LiveATC Discussion Forums
Air Traffic Monitoring => Listener Forum => Topic started by: Greg01 on March 31, 2008, 04:42:05 PM
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Not to nit-pick, but the FAF on an ILS is the glideslope intercept. GS intercept is usually at or near the marker, but it isn't always.
Greg
[MOD] This thread was split from, and refers to "JetBlue wants to play games (http://www.liveatc.net/forums/index.php/topic,4357.0.html)" [/MOD]
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Not to nit-pick, but the FAF on an ILS is the glideslope intercept. GS intercept is usually at or near the marker, but it isn't always.
Greg
I don't think this is entirely true.
Case in point, ILS 25L at KLAX and ILS 25L at KLAS. For LAX, the IAF is at FUELR, which is 26nm from the field. The outer marker for LAX is LIMMA, which is 7nm out. I can guarantee you'll intercept the glideslope before LIMMA.
Same would suffice for Las Vegas, where PRINO is the IAF for 25L, and that's 21nm out. You'll have both the localizer and glideslope prior to even getting to that fix.
I'll agree it isn't always true, because there may not be an outer, middle, or inner marker for a given ILS approach, such as Vegas. But I'm definitely positive you'll have both LOC and GS before the FAF.
BL.
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Not to nit-pick, but the FAF on an ILS is the glideslope intercept. GS intercept is usually at or near the marker, but it isn't always.
Greg
I don't think this is entirely true.
Case in point, ILS 25L at KLAX and ILS 25L at KLAS. For LAX, the IAF is at FUELR, which is 26nm from the field. The outer marker for LAX is LIMMA, which is 7nm out. I can guarantee you'll intercept the glideslope before LIMMA.
Same would suffice for Las Vegas, where PRINO is the IAF for 25L, and that's 21nm out. You'll have both the localizer and glideslope prior to even getting to that fix.
I'll agree it isn't always true, because there may not be an outer, middle, or inner marker for a given ILS approach, such as Vegas. But I'm definitely positive you'll have both LOC and GS before the FAF.
BL.
LIMMA isn't an outer marker though, it's the non-precision (localizer) FAF defined by DME off of the localizer antenna (or SLI R-297 and the localizer course). Regarding the ILS 25L at Las Vegas (http://myairplane.com/databases/approach/npdfs/00662I25L.PDF), the precision approach FAF is just about at RELIN intersection as noted by the lightning bolt symbol on the profile view. You can still be vectored way outside of RELIN, but that is still the legal glideslope intercept (as charted). You can intercept and follow the GS prior to this point, but you must be established on the GS by this point (hence, GS intercept).
I have to agree with Greg on this one. Most of the precision FAFs (glide slope intercept) occur at or near the outer marker if one exists on the procedure.
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Tyketto,
The ILS 25L into LAX does not have marker beacon system. LIMMA is the FAF for the LOCALIZER 25L approach, not the ILS, hence the maltese cross in the profile view.
The FAF for the ILS is the GS intercept. Now, if you fly the approach as charted (basically ATC gets you established at or inside of HUNDA at 3200, you will capture the GS as charted. However, if they authorize 1900 between HUNDA and LIMMA, then you will pick up the GS at LIMMA. It just so happens with this approach that GS intercept will occur at LIMMA (again, if ATC authorizes 1900).
Again, not so for the LAS approaches. The explanation above for the LAX approach applies to the LAS approach. FAF for the ILS 25L into LAS is the GS intercept (the lightning bolt arrow on the profile view).
Now, I can explain why the LAX approach says: ILS or LOC 25L and the LAS approach only says: ILS 25L yet in still includes LOC only minimums...but it'll have to be tomorrow (have to hit the hay).
Respectfully,
Greg
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Jason, looks like we posted at about the same time.
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Now, I can explain why the LAX approach says: ILS or LOC 25L and the LAS approach only says: ILS 25L yet in still includes LOC only minimums...but it'll have to be tomorrow (have to hit the hay).
This question made me think a little, too. I honestly don't know the official answer, but my guess would be that it would allow the controller to issue a clearance for the localizer approach (ie, "cleared localizer runway 25L approach") rather than a clearance for the ILS with a GS unusable advisory (ie, "cleared ILS runway 25L, glide slope unusable"). I can't think of any TERPS requirements that would reflect a change in the title, but there certainly could be.
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I have to agree with Greg on this one. Most of the precision FAFs (glide slope intercept) occur at or near the outer marker if one exists on the procedure.
I'll third this. For us little retractable gear aircraft pilots, the FAF/glideslope intercept on an ILS is where we drop the gear and transition from the straight and level glideslope intercept altitude to a descent down the glideslope. Dropping the gear on my Bonanza slows the aircraft from 153 (max gear down speed, or Vle) to 120 knots and, assuming proper power setting, naturally starts a 500 foot a minute descent with the glideslope due to the drag of the gear.
