RNAV Approaches Simplified: A Guide for New (& old) Pilots
Interested in getting your instrument rating? Well, one important thing you’ll need to know is PBN/RNAV approaches.
The performance-based navigation (PBN) concept specifies that aircraft RNAV or RNP system performance requirements be defined in terms of accuracy, integrity, continuity and functionality required for the proposed operations in the context of a particular airspace concept, when supported by the appropriate navigation aid (NAVAID) infrastructure.
Compliance with world geodetic systems and data quality prescribed in Annex 15 – Aeronautical Information Services is integral to PBN.
The PBN concept represents a shift from sensor-based navigation and requires the use of an RNAV or RNP
system.
Under PBN, generic navigation requirements are first defined based on the operational requirements.
Operators then evaluate options in respect of available technology and navigation services. A chosen solution would be the most cost-effective for the operator, as opposed to a solution being established as part of the operational requirements.
Technology can evolve over time without requiring the operation itself to be revisited as long as the requisite performance is provided by the RNAV or RNP system
In this guide, you’ll learn how RNAV/PBN approaches work, the different types available, and tips to make them feel natural and straightforward.
Ready to simplify RNAV? Let’s get to it!
- Remember: the reference document is the ICAO Doc 9613 Performance-based Navigation
(PBN) Manual, Fifth Edition, 2023
Area navigation system.
A navigation system which is either an RNP system or an RNAV system depending on its performance capabilities.
RNAV, RNP, PBN?
RNAV operations. Aircraft operations using area navigation for RNAV applications.
RNAV system. A navigation system which permits 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.
An RNAV system may be included as part of an FMS.
RNP operations. Aircraft operations using an RNP system for RNP navigation applications.
RNP system. A navigation system which permits 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.
An RNP system requires on-board performance monitoring and alerting. An RNP system may be included as part of
an FMS.
RNP AR operations (RNP AR OPS). Aircraft operations using an RNP system for RNP AR navigation applications.
AR: Authorization Required.
Performance-based navigation. Area navigation based on performance requirements for aircraft operating along an ATS
route, on an instrument approach procedure or in a designated airspace.
Note.— Performance requirements are expressed in navigation specifications (RNAV navigation specification, RNP
navigation specification) in terms of accuracy, integrity, continuity and functionality needed for the proposed operation in
the context of a particular airspace concept. Availability of GNSS signal-in-space (SIS) or some other NAVAID
infrastructure is considered within the airspace concept in order to enable the navigation application.
The performance-based navigation (PBN) concept specifies that aircraft RNAV and RNP system performance
requirements be defined in terms of accuracy, integrity, continuity and functionality, which are needed for the proposed operations in the context of a particular airspace concept.
Performance requirements are identified in navigation specifications, which also identify the choice of navigation sensors and equipment that may be used to meet the performance requirements.
These navigation specifications are defined in a sufficient level of detail to facilitate global harmonization by providing specific implementation guidance for States and operators. This manual contains a very broad
range of information, guidance and other considerations for stakeholders who are choosing to implement PBN applications.
This includes an explanation of the PBN concept, implementation guidance for a PBN application, considerations for States and service providers and guidance/requirements for aircraft and operators.
Under PBN, generic navigation requirements are defined based on operational requirements. Operators then evaluate options in respect to available technology and navigation services, which could allow the requirements to be met.
Technology can evolve over time without requiring the operation itself to be reviewed, as long as the expected performance is provided by the RNAV or RNP system.
Within an airspace concept, PBN requirements will be affected by the communications, air traffic services (ATS) surveillance and air traffic management (ATM) services, the navigation aid (NAVAID) infrastructure, and the functional and operational capabilities needed to meet the ATM application.
PBN requirements also depend on what reversionary, conventional navigation techniques are available and what degree of redundancy is required to ensure adequate continuity of functions.
Instrument approach operations.
An approach and landing using instruments for navigation guidance based on an instrument approach procedure. There are two methods for executing instrument approach operations:
- a two-dimensional (2D) instrument approach operation, using lateral navigation guidance only; and
- a three-dimensional (3D) instrument approach operation, using both lateral and vertical navigation guidance.
Note.— Lateral and vertical navigation guidance refers to the guidance provided either by:
- a ground-based radio navigation aid; or
- computer-generated navigation data from ground-based, space-based, self-contained navigation aids or a combination of these.
- RNAV uses GPS waypoints for direct routes, no beacons needed.
- Types include LPV, LNAV, LP, LP+V, LNAV/VNAV, and RNP.
- Precision systems allow lower minima for safer landings.
