![]() ![]() So for most situations, I teach my students they can ignore the LNAV/VNAV minimums with their WAAS GPS when the approach has LPV minimums available. There are a few RNAV procedures with LNAV/VNAV minimums that are outside of the WAAS service volume that provides adequate vertical guidance, example in Puerto Rico, and the chart has a note that “WAAS VNAV NA”. So a LPV annunciation will never downgrade to L/VNAV, but may downgrade to LNAV. In this case, as long as the WAAS GPS annunciates L/VNAV, the LNAV/VNAV may be flown to its DA.Īll downgrades are from the most accurate APV service to LNAV without any vertical guidance. In some cases, there are RNAV approaches that do not have an LPV option, but do have a LNAV/VNAV option. In most cases, the LPV will offer the best minimums. If the WAAS GPS annunciates LPV, any of the charted minimums are permitted to be flown, including LPV, LNAV/VNAV, or LNAV, as it is the pilot option. An LNAV annunciation does not provide approval to fly the LNAV/VNAV. In order to use a WAAS GPS to fly the LNAV/VNAV DA minimums, one of these annunciations is required: LPV or L/VNAV. When using WAAS for the vertical guidance, the temperature limits do not apply as the WAAS GS is unaffected by temperature. However, the WAAS GPS TSO permits using a WAAS GPS for vertical guidance on LNAV/VNAV procedures, so they may be flown to the LNAV/VNAV DA using WAAS. Although the G1000 is capable of Baro-VNAV, it is not implemented for approach guidance except on a very few aircraft (example King Air). Since MSL altitude is also a function of temperature, these systems will have limits for both cold and hot temperatures.Īll that said, most GA aircraft don’t have a Baro-VNAV system. With a Baro-VNAV system, WAAS is not required. A GS is computed by this equipment to provide the vertical guidance. The system derives the altitude from the barometric pressure and uses GPS to determine the lateral path. This type of system derives its glidepath by a barometric pressure sensor. LNAV/VNAV APV procedures are designed to be used by aircraft equipped with a Baro-VNAV system. ![]()
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