My understanding is that the now old-fashioned outer marker is tied to the FAF on an ILS because it serves as the pilot's audio cue as to the intercept point. As pointed out previously, though, most of the outer markers are being decommissioned across the US due primarily to (I believe) the cost savings of not having to maintain them.
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Tyketto,
The ILS 25L into LAX does not have marker beacon system. LIMMA is the FAF for the LOCALIZER 25L approach, not the ILS, hence the maltese cross in the profile view.
Are you sure about that?
http://www.airnav.com/airport/LAX/ils/25L
Outer marker information
Type: OUTER MARKER BEACON ONLY
Name: LIMMA
Location: 33-56-53.500N / 118-16-32.200W
5.4 nm (32720 ft.) from the approach end of runway 25L
Again, not so for the LAS approaches. The explanation above for the LAX approach applies to the LAS approach. FAF for the ILS 25L into LAS is the GS intercept (the lightning bolt arrow on the profile view).
I'll agree on that, but what I was getting at is that you'll get the GS intercept much further out than that, not just only at the FAF, which is what I think you may have been alluding to before. I've had it pick up out by PRINO and CROWE, which are at least 20DME from the field.
BL.
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Are you sure about that?
http://www.airnav.com/airport/LAX/ils/25L
Outer marker information
Type: OUTER MARKER BEACON ONLY
Name: LIMMA
Location: 33-56-53.500N / 118-16-32.200W
5.4 nm (32720 ft.) from the approach end of runway 25L
The AirNav data is old, it still has the outer marker designation for most of these fixes even though the system no longer exists. Even if the antenna exists and the system is operational, but unmonitored, legally, it can't be used on the approach because the marker beacon is neither monitored or charted.
Again, not so for the LAS approaches. The explanation above for the LAX approach applies to the LAS approach. FAF for the ILS 25L into LAS is the GS intercept (the lightning bolt arrow on the profile view).
I'll agree on that, but what I was getting at is that you'll get the GS intercept much further out than that, not just only at the FAF, which is what I think you may have been alluding to before. I've had it pick up out by PRINO and CROWE, which are at least 20DME from the field.
BL.
I don't think we're talking about actual GS intercept, we're talking about the ILS (precision approach) FAF, which is the glideslope intercept, as indicated by the location of the lightning bolt on the profile view of the procedure.
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I've split this thread from the original, since it doesn't necessarily apply to that discussion.
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I'll agree on that, but what I was getting at is that you'll get the GS intercept much further out than that, not just only at the FAF, which is what I think you may have been alluding to before. I've had it pick up out by PRINO and CROWE, which are at least 20DME from the field.
When a controller is vectoring an aircraft to an ILS they are descending and vectoring so that the aircraft intercepts the glideslope at or very near the FAF, not some point 20 miles out. I would need to look it up, but I am not even sure a glideslope indication could be trusted that far out.
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Found the information about glideslope usability from the US AIM:
http://www.faa.gov/airports_airtraffic/air_traffic/publications/atpubs/aim/Chap1/aim0101.html
3. The glide path projection angle is normally adjusted to 3 degrees above horizontal so that it intersects the MM at about 200 feet and the OM at about 1,400 feet above the runway elevation. The glide slope is normally usable to the distance of 10 NM. However, at some locations, the glide slope has been certified for an extended service volume which exceeds 10 NM.
Personally I don't know what markings there are on a chart that indicate a GS is usable beyond 10NM since I have never required it. I would be curious what scenario is in place that requires a GS to be usable at a range of 20nm.
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Found the information about glideslope usability from the US AIM:
http://www.faa.gov/airports_airtraffic/air_traffic/publications/atpubs/aim/Chap1/aim0101.html
3. The glide path projection angle is normally adjusted to 3 degrees above horizontal so that it intersects the MM at about 200 feet and the OM at about 1,400 feet above the runway elevation. The glide slope is normally usable to the distance of 10 NM. However, at some locations, the glide slope has been certified for an extended service volume which exceeds 10 NM.
Personally I don't know what markings there are on a chart that indicate a GS is usable beyond 10NM since I have never required it. I would be curious what scenario is in place that requires a GS to be usable at a range of 20nm.
Try looking at the CIVET5 or RIIVR1 arrivals into LAX. The localizer (from what I've asked of pilots) goes out that far, but they have said that they capture the glideslope at FUELR or PALAC, which both are about 25DME from the field. This is why the controlers at SoCal give the call 'After FUELR (PALAC), Cleared ILS runway 25L (24R) approach.' No true TAC required for the approach clearance. By the time they hit FUELR, they should have both and descend by it, as the STARs end at the IAF for the ILS approach.
theoretically, you could wash/rinse/repeat for KEPEC2/SUNST2/TYSSN2 into LAS, as those arrivals drop you off at the IAF for ILS 25L as well. So by then, you'd have to have the GS active, otherwise, you wouldn't descend any lower than what you're given in PTAC until roughly 10NM out, right?
