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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 gx" of RNAV-x, RNAV-5 for example. The number gx" 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.

What is PBCS?

The Performance-based communication and surveillance (PBCS) concept is aligned with the concept of PBN. It enables the management of communication and surveillance capabilities by prescription of Required Communication Performance (RCP) and Required Surveillance Performance (RSP) specifications.

The requirements of an RCP specification are defined as values for :

  • RCP transaction time (The maximum time for the completion of the transaction after which the initiator should revert to an alternative procedure).
  • RCP continuity (Probability that a transaction can be completed within the communication transaction time given that the service was available at the start of the transaction).
  • RCP availability (Probability that a transaction can be initiated when needed).
  • RCP integrity (Probability that a transaction is completed with no undetected errors).

The requirements of an RSP specification are defined as values for :

  • Surveillance data transit time (The required time for surveillance data delivery).
  • RSP Continuity (Probability that surveillance data can be delivered within the delivery time parameter given that the service was available at the start of delivery).
  • RSP Availability (Probability that surveillance data can be provided when needed).
  • RSP Integrity (Probability that surveillance data is delivered with no undetected error).

The PBCS performance of an aircraft is approved by State civil aviation authority.

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, communication and surveillance performance of aircraft flying in the airspace where these types of reduced separation minina (performance-based horizontal separation minima: PBHSM) 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 to apply PBHSM.

Operational Approval

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

The JASMA has been maintaining a database of RNAV/RNP, PBCS approval aircraft of Japan in order to monitor operator compliance with State approval requirements.

Operators registered in Japan submit the RNAV/RNP, PBCS operational approval data to the JASMA using JASMA Form2 when receive these approvals from JCAB.

Report of Large Lateral Deviation (LLD)

ATC facilities are required to report all Large Lateral Deviations (LLD) to the JASMA. An LLD is defined as a deviation of 10NM or more without ATC approval. Weather deviations approved by ATC, radar vectoring or change of route with ATC clearance are not recognized as LLDs.

Report of Large Longitudinal Error (LLE)

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. Individual-aircraft (Time-based separation is applied)
    Pilot estimate varies by over 3 minutes from that advised in a routine position report
  2. Aircraft-pair (Time-based separation is applied)
    Infringement of longitudinal separation standard based on routine position reports
  3. Aircraft-pair (Distance-based separation is applied)
    Infringement of longitudinal separations standard, based on ADS, radar measurement or special request for RNAV position report

The JASMA uses these LLD and LLE reports for the collision risk estimate and other purposes.

PBCS monitoring

Means for PBCS monitoring and assessment in the Fukuoka FIR has been established by the Japan Central Reporting Agency (CRA). If the Japan CRA determines that the actual performance of an aircraft dose not comply with the RCP/RSP specification, the JASMA notifies the operator of the monitoring result from the Japan CRA and recommends improvements in accordance with gOperating procedure for the horizontal safety assessment of the PBHSM airspaceh .

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