RNAV

Area Navigation (RNAV) is a method of navigation 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 navigation specification that includes requirements for on-board performance monitoring and alerting is known as an RNP specification. If on-board performance monitoring and alerting is not required, the navigation specification is know as an RNAV specification.

Performance Based Navigation.

Performance based navigation specifies RNAV system performance requirements for aircraft operating along an ATS route, on an instrument flight procedure or in an airspace.

Performance requirements are defined in terms of accuracy, integrity, continuity, availability and functionality needed for the proposed operation in the context of a particular airspace concept. Performance requirements are identified in navigation specifications which also identify which navigation sensors and equipment may be used to meet the performance requirement.

Performance based navigation therefore depends on:

• The RNAV system and installation on the aircraft being approved to meet the performance and
• Functional requirements of the navigation specification prescribed for RNAV operations in an airspace; and
• Air crew satisfying the operating requirements set out by the regulator for RNAV operations; and
• A defined airspace concept which includes RNAV operations; and
• An available Navaid infrastructure;

An Airspace Concept consists of operational scenarios (including the ATS route structure, separation minima and obstacle clearance) which have been developed to satisfy explicit strategic objectives e.g. safety, capacity, environment, efficiency. A Navigation Application is defined to meet the needs of the Airspace Concept. It comprises a Navigation Specification and a specific NAVAID infrastructure. A Navigation Specification is a set of aircraft and air crew requirements needed to support a navigation application within a defined airspace concept.

The following RNAV applications have been introduced in ECAC airspace:

• B-RNAV - is mandatory as the primary means of navigation in all ECAC en-route airspace;
• P-RNAV - is the navigation specification that is required for RNAV procedures in Terminal Airspace within ECAC.
• RNAV (GNSS) Approach - the navigation specification for RNAV approach procedures using GNSS in ECAC is expected to be published by EASA during 2006.

The following RNP applications are being introduced in ECAC airspace:

• RNP SIDs and STARs (1-0.3) - the navigation specification for RNP SID and STAR procedures in ECAC terminal airspace is expected to be published by EASA during 2007.
• RNP 0.3 Approach - the navigation specification for RNP approach procedures in ECAC is expected to be published by EASA during 2007.
• RNP <0.3 Approach - it is anticipated that EASA will publish a navigation specification for RNP<0.3 approach procedures in ECAC during 2007. These procedures will equate to the RNP SAAAR procedures currently being deployed in North America.

The Navigation Strategy currently foresees RNP being mandated by 2015, although the actual RNP specification required for such a mandate has still to be finalized..