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In the example shown above:

  1. Is an aircraft required to have all 3 sensors listed or just one of them to fly the L512 airway? What ICAO reference confirms the answer?

  2. Does 'critical DME' (bottom row) mean an aircraft is required to have DME/DME? Or can an aircraft equipped with GNSS still fly the L512 even when KAE or KPO is out of service?


1 Answer 1



From ICAO Doc 9613: RNAV 5 operations are based on the use of RNAV equipment which automatically determines the aircraft position in the horizontal plane using input from one or a combination of the following types of position sensors, together with the means to establish and follow a desired path:

c) INS or IRS; and
d) GNSS.

In the example given, any one sensor or a combination of the following:

  • INS or IRS
  • GNSS

Critical DME

Critical DME. A DME facility that, when unavailable, results in a navigation service which is insufficient for DME/DME-based or DME/DME/IRU-based operations along a specific route or procedure.

Which means if you have GNSS on board, and a critical DME (ground station) is out of service, you can still fly that RNAV 5 airway.


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