Exploiting Modern Aircraft Navigation Performance through Combining a SAAAR Approach with an LPV Final

We designed and tested a Special Aircraft and Air-crew Authorization Required (SAAAR), also known as Required Navigation Performance (RNP) Authorization Required (AR), to Localizer Performance with Vertical guidance (LPV) supported by the space-based augmentation system of GPS approach for runway 33 of Salzburg Airport, Austria. Approach to landing on runway 33 is severely impacted by mountainous terrain to the south of the airport that lies within the runway extended centerline, rendering all straight-in approaches but those based on RNP AR impossible. That is due to the high navigation accuracy available under RNP AR outside of the final approach segment. It makes it possible to keep the obstacle protection areas, which are constructed around the approach path and must be clear of obstacles to ensure the required obstacle clearance, very small so that they do not extend into the terrain. The combination of RNP AR and LPV, in turn, makes it possible to use the more precise angular guidance for the final approach available under LPV while still being able to exploit the significantly smaller RNP AR protection areas in all approach segments. In Salzburg, the resulting improved performance enables us to reduce the minima from 368 ft to 218 ft above runway threshold level. For the intermediate approach, we use curved legs based on a constant radius between two fixes (Radius to Fix legs) that lead onto the final approach course. The approach is coded as advanced RNP with 0.1 nautical mile values for the 95-percent lateral accuracy (RNP 0.1) on each sequence. Level D full flight simulator tests with an Airbus A350 showed that this coding is sufficient to achieve RNP 0.1 performance under all permitted conditions with the approach being presented to the pilots as RNP AR.