Overview of Performance Based Navigation (PBN)

2.1 Conventional navigation is dependent upon ground-based radio navigation aids, which have been the mainstay of aviation for the last seventy years, and pilots, operators, manufacturers and Air Navigation Service Providers (ANSPs) are all familiar with the associated technology, avionics, instrumentation, operations, training and performance.

2.2  Performance-based navigation (PBN) detailed in the International Civil Aviation Organisation’s (ICAO) ‘Performance-based Navigation (PBN) Manual (ICAO Doc 9613), is based upon area navigation principles. While various methods of area navigation have been in existence for many years, the widespread use of area navigation as a primary navigation function is a more recent phenomenon. The PBN concept is intended to better define the use of area navigation systems and is expected to replace many of the existing conventional navigation routes in the future.

2.3  The fundamentals of PBN operations are relatively straightforward; however, the transition to new technology, new navigation and new operational concepts and the dependence on data-driven operations require careful management. The PBN operational approval process is intended to ensure that the appropriate level of implementation and oversight is provided for all PBN operations and the benefits of PBN are achieved consistently and safely.

2.4  There are 3 components to PBN:

a)  Navigation Specifications

A navigation specification details the performance required of the RNAV or RNP system in terms of accuracy, integrity, and continuity; which navigation functionalities the RNAV or RNP system must have; which navigation sensors must be integrated into the RNAV or RNP system; and which requirements are placed on the flight crew. An RNP specification includes a requirement for on-board performance monitoring and alerting, while an RNAV specification does not. On-board performance monitoring and alerting is the main element that determines whether the navigation system complies with the necessary safety level associated with an RNP application; whether it relates to both lateral and vertical navigation performance; and whether it allows the aircrew to detect that the navigation system is not achieving, or cannot guarantee with 10–5 integrity, the navigation performance required for the operation.

b)  Navigation Applications

A navigation application is the use of a navigation specification and associated NAVAID infrastructure to ATS routes, instrument approach procedures and/or defined airspace. An RNP application is supported by an RNP specification; an RNAV application is supported by an RNAV specification.

c)  RNP/RNAV Designations

RNP and RNAV designations are based upon lateral accuracy in nautical miles. An aircraft must remain + or – the numerical value stated (in nautical miles) for 95% of the total flight time:

RNP Designations

RNAV Designations

RNP 0.3

RNAV 1

RNP 1

RNAV 2

RNP 2

RNAV 5

RNP 4

RNAV 10

d)  RNP Approach Designations

  1. Non-Precision or 2D Approaches

LNAV    (Lateral Navigation): This is a Non-Precision or 2D Approach with Lateral only navigation guidance provided by GNSS.

LP         (Localiser Performance): This is a Non-Precision or 2D Approach with Lateral only navigation guidance provided by GNSS.

  1. APV 3D Approaches

(Note: VNAV (Vertical Navigation). APV (Approach with Vertical Guidance): defined as an instrument procedure which utilises lateral and vertical guidance but does not meet the requirements established for precision approach and landing operations.)

LNAV/VNAV (also known as APV/Baro VNAV): This is a 3D Approach Procedure with Vertical Guidance. The lateral navigation guidance is provided by GNSS. The vertical guidance is provided by a Barometric Altimeter.

LPV       (Localiser Performance with Vertical Guidance): This is a 3D
Approach Procedure with both the Lateral and Vertical guidance provided by GNSS.

e)  Navaid Infrastructure

The NAVAID infrastructure refers to ground- or space-based NAVAIDs. Ground-based NAVAIDs include DME and VOR. Space-based NAVAIDs include GNSS elements.

2.5  PBN requires that aircraft meet certain airworthiness certification standards, including the necessary navigation system performance and functionality, as well as development of the operator’s flight operations procedures and flight crew training/competency requirements:

a)  Airworthiness: The airworthiness element ensures that the aircraft meets aircraft eligibility and safety requirements for the functions and performance defined in the navigation specifications. The installation will need to meet the relevant airworthiness standards, eg US 14 CFR Part 25/EASA CS-25 and the applicable AC/AMC. The AC/AMC may also include other non-navigation equipment required to conduct the operation such as communications and surveillance equipment.

b)  Continued Airworthiness: The operator is expected to demonstrate that the navigation system will be maintained compliant with the type design. For navigation system installations there are few specific continued airworthiness requirements other than database and configuration management, systems modifications and software revisions.

c)  Flight Operations: The flight operations element considers the operator’s infrastructure for conducting PBN operations, including flight crew operating procedures, training (to include classroom and flight training, initial and recurrent, and competency demonstrations). This element also considers the operator’s Minimum Equipment List (MEL), Operations Manual (OM), checklists, instrument flight procedure approval processes, navigation database validation procedures, flight planning and dispatch procedures, etc.


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