Transponder codes: Any rhyme or reason?

Discussion in 'Change to my Frequency...' started by AggieMike88, Feb 27, 2017.

  1. AggieMike88

    AggieMike88 Touchdown! Greaser! PoA Supporter

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    I've been noticing a bit of a pattern when being issued a transponder code for local and cross country Flight Following or IFR flight.

    When doing close in practice work around the home aerodrome, I am frequently issued a code that begins with a zero and sometimes a two.

    On cross country activities, it starts with a five and ranges from five-two to five-six.


    1. Has anyone else noticed similar patterns for their flying?

    2. Is there any "if you're doing this, you're gonna get that" sort of logic to transponder codes?
     
  2. SixPapaCharlie

    SixPapaCharlie May the force be with you

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  3. Ravioli

    Ravioli En-Route PoA Supporter

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    The controllers will be along soon enough, but yes, there are "local codes" that get handed out when you're just going to maneuver in the area, for arrival at some Delta airports, and for short hop Flight Following like DTO to FTW.

    There was a thread recently about the 'number of codes' based on math that also referred to some of the carve outs. It also explained why you sometimes check on to a new frequency and get assigned a new code.
     
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  4. Ryanb

    Ryanb En-Route PoA Supporter

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    I get the same here.

    From my understanding, the 02-- codes are local codes for VFR flights that stay within the local airspace. The Center has a bank of codes for flights that also just remain in their airspace. Different sets of codes for different airspace is organized in a way to minimize the need to change the beacon code's while in the air and also to avoid overlap with other nearby facilities.

    If you are issued a 5--- code, ATC is putting you "in the system." Ex. A VFR cross country flight that will fly through multiple sectors of airspace.

    IFR codes are dispensed in a similar manner, although they are not always limited to a certain series of numbers.
     
  5. weilke

    weilke Touchdown! Greaser! PoA Supporter

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    Sometimes the radar facility has to change your code. Lets say I call up a tracon for local flight following, they may asign one of the local codes (02xx or 04xx seems to be the most common). If I then tell them that I want to go to a spot just outside of their space, they may come back with a change in transponder code to a 5xxx or 4xxx. As it was explained to me, the controller has all the local codes already available on his console and he can just tag up a plane with those available codes. If he needs one that can cross boundaries with center, he has to punch the rudimentary flight plan into the 'national airspace computer' and it spits out an assigned code for that destination. Just one extra step in the process.
     
  6. James331

    James331 Touchdown! Greaser!

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    I've noticed a difference in the codes I get for my personal plane and the work plane too.

    Lots of 53XX codes.
     
  7. Velocity173

    Velocity173 Final Approach PoA Supporter

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  8. AggieMike88

    AggieMike88 Touchdown! Greaser! PoA Supporter

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  9. Approach_controller

    Approach_controller Pre-takeoff checklist

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    There are also subsets of codes exclusively for VFR that are non NAS codes (ie can't hand off automatically to adjacent sectors) that process MSAW data (terrain and traffic alerts) which are to be used only at pilot request or in the case of a mayday call-up and the appropriate 7xxx code is impractical.
     
  10. Tampico Trauma

    Tampico Trauma Line Up and Wait

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    I had my first 7746 squawk code from ZLA a few months ago. My wife likes to help with the transponder... I had to slap her hand on that one.


    Sent from my iPhone using Tapatalk
     
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  11. Velocity173

    Velocity173 Final Approach PoA Supporter

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    I don't even go to standby on those. If ATC sees a 7700 flash for a split second, they won't care. Saw several false alarms when I worked ATC.
     
  12. Tampico Trauma

    Tampico Trauma Line Up and Wait

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    "What's wrong?"

    "If that thing says 7700, we're going to be asked to copy a phone number."

    "But they said 7746"

    "Start from the right"


    Sent from my iPhone using Tapatalk
     
  13. Velocity173

    Velocity173 Final Approach PoA Supporter

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    Oh, I doubt you'd even get a number. It's not a pilot deviation. I've had a student select emergency on our APX-100 before. He rotated right past "normal" to "emergency." ATC queried but that was all. Looks just like this transponder...old school.
     

