Based on what’s being said, you guys are saying you could theoretically capture this glide slope much earlier as long as the 3° descent angle is met? This doesn’t make sense to me. Eventually the antenna broadcasting the ILS frequency for that runway will be out of range. Sure the pilot can manually be on a 3° slope based on aircraft input, but not the captured ILS glide slope.
In contrast, here is one that seemingly doesn’t even make it 10NM out, and attempting to capture at 3000’ at 10NM would seemingly be ineffective here:
If I’m incorrect about the range, what do those little ribbons widening out from the runway mean? My understanding is they also show the width of the localizer range - many of which specifically state on the chart that the localizer will only be reliable if activated once within 10° on either side of the runway centreline - which is why I generally never turn on LOC mode until making the final turn to straight final, and it’s nearly complete/straight:
Thanks for your feedback here. I am quite good at executing ILS landings by interpreting the approach chart data, but still have some details to learn.
Cheers and very kind regards in helping clarify this for me!
No. 10NM at 3000ft is the approximate maximum range. In most cases you can’t reliably intercept the GS from a greater distance.
Terrain permitting you could fly level at 3000ft for 100NM, but intercept would still be 10NM.
IF you intercept the GS during the descent, you need to descend at less than 3° until intercepting, otherwise you will descend parallel with the GS!
In my experience (and watching FR24) GS intercept still occurs mainly from level flight.
Why? ELVIL is at 14NM. Hence you would still intercept the GS at 3000ft and at 10NM
Using the 3 nm per 1000 ft, height above threshold is meant (obviously), for a DME reading zero at the (displaced) threshold and 3 degree glidepath, interception occurs at the same distance versus height.
I thought you were using approach plates? It shows the threshold elevation, easy to calculate I would think?
You can intercept the localizer and glideslope far out, I have intercepted an ILS from roughly 100 nm. That is however outside the operational range of the ILS equipment so don’t rely on it. The localizer is deemed accurate from 25 nm out within 10 degrees from the final approach course, not sure about the glideslope. I noticed that in MSFS the ILS is basically ON or OFF depending if you are within the designated operational range or not. In real life you can intercept the ILS far out, its just not as reliable and a little erratic sometimes.
It doesn’t.
Its just a depiction indicating there is a localizer or glideslope, there isn’t anything too scale about that and it certainly doesn’t show the operational range of the localizer / glideslope. The localizer is indeed useable from 25 nm out within 10 degrees of the final approach track, 17 nm within 25 degrees (usually). The localizer depiction is definitely not 10 degrees wide.
You could either descent to the charted intercept altitude (usually between 2000 ft and 3000 ft above ground) and intercept the glideslope from below. At busy airports with parallel approaches this is usually required. Most efficient would be to keep crosschecking your altitude versus distance to go and adjust the vertical rate accordingly as to fly a 3 degree path all the way to the runway.
In real life I usually manage to turn to final and have LOC* and GS* on the way down during the final turn without level-off. There are situations of course where ATC lets you descent early and fast sometimes, in which case continuous descent technique goes out of the window together with fuel efficiency and noise abatement .
Thank you both for your information, I have learned today!
As I said, I generally can interpret the approach charts and am quite good at ILS landings, I just didn’t know all these details so this is helpful.
With respect to the ribbon localizer symbol, thanks for clarifying. I thought it indicated something to do with the range and the real world beam width. Navigraph said their latest chart updates actually do reflect the localizer beam width, so it’s all a bit confusing. If you look at those localizer beams, they aren’t all identical in width, so I guess there must be some element of range to it.
“From AIRAC Cycle 2110 and onwards, Navigraph updates the localizers to reflect their real-world beam width values that are in the primary range of 2 to 6 degrees.”
In any case, I’m completely fine with ILS landings, just wanted to join this conversation and learn about the details. Very much appreciated.
Cheers
Edit: Here’s the Navigraph blog post if interested about the localizers:
Isn’t Navigraph using Jeppesen charts? I haven’t used Jeppesen charts in years, last time I used them they weren’t to scale. Navblue isn’t to scale either. Not sure what the benefit of that would be, would only clutter the charts with useless information .
Jeppesen’s SID, STAR and approach charts, and the airport diagrams, are to scale and are georeferenced - and can thus be overlaid on the enroute chart and supports moving maps.
I get that part, the discussion was about localizer / glideslope “funnels” and whether the length and shape represents the actual localizer / glideslope operational range to which the answer is no as far as I know. Both Jeppesen and Navblue just use a localizer and / or glideslope funnel depiction to indicate there is LOC / GS, the size or shape does not represent anything.
I haven’t used Jeppesen in some years, when I used Jeppesen for the last time they just started introducing the “new” to scale layouts. I’m using Navblue in the real world now to which (in Europe at least) Jeppesen is vastly inferior, in comparison Jeppesen is a cluttered mess and I truly hope I never have to make the switch back to Jeppesen .
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