The list of FAA GPS procedures using Waas, known by ICAO as space-based augmentation system (SBAS) procedures, continues to grow steadily. These include ILS-equivalent localizer precision with vertical guidance (LPV) approaches, providing centerline and glideslope guidance down to 200 feet at more than 800 Part 139 runways in the NAS, plus another 2,600 at various heights above 200 feet at other NAS Part 139 and non-Part 139 runways. At most of the non-Part 139 runways, of course, there’s no ILS, and probably never will be. SBAS is filling that need.
So do LPV approaches work? Beautifully, is the easy answer, because you can’t tell the difference between an LPV and a Category 1 ILS on the approach, except that you won’t see ILS’s occasional little kinks and jogs with the LPV. Otherwise, since they both drive the same left/right, up/down needles with equal precision, you can’t tell them apart. But the LPV provides a valuable extra: continuous distance to the threshold. So SBAS LPV is impressive, although you almost have to fly one to believe it. Alternatively, ask anyone whose airport has upgraded from a VOR approach to an LPV one. And that’s a cost-free upgrade, because SBAS requires no ground equipment, unlike ILS or VOR.