BL.
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This is why the controlers at SoCal give the call 'After FUELR (PALAC), Cleared ILS runway 25L (24R) approach.'
Don't have time right now to really study the specific chart (will do soon) but in general, controllers clearing an aircraft for an approach does not demonstrate that the aircraft has captured the glideslope (which I believe is what this discussion is about).
Rather, controllers clear aircraft for the ILS approach when they become established on the localizer, and that does have a much further usable range than the glideslope. Once cleared for the approach, the pilot is free to descend to the minimum altitude(s) detailed on the chart for that segment of the approach, if not given a crossing restriction, that is.
Also, from what I understand (not being a pilot who flies into the major airports via STARs I am forced to extrapolate) an approach clearance trumps a STAR procedure. In other words, once the pilot is cleared for the approach he/she would adhere to altitudes, headings, etc, using the approach plate, not the STAR.
Do aircraft really capture the glideslope 25nm out for LAX? I am not so sure about that. Take a look at the profile section of 25L into LAX:
(http://img353.imageshack.us/img353/1040/scrn0054sb7.jpg)
I would have expected to see the glideslope drawn out to FUELR had the approach designers intended the GS be captured there. I could be wrong but that is my interpretation of the chart.
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When a controller is vectoring an aircraft to an ILS they are descending and vectoring so that the aircraft intercepts the glideslope at or very near the FAF, not some point 20 miles out. I would need to look it up, but I am not even sure a glideslope indication could be trusted that far out.
I'm afraid you don't seem terribly familiar with major international airports during busy rushes then.
Look over at DEN and their Triple Simo ILSs. Look at ILS Runway 35L. Find CRUUP. 19.8 DME south of the runway... and ATC must issue instructions for aircraft to be established on the localizer outside of that point by at least one mile. During a busy rush in poor weather, people might well be joining that localizer up to 30 NM out. And I guarantee those pilots are recieving the glideslope info by the time they hit CRUPP, probably much earlier. It's a requirement to run simos.
From a pilot's standpoint, it's difficult to know how far out a particular localizer/GS is flight checked to. But most localizer courses with GS are good for at least a dozen miles, many even more than that. Wouldn't be able to make a string of pearls on final if everyone was turning on "at or very near the FAF."
~Nate
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From a pilot's standpoint, it's difficult to know how far out a particular localizer/GS is flight checked to. But most localizer courses with GS are good for at least a dozen miles, many even more than that. Wouldn't be able to make a string of pearls on final if everyone was turning on "at or very near the FAF."
I knew after rereading my post that someone would misinterpret it. I was referring to glideslope intercept, not localizer intercept. I said nothing about being turned onto the approach right at the marker, but I certainly will admit my wording was nebulous. A better wording would have been: Controllers are descending aircraft below the glideslope well before the FAF so by the time they reach the FAF they intercept. Better?
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Fair enough with the wording,
However, if you look at my example at DEN, you'll see the FAF is at DYMON, a mere 6.8 DME south (closer to 5 miles to the landing threshold really). If one is shooting a triple simo app though, those planes are going to be dead on the needles, both loc and GS, by the time they hit CRUPP, and probably before that.
Aircraft will be up at right about 11k as well when they start their let down on the glide (gotta maintain vertical sep with the parallel runway landers until everyone is established on the Loc/GS for their respective runway). Been to the TRACON many a time, watched it happen with mine own two eyes :-D
Just sayin... the ATC situation is a very fluid one, and glide slopes can go out there a long ways as well with their paired localizer.
~Nate
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Jason has the jist of what I was trying to find. Unfortunately, I'm having a hard time trying to relocate my source. If any of the controllers on here could give an explanation, it would be greatly appreciated.
However, getting back to the main point: it doesn't matter where you join the GS, just that the charted GS intercept on an ILS approach is the FAF.
Thanks,
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Jason has the jist of what I was trying to find. Unfortunately, I'm having a hard time trying to relocate my source. If any of the controllers on here could give an explanation, it would be greatly appreciated.
However, getting back to the main point: it doesn't matter where you join the GS, just that the charted GS intercept on an ILS approach is the FAF.
Thanks,
I had a tough time finding sources as well, Greg. I couldn't find anything in the TERPS manual, just a guess off the top of my head.
I personally think of the glideslope intercept as shown by the lightning bolt symbol as the last possible opportunity to become established on the approach (both laterally and vertically) since ATC can clear you for the approach further out on many procedures. If you don't intercept the glideslope by that point, you should really go missed and try it again (though there are some exceptions, wake turbulence is a good example). If you're not properly established on the approach (which includes heading deviations of less than 2º inside the FAF) by the FAF, it's a good idea to go missed. No sense in trying to salvage what you aren't already ahead of. Of course, varying winds aloft make this difficult, but usually they will cooperate to allow a solid WCA to be maintained on the FAC prior to the FAF.
