were separating IFR traffic using position reporting and altitude and procedure. I was really impressed.
     
  8. aeronav

    aeronav Pre-Flight

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    That is a frightening thought while flying in IMC.
     
  9. Brad Z

    Brad Z Final Approach

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    Every time you fly across the Atlantic or Pacidic they’re doing exactly that.

    The whole IFR system is designed around falling back to position reporting and altitude for separation. At any time if the controller should loose radar he or she should be able to continue to be able to separate IFR traffic.
     
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  10. luvflyin

    luvflyin Final Approach

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    And many places in the US. There are still two Non Radar Approach Towers in the US, Twin Falls Idaho and Helena Montana. And many other places where a Radar ATC facility doesn’t have Radar coverage to the ground and must apply Non Radar Separation. Reference any of the many threads here about hanging out in holding, waiting for the guy ahead of you to cancel.
     
    Last edited: Aug 2, 2020 at 2:01 PM
  11. Pugs

    Pugs Pre-takeoff checklist

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    Local Class D I fly out of doesn't have radar and as other said it's eyeballs and radio calls and there "might" be a iPad or two and a Stratus with FF and ADSB on it. Really a shame as it's busy enough to justify at least a radar repeater.
     
  12. Timbeck2

    Timbeck2 Final Approach

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    This is why radar controllers are trained in "non-radar" procedures which is altitude, heading, speed and position reports from pilots. Radar facilities lose radar, that spinning thing needs it's motor changed every now and then and things just break. It happens.
     
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  13. iamtheari

    iamtheari Pattern Altitude

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    That is why flying in IMC in controlled airspace always requires a clearance. Pilots flying IFR without radar service are required to make position reports. ATC knows all the planes that have clearances. Those two pieces of information are enough to provide separation services. If you have a Cessna coming up on Lubbock and the Piper in front of him on the airway hasn't reported Amarillo yet, you can just tell the Cessna to hold at Lubbock for a while.
     
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  14. N1120A

    N1120A Pattern Altitude

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    Many places in the world don't have radar for IFR separation. We're just not used to that in the US, where radar service is basically constant - especially when IFR. I've had L.A. Center lose me on radar when VFR and I have an IFR style position report till they picked me up
     
  15. Arnold

    Arnold Line Up and Wait

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    I was not aware that VFR flights receiving "flight following" were afforded separation services. Please, tell me more.
     
  16. aeronav

    aeronav Pre-Flight

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    I can't, unless you can tell me whats the difference between radar service and traffic separation?
     
  17. Arnold

    Arnold Line Up and Wait

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    I quoted you.
     
  18. aeronav

    aeronav Pre-Flight

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    Yea, when i am told turn heading xxx to avoid parachute activity, or traffic 10 o'clock 2 miles westbound, i take this as an effort to separate me from other traffic. Correct me if I am wrong though, i'm a newer and less experienced PP than you are, and we're here to learn.
     
    Last edited: Aug 2, 2020 at 12:28 PM
  19. flyingron

    flyingron Touchdown! Greaser!

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    A traffic advisory is NOT separation.
     
  20. kath

    kath Cleared for Takeoff

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    The discussion here is a pedantic one about language.

    When on FF and the controller tells you this, it's a service he or she is providing because their workload permits it, and they feel like being helpful. It's not required of them; if they're too busy, they might not make those calls. Because you're VFR, they know that you can see, can avoid clouds and other planes. The responsibility is still yours, even if getting this service from ATC. Same as at a towered airport: the Tower controller will likely give you helpful callouts, but ultimately, you and your eyeballs do the work.

    IFR aircraft, on the other hand, do not have the eyeball option, and so they are depending on the controller to keep them from collisions. The controller does not have the option of just saying, "oh, that plane'll be fine."

    So "Traffic separation" refers to the IFR thing that controllers *must* do. "Traffic advisories" or "radar services" are the optional service controllers provide for VFR aircraft.


    Edit: you'll also find "traffic separation" (including for VFR's) in a Class B airspace. Which is why the cloud separation requirements are less in there.
     
  21. aeronav

    aeronav Pre-Flight

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    It makes sense, I know all of this except the sticking point is/or was for me that since I am on their radar screen with a squawk code that i would receive instructions for avoiding collision, not just to advise me of where traffic is, it makes sense that they won't always provide with with information even when have an assign squawk since I am also responsible for keeping an eye on things.
     
  22. kkoran

    kkoran Cleared for Takeoff

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    Actually, it's Twin Falls, Idaho and Helena, Montana. Spokane provides approach control service at Missoula.
     
  23. Larry in TN

    Larry in TN Pattern Altitude

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    As others have already said, ATC Towers don't provide airborne separation services to VFR aircraft. What they do provide is SEQUENCING to the runway and RUNWAY separation. RUNWAY separation is the reason why clearances are required to taxi, takeoff, or land at a towered airport.

