9/12/2023 0 Comments Lnav aviation meaning![]() ![]() ![]() WAAS avionics with an appropriate airworthiness approval can enable aircraft to fly to the LPV, LP, LNAV/VNAV and LNAV lines of minima on RNAV (GPS) approaches. If there are no airworthiness limitations on other installed navigation equipment, WAAS avionics enable aircraft navigation during all phases of flight from takeoff through vertically guided approaches and guided missed approaches. Additionally, the WAAS geostationary satellites provide ranging sources to supplement the GPS signals. WAAS improves the accuracy, integrity, availability and continuity of GPS signals. Both WAAS vertical guidance and baro-VNAV support approaches to LNAV/VNAV lines of minima." (bolding mine)įrom paragraph 6 (b): "WAAS Overview. An RNAV function that computes, displays, and provides both horizontal and approved vertical approach navigation. I'll copy and paste from a post I made on the other forum Mark referred to:įrom paragraph 4 ( n ) : "Lateral Navigation/Vertical Navigation (LNAV/VNAV). I posed this question also on the GNS-480 users group, and received a private communication from a member who pointed me to AC 90-107. It seems the only question remaining is the legality. Identical angles, tighter guidance on the LPV. and this confirms my understanding of the relationship between the two glidepaths. I'd fly the LNAV/VNAV, land and go about my life. If I came across this situation, I know what I'd do, without hesitation. If the obstacle affected the LNAV/VNAV too, the DA would be adjusted or the LNAV/VNAV line made NA too. You are flying the same glideslope, just going missed at a higher altitude. If the obstacle in this case only affects the LPV, making it NA, then there is absolutely no safety reason to not fly the LNAV/VNAV line. In other words, WAAS is better than Baro-VNAV, and does a better job of keeping us on course and glideslope. We are allowed to fly L/V using WAAS because it's not affected by those temperature and pressure errors inherent in Baro-VNAV systems. The underlying surfaces are different between LPV and LNAV/VNAV, but that's because LNAV/VNAV was designed for Baro-VNAV systems, not WAAS systems. So we are left to determine what is "safe" to do.įrom a TERPS perspective, a glideslope is a glideslope. I don't believe you will find any definitive guidance on this. We really do try hard to cripple our use of aviation, don't we? Please nobody submit this to the Chief Counsel, nothing good can come of that. In particular, I'm hoping that Collins will weigh in on this. As a matter of safety, I should think the last opinion is correct unless the LNAV/VNAV glide path is different from that of the LPV approach. In another, you cannot even do that unless you turn WAAS off to force annunciation of LNAV.Īnother opinion says that you can fly to any higher DA or MDA that is still authorized. In one version of this opinion, you can still fly to the LNAV MDA even with the unit annunciating LPV. Since the LPV DA is NA, you cannot fly the approach to that DA, but also, you cannot fly to the LNAV/VNAV DA since the unit will not annunciate LNAV/VNAV under these circumstances (WAAS GPS and no Baro-VNAV). Therefore, when flying this approach with a WAAS GPS (in my case, a CNX-80 (aka GNS-480)), the unit will annunciate LPV.Īccording to one opinion, claimed to be based on 91.175 (b), you are legally flying whatever the unit annunciates. The LPV DA is NA by NOTAM due to trees close to the airport perimeter, evidently affecting clearance on the missed. The approach has an LPV DA, an LNAV/VNAV DA that is about 100 feet higher, and an LNAV MDA that is higher still. ![]() The approach in question is the RNAV 17 at KMPV. MHRA 'LNAV - Lateral Navigation', All Acronyms, 10 August 2023, Bluebook All Acronyms, LNAV - Lateral Navigation (Aug. LNAV - Lateral Navigation, All Acronyms, viewed August 10, 2023, MLA All Acronyms. Retrieved August 10, 2023, from Chicago All Acronyms. Please use the following to spread the word:ĪPA All Acronyms. ![]()
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