![]() A LOC+GS approach can get you onto the runway.Let's consider the ILS on its own, with no supplement navigation aids like RNAV / GPS. Hence, there isn't really anything to be gained. What good would a lower minima do you, if, by the time you reached, say, 200ft, you find out that you are not actually aligned with the runway, because the lateral guidance is so inaccurate? So even with accurate vertical guidance, you would need time to align with the runway once you get below the ceiling, which means our theoretical NDB+GP approach would need minima similar to that of a pure NDB approach. ![]() Because of this, it would probably not be possible to define lower minima compared to a NDB/DME approach. If you were to combine an NDB with a GP instead, you would still have accurate vertical guidance, but not very accurate lateral guidance. The reason an ILS approach (LOC+GP) generally has lower minima is because a LOC and GP combined is very accurate. This is relatively inaccurate, so an NDB approach typically has a relatively high minimum descend altitude (the altitude at which the pilot must visually see the runway in order to continue). But if a locator/NDB or RNAV approach is available, the pilot could just use that approach for the vertical guidance as well.įor an NDB approach, there is no actual vertical guidance, but the pilot will descend manually, typically while cross checking distance to threshold using a DME. Where the pilot uses the glideslope for vertical guidance but relies on ground- or satellite-based navigation fixes for lateral guidance.Īs you correctly point out, if using only a glideslope, the pilot would have to rely on other navigation facilities for the horizontal guidance, for example a locator/NDB or RNAV. What allows the use for an approach of a localiser without a glideslope, but not a glideslope without a localiser?īecause there would be no benefit to doing so. ![]() While localiser- sans-glideslope approaches are quite common, there are, to the best of my knowledge (feel free to correct me if I'm mistaken here), no examples of the reverse: a glideslope- sans-localiser approach, where the pilot uses the glideslope for vertical guidance but relies on ground- or satellite-based navigation fixes for lateral guidance. For a localiser-only approach, the pilot uses a specified series of navigational fixes to mark off each segment of the approach each of these segments has a specified minimum safe altitude (which is shown on the approach plate), and the pilot uses this information, and their onboard baroaltimeter, to maintain terrain clearance during the approach. ![]() The two are typically used together, for an ILS approach, but the localiser can also be used on its own, for a localiser-only, or simply localiser ( LOC for short), approach (for instance, if the glideslope is inoperative or nonexistent, the aircraft lacks a functioning glideslope receiver, or the pilot is shooting a back-course approach). The Canadian TSB reported review of the FDR data revealed a severe turbulence inspection was required and the engines had been overtorqued by the windshear escape maneouver.An ILS consists, at its most basic, of two components: a localiser (to provide lateral guidance) and a glideslope (to provide vertical guidance). The crew initiated a windshear escape maneouver using maximum power and diverted to their planned alternate Montreal,QC (Canada) where the aircraft landed without further event. While the aircraft was intercepting the localizer at 3000 feet MSL about 15nm before the runway threshold at 20:07L (01:07Z Dec 6th) the crew observed sudden and significant airspeed fluctuations, the stick shaker activated. A Jazz de Havilland Dash 8-400, registration C-GGMI performing flight QK-8936 from Thunder Bay,ON to Toronto,ON (Canada) with 58 passengers and 4 crew, had been holding for about 30 minutes on approach to Toronto, then was cleared for the ILS approach to runway 06L. ![]()
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