Flying EGNOS Approaches in the Swiss Alps

Abstract

The European Geostationary Navigation Overlay Service (EGNOS) system is being developed in Europe to provide Global Positioning System (GPS) and GLONASS regional augmentation services to aviation, maritime and land users. The EGNOS system, as any other Wide Area Augmentation System (WAAS), relies on the broadcast of differential correction and integrity information in the pseudo-range domain, which are then used to provide a solution in the position domain. EGNOS is a major element of the European Satellite Navigation Program, which is jointly being implemented by the Commission of the European Union, the European Space Agency (ESA) and Eurocontrol (the European Organisation for the Safety of Air Navigation). It is also the first European step to the GALILEO system.

As part of the EGNOS validation activities, flight trials have been organised by ESA and the EGNOS Industrial Consortium at various locations in Europe during Spring 2005. To demonstrate the system capability in a challenging mountainous environment, tests have been conducted at Lugano airport in the Swiss Alps. Due to the difficult topography of the airport and its surroundings, the use of conventional ground based navigation aids present some limitations. For the trials, a new Satellite Based Augmentation System (SBAS) procedure has been designed to take advantage of the system flexibility. In particular, a reduction of the approach glide path angle has been achieved, potentially allowing more aircraft types to fly the approach than today. This article presents the operational benefits that could be obtained with the new test procedure. The very impressive EGNOS performance is also described in details, showing that it can support Approach Procedure with Vertical guidance (APV) operations even in a very challenging environment.