FAA moves toward full WAAS implementation
After 10 frustrating years of technical delays, escalating costs and contractor changes, the FAA’s GPS wide area augmentation system (WAAS) is approaching the level of performance the agency originally envisioned for it back in the late 1980s. With the system’s initial operational capability declared in 2003 and 18 months of satisfactory performance now behind them, WAAS advocates can see light at the end of the tunnel.
Most important, while there are a number of significant program milestones still ahead, WAAS avionics units are now entering the marketplace, allowing pilots to start to sample some of the system’s promised benefits, such as WAAS guided Lnav/Vnav approaches and, when procedures become plentiful later this year, “near Category I” localizer precision with vertical guidance (LPV) approaches down to 250 feet. Accuracy, too, is improved, with users routinely reporting positioning of better than 16.4 feet.
During this year and next year, 13 additional ground-based GPS monitoring stations are planned–five in Alaska and four each in Canada and Mexico–to supplement the 25 stations in use across the continental U.S. and to expand system coverage. These stations gather incoming signals from the GPS satellites and send the results to very-high-altitude geostationary satellites over the equator, which rebroadcast them to users as WAAS accuracy corrections and failure alerts.
Agency officials expect to declare that the system has attained full operational capability by 2007, when two new satellites are forecast to be up and running. Looking ahead even further, the FAA aims eventually to have WAAS provide full, ILS-equivalent, Category I service across the continental U.S.
This is a remarkable turnaround for a program that, during its lengthy gestation, frequently appeared to be teetering on the brink of cancellation. Since the program’s beginning in 1995, things looked distinctly unpromising, with the FAA terminating its initial development contract with Wilcox Electric for non-performance after only nine months. Transfer of the contract to Hughes Electronics, and later to Raytheon, brought things back on the rails, but not without serious problems in achieving the required levels of signal integrity, causing major delays in commissioning.
And all the time the dollar clock kept ticking. In 1994, before the FAA awarded the initial contract, agency officials estimated that WAAS development, production, implementation and follow-on operations and maintenance costs over the system’s planned 20-year life would total $1.4 billion. One year later, Wilcox estimated the total cost to be $1.8 billion.
Hughes increased the estimate to $2.4 billion, and Raytheon’s entry raised it to $3 billion. Currently, unofficial estimates put the bill at around $3.2 billion, although some FAA officials suggest that this figure could shrink eventually by as much $500 million. But others are skeptical. “We’ll probably never know how much WAAS really cost,” one senior DOT official told AIN, “But it’s hard to believe it can possibly be less than $3 billion.”
Will WAAS actually pay off? That’s a hard question to answer. The FAA’s original intent was that WAAS would augment the DOD’s GPS by providing the signal integrity necessary to meet FAA navaid standards, thereby paving the way to “sole means” satellite navigation, allowing the FAA and operators gradually to remove traditional ground-based aids and avionics, for substantial cost savings.
But after 9/11 and the revelation about the jamming vulnerability of GPS, the FAA canceled this policy, and continued to require backup systems. (One exception is in Alaska, where WAAS-equipped Capstone aircraft are exempt from carrying backup systems.) On the other hand, WAAS safety benefits in replacing “step-down” nonprecision approaches at non-ILS-equipped airports cannot be underestimated.
ICAO’s adoption of the WAAS concept–generically known as SBAS, for satellite-based augmentation system–underscores the safety benefits of replacing step-down nonprecision approaches with WAAS guidance. In addition, Europe, Japan and India have followed the FAA’s lead, with plans for their own systems– EGNOS, MSAS and GAGAN, respectively. These and other regional systems are all receiver-compatible with WAAS.
But like the program itself, the process of designating WAAS as the nation’s future Category I precision approach aid has been a roller-coaster ride. When the program was conceived in the late 1980s, it was forecast to achieve Category I by mid-1997. With subsequent changes in contractors and program priorities, the date slipped steadily until, in November 2003, an FAA official told Congress that the agency had canceled the WAAS Category I program in favor of the local area augmentation system (LAAS) for precision approaches.
Unfortunately, continuing difficulties and escalating costs in the development of Category I LAAS, coupled with only lukewarm airline interest, caused the FAA to shelve that program in January last year and relegate it to an R&D endeavor, alongside the previously sidelined Category II and III LAAS projects.
Revamped as GLS
Following the cancellation of LAAS, the FAA’s Joint Resources Council (JRC)–the agency’s senior decision-making body–“re-baselined” the whole WAAS project last year and reinstated its Category I component, under the revamped name of the GNSS Landing System (GLS).
The JRC also extended the WAAS operational life to 2028, with the expectation of implementing Category I GLS after 2013, when the system would use “dual GPS frequencies.” This term refers to additional signals that will be transmitted from the next generation of GPS satellites (known as GPS III), forecast to start to enter service in 2013. Called L2 and L5, these two frequencies are separated enough to be affected quite differently by ionospheric activity, which is now the major cause of errors in GPS accuracy.
This raises an interesting question among industry observers. Since dual-frequency operation will be standard with GPS III starting in 2013, Europe’s Galileo is forecast to become operational after 2010, and both are designed to provide high-integrity and quick failure warnings, some experts now question whether WAAS will become obsolete long before the 2028 date envisioned by the JRC.
It could, assuming untroubled development progress in the two new systems. But that’s never a given. It is just as likely that, having beaten the odds and finally won respectability, WAAS and its overseas siblings will be around for many years to come.