    Towers without a radar display rely on pilot position reports and visual observations. Take the time to visit your local tower for an hour, or so. They'll show you how it is done. AIM 4-1-6 discusses pilot visits to ATC facilities.

    The majority of the Earth's service is non-radar. IFR procedures were developed without any dependence on radar using airways, fixes, and position reporting. Radar allows for reduces separation standards, random routings, and vectors which greatly increases system capacity.

    AIM 5-3-2 covers position reporting, 5-3-3 is additional reports, 5-3-4 is airways and route systems, and it continues through the end of Section 5-3. Those sections describe the en-route procedures upon which non-radar separation are based.

    Start with AIM 4-1-18 Terminal Radar Services for VFR Aircraft.

    When separation services are provided, ATC issues clearances which provide for the applicable minimum separation distance. This comes in the form of routing, altitude, speed, or heading assignments. When ATC is providing advisory service they are not issuing clearances nor attempting to maintain a specific minimum distance of separation.

    From the P/CG:

    RADAR FLIGHT FOLLOWING− The observation of the progress of radar identified aircraft, whose primary navigation is being provided by the pilot, wherein the controller retains and correlates the aircraft identity with the appropriate target or target symbol displayed on the radar scope.

    RADAR SERVICE− A term which encompasses one or more of the following services based on the use of
    radar which can be provided by a controller to a pilot of a radar identified aircraft.

    a. Radar Monitoring− The radar flight-following of aircraft, whose primary navigation is being
    performed by the pilot, to observe and note deviations from its authorized flight path, airway, or route.
    When being applied specifically to radar monitoring of instrument approaches; i.e., with precision
    approach radar (PAR) or radar monitoring of simultaneous ILS/MLS approaches, it includes
    advice and instructions whenever an aircraft nears or exceeds the prescribed PAR safety limit or
    simultaneous ILS/MLS no transgression zone.
    (See ADDITIONAL SERVICES.)
    (See TRAFFIC ADVISORIES.)
    b. Radar Navigational Guidance− Vectoring aircraft to provide course guidance.
    c. Radar Separation− Radar spacing of aircraft in accordance with established minima.

    RADAR TRAFFIC ADVISORIES− Advisories issued to alert pilots to known or observed radar traffic which may affect the intended route of flight of their aircraft.
    (See TRAFFIC ADVISORIES.)

    SEPARATION− In air traffic control, the spacing of aircraft to achieve their safe and orderly movement in flight and while landing and taking off.
    (See SEPARATION MINIMA.)
    (See ICAO term SEPARATION.)

    SEPARATION MINIMA− The minimum longitudinal, lateral, or vertical distances by which aircraft are spaced through the application of air traffic control procedures.
    (See SEPARATION.)

     
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  24. aeronav

    aeronav Pre-Flight

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    Sounds like a nice experience to look at in the future.
     
  25. wayne

    wayne Pattern Altitude

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    Works great until one of those nuts using Track Up on their GPS display doesn't realize where they are. :eek:

    ;) :D

    Flying into RYY, which does have a radar feed from the nearby Dobbins Air Reserve Base, I've heard people reporting their location wrong. Took one guy three tries to get it right. The tower had everyone hold off and give him some space. I was on final, so I got on the ground before he came in from wherever he really was.
     
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  26. Velocity173

    Velocity173 Touchdown! Greaser!

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    A lot of pilots use “flight following” as a generic meaning for anytime a VFR is in comms with a radar facility and receiving radar services. Technically flight following just means traffic advisories but in reality, they’re providing much more. Getting flight following from a facility that is authorized to provide radar service could consist of VFR separation if in a TRSA, Class C service area or Class B airspace. But, basic radar services in Class E or G there is no prescribed separation for aircraft other than conducting a practice instrument approach at SOME airports. Be advised though that just because there is no prescribed separation doesn’t mean the controller doesn’t have the authority to vector you to avoid a collision.
     
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  27. luvflyin

    luvflyin Final Approach

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    Oops. Corrected. Thanks
     
  28. Velocity173

    Velocity173 Touchdown! Greaser!

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    Actually called RYY tower once and asked about their radar. They’ve got a certified tower radar display but they're limited the the same restrictions as a non certified display. Basically an aid to situational awareness and that’s it.
     
  29. GeorgeC

    GeorgeC En-Route

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    Could never figure out why Easton has radar but Frederick doesn't...
     
  30. flyingron

    flyingron Touchdown! Greaser!

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    I can't even figure out why either one has a control tower.
     
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  31. smv

    smv Cleared for Takeoff

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    A student and I hung out in a hold for 30 minutes on a bluebird day during an IFR training flight into Helena just so ATC could "squeeze" a regional in front of us. It was "only" 30 minutes because after several EFCs I finally cancelled IFR and went in on our own VFR.