Aviation's Localizer Performance with Vertical Guidance (LPV) Approach

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A localizer performance with vertical guidance (LPV) approach is a modern aviation instrument approach procedure that uses the wide area augmentation system (WAAS) and very precise GPS capabilities to attain an airplane's position. LPV offers the most accurate aviation position available today. An LPV approach can get a pilot down to a mere 200-foot or 250-foot decision altitude. The benefit is that this makes it possible for aircraft to land at runways in very low visibility. Without WAAS capabilities (i.e., without the ability to fly the LPV approach) deplorable visibility conditions at the airport may force the pilot to fly to an alternate and less desirable airport.

In general, LPV approaches, and WAAS-capable aircraft, open up new (previously unavailable) options for pilots. With properly-equipped aircraft, aircraft operators can save time, and money, by using WAAS because it is an extremely precise navigational aid. In addition, aircraft pilots equipped with LPV can complete landings at airports they could not possibly have landed before, such as remote airfields. They're also able to make approaches not easily supported by radio navigation, in weather that is worse than they're accustomed to.

Instead of relying on radio navigation, pilots can count on an extremely precise and stable satellite navigation system. It is the precision of this type of navigation that allows pilots to descend to lower altitudes (without the usual visual references) or while still flying in the clouds. 

How LPV Works

An LPV approach is similar to an LNAV/VNAV approach, but is more precise and can allow descent to minimums of 200-250 feet. WAAS capabilities are required for precise lateral and vertical guidance, classifying it as a precision approach. On the other hand, the LNAV/VNAV approach is non-precision. In fact, an LPV approach is almost identical to an instrument landing system (ILS) but is more accurate because it utilizes modern-day satellite technology. Also, no expensive ground equipment is necessary which means that there is less downtime and outages. This also means that the cost is less because there is no equipment and no regular maintenance involved.

How WAAS Works

The WAAS takes the error out of standard GPS signals by analyzing the GPS data at a master station and then sending the corrected data information to GPS receivers. The receivers, in turn, can remove any GPS errors. This process makes the GPS information even more error-proof and allows for a much more precise result.

Why WAAS Is Better

GPS accuracy is improved from what would be 100 meters with regular GPS service to about seven meters with WAAS. This leaves hardly any room for error and provides the most precise navigational tool to date.

The benefits of WAAS to the national airspace system as a whole are huge. These benefits include increasing capacity, being able to utilize runways more efficiently, reducing equipment costs (both onboard and on the ground), and, last but not least, increasing approach capabilities for all kinds of aircraft.