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ILS vs. ILS or LOC approaches....???

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ILS vs. ILS or LOC approaches....???

Old 02-01-2007, 12:11 PM
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Default ILS vs. ILS or LOC approaches....???

Ok, here's the million dollar question...

Why are some approaches named "ILS" and others names "ILS or LOC" ???

I have flown both approaches and flown the LOC only approach in the same way. In other words, if you can fly a LOC approach on a "ILS" approach, why name certain approaches "ILS or LOC"?
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Old 02-01-2007, 12:14 PM
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I think that if it says ILS or LOC, you may fly either approach; however, if it just says ILS, you may not fly a localizer approach unless the ILS is OTS. On an ILS approach, if the glideslope fails - you should probably go missed.

Thats just a quick answer w/out much thought. Good Q.
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Old 02-01-2007, 12:34 PM
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Originally Posted by mistarose View Post
I think that if it says ILS or LOC, you may fly either approach; however, if it just says ILS, you may not fly a localizer approach unless the ILS is OTS.

That's what I thought too. But I have flown into airports that have only an "ILS" named approache and requested and flown the LOC only procedure. ATC cleared me for the "LOC" approach.


Originally Posted by mistarose View Post
On an ILS approach, if the glideslope fails - you should probably go missed.
.
I disagree with that. If the GS fails, you may absolutely continue with a LOC approach provided you have a means to identify the MAP and that you are familiar with the LOC-only procedure (ie. you briefed it).
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Old 02-01-2007, 04:27 PM
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Originally Posted by mistarose View Post
I think that if it says ILS or LOC, you may fly either approach; however, if it just says ILS, you may not fly a localizer approach unless the ILS is OTS. On an ILS approach, if the glideslope fails - you should probably go missed.
That is entirely incorrect.

Although I do not know the answer to the original question. I'll research it. If I don't find an answer easily enough and no one else has the answer I'll email the AF Advanced Instrument School and get an answer.
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Old 02-01-2007, 04:34 PM
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No answer yet. Do you have an example?

OK. I think I figured it out. I found a bunch of examples on my own.

Little know fact...Controllers can only clear your for the approach that is in the title. So for an "ILS 17" the controller clears you to fly the "ILS 17" and he doesn't care whether or not you fly the localizer. However in the case of an "ILS or LOC 17" he can clear you the "localizer 17". Hence directing you to use localizer procedures. In all of the examples I found there were reasons why a controller might require you to fly the localizer. They are all places where you may be directed to sidestep or circle and since a precision approach is not compatible with a sidestep or circling maneuver you would have to fly the localizer.

Last edited by Texandrvr; 02-01-2007 at 05:14 PM. Reason: Found the answer
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Old 02-01-2007, 10:06 PM
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On an ILS approach, if the GS fails, you must execute the missed approach.

Why?

Think back to your approach clearance..."Cleared ILS Rwy 17". You weren't cleared for the LOC.

I don't know the contingencies available to ATC. If you report the failure, can they immediately clear you to continue via the "ILS Rwy 17 LOC only"? Or are they required to have you execute the missed? This I don't know. I tend to think that they will send you around if you're IMC.

In the case of an inoperative GS before you commence the approach - I have been cleared for an "ILS Rwy 17 LOC only" approach before, Part 121.

EDIT: Oh yeah, since this is in the pre-interview forum, I just thought I ought to mention that if you are in a sim ride at an airline interview, and this happens, and you continue using the LOC only, don't plan on working there.
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Old 02-02-2007, 01:20 AM
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Originally Posted by schoolio View Post
On an ILS approach, if the GS fails, you must execute the missed approach.

Why?

Think back to your approach clearance..."Cleared ILS Rwy 17". You weren't cleared for the LOC.

I don't know the contingencies available to ATC. If you report the failure, can they immediately clear you to continue via the "ILS Rwy 17 LOC only"? Or are they required to have you execute the missed? This I don't know. I tend to think that they will send you around if you're IMC.

In the case of an inoperative GS before you commence the approach - I have been cleared for an "ILS Rwy 17 LOC only" approach before, Part 121.

EDIT: Oh yeah, since this is in the pre-interview forum, I just thought I ought to mention that if you are in a sim ride at an airline interview, and this happens, and you continue using the LOC only, don't plan on working there.

