Implementing precision approaches supported by satellite-based augmentation systems in the Austrian Alps

Abstract

Aerodromes located in mountainous areas are seldom served by approaches with three-dimensional guidance based on instrument landing systems due to the lack of flexibility to define glide paths free of obstacles. But, three-dimensional approaches are always preferred due to their effectiveness against controlled flight into terrain. Free access to three-dimensional angular approaches is possible today without special authorization and ground infrastructure. Some airports in mountainous areas of the United States, Canada, and Europe already benefit from them due to the latest advances in satellite-based augmentation techniques. The majority of these procedures have not been developed as category-one precision approaches, even though the latest operational service level foresees it. Reported here are the signal assessment and procedure design carried out to enable the first category-one precision approach supported by satellite-based augmentation system at an Austrian airport surrounded by one of the most challenging terrains worldwide. The design and implementation of such a procedure in mountainous terrain is feasible after a thorough signal quality assessment. It can be placed where a classical instrument landing-system-based approach procedure does not work and provides precision guidance for aircraft in instrument meteorological conditions. This in turn enables a higher runway throughput and reduces cost for the users. When the controlling obstacle is located outside of the precision segment, special attention should be put on the availability requirements.