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And I think Nate has it nailed, especially with it being very fluid.
In the case of ILS 25L at LAX, the CIVET5 and RIIVR1 are profiled descents that bring you down to the IAF for the approach at FUELR, so you'll still be on the STAR until being given 'after FUELR, cleared ILS runway 25L approach. So while on the profiled descent of the STAR, you'll already be on the LOC for the ILS approach. you'd stay on the STAR until you pass FUELR, and after that you should have both the LOC and GS for your descent down. It just may be something fluid that is done that it's hard to pinpoint where one ends and the other begins, but the GS is definitely available further out than 10nm.
This was one of the biggest FAQs that was brought up when the old SocalTracon.com forum was up and ran by a controller at SCT.
EDIT: Unless they follow the chart down until HUNDA, which could be possible...
BL.
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However, if you look at my example at DEN, you'll see the FAF is at DYMON, a mere 6.8 DME south (closer to 5 miles to the landing threshold really). If one is shooting a triple simo app though, those planes are going to be dead on the needles, both loc and GS, by the time they hit CRUPP, and probably before that.
Ok, just looked. Just out of curiosity, are you typing from a controller's perspective or a big iron pilot's perspective? I am questioning the idea that in this example pilots are capturing the glideslope that far out but I am not saying it's not possible - just curious: Notice that the minimum altitude at CRUPP and others have a note that reads "Or as assigned by ATC" which seems to imply that assigned altitude could be lower. Note also that the glideslope intercept on the chart also has a note indicating that ATC could assign lower.
Thus, without knowing what the normal ATC practice is there (does ATC routinely descend aircraft to the lower intercept altitude or keep them up at 11,000 at CRUPP before clearing for the ILS approach?) I am not yet convinced that aircraft are intercepting the GS that far back.
Of course, if you are a United 777 pilot then you definitely know that you are intercepting that far back. From the controller's scope? Eh, do you really? :) :)
BTW, I am only a Bonanza pilot but I do fly IFR at least twice to three times every week in the Northeast US for business and Angel Flight. Been doing that since 2004. The biggest airports I have been to are BWI and Boston and I do these once every few months. I almost went to JFK once but was fortunately talked out of it. Hey, let's face it: There really is no need for us little ones to clog up the movement at those monster class B airports with so many suitable satellite airports. I have been to Denver in the Bonanza twice, though, to visit my brother there. Landed one year at Platte Valley and the next at Erie Muni.
edit: removed incomplete thought.
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And I think Nate has it nailed, especially with it being very fluid.
What does it mean to be fluid? I seek some clarification on how that word applies in this case, since my understanding of the word is "always changing."
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Peter,
Give me time to dig up the appropriate references, I will get back to you later tonight.
~Nate
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And I think Nate has it nailed, especially with it being very fluid.
What does it mean to be fluid? I seek some clarification on how that word applies in this case, since my understanding of the word is "always changing."
I believe what he was alluding to was that if the GS intercept is indeed only 10nm out, you're pretty much in no-man's land with the ILS approach, and are only following the descent as indicated on the chart until you have the GS. So if it is available further out, you're not just going from STAR - descent-per-chart - GS intercept, where it's choppy. the GS may be available further out than just 10nm to where it's a fluid even progression from end-of-STAR to GS.
BL.
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Tyketto, forget the STAR. Just take the STAR out of the picture completely. Let's say ATC has you direct FUELR and tells you to "Maintain 7000 until established on a published segment of the approach, cleared ILS 25L approach." After passing FUELR, just follow the minimum altitudes until you reach the GS intercept and your golden.
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I believe what he was alluding to was that if the GS intercept is indeed only 10nm out, you're pretty much in no-man's land with the ILS approach, and are only following the descent as indicated on the chart until you have the GS.
No man's land? Hmmmm... not really. The approach procedure contains very specific information about heading and altitude.
Once cleared for an ILS approach (regardless of where cleared), a pilot is authorized to descend to the minimum altitude for that segment of the approach, that is unless given a crossing restriction. Hardly a no-man's land, which suggests a chaotic, free-for-all. :)
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I believe what he was alluding to was that if the GS intercept is indeed only 10nm out, you're pretty much in no-man's land with the ILS approach, and are only following the descent as indicated on the chart until you have the GS.
No man's land? Hmmmm... not really. The approach procedure contains very specific information about heading and altitude.
