FAA seeks GPS backup strategies from industry

 - May 6, 2008, 8:56 AM

The FAA’s original plan to transition to sole-means GPS is no longer practical and some form of backup will be required for the foreseeable future, according to speakers at a recent Navigation Industry Day. This event was sponsored by the DOT, FAA and Civil Aviation Advanced Systems Development (CAASD), which is a component of the federally-funded MITRE research and development center and  a key FAA think-tank resource.

CAASD researchers are involved in virtually all FAA program planning, and the industry day allowed them to discuss their activities with representatives from aviation trade groups. Because the day was dedicated to navigation, the major focus was on GPS and, particularly, on actions resulting from the DOT Volpe Center report on GPS interference and the follow-on DOT action plan.

The decision to drop the sole-means GPS plan and require backup systems was strongly endorsed at the meeting by former FAA Administrator Langhorne Bond, who later described it as “the most important decision in U.S. air-navigation policy in a decade.”  Bond has been a constant critic of the sole-means concept, insisting from the outset that total dependence on any single system went against aviation’s traditional policy of safety through redundancy.

Unfortunately, the get-together  also showed that even the best forecasts of the future can be overtaken by events. In this case, CAASD researchers predicted to attendees that the GPS wide-area augmentation system (WAAS) would be able to support Cat I precision approaches throughout the NAS “around 2014.” This estimate was based on the availability of sufficient satellites of the new GPS III system, which would provide the two civil frequencies required to eliminate ionospheric errors in the signals. Launch of the new, higher-powered satellites had been scheduled to commence in 2009. But AIN has now learned that the GPS III schedule has again slipped.

Not only are the current, earlier-generation GPS satellites lasting much longer in orbit than originally expected, but the U.S. Air Force is now in a severe budget crunch over other space programs having higher national security priorities. Added to this, the USAF recently learned that the not-yet-built GPS III satellites could cost as much as three times that of the current units. The net result, according to Washington insiders, is that the first GPS III launch will probably slip to 2015 or later, and it could be as long as 2025 before the completely new constellation is in place.All may not be lost, however.

Europe’s GPS-like, two-frequency Galileo system still appears on track for full operation in 2008, although whether or not FAA would agree to approve it for WAAS-supported Cat I approaches in the NAS is an interesting question. After all, the U.S. did expect that foreign nations would jump at the opportunity to use GPS for Cat I approaches at their airports.

Still, Galileo should certainly be acceptable in other parts of the world, where WAAS equivalents appear to be springing up like wildflowers. Europe is almost ready with its European Geostationary Navigation Overlay System (EGNOS), Japan is moving ahead with its Multi-transport Satellite Augmentation System (MSAS), China and India are both busy developing systems of their own as well.