Safety issue: RNAV (GNSS) approach chart waypoint naming convention

The naming convention of using five capital letters for waypoint names, with only the final letter differing to identify each segment of the approach, was reported to cause clutter on the charts and GPS and FMS displays, and also increase the chance of a pilot misinterpreting a waypoint. This can lead to a loss of situational awareness.

With the growing body of international experience using RNAV (GNSS) approaches, it may be timely to review the naming convention.

Safety Recommendation

The Australian Transport Safety Bureau recommends that Airservices Australia address this safety issue.

Waypoint naming has some guidance in internationally agreed criteria and is constrained by what the flight management computer can handle.  PANS-OPS Vol II, Chapter 31, paragraph 31.1.2 states that:

'Each fix shall be published as a waypoint........................with an alphanumeric identifier.'

The database constraint and requirement for the waypoint to have a unique identifier has posed certain problems. 

• There are not enough unique ICAO 5-letter pronounceable identifiers to cover the number of new waypoints generated by RNAV procedures.
• To avoid confusion in the database, each waypoint needs a unique name (certain database coders talk of proliferation of one waypoint name e.g. Final fix Runway 36 - FFR36).

To counter this, various five character alphanumeric protocols have been developed globally, but essentially they all have the same function.  They provide the following:

• Uniqueness
• Attributes to a particular aerodrome
• Hierarchy
• General guidance to the pilot to aid situational awareness.

The Australian naming convention for waypoints used on Airservices Australia GNSS charts was devised by CASA and was endorsed by the industry GPS Implementation Team in the mid 1990s.   This waypoint naming convention is specified in the Manual of Standards Part 173 paragraph 8.9.3 Drafting Conventions.   The naming convention is designed on the following principles:

• RNAV (GNSS) waypoints shall be named using a unique five letter code.  
• The first three letters will be the last three letters of the airport Y code identifier (e.g.; SCB for YSCB).  
• The fourth will be the direction from which the procedure approaches the airport (e.g.; N, S, E, or W).    
• The fifth will identify the procedure fix type (I for the IF, F for the FAF, M for the MAPt, T for the MATF and H for the MAHF). NB: MATF - Missed approach turning fix. MAHF - Missed approach holding fix.
• For IAFs the letter will commence with A and will progress alphabetically, excepting 'O', to each IAF, noting that the identifiers for the succeeding fixes (IF, FAF, etc) shall not be used.

Any review of a naming convention must have global application as pilots from outside Australia must be able to grasp the principles of what is being applied.  Internationally there is still debate over the naming convention, but there is a consistent logic behind the Australian RNAV waypoint naming.

In light of the above, Airservices Australia, in conjunction with CASA, will consult the ICAO Obstacle Clearance Panel and Operations Panel to ascertain the international perspective with regard to waypoint naming to prior to reviewing the Australian naming convention.  

With regard to R20060022, Airservices staff met with CASA in early September [2007] to discuss this matter. CASA representatives expressed the view that the Australian naming convention was logical and consistent with ICAO requirements.

CASA representatives advised that action on this matter is on hold pending budget constraints. In the mean time CASA staff are attending international panels (ICAO OCP [International Civil Aviation Organization Obstacle Clearance Panel]) and taking on international advice as a preliminary step to any further action.

In addressing changes to naming conventions we will be taking into account the human factors aspects, with a focus on the pilot / cockpit environment. Changes will be developed in the context of being long term fixes, and will be implemented with an appropriate transition strategy.

Airservices strongly supports the commissioning of a joint working group with CASA to promote a broader understanding of the topic, as the issues surrounding waypoint naming conventions are outside the regulatory authority of Airservices as a CASR Part 173 Certificate holder.