![]() ![]() That is correct if flown using baro-vnav and the basic TERPS design takes that into consideration. (+) Actually, I believe that the vertical path for LPV is straight, while due to the curvature of the Earth for LNAV/VNAV it is slightly curved, but the difference can’t be operationally significant.Īctually, I believe that the vertical path for LPV is straight, while due to the curvature of the Earth for LNAV/VNAV it is slightly curved, but the difference can’t be operationally significant. There must be a reason for that and whatever the reason why can you simply ignore that just because there is also a LNAV/VNAV procedure? Apparently, compared to LNAV/VNAV, the LPV procedure design calls for greater obstacle clearance, or for considering obstacles in a larger area, or both. I know (+), but it doesn’t answer my question. Lpv_higher_than_lnav_vnav_tta_rnav_21_pdf Here are a few procedures where the normal order of LPV lowest DH, LNAV/VNAV next, and LNAV MDH highest is not true. So regardless of the annunciation, the vertical and lateral path center lines are the same, they both have a CDI FSD the same on the final approach leg with the same PFAF, the only difference is the MDH which is defined by the minimum. The lateral path will be the same but the integrity requirements have to be better with an LPV annunciation than is required for LNA/VNAV. The vertical path using an SBAS is the same for LPV annunciation or LNAV/VNAV annunciations although in some cases, the integrity and accuracy will be better. Stand-alone TSO-C146 Class 2 or 3 systems meet the aircraft qualification requirements for RNP APCH operations using the LNAV/VNAV line of minima provided that the installations meet at least the performance and functional requirements of this AC. This is from AC 90-105A, Appendix A: A.6.4 LNAV/VNAV Line of Minima Qualification.Ī.6.4.1 Stand-Alone Systems. for LPV being what they are, how can you fly a LPV to LNAV/VNAV minima if they are lower than the LPV minima?Ī WAAS GPS is authorized to fly to an LNAV/VNAV minima. I know that the specifications for LPV and LNAV/VNAV are different, but the specs. If the cause of the failure was for HPL, VPL would almost certainly already be out of tolerances for both LPV and LNAV/VNAV. So there is a very narrow range of VPL which would fail for LPV but work for LNAV/VNAV and only for a DH of less than 250 feet. The vertical requirements for a 200 DH LPV are a VPL of 35 meters and for 250+ DH it is 50 meters. Also, if the navigator has the capability to fail down from LPV to LNAV/VNAV, it would be next to impossible for this to occur. Also in the case of LNAV, step down fixes can allow a lower MDA than the constant GP angle allowsģ) Although it is technically possible that a WAAS GPS could fail down from LPV to LNAV/VNAV, this is not supported by the Garmin Navigators, all of which fail down to LNAV without any vertical guidance and never fail down to LNAV/VNAV. These are due to the fact that the LPV and LNAV/VNAV use different specifications and when there are close in obstacles in the visual segment, the LPV may end up with a higher DH than the LNAV/VNAV. In some cases, the DH for LPV exceeds that of LNAV/VNAV and in more cases, the LNAV MDH is below the LPV or LNAV/VNAV, and many more cases, the visibility requirement is lowest for the LNAV. If LNAV is annunciated, only the LNAV or LNAV Circling Minimums may be used. If LNAV/VNAV is annunciated, the pilot may fly to the LNAV/VNAV, LNAV or LNAV Circling minimums. So if LPV is annunciated, the pilot may fly the procedure to the LPV, LNAV/VNAV, LNAV or LNAV circling minimums. SBAS can also be used to fly the vertical of an approach to an LNAV/VNAV minimum, at least in the US.Ģ) Pilots may fly any of the minimums charted on the same procedure if the Annunciate Accuracy is equal to or better than the minimum requirements. If Baro-VNAV is used to fly the procedure, it has temperature limits unless the Baro-VNAV is temperature compensated. GPS is used for the lateral and Baro-VNAV can be used for the vertical to fly an RNAV approach to a LNAV/VNAV minimum. It can be used for enroute descent, terminal or for final approach. Baro-VNAV is a means of using MSL altitude to determine a vertical path. Baro-Aiding is an aspect of the RAIM algorithm that uses pressure altitude to substitute for one satellite, so with Baro-Aiding, RAIM can be determined with four satellites in view rather than requiring 5. I have a few issues with the presentation.ġ) Baro Aiding is not Baro VNAV. ![]()
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