Once cleared for an ILS approach (regardless of where cleared), a pilot is authorized to descend to the minimum altitude for that segment of the approach, that is unless given a crossing restriction. Hardly a no-man's land, which suggests a chaotic, free-for-all. :)
you're right. I was meaning that as a figure of speech. There is the approach segments as depicted on the chart. But what I was getting at is that if the GS is available further out than the 10nm intercept, you wouldn't only have the individual segments of the approach to use, but also the GS as well. Either one should suffice.
And I also need to correct myself. As far as west ops are concerned and ILS approaches, PTAC would be given to TEC routes from the west (say, PSP, ONT, RAL, etc.). They'll be kept out of the CIVET/RIIVR stream until closer to the field (LAHAB) then either given the visual or ILS approach.
BL.
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But what I was getting at is that if the GS is available further out than the 10nm intercept, you wouldn't only have the individual segments of the approach to use, but also the GS as well. Either one should suffice.
I was hoping that one of the airline pilot's who frequent here would have jumped in by now to offer their practice regarding capturing the GS so far back (meaning, is it acceptable or is there some type of airline operating policy that sets a limit as to how far back to do so).
In the meantime, I can only offer my perspective as a little blip: If I were not already descended to an intercept altitude that permitted an intercept within about 10 miles or so and I was not given any type of interim descent limit, I would "dive and drive" to an altitude permitted by the approach when cleared for the approach, rather than capture that far back.
Or, now that my aircraft is equipped with WAAS I would come down the GPS glideslope on an LPV approach, since that signal can be used way out. :) :)
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Technically, the lightning bolt in the profile view is the glideslope intercept altitude (GSIA). It's the altitude you have to be at near where you're supposed to be at where you're guaranteed to capture the real glideslope. Above the glideslope, there are false glideslopes at angles of roughly 6 degrees (upside down), 9 degrees (rightside up), 12 degrees (upside down), etc...
Before you get to the GSIA point, you're not supposed to use the glideslope for vertical guidance. Most of us in bugsmashers without VNAV will do the "dive and drive" to each segment altitude. Airliners with FMS will have the FMS calculate a smooth descent profile that keeps them above the min segment altitudes.
GSIA usually occurs somewhere near the Non Precision FAF.
Oh, and ATC is not supposed to vector you to the FAC above the GS, (due to the false glideslopes up there), and on a vectors to final, the intercept point has to be outside the approach gate, which is either 5 miles away from the airport, or 1 mile outside the FAF/GSIA, whichever is farther.
--Carlos V.
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Or, now that my aircraft is equipped with WAAS I would come down the GPS glideslope on an LPV approach, since that signal can be used way out. :) :)
True, but according to the WAAS TSO, the box won't annunciate LPV/LNAV/LNAV-VNAV/ LNAV+V and generate the synthetic glideslope until you're within 3 miles of the FAF and going in the right direction.
--Carlos V.
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But what I was getting at is that if the GS is available further out than the 10nm intercept, you wouldn't only have the individual segments of the approach to use, but also the GS as well. Either one should suffice.
Drat, I need to go look for my references, but another board had a similar discussion, and that could get you in trouble. I need to look myself since it involves math it might take a while. Some approaches had the GS dip below the intermediate segment min altitudes. I think LAX was one of them. One should always not fly the GS until you capture it at the GSIA.
Edit to add: Yup, it was LAX. Both 25s ILSes put you 400ish feet too low at at least one fix. 25L at 3 degrees puts you at 4590 feet at GAATE (which is 15.2 miles out), which has a min altitude of 5000. 25R puts you at 4560 at FALLT (15.3 miles) who's min is 5000.
--Carlos V.
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But what I was getting at is that if the GS is available further out than the 10nm intercept, you wouldn't only have the individual segments of the approach to use, but also the GS as well. Either one should suffice.
Drat, I need to go look for my references, but another board had a similar discussion, and that could get you in trouble. I need to look myself since it involves math it might take a while. Some approaches had the GS dip below the intermediate segment min altitudes. I think LAX was one of them. One should always not fly the GS until you capture it at the GSIA.
Edit to add: Yup, it was LAX. Both 25s ILSes put you 400ish feet too low at at least one fix. 25L at 3 degrees puts you at 4590 feet at GAATE (which is 15.2 miles out), which has a min altitude of 5000. 25R puts you at 4560 at FALLT (15.3 miles) who's min is 5000.
--Carlos V.
Could you compare that to the 24s? I'm wondering if it is because those coming in from the south or the west via the LEENA2 arrival going to the 24s may be vectored behind and above the 25 stream to keep the separation there through the gates.
This is good stuff all around! :)
BL.
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There are folks here with much more flying experience than me, but as an instrument student, I've been taught (and have read) that the glideslope should be ignored until reaching the lightning bolt. Prior to that, you should use the minimum altitude published for each approach segment.
The fact that the glideslope might be received prior to the GSIA is irrelevant, and should be ignored (due to the false slopes that might exist, or due to published intermediate stepdown fixes along the way).
