![]() With the arrival of the new cool kid on the block (GNSS), a new definition has been added to cover approach and landing operations with vertical guidance ( APV) which use lateral and vertical guidance, but do not meet the PA requirements. In the days of old, only two types of approaches existed: Precision Approaches ( PA) and Non-Precision Approaches ( NPA). In simple terms, here are the three main things a pilot needs to know when planning on flying a GPS-based approach: Types of Approaches available (and their requirements) (Source: Transport Canada AIM) Phase of Flight Let’s have a look at the different requirements for each phase of flight. GNSS may be used for all en-route and terminal operations, as long as the aircraft is also equiped with approved traditional systems (such as VOR and ADF) to serve as backup. Avionics also have to meet the appropriate equipment standards and be approved by the governing flight authority (FAA, Transport Canada, etc.) The tolerance tresholds and levels of performance required vary greatly for the use of a GPS module depending on the phase of flight. Although we (the company) have been able and trained to conduct LNAV approaches where applicable, the introduction of VNAV/LPV technology brings up a completely new dimension (yup, 3D approaches!) So training for the use of the GPS for approaches and a quick review of the related rules was incorporated in the ride.īefore we go any further, I would strongly suggest that you read the first part of this article (if you have not done so already) to familiarize yourself with a few terms and basic underlying principles. As it happens, our fleet of PC12NGs is getting a software update, which will eventually allow us to complete LPVs approaches virtually everywhere. Instead, they're just like an LNAV only approach, decreasing to 0.3 NM sensitivity when you're within 2 miles of the final approach fix, all the way to the missed approach point.I recently had the “pleasure” to complete my yearly recurrent ride. Unlike LPV approaches, LNAV/VNAV approaches don't have increasing angular guidance as you approach the runway. They were originally designed for baro-aided GPS units, but most WAAS receivers can use them today as well. LNAV/VNAV approaches were actually the first type of GPS approach that had vertical guidance. The second type of GPS based APV approach is LNAV/VNAV. (There are a few more details as well, which you can find in AIM 1-2-3, paragraph D.) LNAV/VNAV: Lateral Navigation/Vertical Navigation Since LPV approaches aren't considered precision approaches, you can't use precision alternate minimums for airports that only have LPV.Īccording to the FAA, if you're using an airport with LPV only (no ILS or other ground-based navaid approach) as your alternate airport, you need weather minimums that meet the LNAV or circling MDA, or the LNAV/VNAV DA if you're equipped to fly it. A baro-aided GPS won't work.īut there is a downside. Keep in mind though, to fly them, you need a WAAS receiver. And, just like an ILS, an LPV approach's angular guidance scales down the closer you get to the runway. So how do they work? The extremely accurate WAAS system (7.6 meters or better accuracy) gives you lateral and vertical guidance down to a decision altitude (DA) like an ILS. The precision approach definition also carries a lot of documentation, definition, and cost with it, so the FAA and ICAO adopted the APV definition, so they could build new approaches and not be burdened with the cost and paperwork. So what's the difference? APV approaches don't meet the ICAO and FAA precision approach definitions, which apply mostly to localizer and glideslope transmitters. Instead, they're an approach with vertical guidance (APV). Even though LPV approaches have vertical guidance, they're not considered precision approaches. LPV approaches are a WAAS/GPS based approach, and they're very similar to the ILS. LPV: Localizer Performance With Vertical Guidance So what's the difference between LPV and LNAV/VNAV approaches? They're both GPS based approaches with vertical guidance, but the similarities end there. With GPS, the number of approaches with vertical guidance has tripled. Over the past several years, the FAA has created GPS based LPV and LNAV/VNAV approaches at thousands of airports across the US. And if you weren't flying an ILS, you were managing step-down altitudes on a non-precision approach. It wasn't that long ago when you only had one kind of approach with vertical guidance: the ILS. ![]()
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