1 INTRODUCTION

The European Geostationary Navigation Overlay Service (EGNOS) provides an augmentation signal to the Global Positioning System (GPS) Standard Positioning Service (SPS). Presently, EGNOS augments GPS using the L1 (1575.42 MHz) Coarse/Acquisition (C/A) civilian signal function. While the GPS consists of positioning and timing signals generated from spacecraft orbiting the Earth, EGNOS provides differential corrections and integrity information to GPS signals with a dedicated wide area ground infrastructure and geostationary satellites broadcasting the EGNOS signals over Europe.

EGNOS is providing three type of positioning services:

• The Open Service (OS) is broadcasted through Geostationary satellites and is available since the 1st of October 2009, and intends mainly to support mass market applications. All the details about the OS service may be found in the OS Service Definition Document (see the section 4. Reference Document).
• The Commercial Data Distribution Service (CDDS) uses Internet based resources rather than Geostationary satellites to broadcast EGNOS data, and is intended for ground based customers who require enhanced performance for commercial and professional use. A dedicated CDDS Service Definition Document will be published for the CDDS when the service is declared available (in 2011).
• The Safety of Life Service (SoL) is broadcasted through Geostationary satellites. It is providing the most stringent level of signal-in-space performance to all Safety of Life user communities in Europe, in particular aviation, and it is the subject of this AIC.
  • The SoL signals provided by EGNOS are consistent with the SBAS (Satellite Based Augmentation System) standards promulgated by the International Civil Aviation Organisation (ICAO), and allow providing a positioning service along En-Route, Terminal, Non Precision Approaches (NPA) and Approaches with Vertical guidance (APV).
  • There are two EGNOS SoL service areas. For operations ranging from En-route to NPA, the geographical zone where SBAS avionics may use EGNOS signals is defined by the following geographical coordinates: [40° East, 20° North], [40° East, 70° North], [40° West, 70° North], [40° West, 20° North]. For APV operations using EGNOS vertical guidance, which will be subject to a specific AIC, the service area will be available in the SoL Service Definition Document (to be published for the 1st of November 2010, see the section 4.Reference Document).

Similar SBAS systems, designed versus the same ICAO standard have already been commissioned by the US and Canada (Wide Area Augmentation System – WAAS) and Japan (MSAS).WAAS is currently approved to support navigation for En route, Terminal phases of flight, and approaches classified by ICAO as NPA (Non Precision Approaches) and APV (APproaches with Vertical guidance), over the WAAS designated Service area. MSAS is currently approved to support navigation for En route and Terminal phases of flight, and NPA, over the MSAS designated Service area. Implementation of additional SBAS systems is being investigated in other regions of the world (e.g. GAGAN in India and SDCM in Russia). Users already authorized to fly operations based upon other SBAS signals (e.g.WAAS) must consult this AIC to be aware of differences and operational restrictions.

2 EGNOS SOL SERVICE INTRODUCTION

The SoL service is expected to be promulgated in Europe in two steps

The first step, from the December 2010, consisted of removing from the EGNOS signal the specific message (called Message Type 0) which were limiting EGNOS utilisation to Open Service (OS) users.

Consequently, from December 2010, airspace users equipped with SBAS avionics receivers, as defined within TSO C145(), TSO C146(), ETSO C145(), ETSO C146(), may use the EGNOS signals to improve the accuracy and availability of GPS signals, during En-route, Terminal and Non Precision Approach phases of flight, over the geographical area defined in section 1.2 (this area encompasses the French airspace).

During this first step, the MT 0, may be broadcasted again.

The SBAS avionics standards are compatible with either the use of GPS signals augmented with ABAS (Airborne Based Augmentation System), using integrity provision techniques such as Receiver Autonomous Integrity Monitoring (RAIM), or GPS signals augmented with SBAS. When both augmentations are available, the SBAS receiver evaluates in real time the quality of the positioning service provided by ABAS and SBAS, and automatically selects the best solution. When the message type 0 (MT 0) is removed, it is expected that the superior quality of SBAS positioning will conduct the SBAS avionics to select the use of EGNOS signals, for the lateral guidance of En-route, Terminal and Non Precision Approach phases of flight. Therefore, for users equipped with SBAS avionics, the major change introduced during this first step of EGNOS SoL introduction, will be to rely on EGNOS signals, in addition to GPS signals, rather than on the sole use of GPS signals augmented by ABAS.