Here's a question I've had for a long time, and this seems like the best place to ask it...
Listening to the KSNA feed, the PTACs for the ILS 19R are usually done with reference to LEMON. "4 from LEMON, fly hdg 160, maintain [MVA] until established, cleared ILS RWY 19R approach." Given that the FAF for a precision approach IS the GS intercept point (SNAKE, in this case), and that the aircraft should join the localizer prior to the gate (which is outside SNAKE), why are they referencing LEMON instead of SNAKE?
The chart's here for anyone who wants to review it: http://204.108.4.16/d-tpp/0803/00377I19R.PDF
So, that's the question, why vector with reference to LEMON?
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So, that's the question, why vector with reference to LEMON?
Many controllers reference the outer marker on the procedure (if one exists) in the PTAC, but it varies by facility. I don't exactly know why, but I've heard this done all over the country in many different places. If you ever listen to JFK Final, you can hear them doing it often as well. I would imagine its for situational awareness since the outer marker and co-located intersection are more easily noted on the chart than another random fix on the approach, but you do bring up a good point that the lightning bolt is very close to/in reference of SNAKE intersection.
Also note that if ATC directs a lower-than-published glideslope/path intercept altitude, the resultant actual point of the glideslope/path intercept at the altitude authorized to maintain until established becomes the precision FAF.
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i'm gonna paraphrase the 7110.65 the ATC manual b/c i'm out of town for a few days but the FAA's 7110.65 definition of the FAF on an ILS is "the point the aircraft intercepts the glideslope". most of the time the controller will give the lowest altitude restriction he can depending on his minimum vectoring altitude in the area. He can clear you at the IAF if he wants as long as you are at or below the GS crossing altitude at that point. at bwi, we clear anywhere from 4000' to 2000' on rwy 33L, but you'll notice that the altitude at RUETT is 1500'...we can only go to 2000' due to the MVA. So, right there adds another mile out from the runway, plus a mile for the gate, plus 2 more miles to meet the 7110.65 requirements and you're now 8 miles from the runway...now if i clear you at 3000' for the ILS 33L, add 3.3 more miles to that...
as far as the question of whether or not a localizer or glideslope goes out 25 miles or whatever, just look at the chart...the IAF is most likely as far as the TERPS folks feels the GS is reliable.
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Jason,
I didn't ask the question very clearly. A distance from the marker is indeed very good for situational awareness. That's not my concern. The issue is having the plane join the localizer inside the bolt...however, if the controller is allowed to throw away the lightning bolt, then I guess it works out :)
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The full published procedure is for approaches without RADAR assistance, it keeps you at a safe altitude prior to intercept. (I should say Terminal radar assistance.)
When radar vectors are provided, we TRACONs can vector to intercept below the GS but not below the MVA. If you get a close turn on (say at the gate) you will NOT have to chase the descent while achieving course guidance. We (ATC) aren't ignoring the published procedure, it doesn't apply when ATC is involved (kind of an ATC shortcut). But then you must be working with a TRACON.
For example, Enroute controllers who assume approach control airspace for part-time facilities normally do not have radar coverage to provided detail approach guidance below most altitudes, in my airspace sometimes traffic is not visible below 5000' for a sea level airport. Their radar doesn't update as quickly, they cannot use mode C for separation etc, so they usually vector to an IAF or transition, Terminal controllers will vector (pending on the weather) closer and lower.
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most of the time the controller will give the lowest altitude restriction he can depending on his minimum vectoring altitude in the area. He can clear you at the IAF if he wants as long as you are at or below the GS crossing altitude at that point.
Practically, as a pilot, if I'm getting vectors, and I become established and receive a "cleared for the approach" I will fly the lowest of 1) Assigned altitude or 2) min segment altitude. I.e. assigned 3000, you vector me onto a segment that says 4000, the next segment is 2000, I will fly 3000 when cleared for the approach until I hit the 2000 segment.
as far as the question of whether or not a localizer or glideslope goes out 25 miles or whatever, just look at the chart...the IAF is most likely as far as the TERPS folks feels the GS is reliable.
IAF? You mean precision FAF right? The IAF can be anywhere and be based on navaids other than the localizer.
--Carlos V.
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Could you compare that to the 24s?
Both Glideslopes appear to be above all previous min segment altitudes. They're above JULLI and MERCE by 300 feet.
FYI: a 3% glideslope is 318 feet per nautical mile. The rule of thumb for simplified cockpit calculations is 300 feet/nm.
--Carlos V.
