Design and Testing of a Vertically Guided High-Precision Approach into Salzburg Airport

The approach to landing on runway 33 of Salzburg Airport in Austria is severely impacted by mountainous terrain on the extended runway centerline. This renders all straight-in approaches, except those based on required navigation performance (RNP) with authorization required (AR), impossible. Only the high navigation accuracy available under RNP-AR minimizes the required obstacle protection areas sufficiently to not be penetrated by the terrain. The combination of RNP-AR and localizer performance with vertical guidance makes it further possible to use a more precise angular guidance for the final approach. In Salzburg, this enables a reduction of the decision height from 368 to 218 ft above aerodrome level because the critical terrain and obstacles now fall outside of the protection areas. A level D full flight simulator test with an Airbus A350 showed that advanced RNP 0.1 coding is sufficient to achieve RNP 0.1 performance under all permitted environmental conditions.