How to fly an ILS??

[Rank&File]

ATC: "...descend and maintain 3,000 until established on the localizer, cleared for the ILS 36L approach."

This is easy enough, right? Stay at 3,000 feet and pick up the glideslope and fly it down. But what if the published glideslope intercept altitude is 2,200? Should you descend to that altitude when established on the localizer and intercept the GS there?

Some people say yes, some say who cares. Anyone know where I can find any info on how to fly an ILS legally. I'm not talking about "mandatory" stepdown fixes (IAH ILS 27 comes to mind), but the normal ones that almost all ILS approaches have published on the profile view of the chart.

 

[panampilot]

When you are cleared for an approach you are cleared to descend on the approach. So, as soon as you have course guidance you are expected to descend down to the glideslope intercept altitude. Again, this is what ATC expects you to do.

As far as regs to back this up, I don't have the FAR/AIM to back anything up. But, if you turn to Chapter 5 of the AIM you should get some answers there. Hope this helps.

 

[prpjt]

I think the legal documentation is in the chart legend. In the IAH example, on the ILS 26, the only mandatory altitude is at the glide slope intercept point. You must be at 2000 , line above and below it. On all altitudes previous to that there is only a line below the number, which means, according to the legend, fly at or above that altitude. This I believe is what gives you the legal right to stay at 3000 and intercept at that altitude if you so chose.

So as long as the GS keeps you above the minimum altitudes on the chart at the particular fix, your legal.

 

[FSB99]

In the IAH example, on the ILS 26, the only mandatory altitude is at the glide slope intercept point. You must be at 2000 , line above and below it. On all altitudes previous to that there is only a line below the number, which means, according to the legend, fly at or above that altitude. This I believe is what gives you the legal right to stay at 3000 and intercept at that altitude if you so chose.

that's the way i interpret it as well.. unless there's a mandatory stepdown, the published altitudes are just minimum altitudes.
so, yeah, you can catch the glideslope anywhere above 2200 feet and ride it down, as long as 2200 is not a mandatory stepdown.

 

[Rank&File]

I've heard the argument that the only part of the glideslope that can be used for vertical guidance is the portion that is beyond the published glide slope intercept altitude. I'm just looking for a reference that supports that.

 

[bobbysamd]

"Cleared for the Approach"

ATC: "...descend and maintain 3,000 until established on the localizer, cleared for the ILS 36L approach."

This is easy enough, right? Stay at 3,000 feet and pick up the glideslope and fly it down. But what if the published glideslope intercept altitude is 2,200? Should you descend to that altitude when established on the localizer and intercept the GS there

If it were me, I would maintain 3000 until the LOC comes alive, then I would fly the approach as published.

I still remember from my instrument ground school how "cleared for the approach" were magic words that as soon as you are established on published routing that the approach was all yours. Meaning that at that point you have clearance to descend to published altitudes.

I have not cracked the AIM in years, but I agree with the above about its comments being helpful.

Hope that helped a little.

 

[skyking1976]

I can recall several times shooting an ILS into KAPA (Denver, Centennial) and ATC would clear me to intercept the GS at 2000' above the intercept altitude listed on the approach. As far as I can tell, as along as you are protected by the radius of an MSA or airway MEA this is completely legal.

Skyking

 

[DrEvil]

ATC: "...descend and maintain 3,000 until established on the localizer, cleared for the ILS 36L approach."

This is easy enough, right? Stay at 3,000 feet and pick up the glideslope and fly it down. But what if the published glideslope intercept altitude is 2,200? Should you descend to that altitude when established on the localizer and intercept the GS there?

Some people say yes, some say who cares. Anyone know where I can find any info on how to fly an ILS legally. I'm not talking about "mandatory" stepdown fixes (IAH ILS 27 comes to mind), but the normal ones that almost all ILS approaches have published on the profile view of the chart.

Once you are established on the LOCALIZER, i.e. it "comes off the wall" you are established on a segment of the approach and you can descend to the minimum altitute at that point of the approach. For example, if you are to be at or above 3,000ft until 15 DME, then you can descend to 2500ft inside 15 DME, once you have course guidance (LOC) you can descend at YOUR discretion to 2500. Pickup the glideslope and ride it down, or descend to the minimum altitude, even if it's 2200FT prior to the FAF or GlideSlope Intercept, then once you are on the glideslope, ride it down.

The key is "established on a segment of the approach" which is LOC guidance, then you descend according to the approach requirements published.

HTH

 

[KickSave]

My understanding is that intercept altitudes and MSA's and such are for lost comms, and that ATC instructions over rides any altitude on a chart. ATC will vector you based on their needs and the altitudes they assign you will allow you to intercept the GS and follow it the rest of the way, even if you are outside or inside certain fixes. But my understanding is whatever they tell you supercedes anything published, until they release you to follow the published procedure. If they bring you in above or below a published alt, you just follow what they gave you until you have guidance. Does that sound right?

 

[midlifeflyer]

I agree with Bobbysamd and DrEvil. Once you are

1. Cleared for the approach and
2. On a track line or feeder route

You may descend to the minimum altitudes shown for the segment in the absence of a restriction from ATC.

So in the original question,

ATC: "...descend and maintain 3,000 until established on the localizer, cleared for the ILS 36L approach."

, once established o the localizer (which is usually on a track line) you may descend to the depicted minimum altitude for that segment of the approach.

 

[vossdr1]

ils

Before descending, you must be on course (localizer), cleared, and within the proscribed distance (usually 10 miles from some fix i.e. the OM).

It is possible to receive a navigable localizer outside of the proscribed distance. It is also possible for a controler to clear you for the approach outside of the proscribed distance. If you descend to the Glide Slope intercept altitude (as depicted on the profile view of the Government Plates an altitude near the lightning bolt) and you are beyond the proscribed distance, you are not guaranteed obstacle clearance.

