LPV is the most desired APV approach. It is similar to LNAV/VNAV except it is much more precise (40m lateral limit), enables descent as low as 200-250 feet above the runway and can only be flown with an approved SBAS Avionics receiver. LPV approaches are operationally equivalent to the legacy instrument landing systems (ILS), but are more economical because no navigation infrastructure is required at the runway. There are over 2,327 LPV approaches in use today and the FAA is publishing over 500 new LPV approaches per year.
Localizer Performance (LP) is a recent non-precision approach (NPA) procedure that uses SBAS precision of LPV for lateral guidance and barometric altimeter for minimum descent altitude (MDA) guidance. These approaches are needed at runways where, due to obstacles or other infrastructure limitations, a vertically guided approach (LPV or LNAV/VNAV) cannot be published. LP approaches can only be flown by aircraft equipped with SBAS Avionics receivers. The MDA for the LP approach is expected to be nominally 300 to 400 feet above the runway.
LNAV / VNAV approaches use lateral guidance (556m lateral limit) from GPS and/or SBAS and vertical guidance provided by either the barometric altimeter or SBAS. Aircraft that don’t use SBAS for the vertical guidance portion must have a Baro-VNAV system, which are typically part of a flight management system (FMS). When the pilot flies an LNAV / VNAV approach, lateraland vertical guidance is provided to fly a controlled descent and a safer maneuver to the runway. The decision altitudes on these approaches are usually 350 feet above the runway.
GPS NPA (LNAV) refers to a Non-Precision Approach (NPA) procedure which uses GPS and/or SBAS for Lateral Navigation (LNAV). On an LNAV approach, the pilot flies the final approach lateral course, but does not receive vertical guidance for a controlled descent to the runway. Instead, when the aircraft reaches the final approach fix, the pilot descends to a minimum descent altitude using the barometric altimeter. LNAV approaches are less precise (556m lateral limit) and therefore usually do not allow the pilot to descend to as low an altitude above the runway. Typically, LNAV procedures achieve a minimum descent altitude (MDA) of 400 feet height above the runway.