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  14. geneseib

    geneseib Line Up and Wait

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    I'm not in the system often. The one class C I fly into has a block of numbers and assigns them sequentially.

    Many years ago I flew in an area where a facility had a block of numbers, but would usually incorporate a part of your tail number into the code. I suppose that was before the computers would tag a target. Not sure which facility assigned, the codes. It may have been military.
     
  15. ZeroPapaGolf

    ZeroPapaGolf Line Up and Wait

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    That's silly. Dial the code and get on with it. ATC isn't stupid, they know you might pause on 7700 for a moment.
     
  16. frfly172

    frfly172 Touchdown! Greaser!

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    Plug in the code given,and don't worry where the number comes from.
     
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  17. Harold Rutila

    Harold Rutila Pre-takeoff checklist

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    Great question. Few people care about this, but I always found it interesting. There are a few problems with getting a local code in that they usually do not permit inter-facility handoffs, especially when the radar systems at two facilities are different.

    There are a few subsets:
    1. VFR being worked by a control tower - local (Regional Approach's database)
    2. VFR flight following - local.
    3. VFR practice approaches or IFR - local.
    4. VFR flight following or IFR, terminating inside ZFW - center database. (aka "Internal")
    5. VFR flight following or IFR, terminating outside ZFW - center database. (aka "External")

    Subsets 1 and 2 above inhibit minimum safe altitude warnings. Subsets 3-5 will result in minimum safe altitude warnings if the system detects you descending too fast or operating below the MVA.

    All of the codes issued by our local control towers (except for IFR clearances) are tied into the Regional Approach database. Regional Approach is delegated the following subsets by the National Beacon Code Allocation Plan: 0100, 0200, 0400, 4300, and 4600. You'll notice the control towers will issue 04XX codes if they want to "tag up" VFR inbound aircraft on their radar display. A couple controllers at Dallas Executive and other area towers do this regularly. If you call up Regional Approach for flight following and are not conducting practice approaches, they'll usually issue a 46XX code. Practice approaches around here usually get a 52XX code.

    If your route will take you from ZFW to another center's airspace, you'll be assigned a 0500, 0613-0677, 2200, 2300, 3021-3077, 3241-3264, 3400, 3600, 6200, or 7041-7077 code.

    If your whole route will remain within ZFW, you'll get an internal code in the range of 4500, 5100, 5200, or 5300.

    If Regional Approach changes you from a 46XX code to a 53XX code, that means they just "put you in the NAS," and you can expect flight following all the way to your destination.

    All of this is contained in NBCAP documentation, available publicly online.
     
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  18. AggieMike88

    AggieMike88 Touchdown! Greaser! PoA Supporter

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  19. Cooter

    Cooter Cleared for Takeoff

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    That looks familiar!!
     
  20. Velocity173

    Velocity173 Final Approach PoA Supporter

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    Yeah, a museum piece...literally. :D Ours looked just like it, only mode 2 could be manually dialed in. Not that you'd need to in flight though.
     
  21. DesertNomad

    DesertNomad Cleared for Takeoff

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    I would guess that on a GTX330, you have to enter from the left but nothing happens until the full code is in - unlike the older 4 physical dials.
     
  22. luvflyin

    luvflyin En-Route PoA Supporter

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    That would have been an early version of a system called TPX42. It didnt do data processing and didnt put the aircraft call sign on the scope. It did display the 4 digit numeric code on the scope. A facility would have a block of codes assigned like 0400-0477. They could get as creative as they wanted with the last 2 digits as memory joggers. The Navy used it a lot back then, don't know about the Air Force.
     
  23. Dave S.

    Dave S. Pre-Flight

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    In short, yes, there is a pattern to code assignments. There are nationally mandated non-discrete codes (xx00) that are based on certain kinds of operations. There are a few discrete subsets (a range of discrete codes) that are nationally reserved.