- RNAV improves access and efficiency, with beacons as backups.
Context of performance-based navigation
PBN is one of several enablers of an airspace concept. Communications, air traffic services (ATS)
surveillance and air traffic management (ATM) are also essential elements of an airspace concept. This is demonstrated in Figure I-1-1. PBN relies on the use of area navigation and comprises three components:
- the NAVAID infrastructure;
- the navigation specification; and
- the navigation application.
Note.— Application of a) and b) in the context of the airspace concept to ATS routes and instrument
procedures results in c).
NAVIGATION SPECIFICATION
Overview
The navigation specification is used by a State as a basis for the development of their material for
airworthiness eligibility and operational authorization for PBN operations. 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. ICAO navigation specifications are contained in Volume II of Doc. 9613.
A navigation specification is either an RNP navigation specification or an RNAV navigation specification.
An RNP navigation specification includes a requirement for on-board performance monitoring and alerting, while an RNAV navigation specification does not.
On-board performance monitoring and alerting
On-board performance monitoring and alerting (OBPMA) is the main element determining:
- whether the navigation system supports the safety level associated to an RNP application;
- whether it relates to both lateral and longitudinal navigation performance; and
- whether it allows the aircrew to detect that the navigation system is not achieving, or cannot guarantee
with sufficient integrity, the navigation performance required for the operation.
RNP systems improve the integrity of operations, thereby permitting closer route spacing and providing
sufficient integrity to allow only RNP systems to be used for navigation in a specific airspace.
RNP systems may therefore offer significant safety, operational and efficiency benefits over RNAV systems.
Note.— RNP navigation specifications usually have higher performance requirements than RNAV and
optional advanced functionalities such as radius to fix (RF) and fixed radius transitions (FRTs) , which can only be associated with RNP navigation specifications.
Flight planning of RNAV and RNP designations
Manual or automated notification of an aircraft’s qualification to operate along an ATS route, on a procedure or in an airspace, is provided to the ATS unit via the filed flight plan.
Note.— Flight plan procedures are addressed in the Procedures for Air Navigation Services – Air Traffic
Management (PANS-ATM, Doc 4444).
Accommodating inconsistent RNP designations
The existing RNP 10 designation is inconsistent with PBN RNP and RNAV navigation specifications. RNP 10 does not include requirements for on-board performance monitoring and alerting. For purposes of consistency with the PBN concept, RNP 10 is referred to as RNAV 10 in this manual. Renaming current RNP 10 routes, operational authorizations, etc., to an RNAV 10 designation would be an extensive and expensive task, which is not cost-effective. Consequently, any existing or new operational authorizations will continue to be designated RNP 10, and any charting annotations will be depicted as RNP 10 (see Figure I-1-3).
NAVAID INFRASTRUCTURE
The NAVAID infrastructure refers to ground- or space-based NAVAIDs. Conventional ground-based NAVAIDs include distance measuring equipment (DME) and VOR. The PBN concept requires that NAVAID infrastructure provides position information to the aircraft through an on-board area navigation system. Space-based NAVAIDs include GNSS elements.
Further guidance on implementing GNSS is given in the Global Navigation Satellite System (GNSS) Manual (Doc 9849).
All NAVAID requirements are defined in Annex 10 – Aeronautical Telecommunications. The Manual on Testing of Radio Navigation Aids (Doc 8071) also contains information concerning the testing of navigation aids supporting PBN.
NAVIGATION APPLICATIONS
A navigation application is the use of a navigation specification and associated NAVAID infrastructure for ATS routes, instrument approach, departure or arrival procedures and/or to enable user defined routeing in a specified airspace volume in accordance with the airspace concept. An RNP application is supported by an RNP navigation specification; an RNAV application is supported by an RNAV navigation specification.
The navigation application is the PBN component providing the direct connection with the airspace concept,
which is comprised of routes and procedures, amongst other things. The navigation application is the only PBN component that is neither fixed nor ‘static.’ A variety of different navigation applications can be created using a single navigation specification, for example the RNAV 1 specification can be used to design ATS routes, departures or arrivals.
Where a navigation application is realised as a fixed ATS route, the navigation performance requirement (in the navigation specification) will apply for operation on the published ATS route. This enables strategic de-confliction of proximate flight procedures, that is, two RNP 1 STARs can be strategically de-conflicted or spaced at a determined distance, allowing aircraft to self-navigate thus requiring minimum ATC intervention.
Where a navigation application is realised in en-route continental/remote or oceanic airspace as either a
user-defined route or a fixed ATS route associated with strategic or tactical de-confliction, a navigation specification required to operate along the flight path within this airspace is a condition for entry into the designated airspace.
