ILS Glide Slop Intercept Altitudes ??

I think I just misunderstood the question. I was thinking about, once on GS, if there were stepdowns. Which made no sense. Now I understand what you are talking about just staying at a higher stepdown and joining the GS higher and farther out. As I understand it you wont get a false GS below the GS, false GS's are only above the true GS right?

Are the stepdowns required so-to-say? I've always done the stepdowns as depicted on the approach plate, but I only have a little over 100 approaches I guess and they doesnt really compare to some of you that have thousands!
 
S40_flyer said:
Looking at the LAX ILS 25L NACO approach plate I dont see what you mean. Granted I don't know NACO nearly as well as Jepp , after you intercept the GS it looks like you still just follow it all the way down, correct?

Maybe I'm missing something. Im just curious as it would be good to know for future reference if I am missing something.:insane:

LAX ILS 25L:
http://204.108.4.16/d-tpp/0607/00237IL25L.PDF
Click to expand...


I don't have much time to look for a reference...but the ILS glideslope will not guarantee compliance with the stepdown fixes prior to the Final Approach Segment. It can be followed with proper monitoring...and most times will be compliant with the stepdown fixes...but a blanket statement that the ILS glideslope will comply with all stepdown fixes is false. We had some issues a while back at KLAX where guys were following the GS without monitoring crossing altitudes because they thought the GS would suffice...and was taking them below.

The ILS GS can be flown without regard to stepdown fixes when on the Final Approach Segment only.
 
You can get a false glide slope from being too far out, always important to cross check your position and altitude, a couple of times. If I remember correctly a true false glide slope will be upsided down, the 150hz on the top, the 90hz on the bottom, thus a fly up command is actually a fly down command, I THINK!!!!

Merit is refering to the GSIA (lightning bolt on NOS) and the minimum altitude on the profile inbound to the FAF. He was having a disagreement with friends on which altitude you can maintain if you are cleared and established. The profile min altitude is the answer, unless ATC has you lower.

edit:

Disregard the inverted glideslope reference, I can't fine where I read that, and I may be confusing two things, I have found a couple of accident reports on following too steep false glideslopes.
 
S40_flyer said:
I think I just misunderstood the question. I was thinking about, once on GS, if there were stepdowns. Which made no sense. Now I understand what you are talking about just staying at a higher stepdown and joining the GS higher and farther out. As I understand it you wont get a false GS below the GS, false GS's are only above the true GS right?

Are the stepdowns required so-to-say? I've always done the stepdowns as depicted on the approach plate, but I only have a little over 100 approaches I guess and they doesnt really compare to some of you that have thousands!
Click to expand...

Wow, holy grammer batman! I think I understand what you're getting at here. Let's hit it one by one.

1. Once on GS, what do I do about the step down restrictions?
--You don't worry about them. You stay on glideslope, which should keep you above all of the step downs anyway. If you were flying a LOC then they would apply, or if for some reason you have to transition to the LOC (like your GS stopped working in the middle of the approach or something) then they would apply.



2. Can I get a false glideslope below the true glideslope?
--No. When the FAA flight checks an approach, this is one of the things they check for. You CAN get false glideslopes ABOVE the true glideslope, but not BELOW. Generally they have a shorter range than the true glideslope, though, so the only time you would see them is close to the field, and well high on the approach, like maybe during a missed.

Incidently, there are false localizer signals as well. Sometimes you'll see them when you are being vectored on Radar downwind or base. Your CDI will center up for just a second, and then go back to full scale deflection. You'll probably see these more often than you'll see false glideslopes.
 
B767Driver said:
I don't have much time to look for a reference...but the ILS glideslope will not guarantee compliance with the stepdown fixes prior to the Final Approach Segment. It can be followed with proper monitoring...and most times will be compliant with the stepdown fixes...but a blanket statement that the ILS glideslope will comply with all stepdown fixes is false. We had some issues a while back at KLAX where guys were following the GS without monitoring crossing altitudes because they thought the GS would suffice...and was taking them below.

The ILS GS can be flown without regard to stepdown fixes when on the Final Approach Segment only.
Click to expand...

