![]() ![]() LPV minimums are a subset of an RNAV (GPS) approach and, with the increased accuracy, can provide minimums that are comparable to a category 1 ILS using GPS navigation. Unlike most traditional RNAV approaches, the lateral and vertical deviations for LPV come directly from the GPS receiver and are not part of the FMS solution. Where an ILS is projected by two overlapping lobes of energy, LPV is a result of increased accuracy from a Satellite-Based Augmentation System (SBAS). Despite their similar appearance from the cockpit, internally, they are completely different animals. LPV was purposely developed to look and fly like an ILS. In fact, the same control laws are used for both ILS and LPV. Unlike LNAV/VNAV, using linear deviation, LPV is designed to use angular deviations (like an ILS), meaning they get more sensitive closer to the runway. ![]() Localizer Performance with Vertical guidance was introduced about 15 years ago. The glideslope antenna on most aircraft is near the nose of the airplane to give maximum reliability for tracking the signal. The glideslope transmitter is calibrated to deliver the aircraft down a vertical path, usually 3°, cross the runway threshold at 50 feet and touchdown approximately 1000 feet down the runway. Without going into too much detail of the localizer and glideslope lobes, the ILS accurately defines a path in space that safely and reliably guides the aircraft to the runway. Despite being more than 75 years old, it was probably ahead of its time. ![]() Let’s look at each approach type and explore where differences can occur and what to do if there’s a discrepancy.įirst, we’ll look at ILS considered the gold standard of approaches because it has a fixed path in space that isn’t susceptible to temperature or pressure variations. Unfortunately, with various technologies, there are still many shades of gray. We live in an age where we like black and white answers. Visual Glide Slope Indicators (VGSIs) have their own variables that can come into play causing operators to question – shouldn’t they all agree? The answer is sort of. The big difference: how they are constructed. This is one reason an LPV is not a precision approach by definition.Īn ILS Glideslope and an LPV Glidepath are similar in that they both provide an obstacle-free path to the runway. For example, LNAV/VNAV and LPV are APV approaches.”įor pilots that may not be familiar with ICAO Annex 10, it’s a long list of requirements to which an ILS must conform. ![]() For example, PAR, ILS and GLS…Īpproach with vertical guidance (APV) is an instrument approach based on a navigation system that is not required to meet the precision approach standards of ICAO Annex 10 but provides course and glidepath deviation information. “ a precision approach is an instrument approach based on a navigation system that provides course guidance and glidepath deviation meeting the precision standards of ICAO Annex 10. An ILS is a precision approach by definition, whereas an approach with LPV minimums is an approach with vertical guidance. This article will explain why an LPV glidepath may differ from an ILS glideslope, especially when descending below the DA.ĭespite the operational consistency, these approach types are very different, beginning with their definitions. Behind the scenes, there is vastly different technology at work to make it all appear the same on the surface. From an operational perspective, we load the approach, press the approach button, and watch the magic happen. ILS and LPV have become almost synonymous with how operators perceive them.
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