Note 1.— Strategic de-confliction refers to the placement of proximate routes to ensure safe separation.
Tactical de-confliction requires surveillance monitoring by ATS for purposes of conflict resolution.
Note 2.— It is possible for the same navigation specification to be required for the navigation application referred to in 1.4.2.1 and 1.4.2.2.
RELATIONSHIP BETWEEN NAVIGATION SPECIFICATION, NAVAID INFRASTRUCTURE
AND NAVIGATION APPLICATIONS
PBN consists of three components and there is a direct relationship between them.
Each navigation application must be based upon a particular navigation specification and associated
NAVAID infrastructure, which can be different in a different airspace concept – see Example 2.
Example 2
A navigation application (for example arrival/departure) is designed using the navigation specification
(for example RNAV 1) based upon a specific NAVAID infrastructure (for example GNSS) which may
differ in another State.
The RNAV 1 specification in Volume II shows that any of the following navigation sensors can meet its performance requirements:
GNSS;
or DME/DME/inertial;
or DME/DME.
Sensors needed to satisfy the performance requirements for an RNAV 1 specification in a particular
State are not only dependent on the aircraft on-board capability. A limited DME infrastructure or GNSS
policy considerations may lead the authorities to impose specific navigation sensor requirements for
an RNAV 1 specification in that State.
As such, the aeronautical information publication (AIP) of State A could stipulate GNSS as a
requirement for its RNAV 1 application because State A only has GNSS available in its NAVAID
infrastructure. The AIP of State B could require the capability of DME/DME/inertial for its RNAV 1
application.
Each of these navigation specifications would be implemented as an RNAV 1 application. However:
- aircraft equipped only with GNSS and approved for the RNAV 1 specification in State A would not be approved to operate the RNAV 1 application of State B; and
- aircraft only fitted with DME/DME/inertial and certified to RNAV 1 will comply with the
requirement of State B, but would not be approved to operate the RNAV 1 application of State A.
Aircraft certified to RNAV 1 with both sensors will be able to operate RNAV 1 application in both
States with no limitations.
A navigation specification, its associated NAVAID infrastructure and its navigation application can support a
number of airspace concepts. One example is the RNAV 5 application, which is used for different continental ATS routes and can support the performance requirement for user-defined routeing.
FUTURE DEVELOPMENTS
Overview
PBN aims to harmonize longitudinal and lateral performance requirements (that is, 2D) for both RNAV and RNP navigation specifications. Vertical path performance requirements (that is, 3D) are included in some RNP navigation specifications. In the future, PBN is expected to include 4D trajectory-based operations (TBO).
Although PBN implementations will continue to be based on both RNAV and RNP navigation specifications,
future developments will focus on new RNP navigation specifications.
As more reliance is placed on GNSS, airspace concepts will increasingly need to ensure the coherent integration of communications, navigation and ATS surveillance enablers. Safety cases should consider the impact of losing GNSS in terms of CNS (see Chapter 2, 2.2.2.5 od Doc. 9613).
GNSS dual-frequency multi-constellation
Annex 10 – Aeronautical Telecommunications, Volume I – Radio Navigation Aids contains Standards and Recommended Practices (SARPs) and guidance material for one signal of Global Positioning System (GPS) and
GLONASS and similar work is under progress for BEIDOU and GALILEO. All four core constellations are intended to provide a second signal, and the standardized augmentations (that is, aircraft-based augmentation system (ABAS), GBAS and satellite-based augmentation system (SBAS)) are currently evolving to support these dual frequency signals. This significant evolution in GNSS is described under the Concept of Operations for dual-frequency multi-constellation (DFMC)1.
Annex 10 introduces the notion of the GNSS element to describe the existing and new individual core-constellation signals and augmentations. To support PBN operations, the different GNSS elements would be used through specific compatible DFMC avionics.
The concept of operations describes all such GNSS elements as potentially useable in support of PBN.
The transition from a single-frequency single-constellation (that is, GPS/L1) to a DFMC PBN context is significant. Conditions to be met by new GNSS elements other than GPS/L1, to support PBN operations within a given State airspace include:
- the new GNSS element has to be standardized within Annex 10;
- the new GNSS element performances might require acceptance by the safety authority in charge of the
intended airspace of use; and - the State, or group of States responsible for the airspace where the new GNSS element is intended to be used, has to document its acceptance to airspace users within the AIP; and
Note 1.— Some States may not formally declare accepting GPS/L1 in their AIP, despite
Recommendation 2.2/2 from the Thirteenth Air Navigation Conference (AN-Conf/13). Further guidance
on how to publish GNSS elements in the AIP is under development.
