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RNAV/RNP Operation



What is RNAV/RNP?


Area Navigation (RNAV) is a method of air navigation which permits aircraft operation on any designated flight path, such as a direct route between airports or parallel routes independent from the fixed routes between navigational aids (NAVAIDs). Various navigational data sources such as radials from VHF Omni Range (VOR), distance from Distance Measurement Equipment (DME) and position data from Global Positioning System (GPS) are used to calculate the position and flight path of an aircraft. The accuracy of RNAV is indicated by number “x" of RNAV-x, RNAV-5 for example. The number “x" shows the tolerated magnitude of error in NM for 95% probability.

Required Navigation Performance (RNP) as a concept applies to navigation performance within an airspace and therefore affects both the airspace and the aircraft. RNP is intended to characterize an airspace through a statement of the navigation performance accuracy (RNP type) to be achieved within the airspace. The RNP type is based on a navigation performance accuracy value that is expected to be achieved at least 95 per cent of the time by the population of aircraft operating within the airspace. The development of the RNP concept recognizes that current aircraft navigation systems are capable of achieving a predictable level of navigation performance accuracy and that a more efficient use of available airspace can be realized on the basis of this navigation capability. .

Performance Based Navigation (PBN) is another operational concept that links the navigation standards to the navigation accuracy and integrity of an aircraft. RNAV and RNP are both included in PBN. The navigational performance of an aircraft is approved by State civil aviation authority within one or more specific categories.



Reduction of Lateral/Longitudinal Separation


To solve traffic delay in peak hours and improve airspace capacity to accept increasing demand, reduction of lateral and longitudinal separation minima utilizing advanced navigation equipments and procedures are essential. For example, 3 parallel routes with 50NM Lateral Separation Minimum in 150NM wide airspace will be able to be restructured to have 5 parallel routes with 30NM Lateral Separation Minimum. An ATS route segment with 50 NM Longitudinal Separation Minimum between aircraft will be able to accept 66% more aircraft in the same segment, if 30NM Longitudinal Separation Minimum is applied.

However, the navigation performance of aircraft flying in the airspace where these types of reduced separation are applied must be approved by the State civil aviation authority. Additionally, assessment of airspace safety before implementation and on-going monitoring after implementation is required for this kind of separation reduction.



Operational Approval


In order to obtain RNAV/RNP operational approval, an operator must satisfy their state regulatory authorities.

The JASMA has been maintaining a database of RNAV/RNP approval aircraft of Japan.

Operators registered in Japan submit the RNAV/RNP airworthiness and operational approval data to JASMA using JASMA Form2 when receive RNAV/RNP operation approval from JCAB.


Report of Large Lateral Deviation (LLD)


Pilots of aircraft and ATC facilities are required to report all Large Lateral Deviations (LLD) to the JASMA. An LLD is defined as a deviation of 15NM or more without ATC approval. ATC approved weather deviations, radar vectoring or change of route with ATC clearance are not recognized as LLDs.

The JASMA uses these LLD reports in airspace safety evaluations for all or specific parts of airspace in the Fukuoka FIR by Collision Risk Model (CRM).



Report of Large Longitudinal Error (LLE)


Pilots of aircraft or ATC facilities are required to report Large Longitudinal Errors (LLE) to the JASMA, if one of the following categories of longitudinal error in the criteria is observed:


  1. Aircraft-pair (Time-based separation is applied)
    Infringement of longitudinal separation standard based on routine position reports
  2. Aircraft-pair (Time-based separation is applied)
    Expected time between two aircraft varies by 3 minutes or more based on routine position report
  3. Individual-aircraft (Time-based separation is applied)
    Pilot estimate varies by 3 minutes or more from that advised in a routine position report
  4. Aircraft-pair (Distance-based separation is applied)
    Infringement of longitudinal separations standard, based on ADS, radar measurement or special request for RNAV position report
  5. Aircraft-pair (Distance-based separation is applied)
    Expected distance between an aircraft pair varies by 10NM or more, even if separation standard is not infringed, based on ADS, radar measurement or special request for RNAV position report

The JASMA uses these LLE reports in airspace safety evaluations for all or specific parts of airspace in the Fukuoka FIR by Collision Risk Model (CRM).




Copyright(C) 2011 Japan Airspace Safety Monitoring Agency. All Rights Reserved.