43RD ANNUAL CONFERENCE, Hong Kong, China (SAR), 22-26 March 2004
WP No. 98
Review of Policy on Area Navigation
Presented by SC1
1.1 Area Navigation (RNAV) procedures are proliferating throughout various regions of the world. IFATCA has previously established policy for RNAV. However, the last RNAV policy was created and adopted in 1994.
1.2 RNAV procedures have developed considerably since 1994. SC1 has therefore undertaken a comprehensive review of global RNAV procedures and existing IFATCA policy on RNAV.
1.3 The paper identifies new and emerging RNAV procedures and recommends changes, where required, to IFATCA policy.
2.1 En-Route (Non-Radar)
2.1.1 RNAV applications are being introduced into Procedural En-Route environments so as to reduce the amount of Procedural Separation Minima required between routes. RNAV applications in the procedural environment will enable improved airspace utilisation by permitting routes to be spaced closer together. This will enable capacity within given areas to be increased as a higher number of aircraft will be able to operate on routes that will result in reduced distance and time flown.
2.1.2 There are parts of the world, such as Australia and the Pacific region, in which RNAV procedures are being introduced together with Automatic Dependent Surveillance (ADS) to provide a means of monitoring the track keeping of the aircraft on the routes that are separated by a reduced minima.
2.1.3 In Australia, Global Positioning System (GPS) is approved for use in Oceanic and Remote regions as a primary means of navigation. The equipment standard for GPS OCEANIC complies with the requirements of ICAO Annex 6. GPS distance reports may also be used as a substitute for DME in domestic Australian, USA and Canadian controlled airspace.
2.1.4 In the Pacific, the introduction of RNAV has enabled route spacing to be reduced on the Ocean, where a Required Navigational Performance (RNP) of RNP10 is in place.
2.1.5 IFATCA has current policy for Longitudinal Distance Separation which states the following:
|“The introduction and application of RNAV distance based separation minima is dependent upon the following conditions:
a) When the use of this separation minima will result in an increase in traffic volume/complexity, the appropriate ATS authority responsible must have in place an infrastructure, (in terms of equipment and personnel) capable of accommodating such an increase.
b) The safety of a particular minima must have been established by ICAO.
c) ATC personnel must have received adequate training in the application of distance-based separation, including Mach Number Technique.
d) A change in assigned airspeed/Mach Number must be approved by ATC.
e) An acceptable communications link must be in place between Air Traffic Control and Flight Crews to enable a distance standard to be applied. (The Controller will determine the adequacy of the communications link.) Any reduction below a distance standard of 80NM will require direct pilot/controller communications.”
2.1.6 This policy relates only to longitudinal separation. As such, RNAV criteria in terms of lateral navigation accuracy, doesn’t really apply. Improved navigational performance offers the ability to space routes more closely together in the oceanic and remote areas. The introduction of RNAV capabilities will permit traditional lateral separation standards to be challenged in oceanic and remote areas.
2.2 En-Route (Radar)
2.2.1 RNAV applications are being introduced into en-route radar environments. The introduction of RNAV routes offers several benefits to ATS Providers, including improved design flexibility resulting in increased airspace flexibility. The ability to place routes where they are best suited, rather than being constrained to ground- based navigational aids, means that ATS routes can be better positioned, resulting in potential capacity increases.
2.2.2 There is an on-going attempt to harmonise RNAV standards for use in the en- route radar environment. In the ECAC region a common standard, known as Basic Area Navigation, or B-RNAV, was introduced to ensure harmonisation throughout the region.
2.2.3 Basic Area Navigation (B-RNAV) is the forerunner of the RNAV programme. It was introduced to enable capacity gains to be achieved through modifications to the en-route structure. It requires aircraft conformance to a track-keeping accuracy of 5NM for at least 95% of flight time to ensure that the capacity gains are achieved whilst meeting the required safety targets.
2.2.4 B-RNAV can be achieved using inputs from a variety of sensors, including VOR/DME, DME/DME or GPS. Inertial Navigation Systems (INS) may be used for up to 2 hours after the last radio or on-ground update. Loran C may be used in European airspace where suitable coverage exists and the aircraft system has been certified to FAA AC 20-121A
2.2.5 B-RNAV requirements became mandatory in ECAC airspace on 23 April 1998 on the entire ATS route network above FL 95. B-RNAV is also being used on selected routes into and out of terminal airspace in some States.