EDIT: Fixed the quote, to make it show up as a quote

Good point here. Yes, you can probably pick up the glideslope before the FAF/glideslope intercept point. It's supposed to have a useable range of at least 10 miles, and most FAF's aren't out that far. But BEFORE the FAF, there is no guarantee that following the GS will keep you in compliance with all of the altitude restrictions, that only works AFTER the FAF.
 
B767Driver said:
I don't have much time to look for a reference...but the ILS glideslope will not guarantee compliance with the stepdown fixes prior to the Final Approach Segment. It can be followed with proper monitoring...and most times will be compliant with the stepdown fixes...but a blanket statement that the ILS glideslope will comply with all stepdown fixes is false. We had some issues a while back at KLAX where guys were following the GS without monitoring crossing altitudes because they thought the GS would suffice...and was taking them below.

The ILS GS can be flown without regard to stepdown fixes when on the Final Approach Segment only.
Click to expand...
Unless the approach has changed since August of 2001 (admittedly very possible) then the GS clears all stepdown fixes by at least 150'.
 
I've flown it recently as well and the GS remained above the fixes outside the final approach segment as well. The point to be made, is that if you use the GS outside of the Final Approach Segment...you are responsible to ensure that the GS remains above the stepdown fixes. This may not always be the case. Sounds like an approach to KPIT does not...and emphasizes the issue.

An FMS technique commonly employed with an ILS with multiple stepdown fixes is to use the FMS VNAV with hard altitudes programmed with the stepdown fixes...and only when the last altitude has been cleared...then couple up the ILS.
 
B767Driver said:
It sounds to me that the controllers at KPIT are enforcing the approach properly.
Click to expand...

I will give you a situation and tell me what you would do:

Here is the approach:
http://204.108.4.16/d-tpp/0607/00570I28L.PDF

We were well outside Halin at 5000'. Approach told us to join the LOC, cleared for the approach. No altitude was mentioned.

She queried why we didn't decend to 4000' right away after being cleared for the approach. If she wanted us down to 4000', she should have said "maintain 4000' until established, cleared for the ils 28L", do you not agree? A simple 3:1 calculation puts you well above the required 4000' at Halin if you are on GS.

Keep in mind it is only one controller that expected this...
 
Wheelsup, you were perfectly correct that you didn't need to descend to 4000'. All of the altitude restrictions were AT OR ABOVE restrictions. In fact, you weren't even legally required to descend at any point on that approach, until you started to fly the missed approach portion. That's the first place where a specific altitude is required (by the phrase Climb to 4000). So when you get to the Missed Approach portion, you are expected to be no higher than 4000, in a climb, and eventually AT 4000' as a hard altitude.

So legally, you could have flown the whole thing at 5000', and somewhere on final, began a descent to 4000' so as to be over the MAP at 4000'.

Obviously, this (flying the entire approach at your last vectored altitude of 5000' and then being at the MAP at 4000') would kind of violate the common sense and do what is expected of you rules, however it would still be legal with the clearance that you received.

Just not smart.
 
fish314 said:
Wheelsup, you were perfectly correct that you didn't need to descend to 4000'. All of the altitude restrictions were AT OR ABOVE restrictions. In fact, you weren't even legally required to descend at any point on that approach, until you started to fly the missed approach portion. That's the first place where a specific altitude is required (by the phrase Climb to 4000). So when you get to the Missed Approach portion, you are expected to be no higher than 4000, in a climb, and eventually AT 4000' as a hard altitude.

So legally, you could have flown the whole thing at 5000', and somewhere on final, began a descent to 4000' so as to be over the MAP at 4000'.

Obviously, this (flying the entire approach at your last vectored altitude of 5000' and then being at the MAP at 4000') would kind of violate the common sense and do what is expected of you rules, however it would still be legal with the clearance that you received.

Just not smart.
Click to expand...

I think you are making this more complicated than it needs to be. It's an ILS, not rocket science. I expected to be able to fly 5000' until hitting the GS, then descending down on it to the DA. That's what we did (or were going to do) but she wanted us to descend on our own to 4000' before intercepting. We didn't want to go to the MAP at 5000'.

