The FAA has just reduced WAAS approach minima to a 200-foot decision height and 1/2-mile visibility. And that means pilots flying instrument approaches using GPS enhanced by the Wide Area Augmentation System (WAAS) can get virtually the same performance as they do now from a ground-based ILS.
AOPA says that's potentially great news for thousands of general aviation airports that can now get instrument approaches with the same minima as ILS, without all the expenses of an ILS system.
"AOPA has been a strong supporter of WAAS for more than a decade," said AOPA President Phil Boyer. "We have urged both Congress and the FAA to press ahead with the program because it improves air safety by providing the precision vertical guidance needed especially in poor weather conditions. And it makes better use of the nation's system of airports because thousands that currently may only be used in good weather can become all-weather capable."
Currently, it costs the federal government between $1 million and $1.5 million per runway end to install an instrument landing system (ILS). By comparison, mapping and publishing a new WAAS-based instrument approach procedure with vertical guidance (WAAS LPV approach) costs about $50,000.
However, that may not get the lowest minima. Typically, a GA airport might expect minima of 300 feet decision height and 1 mile visibility from a WAAS approach without any improvements to ground infrastructure. To get the lowest minima possible from WAAS, the airport will need much of the ancillary ground infrastructure required for an ILS system, including approach lights, precision runway markings, and a parallel taxiway.
"The one thing we would still like to see the FAA do is recognize WAAS LPV approaches for the precision approaches they are, especially in light of today's announcement," said Randy Kenagy, AOPA senior director of advanced technology. "The agency currently regards them as nonprecision approaches with vertical guidance and expressly forbids their use on an instrument rating checkride as the required precision approach. AOPA questions that thinking, especially if the approach has the same minimum standards as an ILS approach."
Although the FAA has not announced its implementation plans, AOPA expects that the first WAAS LPV approaches with the improved minima are likely to be overlays for existing ILS approaches, most of which are at air carrier airports, with new stand-alone LPV approaches with lower minimums to follow. Although these approaches are "quick wins," adding to the number of LPV approaches, the real benefit to general aviation will come at airports or runways that do not currently have an ILS.
"While the FAA's announcement is most welcome, there is more work for everyone to do," Boyer concluded. "The FAA needs to set a brisk pace for approving more vertical guidance WAAS approaches and to create a set of standards that recognize the needs and realities of smaller airports.
"And owners need to upgrade to WAAS-enabled avionics to take advantage of the new approaches and to show the government that the billions of dollars already spent on WAAS was a wise investment - one worth continuing to fund."
March 7, 2006