2.2.6 RNAV operations in en-route airspace provide a number of advantages over the conventional ground based navigation, whilst maintaining existing safety standards. These advantages and their related benefits include:
a) improved management in the flow of traffic by repositioning of intersections;
b) more efficient use of available airspace, by means of a more flexible ATS route structure and the application of the Flexible Use of Airspace (FUA) Concept, permitting the establishment of:
- more direct routes (dual or parallel) to accommodate a greater flow of en-route traffic;
- bypass routes for aircraft overflying high-density terminal areas;
- alternative or contingency routes on either a planned or an ad hoc basis;
- establishment of optimum locations for holding patterns;
- optimised feeder routes;
c) reduction in flight distances resulting in fuel savings;
d) reduction in the number of ground navigation facilities.
2.2.7 B-RNAV has been widely implemented throughout the world. The use of B-RNAV applies to all IFR flights operating as GAT, in conformity with the ICAO procedures.
2.2.8 In some cases B-RNAV has also been implemented on certain SIDs and STARs provided that the following criteria are met:
a) The B-RNAV portion of the route is above Minimum Sector Altitude / Minimum Flight Altitude / Minimum Radar Vectoring Altitude (as appropriate), and has been developed in accordance with established PANS-OPS criteria for en-route operations and conforms to B-RNAV en- route design principles.
b) The initial portion of departure procedures is non-RNAV (or P-RNAV) up to a conventional fix beyond which the B-RNAV procedure is provided in accordance with the criteria given above.
c) The B-RNAV portion of an arrival route terminates at a conventional fix in accordance with the criteria given above and the arrival is completed by an alternative final approach procedure, also appropriately approved.
d) Due regard has been taken, during the design process, of the operating procedures of the users.
2.2.9 The specific procedures for B-RNAV operations are incorporated in ICAO Doc 7030/4 Ed. 1997.
2.2.10 In the ECAC region, the Joint Aviation Authorities (JAA) has published Temporary Guidance Leaflet (TGL) 2 that contains the airborne system criteria for certification.
2.2.11 The relevant State Authorities are responsible for ensuring that adequate provision is made for the training of air traffic controllers in RNAV operations.
2.2.12 From the ATC point of view, the handling of traffic on B-RNAV routes will not require any different handling from traffic on routes defined by VOR/DME (conventional ATS routes). It is likely, therefore, that the requirement for additional specific ATC training will be minimal. The revised route structure will be designed to ensure that ATC workload is not increased and where possible it is reduced in spite of increased traffic.
2.2.13 IFATCA does not have any published policy specifically relating to B-RNAV. There is however policy relating to generic RNAV principles.
2.2.14 IFATCA policy states:
|“Controllers should be presented with information, by any suitable means, concerning navigational capability of aircraft under their control.”|
This policy is still valid, especially as various types of RNAV are introduced. The variety of RNAV applications may result in a level of confusion arising amongst controllers. Certain types of RNAV equipage and / or capability will be required to operate on certain routes or fly certain procedures. The controller needs to have knowledge of the level of equipage and / or capability of the flight so as to be able to know whether a specific flight can be cleared on routes or procedures requiring such equipment or capability. The need for controllers to be aware of the navigational capability of aircraft under their control is increasing.
|“In airspace where random RNAV routings are permitted, the ATS system should be capable of processing random RNAV flight plans and controllers should be able to amend/update such information.”|
This policy may refer to airspace where random RNAV routings are feasible. Currently, RNAV routes tend to be fixed published routes. Some routes are available on a conditional basis, but the actual route is fixed and it is just the availability that varies. This policy is probably still applicable for areas where random RNAV routings may be feasible and should therefore remain in place.
|“Track prediction vectors should be available on radar displays used to control airspace where random RNAV procedures are permitted.”|
This policy refers to vectors on radar displays, which would suggest an en-route radar environment. Random RNAV procedures are generally associated with oceanic or remote airspace. However, there are Air Traffic Service Units (ATSUs), such as in Iceland, where SSR is used to monitor and control a large area of Oceanic airspace. In the case of Iceland, there are dynamic RNAV routes in the North Atlantic Track region, and aircraft fly using RNAV between lat/long coordinates. The radars are set on long range and prediction vectors are used on the radar to monitor the flights. As there are ATSUs that continue to use track prediction vectors in an RNAV environment, this policy statement should be retained.
