Some are working though, used for calibration purposes. They will allow category II and III approaches but are not actually working at least outside US and they are not planned to be in a short future. They are identified as GLS RWY xx and benefit from ground reinforcement instead of satellite reinforcement. But that does not have any consequence on aircraft flying. RNAV systems suffer from longitudinal error, RNAV procedures are therefore built with a slope origin that is displaced upstream from runway threshold. For example, minimas at Lyon Bron are 200 ft AGl as compared to minima's at Reims where LPV minimas are 493 ft AGL. If one or several of these criteria are not fulfilled, an LPV approach has higher than 200 ft AGL minimas. To allow CAT 1 vertical approach minima's (200 ft AGL), the airport must fulfill with precision approach structures which are the same as for an ILS approach. At which point the beam ceases to converge. Vertical precision increases regularly from 150 m deflection at FAF down to 15 m deflection. Horizontal guidance's precision increases as the beam converges (according to a 2° angle) from FAF to opposite runway threshold. They differ from LNAV/VNAV because they provide a convergent beam pretty much similar to ILS beam. These procedures are available to airplanes GPS WAAS equipped. Initially, APV/SBAS provided a DH (Decision Height) in between 246 ft and 295 ft depending on terrain configuration. LPV approaches are said APV SBAS (Approach with Vertical Guidance, Satellite Based Augmentation System) because the normal satellite constellation is increased by two geostationary satellites which for Europe provide EGNOS augmentation. At which point, the beam ceases to converge. Vertical guidance precision increases regularly, starting with a 150 m deflection at FAF down to 45 m. Horizontal guidance precision increases by steps (5 NM, 1 NM and 0.3 NM) exactly as for LNAV alone. Note: This service is essentially provided for northern hemisphere where different systems overlap. WAAS GPS's receptors provide vertical and horizontal guidance for LNAV/VNAV approach (as well as FMS) and for LPV approach, if satellite constellation is enough to provide that service which means that 2 geostationary satellites have to be covering the zone. LNAV/VNAV and LPV approaches for WAAS receptors (3D) Some systems are able to compute corrections for temperature. The approach is not allowed then, if temperature is at that minimal temperature and it is specified on the approach plate. Obstacle clearance slope is then reduced with reference to a minimal temperature that sets the exploitation limits of that procedure. Obstacle clearance margins - grey zones on approach profile - are computed with reference to ATI (International Type Atmosphere) + 15☌. Obviously, when flying an ILS, the problem is different, as ILS beam does not rely on altimeter source. Especially when flying in cold weather, altitude and glide are false and it is not possible to double check altitude passage because the check would rely on the altimeters as well. That renders the system vulnerable to the same errors as altimeter's. Indeed, FMS system relies on altimeter to compute arrival altitude and glide slope. Horizontal guidance is identical to LNAV approach: their precision is 5 NM in Enroute mode, 1 NM in Terminal mode and 0.3 NM in Approach mode. These approaches provide lateral and vertical guidance in the same cockpit presentation as an ILS. LNAV/VNAV approaches for FMS receptors (3D) It is pilot's responsibility to check and announce scale transition. Scale transition is made automatically assuming the pilot does not intercept final approach segment at less than 2 NM from FAF, because Intercepting final approach segment at less than 2 NM from FAF, would prevent automatic scale transition. Which is to say that when the needle just arrived at full deflection, cross track deviation is 5 NM, 1 NM or 0.3 NM depending on plane's mode at the time. Their precision is 5 NM in Enroute mode, 1 NM in Terminal mode and 0.3 NM in Approach mode. Non-WAAS GPS systems allow for approach with horizontal guidance only. We shall ignore GBAS procedures which are not yet installed on a regular basis in Europe. Those which benefit from horizontal and vertical guidance and are intended for WAAS equipped GPS (EGNOS as well): LPV. Those which benefit from horizontal and vertical guidance and are intended for baro-integrated FMS equipped aircraft: LNAV/VNAV. Those which only benefit from horizontal guidance: LNAV.
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