    In general each approach facility will be assigned a subset of discrete codes with which they will utilize at their discretion based on the local operating procedures. For example, VFR practice approached may use codes from one subset while VFR inbounds or outbounds my use another. Each facility fashions their usage to best meet their needs. That includes, possibly, changing the code during the flight to reflect a change in the type of operation, ie., a change from VFR practice approach to IFR practice approach.

    A lot of the recent (last 10 years) code procedures are also associated with the way facilities count traffic. A software program called Count-Ops automatically counts traffic based on a set of rules set up in the program and many of those rules depend on code subsets. These counting rules can use the code subset, data block scratch-pad entry, and data block special designator in their design. By having aircraft squawk different codes based on their operation and location the computer can keep track of traffic count with at least a 98% accuracy.

    Just as an example, an aircraft going to a satellite airport will be counted as at least a VFR count. It might also include multipliers to that count value based on if it goes to a satellite airport in a Class B or outside a Class B. Or any other rule established in the counting program. These rules follow strict national guidelines. This "counting" established the levels of each facility.

    So there are many reasons for the assignments of local codes, some procedural and some designed to facility traffic count. All of them locally designed, either local to approach facilities or enroute facilities.

    In addition, going enroute from one center to another, or better stated, one ERAM host computer to another, will generally require a new enroute code assigned by the receiving ERAM host computer.

    tex
     
    Last edited: Mar 3, 2017
  24. TRocket

    TRocket Pre-takeoff checklist

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    I got 1011 coming out of DAB headed home to EQY a couple of weeks ago...VFR flight following. Binary code???
     
  25. flyingron

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    I was very amused one time to get 5327 as my squawk (the same as my N number).
     
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  26. arnoha

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  27. AggieMike88

    AggieMike88 Touchdown! Greaser! PoA Supporter

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    I wonder if the issuing controller saw that too...
     
  28. flyingron

    flyingron Touchdown! Greaser! PoA Supporter

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    Yeah, there was a little chuckle when he issued it, so I think he knew it matched (either a great coincidence or he pulled it out of the pool specifically).
     
  29. Clark1961

    Clark1961 Touchdown! Greaser!

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    Interesting. All those aircraft were capable of entering/exiting the NAS from above.
     
  30. danhagan

    danhagan Cleared for Takeoff

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    Could be worse, she could have entered 7777 (used around here on the border when you're intercepted and getting formation experience with a F-15:confused:).
     
  31. skippy101

    skippy101 Filing Flight Plan

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    When requesting FF for example out of PHX. and flying to TUS. tell them you want FF "with a center handoff" you will get a center squawk. makes things easier for the controller. otherwise they might dump you and you have to call up center as a cold call. or you will waste the controllers time by them asking if you want FF the whole way and assign you another code.
     
  32. Ken Thompson

    Ken Thompson Pre-Flight

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    I had 7074 recently with DFW Bravo, Dallas departure, Waco, and Houston Approach. VFR FF.
     
  33. Pilawt

    Pilawt En-Route

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    There are some special ones that aren't well known. '3333', for example, is used for flying over a large forest. Tomorrow you might get '1776'. And if a pilot squawks '0000' it means "Do not disturb -- Mile High Club initiation in progress."

    :D:D
     
  34. Timbeck2

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    On that flight, you don't have to tell them you want a "center handoff" as you go from PHX approach, ABQ Center and TUS approach anyway if you request flight following. I just wish the Class Ds could give a code other than 1200. I've had to cold call PHX approach every time to get flight following to TUS.
     
  35. Harold Rutila

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    If they have a radar display they can, unless the TRACON doesn't want them to.
     
  36. skippy101

    skippy101 Filing Flight Plan

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    Yep coming out of SDL. you need to contact PHX TRACON quickly before entering class B. Would be nice if SDL TWR would set you up on Clearance del freq.