This Aeronautical Information Circular (AIC) aims to publicize the use of the SATDIS tool, a tool for predicting the availability of the RAIM (Receiver Autonomous Integrity Monitoring) service at the main domestic airports. The information provided by this tool is essential for the planning of aircraft users or operators who intend to carry out performance-based approach operations (PBN) at Brazilian aerodromes that have an Instrument Approach Chart (IAC) published with RNAV, RNP APCH and RNP (AR) navigation specifications.

The provisions established in this AIC apply to all SISCEAB (Brazilian Airspace Control System) users and aircraft operators who intend to carry out RNAV and RNP APPROACH operations at Brazilian aerodromes.

None.

2.1. With technological advances and the development of autonomous navigation systems, a new navigation concept has been implemented, based on principles different from those that rely on ground-based sensors for air navigation. This concept emerged and has been widely used for en-route air operations, as well as for airport approaches and departures: these are performance-based air navigation procedures, known as PBN operations.

2.2. When establishing the concept of Performance-Based Navigation (PBN), ICAO specified requirements to be met for conducting these operations in terms of accuracy, integrity, and availability of GNSS signals, which are necessary for operation within a given airspace.

2.3. The PBN concept specifies that on-board navigation systems must be evaluated in terms of accuracy, integrity, continuity and functionality for the execution of PBN procedures. Regarding the concept of integrity, it has been established that aircraft, in order to carry out more precise operations such as RNP, must be equipped with navigations systems that monitor and alert the flight crew when the performance required for the operation is outside the safety parameters established for that portion of the airspace (p. 89, Doc 9613).

2.4. The implementation of tools that allow for the early prediction of the availability of GPS satellites for a desired air operation has led ICAO to issue recommendations to all users or operators wishing to carry out RNP operations. They must ensure the availability and integrity of the GNSS signals used for navigation even before starting the flight, through a pre-flight prediction. Such guidelines were incorporated into the Service Instruction (IS) No. 91-001I, Operational Approval of Performance-Based Navigation (PBN), of the Brazilian National Civil Aviation Agency (ANAC).

2.5. In light of the above, operators of aircraft certified for PBN operations must, in the pre-flight phase, consult a RAIM prediction tool in order to ensure the availability of the minimum number of GPS satellites required for the intended operation and the integrity level of the signals, concerning the type of PBN operation to be employed. This aims to ensure that this requirement is not degraded to the point of compromising the required operation. In Brazil, the RAIM availability prediction will be provided through NOTAM, but it will be limited only to aerodromes that have RNP/RNAV Standard Instrument Departures (SID), Standard Terminal Arrivals (STAR), and Instrument Approach (IAC) procedures. Route predictions will not be made available.

2.6. The RAIM prediction service differs from the aircraft's on-board integrity monitoring system because, while the latter is inherent to the aircraft's avionics and is designed to indicate integrity in real-time, at the moment the aircraft performs the operation, the service provided by SATDIS refers to a forecast of the satellite architecture 72 hours in advance. Paying attention to the availability and integrity information provided by this tool allows users to plan their flights and, depending on the degradation status of the signals, to reschedule their flights or cancel the operation.

2.7. ICAO Doc 9613 - Performance-Based Navigation (PBN) Manual recommends that, if a continuous loss of detection of GPS satellite signals is identified through prediction for more than five (5) minutes, PBN operations should be reviewed (delaying the departure, planning a different type of procedure or even canceling the operation). The RAIM unavailability NOTAM information can be used by the operator, with sufficient advance notice, to plan the operation of their aircraft more efficiently, adopting the procedures mentioned above.

2.8. ATS authorities may suspend PBN operations following the issuance of a NOTAM that establishes the degradation of PBN operations due to the unavailability of the GPS constellation for a given location.

3.1.1. It is a RAIM prediction tool developed by NAVBLUE, which informs the expectation of meeting conditions for a given PBN operation. Therefore, the user must be aware that SATDIS RAIM or GPS availability may be lost in flight and must provide alternative procedures if this occurs.

3.1.2. The information contained in the RAIM prediction service presented by the SATDIS RAIM tool takes into account the latest information regarding the almanacs relating to the constellation of GPS Satellites and the latest NANUS (Notice Advisory to Navstar Users) issued by the Navigation Center of the United States Coast Guard.

3.1.3. The Department of Airspace Control (DECEA) will make available through NOTAM information obtained from the SATDIS RAIM Prediction Service for up to 72 hours. This information will be useful for users and ATS units to plan the implementation of alternative means for operations.

3.1.4. The availability and integrity information to be provided by DECEA will be obtained through the SATDIS SAM website (available at https://satdis.gnss.navblue.cloud/satdis/home.html?0) for the RAIM prediction service, to domestic airports.

3.2.1. RAIM unavailability information will be disseminated by the Air Navigation Management Center (CGNA) at least two days prior to the event, via NOTAM, for all Brazilian locations that have published RNP/RNAV Standard Instrument Departure (SID), Standard Terminal Arrival (STAR), and Instrument Approach (IAC) procedures.

3.2.2. The information disseminated by NOTAM refers to the parameterized conditions, presented below by the fixed parameters provided by NOTAM:

a) Receiver – defined only for TSO 145/146 compatible receiver;
b) Baro Aid – availability of Baro VNAV procedure always present: “ON”;
c) SA – selective availability will be considered as not active, that is, “SA-OFF”;
d) Algorithm – defined for FDE or “Fault Detection and Exclusion”; and
e) Mask angle – is the angle (set to 5º) established between the azimuth of the satellites' orbital plane and the horizontal plane of the earth at the location's reference point. (p. 297, Doc 9613).

3.2.3. The NOTAM regarding RAIM unavailability will be published at least to two days in advance, allowing the users to better plan their flights, taking into account the GPS constellation scenario. Below is an example of a NOTAM on RAIM unavailability. The example refers to Santos Dumont Aerodrome (SBRJ), where the time periods are indicated in which there will not be an adequate satellite geometry for the RNP approach operation, according to the aforementioned parameters.

(E0025/24 NOTAMN
Q) SBCW/QGAAU/I/NBO/A/000/999/2255S04310W/025
A) SBRJ
B) 1107060600
C) 1507062143
D) 0600-0615 0812-0834 2127-2143
E) GNSS RNP NEG AVBL)

4.1. Cases not provided for in this AIC shall be settled by the Head of DECEA’s Operations Subdepartment.

4.2. This AIC republish the AIC A 26/24.