Note 2.— Failure to provide airspace users with information on the GNSS elements permitted within
the airspace could lead operators to use unmonitored satellite navigation signals or those not providing
the required level of integrity. - the operator’s fleet should include compatible aircraft avionics.
When the above conditions are met, the PBN operations described within this text can be supported by
the new GNSS elements, provided that they meet the specific performance and operational requirements of the intended operation.
CONTEXT, SCOPE AND USE OF NAVIGATION SPECIFICATIONS
If a change from the originally intended operating environment occurs, then an implementation-specific safety assessment is needed to ensure the adequacy of safety requirements in the new operating environment. The requirements of the navigation specification may not be changed (see note under 1.2.1.2.1) and neither can the flight phase in which the specification can be used, that is, the RNP 4 (oceanic specification) cannot be used for terminal SIDs/STARs, and similarly RNP 1 cannot be used for oceanic operations.
Proliferation of regional or State navigation specifications is avoided by publishing these navigation
specifications in this manual, which allow regions and States to use existing navigation specifications rather than developing new ones.
The navigation specifications included in Parts B and C of this volume do not address all the requirements that may be specified for operation in a particular airspace concept. Such additional requirements are specified in other documents such as operating rules, AIPs and the Regional Supplementary Procedures (Doc 7030). Before conducting flights into an airspace, the appropriate State regulations of that airspace require that operators and pilots take account of all operational documents relating thereto.
Note.— Mindful that navigation specifications seek to ensure interoperability and international
standardization, States are strongly discouraged from diverging from requirements in the navigation specification when publishing their State regulatory material. If differences are published by States, these should not place any additional burden on the aircraft qualification and operational authorization. State regulatory material based on a navigation specification should include a specific section to highlight any difference from requirements in the reference navigation specification.
States should undertake a safety assessment in accordance with the provisions contained in Annex 19 –
Safety Management, Annex 11 – Air Traffic Services and PANS-ATM (Doc 4444), Chapter 2.
A navigation specification published in Doc. 9613 does not constitute regulatory guidance material against
which either the aircraft or the operator will be assessed and authorized. National, or regional, certification and operations authorization documentation for PBN applications must be published, as necessary. The navigation specification provides the technical and operational criteria but does not imply a need for recertification. For example, with RNAV 2/RNAV 1 an operational authorization process is still needed. This could be either through a dedicated authorization document or through recognition that existing regional RNAV implementation certification documents can be applied with the necessary differences, to satisfy the objectives set out in the PBN specification. The applicable documents related to airworthiness
and/or approval process are listed in Attachment E of Doc. 9613.
Compliance should be determined against each relevant navigation specification.
Compliance with one navigation specification does not automatically imply compliance with another. Navigation specifications are not written to be automatically consistent with State-specific regulatory guidance or documentation processes and may be incomplete.
The navigation specifications are not specifically intended to be invoked for compliance because a State must scrutinize the material to assure consistency between the navigation specification and the State-specific regulatory guidance (this could be as simple as a cover sheet and a reference to the navigation specification or as extensive as a regulatory circular containing all of the navigation specification material along with any State-specific guidance, processes or procedures).
Use of navigation specifications
Table II-A-1-1 shows the navigation specifications published in Parts B and C of Doc. 9613 and that some
navigation specifications are used in particular flight phases and/or routes or procedures, whilst other navigation specifications are more versatile.
Note.— Although this table uses the RNAV/RNP value (lateral navigation accuracy) requirement of a navigation specification to denote its applicability for a particular flight phase, the RNAV/RNP value is only one of several performance and functional requirements in a navigation specification and is often not the only determining characteristic.
It is possible that a sequence of RNAV and RNP navigation specifications is used. A flight may commence in an airspace using an RNP 1 departure, transit through en-route continental and then oceanic airspace requiring RNAV 2 and RNP 4, respectively, and culminate with terminal and approach operations requiring RNAV 1 and RNP APCH (see Figure II-A-1-1 and Table II-A-1-1).
Table II-A-1-1 identifies a number of instances where different navigation specifications can be applied on
the same phase of flight; for example, in the arrival, approach or missed approach phases of flight. However, since not all of the specifications provide the same functional capability for the particular phase of flight, this may limit the number of navigation specification options for a particular application. Consequently, it is important in the design of the procedures to appropriately identify the applicable navigation specification(s), and to require only the capability that is provided by those navigation specification(s).