2.3 Terminal Areas
2.3.1 RNAV operations in Terminal Areas, where issues such as traffic density, route interaction, complex traffic flows and terrain clearance start to come to the fore, generally require a more stringent navigational accuracy than that used for the en- route environment.
2.3.2 P-RNAV is being promoted for use below the Minimum Safety Altitude (MSA), due to the improved lateral navigation accuracy that can be obtained from P-RNAV. In the ECAC region, the use of B-RNAV below MSA is, effectively, being prohibited and the use of a new standard, Precision Area Navigation, or P-RNAV, is being encouraged.
2.3.3 Agenda item B.5.12 details discussion on P-RNAV procedures and IFATCA policy on P-RNAV.
2.4.1 There are various types of RNAV approach in use throughout the world. Standards vary considerably from State to State or region to region, although there are attempts to harmonise them underway.
2.4.2 RNP RNAV is being promoted as the industry standard for approach operations. It is being implemented on instrument approach procedures to provide increased availability, enhanced safety and reduced operating minima over and above that provided from traditional non-precision approaches.
2.4.3 The concept of RNP-RNAV is introduced in the Minimum Aviation System Performance Standards (MASPS) for Required Navigation Performance for Area Navigation (RNP-RNAV), (reference: RTCA DO 236A / EUROCAE ED 75).
2.4.4 RNP-RNAV combines the accuracy standards laid out in the ICAO Manual (Doc 9613) with specific containment integrity and containment continuity requirements, as well as functional and performance standards for the RNAV system to realise a capability that can meet future ATM requirements.
2.4.5 Vertical navigational accuracy is addressed by RNP RNAV as well as horizontal accuracy.
2.4.6 RNAV approaches are in use throughout the world. Procedures are available in locations as diverse as Juno in Alaska, the Caribbean, Europe and southern Africa. Harmonisation is required so as to ensure that aircrews don’t face differing procedures from region to region, or State to State.
3.1 There are numerous varieties of RNAV in use at a multitude of locations around the world. Attempts have been made, and are continuing to be made, to introduce a degree of harmonisation for RNAV standards. IFATCA should support the harmonisation of RNAV standards and requirements.
3.2 The continued introduction of RNAV procedures around the world will require that policy be developed and reviewed on a regular basis to ensure that procedures are introduced in a manner that will be beneficial to controllers.
3.3 IFATCA should actively participate in ongoing discussions about the use of RNAV and the formulation of policy regarding the use of RNAV procedures.
3.4 For RNAV systems to be able to operate reliably and accurately there is a need for the navigation infrastructure (i.e. the ground-based and/or space-based navigation systems) to provide adequate coverage for the proposed RNAV route / procedure.
3.5 The integrity and reliability of RNAV systems requires that navigation co-ordinate data published for RNAV routes / procedures meet ICAO accuracy and integrity requirements. All co-ordinates published in the AIP and used in the aircraft navigation databases for RNAV purposes must be referenced to WGS 84. The user must have the necessary assurance that this data has not been corrupted or inadvertently modified.
3.6 RNAV routes and procedures must be designed and published in accordance with ICAO SARPS and regional guidelines.
3.7 Airborne systems used for RNAV routes and procedures must be certified for such use by the appropriate authority. Such certification will cover accuracy, integrity, reliability and availability requirements, subject to the type of RNAV required.
3.8 Flight crew must have the necessary approval to operate on the RNAV routes and procedures.
3.9 The concepts of 2D RNAV, 3D RNAV and TRNAV have developed during recent years. RNAV is no longer generally referred to in these terms. It is proposed that some of the existing IFATCA definitions are either deleted or amended.
3.10 IFATCA has existing policy that remains valid and should be left in place. Some of this policy has been highlighted previously in this Working Paper. The generic RNAV policy statements below also remain current and should be retained:
|3.10.1 “Adequate training must be provided for controllers managing RNAV operations; such items as RTF phraseology, co-ordination procedures and conflict identification need to be considered.”
