Moving towards wide-scale SBAS CAT-I deployment
The EGNOS Safety-of-Life (SoL) Service became available for its primary purpose of aircraft navigation in March 2011, supporting the implementation of Approach Procedures with Vertical guidance (APV) down to LPV minimum. On Sept 29, 2015, the LPV-200 Service Level was declared operational and added within the SoL Service, enabling the implementation of LPV approaches down to a Decision Height (DH) of 200ft (also known as SBAS CAT I). It became an even more attractive alternative to ILS CAT I and today many airlines are implementing this technology.
During the period that the APV was provided alone (nearly 5 years), almost 220 LPV approaches based on EGNOS were put in operation, plus around 90 LNAV/VNAV approaches were EGNOS was usable as the source of vertical navigation. By mid-2018 the figure has almost doubled and today we can find about 430 LPV approaches deployed all around Europe, and more than 100 of the above mentioned LNAV/VNAV.
It is interesting to look at how the process has taken place and, in particular, how ANSPs have made use of the more performing CAT I capability provided by EGNOS. When looking at the overall 430 LPV figure, it should be noted that 300 are based on the APV service level, and that 130 have been implemented as CAT I approaches. But it is worth noting that out of the 130 CAT I LPVs, a conversion from APV to CAT I took place at least for 54 of them, confirming how relevant the improvements brought by the CAT I approaches over the APV ones might be for some scenarios and/or ANSPs.
A survey carried out by ESSP SAS during 2016 among early LPV-200 adopters indicated that:
- The main interests behind SBAS CAT I implementations were to achieve a cost-effective option and the best-quality back-up for ILS CAT I approaches, followed by an intention to reduce the landing minima and improve the airport’s accessibility;
- Over 90% of the CAT I approaches would be published at runways qualified as Precision Approach Instrument Runway within aerodromes with ATC services;
Almost 3 years after the declaration of the LPV-200 service level, two additional observations can be made. On the one hand, France leads the implementation of SBAS CAT I approaches with 61 of them, having implemented a lot of them at those runways affected by the ILS CAT I rationalization campaign initiated in 2016. As a consequence, also aircraft operators are increasingly showing interest in the technology.
On the other hand, today 10 States have already implemented SBAS CAT I approaches. But the number of States who plan to implement such kind of approach procedures keeps growing, and so does the total number of LPV approaches that will be deployed in Europe in the coming years. It should be reminded that its performances are similar to those provided by ILS CAT I but avoiding investment and maintenance costs.
Austria is one of the States who has firmly bet for EGNOS benefits since the very beginning, and in the next paragraphs the Austro Control Instrument Flight Procedures design team provides a few words about their experience:
Austro Control looks back on a long history of PBN activities and has always pursued a continuous implementation strategy for innovative procedures. After expanding the RNP approach concept throughout the country, the Austrian ANSP became an early adopter of Europe’s SBAS system EGNOS. In the scope of the FP7 ACCEPTA project, the first LPV approach procedures (based on APV criteria) for Linz and Graz airports were published in 2014, thereby adding vital experience in this field to Austro Control’s IFP team. Heavily used by general & business operators as well as the Austrian aircraft manufacturer Diamond Aircraft, the implementation has proven to be successful right from the beginning.
Given the fact that Austria is located inside the core coverage area of the European SBAS system and with the goal to increase operational safety and all-weather accessibility of airports, Austro Control has continued the roll-out of LPV approaches based on CAT-I criteria throughout the country, starting with Vienna airport, where all LPV approaches provide a Decision Height of 200ft, supposing the best quality back-up for ILS CAT II/III approach in RWY16, an equivalent performance for RWY11 and even improving the minimum for RWY34.
As a logical consequence, Austro Control’s IFP team also initiated the process of transforming “legacy” APVs at Linz and Graz into SBAS CAT-I approaches. This renewal process has been completed with the March 2018 AIRAC update which now has all Austrian SBAS procedures upgraded to CAT-I standards. Thus, Austro Control’s success story in EGNOS usage already has a lot to offer…but the journey continues.
- Both SBAS APV and SBAS CAT-I approaches are published in the Instrument Approach Charts in the form of an LPV minimum.
- Avionics equipment and certification and on-board installations do not distinguish between both types of approaches, hence being transparent from an airworthiness perspective.
- Source of the image: Vienna Airport.