That is utter nonsense.
From "The Pilot's Manual - Instrument Flying" 4th Ed, page 322: "If only the full ILS procedure is approved for a particular runway, and a localizer only approach without the use of a glideslope is not authorized, then the chart will carry the warning LOC ONLY N/A".


To be honest I am quite shocked to hear that you guys believe the loss of GS requires an immediate missed approach. I am not really sure who came up with this misconception.
Having said that, if you re-read my first post, I said that you should only continue with the LOC-only procedure IF you have adequately briefed the procedure and have taken the appropriate steps to ensure you are able to identify the LOC MAP (ie. starting time over OM). Personally I include a briefing for a LOC-only approach for every ILS I fly (that's how I was taught from day 1).

Now a few years ago we had an issue at the university where I was instructing, where several FAA DE at the local FSDO were "busting" applicants for their Instrument rating or CFII on the basis of their failure to start the time over the FAF while executing an ILS approach. Their resoning was that, if the applicant had lost the glideslope, he would not be able to revert to a localizer only approach because they would be unable to identify the missed approach point. It is therefore implied that reversion to a LOC after GS failure is perfectly acceptable. In fact, according to these FAA examiners, reversion to a LOC approach was so important to warrant the failure of the ILS approach if the applicant did not plan for this possibility. While I always taught the good operating practice of starting the time over the OM on ALL ILS approaches (except for those approaches where the localizer MAP can be identified by a means other than time), I did not agree with the FAA's decision to fail an applicant for failure to do so. In other words, if you are evaluating me on an ILS approach, and you simulate failure of the GS, and I forgot to start the time over the OM, I should be able to execute the missed approach without failing the maneuver. You always have the option of executing the missed approach if the GS fails (like with any other IAP), but you also have the perfectly legal option of continuing with a localizer approach.

Whether or not it is a good idea to continue the approach or go missed is purely subjective. In the past few years I have asked many very experienced pilots, both military and civilian, and received mixed answers. The main factors are height above ground where the failure occurs, familiarity with the approach, basic airmanship abilities, sinhle-pilot vs 2 crew, weather, ect

Generally speaking, most people would agree that if you failed to brief the LOC-only minimums during the approach briefing, then you should probably go missed since looking up that information when close to the ground, in IMC, is probably not a smart idea.
However I can list several airports where I am very familiar with the ILS/LOC procedures and I would not hesitate to switch from ILS to LOC-only if the GS were to fail.

Quick IFR 101 review.....back to basics. Look at what question I found in the FAA Airman Knowledge Test Question Bank for the Instrument Airplane rating:

480. J01 IRA
Immediately after passing the final approach fix in bound during an ILS approach in IFR conditions,
the glide slope warning flag appears. The pilot is
A) permitted to continue the approach and descend to the DH.
B) permitted to continue the approach and descend to the localizer MDA.
C) required to immediately begin the prescribed missed approach procedure.

Taken from http://www2.faa.gov/education_resear.../media/ira.pdf

I'll give you a hint..... the correct answer is NOT C.
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Old 02-02-2007, 01:22 AM
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I forgot to mention this: If a company's SOPs specifically say that you should execute an immediate missed approach if the GS fails, then you should abviously follow the SOPs and do it. But that has nothing to do with the fact that it is perfectly legal to continue with a LOC approach.
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Old 02-02-2007, 01:28 AM
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Hi Texandrvr,
thanx for you efforts in trying to shed more light on the topic. I am curious to know if you can find any more information from the AF Advanced Instrument School.

Originally Posted by Texandrvr View Post
since a precision approach is not compatible with a sidestep or circling maneuver you would have to fly the localizer.
Can you show me a reference for the above? I have flown many ILSs to both a sidestep and circle maneuver. Otherwise why would they put circle-to-land minimums on a "ILS RWY XX" approach?
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Old 02-02-2007, 03:17 AM
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Originally Posted by palgia841 View Post
Can you show me a reference for the above? I have flown many ILSs to both a sidestep and circle maneuver. Otherwise why would they put circle-to-land minimums on a "ILS RWY XX" approach?
After looking into this just a little I think that this is only what the af/navy teach and it was always taught just as I said it, "...not compatible..." Not that it is illegal. But the idea of a precision approach is that you make one continuous descent to landing. The idea of a non precesion is that you descend to an MDA and drive straight in or maneuver, as in a circle. So I guess you could fly an ILS to circling mins only, but you have to make sure you ident the FAF if it's timing only otherwise you have no way to identify the MAP.
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