Performance Based Navigation and RNP

Performance Based Navigation and RNP

PBN stand for Performance Based Navigation. PBN is a new concept and it is based on the use of Area Navigation systems. PBN aims to ensure global standardisation of Area Navigation and Required Navigation Performance specifications and to limit the proliferation of navigation specifications in use, world-wide. PBN represents a fundamental shift from sensor based navigation system to performance based navigation system.

RELEVANT REGULATORY DOCUMENTS for PBN

The regulatory guidance on this subject are available in

  • ICAO Document 9613 (PBN Manual)
  • Regulatory Civil Aviation Requirements like Indian CAR Section 8, Series S, Part IV
  • Relevant Aircraft Manufacturer’s Documents

Area Navigation (RNAV)

A method of navigation which permits the aircraft operation on any desired flight path within the coverage of station referenced navigation aids or within the limits of the capability of self-contained aids, or a combination of these. It is generally referred as RNAV. It improves route efficiency and enhances capacity of route network.

Required Navigation Performance (RNP)

RNP is a type of PBN (Performance Based Navigation) that allows an aircraft to fly a specific path between two 3D-def‌ined points in the space. RNP offers safety benefits by means of its accuracy and precision.

Difference between RNP and RNAV

Required Navigation Performance (RNP) is similar to Area Navigation (RNAV); but, RNP requires on-board navigation performance monitoring and alerting capability to ensure that the aircraft stays within a specific containment area.

RNP is RNAV operations. RNAV and RNP systems are fundamentally similar. The key difference between RNAV and RNP is the requirement for on-board performance monitoring and alerting.

A navigation specification, which includes a requirement for on-board navigation performance monitoring and alerting is referred to as RNP specification.

The critical component of RNP is the ability of the aircraft navigation system to monitor its achieved navigation performance and to identify for the pilot whether operational requirement is, or is not being met during the operations.

RNP capability of an aircraft is a major component in determining the separation criteria, to ensure that, the overall containment of the operation is met. This is a distinguishing feature of RNP.

EVOLUTION OF PBN

The conventional navigation system is dependent upon ground based radio navigation aids. It has been the mainstay of aviation for many years, and pilots, operators, manufacturers and ANSPS are all familiar with the associated technology, avionics, instrumentation, operations, training and performance.

Area navigation systems are developed in a manner similar to conventional ground based routes and procedures. Early systems used the very high frequency omnidirectional radio range (VOR) and the distance measuring equipment (DME) for estimating their position in domestic operations, and inertial navigation systems (INS) were employed in oceanic operations.

Subsequently, RNP specifications developed from a need to support operations that require greater integrity assurance, Where the pilot is able to detect when the navigation system is not achieving or cannot guarantee with appropriate integrity, the navigation performance required for the operations. Such systems are known as RNP systems.

RNP system provides the greater assurance of integrity and, therefore, they can offer safety, efficiency, capacity and other operational benefits.

RNP ANNOUNCEMENTS on FMC CDU and ND

In the route pages the related RNP for the airspace will be uploaded automatically from the NAV database of FMC.

Alarm generation when RNP exceeded

Green : Within the RNP value

Yellow : Within the containment region

Red : Exceeding the value

ADVANTAGES OF PBN

Performance Based Navigation can provide capacity, efficiency, safety and access benefits in response to the challenge of aviation growth and rising costs.

MEL REQUIREMENTS FOR RNP

The MEL requirements are based on the type of RNP airspace.

For airspace within the radio NAVAID (Navigational Aid) coverage, one RNAV system is required, taking into account that conventional navigation from NAVAID to NAVAID and radar guidance remain available case of system failure.

For airspace outside the radio NAVAID (Navigational Aid) coverage, two RNAV systems are required to ensure the appropriate redundancy level.

When invoking a MEL on NAV systems which will be affecting the RNP operations, follow the def‌ined procedure.

SUMMARY

RNP provides an opportunity to improve Safety, Efficiency and Capacity.

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