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Clarification of RNAV and BARO/VNAV Instrument Procedure Design Criteria

Topic code: 
Airspace and Aerodromes
Project status: 
Closed

Project Closure Notes

Project closed 14 December 2009

Amended AC 173-4(1) - Instrument Procedures Design Clarification of RNAV and BARO/VNAV Criteria has now been published. AC 173-4 has been amended to correct an error in the formulae located in paragraph 7.2 - Diagram

AC 173-4(0) was published on 8 December 2009.

Issue

Application of ICAO instrument procedure design criteria are mandated by CASR Part 173. Certain aspects of RNAV and BARO/VNAV criteria contained in ICAO Doc 8168 (PANS - Aircraft Operations) are unclear. Consequently, application of these criteria attract interpretation that may or may not be accurate.

The criteria that pertain to RNAV are contradictory while those that apply to BARO/VNAV are counter-intuitive. Strict application of the RNAV criteria applicable to segment blending is not possible without choosing between the two ideas that are presented. The BARO/VNAV criteria applicable to the missed approach use factors normally applied to other than the missed approach. Such counter-intuitive operations invite interpretation and are a possible source of errors. The confusion raised by the way the criteria are expressed may result in an inappropriate interpretation with consequent incorrect application.

The risk has been assessed as moderate for both the RNAV and BARO/VNAV issues.

If no action were taken, and an incorrect interpretation crept into the operating practices of a Certified Designer, the consequent procedures would not afford the level of safety expected of them with a resultant increased potential for impact with the ground or obstacles that would grow as that Designer continued to operate.

Project Objective

Develop an Advisory Circular under CASR Part 173 that removes the potential for confusion outlined above.

Status

This project was approved by Peter Boyd, Executive Manager, Standards Development & Future Technology Division on 7 August 2009.

Project management

Project Leader: Martin Chalk, Project Officer, Airways & Aerodromes Branch

Project Stakeholder: Peter Cromarty, Executive Manager, Airspace & Aerodrome Regulation Division

Standards Development Program Manager: Nick Fisher

Project Priority

Medium

Airspace and Infrastructure Users Group (SCC)

Airspace and Infrastructure Users Group Sub-committee

History

Title Details Date
Consultation updates in 2010
Final AC 173-4(1) – Instrument Procedures Design Clarification of RNAV & BARO/VNAV Criteria This Final AC has been updated and is available on the CASA website. 3 Aug 2010
Consultation updates in 2009
Project AS 09/12 - Clarification of RNAV and BARO/VNAV Instrument Procedure Design Criteria This project is now closed

See project closure notes.
14 Dec 2009
Final AC 173-4(0) – Instrument Procedures Design Clarification of RNAV & BARO/VNAV Criteria This Final AC has been published. 8 Dec 2009
Draft AC 173-4(0) - Instrument Procedures Design Clarification of RNAV and BARO/VNAV criteria Comments closed Monday 26 October 2009. 12 Oct 2009
Project AS 09/12 - Clarification of RNAV and BARO/VNAV Instrument Procedure Design Criteria Project approved. 12 Aug 2009