ATM Modernization

Editor’s Note: Advances in Satnav

By David Jensen | March 1, 2003
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Satellite navigation has made some giant strides in recent months. As we report in our story on the Federal Aviation Administration’s (FAA’s) Capstone Program (page 17), a wide area augmentation system (WAAS)/GPS receiver was to have gained technical standard order (TSO) approval in February, for use in aircraft participating in the program. Subsequently, a special federal aviation regulation (FAR) was to be implemented this month. It approves procedures in which GPS serves as a primary means of navigation in the parts of Alaska where Capstone is taking place.

Primary means approval gives GPS a new status and represents a major milestone for satellite navigation. Not surprisingly, it emerges from the Capstone Program Office, whose innovative staff also is establishing a low-level, instrument flight rules (IFR) route structure in southeastern Alaska, based on GPS navigation.

Indeed, the folks in the Capstone Program Office seem to greatly enjoy the inventive atmosphere they have created to develop safer, more efficient air travel in what one official calls "our mini-NAS" (National Airspace System). "I won’t say we’re a designated test area," the official says. "But if there wasn’t Capstone, the FAA would have to invent a test area like this."

More than testing new ideas, the Capstone Program Office invents new ideas. For example, the Capstone staff has demonstrated an approach tool that will alert pilots of an encroachment upon the runway boundary by another aircraft or ground vehicle. The system, which uses GPS for vehicle positioning, has been proven to work. "We just need transmitters for the ground vehicles," the official reports.

But not all new developments for satnav have been taking place in Alaska. At a late-January RTCA meeting in Washington, D.C., FAA officials announced the contractor acceptance of the WAAS system. The acceptance followed a 60-day test period at FAA Technical Center, in which WAAS reportedly "met all requirements."

The WAAS system even exceeded a few requirements. It was to provide 95 percent availability over 75 percent of the continental United States (CONUS), but testing reportedly shows that WAAS provides such availability over 96 percent of the CONUS. The Raytheon system met the requirements for both lateral and vertical navigation (LNAV/VNAV), and it could be commissioned in the NAS for non-precision approach and en-route navigation by as early as July 10. Currently, about 400 LNAV/VNAV approaches have been published and the FAA’s goal is to have 700 to 800 published by July.

FAA acceptance of WAAS has been a long time coming. The program has struggled to meet all of its requirements. However, with WAAS commissioning apparently imminent, FAA plans to proceed aggressively by establishing procedures for LPV (loosely meaning Localizer Performance with Vertical guidance) approaches, using WAAS. Essentially, FAA must find that LPV performance equals that of a localizer on an ILS. FAA plans to have five LPV approaches published by September. Most of them reportedly will be in the Washington, D.C., area.

Meanwhile, not far from the RTCA headquarters in Washington, the Air Traffic Controller Association sponsored a symposium Jan. 30 titled "Navigation and Landing Transition Strategies for Aviation." The symposium was conceived to inform attendees about the status of the transition to satellite navigation and to discuss backup strategies to GPS.

Ground navaids are not all going away, because satellite navigation is neither jam-proof nor interference-free. The issue facing FAA is how many navaids to keep and how many to phase out. FAA indicates that by 2015, it plans to reduce the number of VORs and Category I ILSs by about 50 percent. The agency plans to increase slightly the amount of Cat II/III ILSs over the next 15 years, from 117 to 125. The number of NDBs and DMEs will remain more or less constant.

The question most discussed, but not resolved at the symposium was what to do about Loran-C. FAA’s decision on Loran-C’s continued use, in light of technological improvements to the navaid, was to be made early this year.

Meanwhile, the Capstone Program Office continues its experimentation and testing with satellite navigation and other new technologies. One Capstone official referred to the job as "wrestling one porcupine after another," because each technological challenge is multifaceted, thus "prickly."

There remain many porcupines to wrestle. However, early 2003 brought some significant successes to satellite navigation.

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