33RD ANNUAL CONFERENCE, Ottawa, Canada, 18-22 April 1994
WP No. XX1
Monitor the Application and Implementation of RNAV
At the 32nd IFATCA Conference in Christchurch New Zealand , SC 1 was given the task of continuing to monitor the application and implementation of RNAV. The WP 88 on this subject presented at Christchurch conference proposed various Policy Statements, and for the first time IFATCA now has some policy on this subject.
In 1993 two major initiatives have been taken with respect to the use of RNAV within the ATC system.
Firstly, ICAO proposals for changes to lateral separation minima for RNAV equipped aircraft have been published. Although these proposals are detailed, they do contain a ‘Note’ stating:
|“As no collision risk/target level of safety method has yet been developed for non parallel routes, the protected airspace values outlined in para 22.214.171.124.3 (of the proposals) were determined using a containment approach and the extensive operational experience of Australia and Canada in the application of RNAV distance – based separations”.|
It is understood that these proposals were not developed in time to meet the 1994 ICAO Air PANS RAC publication deadline, so there is time for IFATCA to comment on them. With this in mind, they are attached to this paper as annex 1.
The second initiative is within the European region, and involves the introduction, in November 1993, of an RNAV ‘Trunk Route’ system. European ATS authorities have co-operated in a serious attempt to take advantage of the navigational capability of modern aircraft. In some cases, more direct routes; in other areas, where this approach has not been possible, the current ATS route structure has been over-laid with co-incident RNAV routes, allowing flight on the routes solely by reference to RNAV instrumentation. This has made flight planning – for the operators at least – a much simpler matter, since in some cases a single RNAV route designator can replace several airways in the flight plan. There is also less likelihood of errors in the routing when fewer designators are involved. However , in some countries, the controller still does not know , from the information presented on his/her data display , whether a particular aircraft is RNAV equipped. This could cause unnecessary RT loading, when the crew are asked if they can accept an RNAV routing. In some cases it is assumed that this will be the case, from the fact that the RNAV routes are filled, but whether or not this is good ATC practice remains open to question.
Direct routing has been a practical ‘fact of life ‘ for many years during quiet periods or within airspace not subject to heavy traffic loads. However, one of the big advantages of now having many of these direct routes defined and documented is that operators can plan to use them, rather than having to flight plan a longer route and being required to carry the appropriate fuel for the greater distance.
Whilst direct routeing pose no major problems to ATC in light traffic conditions, the same is not true once the traffic loading becomes greater. Potential conflict points are generated in diverse positions, and controllers workload can be increased considerably , such problems are identified and dealt with. Automatic conflict detection/conflict alert is a pre-requisite when dealing with more or high volumes of traffic on direct routeing.
No information has been presented to SC1 to indicate that problems have arisen in any country as a result of implementation or development of already established , RNAV routes during the period since the Christchurch Conference.
Work continues internationally to bring the benefits of RNAV operation into use. Many countries now offer RNAV routes as part of their ATS structure, and some make use of aircraft’s Precision RNAV capabilities and/or offer random RNAV routings.
The IFATCA policy, established at the Christchurch conference, remains valid, and still needs to be implemented in many countries. It is highly desirable to have appropriate ATC documentation and training in place before controllers are faced with new routing and navigation arrangements. This will probably be even more important in the sphere of Precision RNAV than it is for Basic RNAV.
Last Update: September 20, 2020