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Jason,
I didn't ask the question very clearly. A distance from the marker is indeed very good for situational awareness. That's not my concern. The issue is having the plane join the localizer inside the bolt...however, if the controller is allowed to throw away the lightning bolt, then I guess it works out :)
I suppose I didn't answer it too clearly either. As Natasha alluded to, the charted lightning bolt in practicality, is to be used if you've been cleared for the full approach (no VTF) outside of radar coverage. Since ATC can change the intercept altitude to whatever they want (though it must be below the GS and above the MVA) the resultant point of the altitude assigned and the glideslope/glidepath intercept becomes the new precision FAF, and thus, the charted lightning bolt does not apply.
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As Natasha alluded to, the charted lightning bolt in practicality, is to be used if you've been cleared for the full approach (no VTF) outside of radar coverage.
Incorrect. Even with VTF, the pilot should descend to the GSIA before following the glideslope.
For example, CNO ILS 26R (http://204.108.4.16/d-tpp/0803/05599IL26R.PDF) that I got tons and tons of time in training. SoCal usually gives us vectors to final at 3000 outside LINDN. By coincidence, the GS intersects at LINDN right at 3000, and when I'm flying the needle does come down to center at that point. HOWEVER, once I hit LINDN, I don't follow the GS down, but do a non-precision descent to 2100, and begin following the GS once it re-centers at DEWYE. TERPS chose that point for a reason, and we as pilots don't know it. The GS is not guaranteed out beyond the normal GSIA point so we have to fly it as charted.
Of course, if I'm below the GSIA when I am established on the FAC I'll start down at whatever point I intercept, but in practicality, I should never receive that since ATC is supposed to vector us at least a mile farther out from that point. I have a copy of .65 at home that I'll look up for reference.
--Carlos V.
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Incorrect. Even with VTF, the pilot should descend to the GSIA before following the glideslope.
There is nothing that requires a pilot to descend to the GSIA before using the glideslope signal. If ATC clears you for the approach 10 or 15 miles out, maintaining 1,000 feet above the GSIA (which is still below the glideslope), you have two options. You can either maintain 3,000 feet until you intercept the glideslope, or you could descend down to the GSIA and intercept down there. The only thing you can't do is descend below the minimum altitude for the prescribed route segment on the approach. If you use Jepps, you'll notice the second method is depicted much more clearly than on the NACO charts (shown as stepdowns), but most commercial pilots (airline, corporate, fractional, etc) opt to remain at the altitude assigned by ATC until GS intercept since it provides a much smoother descent.
As long as ATC assigns an altitude below the glideslope and above the GSIA, you're cleared to remain at that altitude until you capture the glideslope.
b. For a precision approach, at an altitude not
above the glideslope/glidepath or below the
minimum glideslope intercept altitude specified on
the approach procedure chart.
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no, carlos, i meant the IAF...it's my understanding along with numerous controllers i work with that the IAF is placed at it's location on each approach by the TERPS folks basically saying that this fix is as far out as the GS can be 100% trusted.
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no, carlos, i meant the IAF...it's my understanding along with numerous controllers i work with that the IAF is placed at it's location on each approach by the TERPS folks basically saying that this fix is as far out as the GS can be 100% trusted.
Drat, the on-line version of TERPS is missing so many chapters I have to go to anecdotes instead of refrences.
To that point I present RAL ILS 9 (http://204.108.4.16/d-tpp/0803/00769I9.PDF) as a counter-example. SLI is an IAF and is 30 miles away, way off angle, roughly 35-40 degrees, and on the other side of a mountain (Pleasant's peak). I doubt you can get either the localizer OR the glideslope from over SLI. What SLI does have is a route segment that tells you how to get to the LOC. From SLI is not a feeder route, it is a full blown IAF and intermediate segment of the approach.
And I can't provide a reference to intercepting at GSIA since both TERPS and whole chunks of Part 97 are not on line. But to nitpick, 7110.65 5-9-1 is an instruction to controllers on where to put pilots on a VTF, not what the pilot is cleared to do.
The header to 5-9-1
Except as provided in para 7−4−2, Vectors for Visual
Approach, vector arriving aircraft to intercept the
final approach course:
And thanks, 5-9-1 (b) provided a reference to my statement that ATC isn't supposed to put you below GSIA either.
--Carlos V.
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Drat, the on-line version of TERPS is missing so many chapters I have to go to anecdotes instead of refrences.
To that point I present RAL ILS 9 (http://204.108.4.16/d-tpp/0803/00769I9.PDF) as a counter-example. SLI is an IAF and is 30 miles away, way off angle, roughly 35-40 degrees, and on the other side of a mountain (Pleasant's peak). I doubt you can get either the localizer OR the glideslope from over SLI. What SLI does have is a route segment that tells you how to get to the LOC. From SLI is not a feeder route, it is a full blown IAF and intermediate segment of the approach.
And I can't provide a reference to intercepting at GSIA since both TERPS and whole chunks of Part 97 are not on line. But to nitpick, 7110.65 5-9-1 is an instruction to controllers on where to put pilots on a VTF, not what the pilot is cleared to do.