3.10.2 “IFATCA should ensure that controllers’ expertise is used in the deliberations taking place to provide appropriate specifications for the use of RNAV.”
3.11 Policy should be developed to enable RNAV to be deployed where operational and environmental benefits can be obtained. At present there is limited policy available. Some of the existing policy remains valid. However, there is a need to introduce new policy to ensure that RNAV routes and procedures are introduced in a standardised manner that will ultimately be beneficial to controllers.
3.12 There are few ICAO standards available regarding separation minima to be used in conjunction with RNAV procedures. This issue is perhaps the single largest problem stopping the widespread introduction of RNAV procedures in all of the ATC environments, ranging from Oceanic areas to Approaches. To date, ICAO has only published route spacing criteria for a limited number of RNP values. Separation minima for use for RNAV procedures need to be developed and published as a matter of priority.
3.13 The introduction of RNAV procedures will result in a fundamental change to the way in which controllers work. RNAV will enable systemisation to occur. For instance, the implementation of 3D RNAV profiles will enable SIDs and STARs to be deconflicted, resulting in the removal of the need for the same level of tactical intervention by controllers. The controller’s role moves from a tactical one to more of a monitoring task. This change is significant and should be investigated by means of Human Factors studies.
It is recommended that:
4.1 RNAV route structures must be designed to ensure that ATC workload is not increased and, where possible, it is reduced in spite of increased traffic.
4.2 RNAV standards should be harmonized throughout the world. Harmonisation will result in common standards, decreasing the diverse types of RNAV procedures that are currently encountered by air crews operating around the world.
4.3 SC4 undertake Human Factors studies to investigate the impact on controllers of moving from a positive control methodology to one of monitoring
IFATCA Christchurch 1993, WP88 – RNAV: Monitoring the Implementation.
IFATCA Christchurch 1993, WP90 – RNAV Procedural Separation Longitudinal Distance Standard Minima.
IFATCA Ottawa 1994, WP91 – Amendment to Current Policy on RNAV Procedural Separation Minima.
IFATCA Ottawa 1994, WP99 – RNP for Approach and Landing.
ICAO Manual of RNAV Operations (Doc 9573).
ICAO Annex 11 – “Air Traffic Services”, 1994.
ICAO Doc. 9613-AN/937 Manual on Required Navigation Performance (RNP), First Edition – 1994.
ICAO PANS-RAC Doc 4444 – “Rules of the Air and Air Traffic Services”, 1985.
ICAO Doc 7030 – “Regional Supplementary Procedures”, 1987.
ICAO Doc 8168 – “Procedures for Air Traffic Services – Aircraft Operations (PANS-OPS).
SPECIMEN AIC – Implementation of B-RNAV in the Airspace of the Member States of ECAC.
EUROCONTROL Doc 003-93 – Area Navigation Equipment – Operational Requirements and Functional Requirements.
JAA TGL-2 – “Advisory Material for the Airworthiness Approval of Navigation Systems for use in European Airspace designated for Basic RNAV Operations”, 1997.
RTCA Do236/EUROCAE ED75 – Minimum Aviation System Performance Standards: Required Navigation Performance for Area Navigation, 1996.
JAA TGL-10 – Airworthiness and Operational Approval for Precision RNAV Operations in Designated European Airspace.
JAA TGL-10 – Frequently Asked Questions.
JAA TGL-3 Rev 1 – JAA Interim Guidance Material on Airworthiness Approval and Operational Criteria for the Use of the NAVSTAR Global Positioning System (GPS).
JAA TGL-2 Rev 1 – JAA Guidance Material on Airworthiness Approval and Operational Criteria for the Use of Navigation Systems in European Airspace Designated for Basic RNAV Operations.
Advisory Circular AC No: 90-96 – US Department of Transportation – Federal Aviation Administration. Advisory Circular describing Approval of U.S. Operators and Aircraft to Operate under Instrument Flight Rules (IFR) in European Air space Designated for Basic Area Navigation (BRNAV/RNP-5).
AC 120.29A – Approval Guidance for Approach and Landing.
Notice of Proposed Rulemaking for RNAV Routes.
FAA Order 8260.51 – basic TERPS Criteria for RNP Operations.
Last Update: September 29, 2020