:?: confused :?: An ILS by nature is a precision approach. I've never heard of a non-precision ILS approach. Unless I slept through some important part of instrument classes and refreshers, I've never heard of an ILS referred to as anything other than a precision approach. Even the AOPA refers to and ILS as a precision approache. (http://www.aopa.org/pilot/features/ii_9805.html) A non-precision approach would be a LOC, VOR, TACAN, NDB, ASR, GPS (non LPV/LNAV/VNAV).Originally Posted by mmedford
Anyone else, thoughts?
OK, wait, that's what I've been saying all along - most of the time the actual localizer IS located at the departure end (far end) of the runway you are shooting the approach to. Sometime (as is the case here, and is the case with the ILS to 22R at JFK) they are "closer" (but still not prior to) the approach end and are offset.Localizers located on the approach end, are probably for the the opposite end runway...backcourse isn't really used much; learned through my talks with people from other airports.
BTW - the expired chart I linked to does give you some clues as to where the physical position of the antenna are. Looking at that chart, you can see that at the runway approach end (i.e. threshold) you are 0.2nm from the localizer. Therefore, the localizer is 0.2 nm past the approach end. This is one of those cases where the localizer is not at the departure end. Also, if you look at the chart, you can see the localizer is offset. I BELIEVE the reason the minimums are higher on this approach is because the localizer is closer to the approach end and therefore more sensitive the closer you get. If you look at JFK 22R, it's the same deal. The actual localizer is offset and closer to the approach end.
Back courses were never used very much and are being phased out with the advent of GPS approaches. Localizers are not course dependent like VORs are (i.e you are going to get the same deflection on your HSI regardless of what course you have set in) and emit signals in both directions. When you fly a LOC/BC, you are using the "front course" of the approach to the opposite runway - this is why when we fly LOC/BC we don't tune in the runway course for the runway we're landing on, we tune in the front course (i.e. if you're shooting the LOC/BC to RWY 36, you're using localizer information for RWY 18, and therefore you would tune 180 in your course to get normal looking movement on the HSI). If you left in 360 in your course, you'd get a "flip flop" image on the HSI (i.e. your HSI would show you "left" of course when you were really right of course).
There's less of a point in spending the money to TERPS BC approaches when almost everything can fly a GPS approach.
I've flown countless ILS', LOCs and a handful of LOC/BC approaches - please don't tell me that the localizer and glideslope sensitivity on the HSI don't get more sensitive the closer you get to them....That whole sensitivity thing, doesn't make much sense and is pretty inaccurate to what really happens...especially since backcourse also depends on the actual antenna inuse.
Reference the "How Accurate?" portion of the AOPA online document on ILS'...
http://www.aopa.org/pilot/features/ii_9805.html
I apologize if any of this is getting way too technical (probably way too much so for this board), but I will say if anything it's made me brush up on some of this instrument stuff!
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