Therefore no specific EGNOS procedures will be published by Avinor or other European Air Navigation Service Providers (ANSP) during this phase, and until the second step defined in section 2.3 below. Users equipped with ABAS avionics, which do not support SBAS positioning, will not be impacted by EGNOS MT0 removal.

Note: Some SBAS receiver manufacturers have included the possibility within the airborne receiver to deselect one specific SBAS provider. This selection/deselection scheme may be exerted through positioning of a specific bit, on an AIRAC database update cycle (every 28 days).When equipped with those SBAS receivers, currently deselecting EGNOS, users may not be capable to use EGNOS signals, and are invited to contact their avionics manufacturers.

Continental United States or Canadian airspace users equipped with WAAS capable receivers are generally approved to fly APV operations based on Barometric Vertical Guidance in this airspace, with the use of WAAS vertical guidance alternatively to Barometric vertical guidance. Barometric based APV operations are published on some RNAV(GNSS) approach charts, and materialize with a minima line designated as LNAV/VNAV on those approach charts. However, the use of EGNOS vertical guidance to fly such operations, is currently not supported by the APV airworthiness material in Europe and therefore is not authorized in Norwegian airspace, until further notice.

The second step (planned 2 March 2011) will support the full SoL Service, including APV approaches based upon the use of EGNOS vertical guidance, in addition to Enroute, Terminal and Non Precision Approach phases of flight.

In opposition to the first step discussed above, APV operations based upon the use of EGNOS vertical guidance will require a specific procedure publication by Avinor or other ANSPs, as well as a corresponding specific approach procedure loaded within the aircraft database. This ANSP publication will materialize as a minima line designated as LPV on RNAV(GNSS) approach charts, usually in addition to the LNAV minima line, representing the Non Precision Approach minima.

This step is only mentioned here for information and will be subject to a specific AIC.

3 OPERATIONAL IMPACT

The availability of the lateral positioning based on EGNOS allowing Non Precision Approaches, is expected to vary within the area where SBAS avionics are currently allowed to use EGNOS signals ([40° East, 20° North], [40° East, 70° North], [40° West, 70° North], [40° West, 20° North]). As explained in section 2, when and where EGNOS signals will not allow supporting a lateral positioning based on SBAS, the SBAS avionics will automatically revert to a positioning mode based on ABAS. Therefore no operational impact, due to the unavailability of the lateral positioning service of EGNOS, is expected with respect to users only equipped with ABAS avionics.

The changes described in this AIC only impact the type of lateral positioning service, along already published procedures. Therefore, no specific or new operational requirements are required for the flight crew. Airspace users equipped with SBAS receivers are invited to refer to their Aircraft Flight Manuals / Pilot Operating Handbook.

4 REFERENCE DOCUMENTS

Open Service / Service Definition Document

http://www.essp-sas.eu/printed_documents/egnos_sdd_os_v1.pdf

Safety of Life Service / Service Definition Document
http://www.essp-sas.eu/printed_documents/

AMC 20-27 : Airworthiness Approval and Operational Criteria for RNP APPROACH (RNP APCH) Operations Including APV BAROVNAV Operations, published 23/12/2009

AMC 20-28 : Airworthiness Approval and Operational Criteria for RNAV GNSS approach operation to LPV minima using SBAS, NPA 2009-04, draft version 19/03/2009

5 OTHER INFORMATION

Information related to certification and operational approval for the operations described in this AIC may be obtained at:

Luftfartstilsynet
Postboks 243
8001 Bodø
Norge

Telefon: +47 75 58 50 00
Telefaks: +47 75 58 50 05
E-post: postmottak@caa.no
Postadresse: Postboks 243, 8001 BODØ