FAA Developing RAIM Prediction Tool

 - April 9, 2007, 11:26 AM

To help business aircraft operators cope with new Rnav routes and procedures as of September 1, the FAA is developing a Web-based RAIM (receiver autonomous integrity monitor) prediction service that will be made available for general use by flight crews, according to NBAA. Some FMS manufacturers have said their Rnav systems do not comply with the criteria of Advisory Circular 90-100 for DME/DME-based Rnav, meaning operations with affected avionics should be based solely on GPS. That led to concerns among some operators that they would not be able to accept clearances for the new Rnav routes and procedures unless they determined before departure that no GPS satellite outages were scheduled along their route of flight. However, the FAA has issued a reprieve of sorts by stating that between September 1 and the time its Web-based RAIM prediction tool is made available, RAIM prediction does not need to be performed for Rnav routes conducted in places where ATC provides radar monitoring or for Rnav departure/arrival procedures that have an associated “radar required” note on the chart. Also effective September 1 are new aircraft suffixes designed to allow controllers to identify aircraft capable of operating on the Rnav routes and procedures. Previous “/E” and “/F” requirements for flight director, vertical navigation and speed/altitude constraints no longer apply, while “/G” and “/L” suffixes apply to aircraft with global navigation satellite system en route and terminal capability, including GPS or WAAS navigation equipment, as well as FMS with GPS or WAAS sensors.