Airway traffic restrictions

Not all airway segments are available at all times and to all aircraft.

The system implements constantly updated database of restrictions for Europe, as defined by Eurocontrol.

There are different types of restrictions:

• RAD (Route Availability Document) - quoting from the RAD introduction:
  The RAD is a sole-source-planning document that combines AIP Route Flow Restrictions with ATFM routeing requirements designed to make the most effective use of ATC capacity. The RAD is finalised during the ATFM strategic planning process organised by the EUROCONTROL Central Flow Management Unit (CFMU).
• CDR (Conditional routes) - Each state publishes in its AIP (Aeronautical Information Publication) the conditions under which some airway segments are made available or unavailable. Quoting from the EATCHIP ASM Handbook (Eurocontrol):
  A Conditional Route (CDR) is a non-permanent ATS route or a portion thereof which can be planned and used only under certain specified conditions.
  Such route segments are categorized into:
  • CDR 1 - Permanently plannable CDR during the times published in AIPs
    Available most of the times, not available on specific conditions (e.g. activation of a military training zone)
  • CDR 2 - Non-permanently plannable CDR
    Available on specific conditions such as facilitating traffic flow and increasing ATC capacity
  • CDR 3 - Not plannable CDR
    Available on short notice, useable only on ATC instructions

The availability (CDR2) or unavailability (CDR1) of routes is reported in the CRAM (Conditional Route Allocation Message), published daily by the Eurocontrol CFMU.

RouteFinder implements the following scheme to consider those restrictions:

• When options RAD, CDR and CRAM are disabled, the restrictions are ignored and not reported.
• When options RAD and/or CDR is enabled, after the auto-routing process the system generates a report of restrictions which are potentially applicable to the computed route.
• If CRAM option is enabled, the CRAM message currently in force is checked against the flight plan, and the report is completed with the indication "currently CLOSED" or "currently OPEN" if such information is applicable to the flight plan.
• Moreover, for convenience, CDR2 routes are pre-selected for exclusion, unless the current CRAM reports them as OPEN. Similarly, CDR1 routes are pre-selected for exclusion when CRAM reports them as CLOSED. CDR3 routes are always pre-selected for exclusion.
• The user can interactively decide to exclude the flight plan segments which have applicable restrictions (For example "Not available between FL300 and FL390" - should be excluded if the flight plan will be filed for FL330)
• If any segments used in the flight plan are to be excluded, it is possible to ask the system for another route, avoiding the excluded segments.

Using an interactive process it is possible to determine a routing which will pass the Eurocontrol Flight Plan Validation most of the times.

However, compulsory RAD routings are not yet implemented, so ignore them for now.

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