 

[TXCAP4228]

I have significantly less time than some of the folks that have posted but there are some things to consider.

Due to the way the glide slope signal radiates, there are false glideslopes above the correct glideslope. Keep that in the back of your mind for a minute.

When ATC says maintain xxxx until established, they mean established on the localizer. Once you have the loc, you have a protected area to descend safely as the chart depicts. ATC's job is to give vectors for the final approach course - once you're there (the loc) they expect you to intercept as shown.

Now, when you consider the point from above, it seems to me that it is advisable to intercept the glideslope at the published altitude or as otherwise instructed by ATC because otherwise you risk being on a false glideslope. To make sure this doesn't happen, intercept at the published altitude.

If I am smoking crack, let me know.

 

[DrEvil]

ATC's job is to put you on a vector to intercept, within a certain angle, the LOC/ILS approach. True, while you have LOC guidance, you can only descend to LOC minimums if not withing ILS GS limits. If you are on the segment of the approach and it says at or above 3000 and you are at 5000 trying to intercept the glidepath, you're making trouble for yourself. It's best to fly the approach at the recommended altitudes (at or above's) on the segment of the approach, and all will work fine. As you drive in on these published segments, you will intercept and capture the GS, then fly that until you are at DH and voila, you've done it! It's not as hard as this thread is making it out to be. I think your question has been answered, ask again if not. I don't think we need 9,000 opinions on the ILS technique!

 

[prpjt]

Everyone has some great points and info, but I think we're getting away from the intent of the question. Only Rank&File can clear this up. What I got from his question is can you intercept the GS outside the GS intercept point , or do you have to dive and drive at each stepdown, and what is in print to back it up. I say configure once.

In the example you were at 3000, and that would put you on a 7 or 8 mile LOC intercept at the shortest if the controller didn't mess up. I think Vossdr1 was on the right track as far as legaleze, what is the prescribed usable distance for the GS. Don't have an AIM here cause I'm in Cape Cod. Any suggestions on the "have to go to" resturaunts here. We're going on a mission tomorrow to find a fish market that will pack some lobsters for the trip home Monday.

 

[eddie]

I flew with an idiot standards captain who insisted if you were told 3500 'til established (with an intercept altitude of 3000) you are not allowed to descend until you are on the glideslope.

Talk about needing to get out of the office and into the airplane more often...

 

[Rank&File]

originally posted by prpjt:
What I got from his question is can you intercept the GS outside the GS intercept point , or do you have to dive and drive at each stepdown, and what is in print to back it up.

That's exactly what my question is. I think I've found the answer
here . In a nutshell, it says once cleared for the approach, you are expected and required to descend via the step down fixes until the published glide slope intercept altitude and pick it up there and only there.

 

[eddie]

rank&file -

I think you are going a little far saying that stepping down is REQUIRED outside the Glideslope intercept altitude. You are required to make sure you cross the FAF at the published g/s crossing altitude, this makes sure you haven't intercepted a false glideslope. Then you are legal to continue the precision approach.

Outside the final approach segment, the altitudes are minimums not mandatory. (except as noted) Anyway, it looks as though you posted yet another opinion, not a published legal document.

 

[A Squared]

Rank & File,

With all due respect, the post you've linked doesn't prove anything, it's just another opinion.

I would agree that it is not correct to use the Glideslope for *Primary* vertical guidance, outside of the GSIA. As Al (in the lnked post) pointed out, blindly following the GS could cause you to go below a minimum altitude at a stepdown fix on certain approaches. A minumun altitude is exactly that, a minimum altitude, it's not a mandatory altitude. If all altitudes on an approach plate were intended to be mandatory altitudes, there would be no need to have symbology for mandatory altitudes, because they would *all* be mandatory. Legally you may be at any altitude between your last cleared altitude and the minimum altitude. So, if you own the airspace between your last cleared altitude and the minimum altitude, why not use the GS as a guide to help you establish a nice uniform descent to the GSIA ? You of course are using your altimeter and VSI as your primary descent guidance, and you are carefully monitoring your horizontal position to ensure that you don't descend below any minimum altitudes on the procedure. Once you have passed the intercept point, confirmed by DME, Marker beacon, LOM, Cross radial...etc, the GS becomes your primary vertical guidance.

to add to prpjt's comment "I say configure once.", look at what you would have to do: You're cleared for the approach at 3000 ft, the GSIA is 2200. If you dive and drive, you reconfigure, de-stabilize and re-stabilize in the descent, then when reaching 2200 you reconfigure, stabilize in level flight, they when reaching the GS you re-configure again and re stabilize in a descent again. That just soulds like way too much work for me at a time when I'm already busy. It seems far simpler to re-configure once and stabilize once, then keep close watch on your altitude relative to the outer marker. The goal here is to keep from hitting the ground, and keep from hitting another airplane, if you're between the Minimum altitude and the last cleared altitude, you can't hit an airplane or the ground.

 

[metrodriver]

You are required to maintain the altitude specified by the controller until established on a published part of the approach. Descending to the minimum glideslope intercept altitude is an option unless it is mandatory like at the ILS 26 and 27 approaches into Houston intercontinental. Like someone else said it's easier to get configured and stabilized once than to make it a constant progress.
The thing with the false glideslopes above the glideslope is quite irrelevant: you are still approaching the g/s from below, eventhough you are at a higher altitude. You can check this pretty quick too: usually the controller will say how far you are from the final fix, multiply that distance by 300' and you know at what altitude the glideslope should be (for a 3 degree glideslope) above the minumum intercept altitude