RNAV Approaches

Instrument approach procedures using RNAV with GPS positioning have been possible since 1998 when ICAO published the Basic GNSS approach design criteria. Certain ECAC states introduced GPS approach procedures based upon these criteria and used the JAA TGL 3 guidance material to develop national regulations for certification and operational approval.

The JAA subsequently decided that TGL 3 provided insufficient guidance on the subject and a new guidance document, provisionally entitled TGL xx, has been under development for the past 3 years. It is anticipated that this material will be published by EASA during 2006, as part of the AMC 20 series, after the appropriate consultation period.

In 2001 ICAO published procedure design criteria for RNAV approaches using Barometric VNAV and certain States have conducted trials based upon these criteria. The RNAV/Baro VNAV criteria are based upon a lateral navigation performance associated with RNAV (GNSS) or RNP 0.3 and a vertical navigation performance based upon the use of Barometric inputs with a VNAV functionality in the airborne system.

TGL xx addresses the use of LNAV/VNAV as well as LNAV-only approach operations. An additional TGL xz is also being developed by JAA/EASA to cover RNP operations within terminal airspace, including RNP LNAV/VNAV approach operations down to RNP 0.1. This document is expected to be published by EASA in late 2006 or early 2007.

EGNOS becomes operationally available in 2006 and can be used to support APV II approaches. ICAO has also published design criteria for APV I and APV II approaches and some States have indicated their intention to implement such approaches. EASA proposes to update the TGL xx material to include APV operations.

EUROCONTROL has sponsored the development of a Safety Case covering RNAV approaches (LNAV and LNAV/VNAV) and APV operations which are both currently undergoing peer-review by State organizations. EUROCONTROL is also developing an OCA/H Estimator tool to assist States in deciding which approach variant to implement at any given airport.