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Question ID: 100331

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  • Question ID: 100331


    A minimum radar separation shall be provided until aircraft are established inbound on the ILS localizer course and/or MLS final approach track. This minimum is, when independent parallel approaches are being conducted:

    3nm
    2
    1
    5

    Answer given is 3nm.



    By the wording of this, should the answer not be 5nm?

    "Minimum radar separation until aircraft established on localiser" - implies the aircraft are NOT established on the localiser and so minimum separation is 5nm.


    Where are I going wrong?
    Thank you

  • #2
    Funny business this. I'll try and put it in another way.

    On approaches to single runways the separation is normally 5 NM, unless special criteria can be met. However, on parallel runways there is a need to pack aircraft closer (because there are two runways) so, the special criteria are a part of the standard set up for parallel runways thereby permitting a separation of 3 NM. The 3 NM applies both to pre- established and established on the LOC. On Dependent parallel approaches a separation of 2.5 NM between aircraft on adjacent approaches is possible.

    Comment


    • #3
      Thanks a lot, hadn't realised the 3nm comes into play before established on localiser.



      When you say "On Dependent parallel approaches a separation of 2.5 NM between aircraft on adjacent approaches is possible"

      I think that this is in disagreement with ICAO doc 4444 which says:

      ​​​​​​6.7.3.4.3 The minimum radar separation to be provided between aircraft established on the ILS localizer course and/or MLS final approach track shall be:

      a) 5.6 km (3.0 NM) between aircraft on the same ILS localizer course or MLS final approach track unless increased longitudinal separation is required due to wake turbulence; and
      b) 3.7 km (2.0 NM) between successive aircraft on adjacent ILS localizer courses or MLS final approach tracks.



      As far as I knew, the 2.5nm referred to a reduced separation on the same localiser and within 10nm of the threshold. :

      8.7.3.2 The separation minimum in 8.7.3.1 may, if so prescribed by the appropriate ATS authority, be reduced, but not below:

      a) 5.6 km (3.0 NM) when radar and/or ADS-B and/or MLAT systems capabilities at a given location so permit; and
      b) 4.6 km (2.5 NM) between succeeding aircraft which are established on the same final approach track within 18.5 km (10 NM) of the runway threshold. A reduced separation minimum of 4.6 km (2.5 NM) may be applied, provided:


      Is ICAO 4444 the wrong source to be looking at here?

      Thanks

      Comment


      • #4
        Doc 4444 is ok. Depends what bit of it you use. I was quoting from Chapter 6.7 which is specific to parallel runways. You were quoting from Chapter 8 which is Use of Surveillance in ATC Service - a more generalised perspective.

        Comment

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