GBAS Instrument Flight Procedures, also named as GLS Procedures, are designed as per the provisions of ICAO Doc 8168 Vol. II by authorized procedure designers using available tools with latest survey reports and Obstacle & Terrain data. The two key outputs of the Procedures Design process are the corresponding Instrument Approach Procedure Chart and Final Approach Segment (FAS) Data Block. The FAS Data Block contains the information detailed within ICAO Annex 10, Volume 1 defining the final approach path. Validation of the parameters contained within the FAS Data Block is critical to assuring the safety of the approach. Flight Validation may be carried out for each GLS procedure either on a simulator or actual flight.
The GLS procedure design criteria defined in ICAO Doc 8168 Vol. II are based on ILS criteria and are related to the ground and airborne equipment performance and integrity required to meet the operational objectives described in ICAO Annex 10.
The procedure from en‐route to the GLS final approach segment and in the final missed approach phase conforms to the general criteria. The differences are found in the physical requirements for the GLS precision final approach segment as well as the initial and intermediate phases of the missed approach segment. These requirements are related to the performance of the GBAS system.
The FAS data block is prepared by the procedure designer and the accuracy of the path is dependent on the accuracy and integrity of the original data on the runway and calculations carried out by the designer. The final approach path parameters are designed using geodetic and geometric calculations and the parameters are formatted into a FAS data block in electronic media with a cyclic redundancy check (CRC). To insure the integrity of the data, the complete block is transferred electronically to users for inclusion of the path data in the GBAS system for transmission to user airborne systems.
Validation of GLS procedures could take reference to relevant information stipulated in ICAO Doc 9906 Volume 5 Validation of Instrument Flight Procedures.
