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Innsbruck Airport joins the EGNOS family

Monday, October 29, 2018
Innsbruck Control Tower

Performance Based Navigation (PBN) has a long history in Innsbruck, the picturesque capital city of the Austrian province Tyrol. Innsbruck has around 125,000 inhabitants and is located in the Inn Valley, surrounded by two mountain ranges with an elevation of up to 2,500m/8,200 feet.

Since its beginnings, Innsbruck Airport has always faced the challenge of accessibility under Instrument Flight Rules (IFR) in inclement weather situations. Early ground-based navigation procedures evolved from and Non-Directional Beacon (NDB) approach to a localizer approach (a full Instrument Flight Rules - ILS - is not possible due to the winding Inn Valley’s geometry) in the 1970s but always resulted in high approach minima in order to comply with ICAO regulations. Thus, in low ceiling or reduced visibility situations, the accessibility of Innsbruck airport became vastly compromised, leading to chronically high missed-approach and diversion rates.

A first PBN revolution came in 2005, when Austro Control designed on of the world’s first RNP AR (Required Navigation Performance, Authorization Required) approaches to Innsbruck’s runway 26, cutting the decision height by half and being a major breakthrough in stabilizing all-weather operations, whilst attracting additional winter traffic.

Later in 2012, Austro Control together with a number of operators who were involved in all phases of the development, also pioneered a PBN/conventional “hybrid procedure”, by combining the existing localizer approach with the missed approach phase of the RNP procedure, providing an additional 300ft reduction in the decision height over the RNP AR approach. Finally, and in a logical evolution of innovative PBN tools available, Innsbruck has quite recently also entered the world of EGNOS approaches by featuring a full SBAS CAT-I procedure to runway 26, which particularly aims at serving the considerable business aviation operating at the alpine Airport. Again, the design was especially complex and challenging due to the surrounding mountains of the area. Actually, prior to the design phase we performed a quality assessment of the GPS/EGNOS Signal-In-Space by means of simulations and measurements on site. The analysis was carried out within the framework of the IMPROWE project by the German Aerospace Center (DLR) taking into account signal shading effects. The result showed that EGNOS LPV-200 Service Level is available despite potential high terrain masking values. As with any other flight procedure that has to be published in the national AIP, the procedure was properly flight inspected/validated.

Despite not having a lower minima than the above-mentioned LOC/RNP approach, the resulting LPV approach offers a high-quality vertical guidance based on SBAS CAT-I for the very first time in Innsbruck.

The outcome is therefore a great success for airspace users and proves once again the fruitful cooperation between Austro Control, DLR, ESSP/GSA and the diverse airspace user community.