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RNAV and RNP Navigation Specifications: Keeping It All Straight

RNAV and RNP Navigation Specifications

Keeping it all Straight

A recent Aeronautical Information Circular issued in France stated that aircraft operating IFR into Nice-Cote D’Azur airport must be equipped “with an area navigation system in conformity with RNP APCH navigation specification as defined by ICAO document 9613 - Performance Based Navigation (PBN) manual.”

As a result, many Honeywell customers began questioning whether they could operate into Nice with their current equipment and approvals. There was also confusion as to whether an approval for RNP AR (Required Navigation Performance - Authorization Required) approaches was necessary. This confusion is understandable since these terms aren’t standardized across all regulatory agencies and many countries have started charting RNAV and RNP procedures with various terminology.

The following will provide a short overview of the naming conventions for the different navigations specifications in effort to clarify future requirements.

RNAV vs RNP

As a quick review, remember that:

RNAV = A method of navigation which permits aircraft operation on any desired flight path within the coverage of ground or space-based navigation aids. RNAV allows flight from point-in-space to point-in-space, rather than navaid to navaid. Pilots have used RNAV for many years now (both enroute and in the terminal area) and with the use of GPS, RNAV has become highly accurate and worldwide.

RNP = RNAV operations that include the requirement for onboard navigation system performance monitoring and alerting. RNP is used enroute (e.g. oceanic RNP-4) and in the terminal area (e.g. RNP-1 SIDS and RNP approaches). All RNP routes and procedures other than RNP-10 currently require GPS.

RNP AR = RNP operations that require additional equipment, training and approval. RNP AR is analogous to ILS CAT II/III procedure: an ILS CAT II/III is still an ILS, however, it requires equipment, training and approval over and above that required for an ILS CAT I approach. Currently, only approaches are available as RNP AR, however FAA specifications are now in development for RNP AR departures.

Advanced RNP = RNP operations requiring additional capabilities:

  • Radius-to-Fix (RF) leg types - fixed radius turns
  • RNP scalability - ability of the system to retrieve and set RNP values from the navigation database, and display the required value for each leg segment
  • Parallel offsets - ability to fly offset from the parent track
  • Fixed radius transitions - an arc at a constant radius that is tangent to both the inbound and outbound enroute path segments at an enroute fix
  • Time of Arrival Control - capability to control speed to cross a fix at a designated time

Nav Specs, Naming Conventions and Charting

Now for a look at the terminology and naming conventions pilots may see. They are sorted by procedure/route type and chart name:

Back to the French Circular mentioned in the opening of the article which calls for operators flying to Nice be capable of RNP APCH. This simply means that an aircraft and its flight crewmembers must be capable of flying an RNAV (GPS) approach.