If you are just pointing out another example, then disregard.

PS Your explanations are excellent and I look forward to your informative posts.
 
Thanks!

Yeah, I was just using that as an example/explanation. I was trying to point out that not only was staying at 5000' legal until GS intercept, but it would have been legal to stay there a whole lot longer. If the controller wanted you to be at 4000' she needed to say something like:

"Descend and maintain 4000', cleared the approach"

or:

"Cross halin at 4000' cleared the approach"

or something like that.
 
wheelsup said:
I will give you a situation and tell me what you would do:

Here is the approach:
http://204.108.4.16/d-tpp/0607/00570I28L.PDF

We were well outside Halin at 5000'. Approach told us to join the LOC, cleared for the approach. No altitude was mentioned.

She queried why we didn't decend to 4000' right away after being cleared for the approach. If she wanted us down to 4000', she should have said "maintain 4000' until established, cleared for the ils 28L", do you not agree? A simple 3:1 calculation puts you well above the required 4000' at Halin if you are on GS.

Keep in mind it is only one controller that expected this...
Click to expand...

That's a different situation than what I was hearing earlier.

While I think it's always good practice to descend to the minimum altitude specified on the approach, I see no problem hanging out at 5000' to intercept the glideslope.

A couple of items...

#1) if you were being radar vectored to final...which I think you were, the controller is required to assign you an altitude to maintain until established on course. My guess is she meant to assign you 4000' and forgot.

#2) When being radar vectored to final...you are not to execute a procedure turn or course reversal from your current positon. This IAP says to descend to 4000' during the course reversal...and to fly it for one minute. If you are radar vectored straight in at 5000'...how are you supposed to know when it's safe to descend to 4000'? I've never like those 1 minute course reversal approaches for that reason.

ATC should have been more proactive in your altitude assignment if you ask me. If I don't get one in that situation...I make them give me one.

A related note...I got my first real TCAS RA last week at FL240. We had to descend 1000'...the other aircraft was commanded to climb. Once the RA ceased...the controller was not assertive on putting the pieces back together for everyone. After a couple of hints telling ATC we were at FL230...and only getting a 'Roger' for a reply...I finally requested a clearance to an altitude as we were now at FL230 with a clearance for FL240. I know the procedure is to resume the previous clearance...but it would have been nice to receive a confident clarification from ATC.
 
Absent a mandatory intercept altitude, be it published or assigned, my strong preference to to maintain my altitude until glideslope intercept. There are several reasons for this, but the main ones to me are:

1. less noise footprint
2. more fuel efficient
3. fewer birds higher up
4. smoother air
5. possibly less other traffic
6. more options in the event of an emergency (be that an engine failure, flight control failure, or about anything else, altitude gives you more time).

I really can't think of any reason to do otherwise. As for PIT, if they ever gave me trouble about not descending when they did not issue instructions for me to do so, I'd get their initials and have a chat with them, or, these days, have our ATC folks do it, done it more than once!
 
seagull said:
Absent a mandatory intercept altitude, be it published or assigned, my strong preference to to maintain my altitude until glideslope intercept. There are several reasons for this, but the main ones to me are:

1. less noise footprint
2. more fuel efficient
3. fewer birds higher up
4. smoother air
5. possibly less other traffic
6. more options in the event of an emergency (be that an engine failure, flight control failure, or about anything else, altitude gives you more time).

I really can't think of any reason to do otherwise. As for PIT, if they ever gave me trouble about not descending when they did not issue instructions for me to do so, I'd get their initials and have a chat with them, or, these days, have our ATC folks do it, done it more than once!
Click to expand...



7. Avoiding wake turbulence.

or is that what you meant by number 4 ?


TP
 
Isn't this redundant?:confused:
3. fewer birds higher up
5. possibly less other traffic
Click to expand...



Just kidding. I throughly enjoy these 'real world' flying post. I've learned somthing here.
 
Typhoon,

Yes, wake turbulence is another good reason, I didn't think about that when I was typing it.
 
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