In less than 25 years, the “miracle” of GPS has transformed how even the smallest and least expensive aircraft navigates. Thanks to the wide area augmentation system (WAAS) in the U.S. and similar technologies deployed in other countries, GPS is more accurate, more reliable and more repeatable than what came before. If you need proof, look no further than comparing the faithful instrument landing system (ILS) to its WAAS GPS-based equivalent, the LPV (localizer performance with vertical guidance) approach. In typical configuration, either one can take us down to 200 feet agl and a half-mile visibility. There are other similarities, of course, including how we fly them. But which is better?
Some pilots are convinced the steadier signal digital GPS provides—when compared to the waviness of the analog ILS localizer and glideslope components—makes WAAS-enhanced approaches a no-brainer, even when there’s an ILS serving the same runway. At the same time, there’s something rather simple and perhaps romantic about an ILS. But when ATC wants to know which approach you’re requesting, do you automatically choose the newfangled GPS procedure or do you go with the old standby, the ILS? Which is best? As with so many things in aviation, it depends. By way of explanation, we’ll take close looks at two procedures serving the same strip of pavement, Runway 35 at the Asheville (N.C.) Regional Airport. Approach plates for both procedures are reproduced on this and the opposite page.