The header to 5-9-1
Except as provided in para 7−4−2, Vectors for Visual
Approach, vector arriving aircraft to intercept the
final approach course:
And thanks, 5-9-1 (b) provided a reference to my statement that ATC isn't supposed to put you below GSIA either.
--Carlos V.
There is no requirement of any sort in the federal aviation regulations that a pilot must descend to a minimum altitude on an instrument approach unless a mandatory altitude is published. Of course, what I posted above also applies as well (a pilot may not descend below the minimum altitude for the prescribed route segment on the approach). Rod Mochado also gave the same answer (http://flighttraining.aopa.org/ft_magazine/fullstory.cfm?id=5417&issue_title=September%202005) to a pilot whose friend's instrument student failed an instrument checkride for not descending to the GSIA on an ILS approach.
Since you brought it up, JO 7110.65S §5-9-1 absolutely does concern what altitude ATC may assign an aircraft when vectoring ato intercept the final approach course. As I referenced in my last post, sub-para (b) of this section makes that distinction. ATC may not vector an aircraft to intercept the FAC below the GSIA, or above the glideslope/glidepath at the point of interception. If the altitude assigned meets this criteria, then the pilot may fly that altitude to capture the glideslope.
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Since you brought it up, JO 7110.65S §5-9-1 absolutely does concern what altitude ATC may assign an aircraft when vectoring ato intercept the final approach course
By the way, we've been violently agreeing on .65 and ATC's requirements. I was just nit-picking about using .65 to justify Pilot behavior. I'm just spending my time looking through Government sources on what the Pilot should do. This weekend I'm probably hitting the ACs.
In praticality, unless you're a good math whiz in the cockpit while flying, and know the surrounding terrain/airspace. It's best to follow the profile as charted. The aforementioned LAX ILS 25s have produced many violations for pilots following the GS too far out. Especially on hot days where true altitude is higher than indicated altitude. The GS doesn't move, but Ontario's traffic was closer to the GS as their true altitude was higher on a hot day and caused separation issues. (which was the LAX traffic's fault, not the Ontario traffic's fault)
I'm of the opinion that if I make a statement, I've got to back it up.... which is why I'm still looking. *grin*
--Carlos V.
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unbeliever,
The IAF doesn't need to be located on the LOC. we have one at BWI ILS 10...it's offset at least 20 degs. still, you will get the clearence to cross DATED at or above 2500', cleared ils 10 app. it's the pilot's perogative to track inbound to COLUM and join the LOC. I don't see how this relates to the original topic of FAFs...because regardless of where the IAF is or where you join an approach, the FAF on an ILS is the point at where the aircraft intercepts the glideslope. on the ILS10 at BWI if you were cleared over DATED, you would intercept the GS at COLUM at 2500'. if i vector you to final you will get a descent to 2000' and then the FAF would be between COLUM and JEANS.
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I'm of the opinion that if I make a statement, I've got to back it up.... which is why I'm still looking. *grin*
Carlos, any more information on this? I am curious what official source states that one must descend before intercepting the GSIA at the published point, too, since I don't recall ever running across this throughout training or in the real IFR world.
As stated, I do this now but I don't recall a published regulation/Instrument manual requirement to do so.
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Haven't found it amongst government publications, just amongst training manuals. Though I haven't spent as much time on it as I wanted.
I'm thinking of putting the question on AOPA's board. I'm sure Capt. Ron would have an opinion and a source. *grin*
--Carlos V.
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Still looking for something stronger. 91.175 (a) says you must use a SIAP, and the chart itself is a graphical description of the SIAP, which is part of Part 97, itself regulatory. The chart says "This is where you intercept the glideslope"
Other than common sense, I'm still looking for a stronger statement of "don't fly the GS until the charted point."
--Carlos V.
ETA: Hmmm. a blow to me. AC120-29A uses the phrase "published minimum GSIA" which suggests by inference contrary to my position. Still looking.
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Still looking for something stronger. 91.175 (a) says you must use a SIAP, and the chart itself is a graphical description of the SIAP, which is part of Part 97, itself regulatory. The chart says "This is where you intercept the glideslope"
Other than common sense, I'm still looking for a stronger statement of "don't fly the GS until the charted point."
--Carlos V.
ETA: Hmmm. a blow to me. AC120-29A uses the phrase "published minimum GSIA" which suggests by inference contrary to my position. Still looking.
The chart indicates the minimum altitude for glideslope intercept, not the only altitude. There is no regulation that prohibits use of the glideslope prior to the charted PFAF, since the usable distance of the signal from the antenna is often greater than the distance from the PFAF to the TDZ. I don't really follow your suggestion that your statement is common sense; thousands of commercial pilots seem to believe otherwise.
I'm all ears for what Ron says, I have a lot of respect for his well supported opinions and interpretations.