IFR chart question

durind

durind

Well-Known Member
Wow, I wonder why I am still amazed, when I find out about how little I really know about aviation. I was recently taking an AOPA online course testing my chart knowledge for fun to stretch my brain and so forth. I came upon an approach to KBFL Bakersfield for the ILS or LOC DME Rwy 30R. When the question came up, your DME fails on the approach, what should you do? With my knowledge I responded: of course you execute a missed approach because it had been explained to me that it is an ILS w/ DME or LOC w/DME requirement, essentially you need DME for either the ILS or LOC part of the approach. Well AOPA told me I'm wrong and now I'm inclined to believe it. Anyone else care to chime in? I regularly instruct this approach:

http://155.178.201.160/d-tpp/1301/00142ILDZ16R.PDF

And have been teaching my students that to execute this approach they would need DME for either the LOC or the ILS. Would appreciate to inform my students I have been teaching them wrong since day 1 have to be honest. :(
 
One additional thing: when I asked why it had become an ILS/LOC DME approach, I was told that it used to be a normal ILS / LOC approach but they didn't want to maintain the marker beacons so they replaced them with DME fixes instead which is why DME is required for either approach. Maybe I need to question more in the future when I am told things.
 
What is the explanation that AOPA gave?

I believe that PAR can be substituted for DME and/or an inoperative marker beacon... but I'd have to go find a reference to back that up.

Did AOPA's answer reference PAR?

* Note: If precision radar assistance is not provided, I disagree with the AOPA... until I hear their explanation otherwise.

* Update: found the reference I was thinking of in 91.175(k)

(k) ILS components. The basic ground components of an ILS are the localizer, glide slope, outer marker, middle marker, and, when installed for use with Category II or Category III instrument approach procedures, an inner marker. A compass locator or precision radar may be substituted for the outer or middle marker. DME, VOR, or nondirectional beacon fixes authorized in the standard instrument approach procedure or surveillance radar may be substituted for the outer marker. Applicability of, and substitution for, the inner marker for Category II or III approaches is determined by the appropriate part 97 approach procedure, letter of authorization, or operations specification pertinent to the operations.​
 
If your shooting the ILS you don't need DME for anything. FAF is identified by GS intercept and MAP is the DA. Missed approach is an intersection hold. Still no DME required for an ILS.

The DME is required for the LOC though to identify the FAF and the MAP using DME from PAE.

The name of the approach omits the DME off the ILS part for this reason.





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jeflies said:
If your shooting the ILS you don't need DME for anything...The name of the approach omits the DME off the ILS part for this reason.
Click to expand...

I disagree.

From the Instrument Procedures Handbook:

APPROACH CHART NOTES
The navigation equipment that is required to join and fly
an instrument approach procedure is indicated by the title
of the procedure and notes on the chart. Straight-in IAPs
are identified by the navigation system by providing the
final approach guidance and the runway with which the
approach is aligned

In this case it's "ILS" or "LOC/DME".

OK, so we say we are flying the ILS....so what is an "ILS"?

Back to FAR 91.175(k).

(k) ILS components. The basic ground components of an ILS are the localizer, glide slope, outer marker, middle marker...​
​
Those all must be represented.

So, how can we identify the markers?
​
A compass locator or precision radar may be substituted for the outer or middle marker. DME, VOR, or nondirectional beacon fixes authorized in the standard instrument approach procedure or surveillance radar may be substituted for the outer marker.​

​
So, regardless you must be able to identify the marker locations or you do not have the ability to fly the ILS... he already explained the marker beacon transmitters are inop, so the only remaining options are DME or PAR for the OM and MM, and also optionally an intersection and/or LOM for the OM.

The only way to identify the MM on this chart is with DME or radar assistance, otherwise you are not equipped to fly the ILS
​
​
​
 
If that we're the case the approach would have ILS/DME written in the name. The key word in the name is "OR". This specifically distinguishes this as two different approaches sharing one piece of paper.

There are ILS approaches out there with no marker beacons. Beacons are nice to have but not required universally on all ILS's

I could be wrong and I've been diggin through the AIM trying to find proof otherwise. Regardless, this is a good review.


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jeflies said:
If that we're the case the approach would have ILS/DME written in the name. The key word in the name is "OR". This specifically distinguishes this as two different approaches sharing one piece of paper.
Click to expand...

Re-read my answer. Nobody is arguing about the name of the approach. I'm saying that the name "ILS", by definition, requires the identification of the outer and middle markers. If there are not functioning radio beacons, then you can use DME. If there is not DME then you can use precision approach radar advisories from ATC. If you cannot do any of that... then it's not an ILS. An ILS is not just a localizer and glideslope pair.
 
The only seed of doubt I have in my mind stems from the notes. Simultaneous reception of the LOC and that VOR's DME are required.

Does that apply for both? If so then I'm wrong. The wheels are turning...


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jeflies said:
The only seed of doubt I have in my mind stems from the notes. Simultaneous reception of the LOC and that VOR's DME are required.

Does that apply for both? If so then I'm wrong. The wheels are turning...
Click to expand...

That's simply because there is no DME paired on the localizer, so you have to use the VOR's DME.
 
rframe said:
What is the explanation that AOPA gave?

I believe that PAR can be substituted for DME and/or an inoperative marker beacon... but I'd have to go find a reference to back that up.

Did AOPA's answer reference PAR?

* Note: If precision radar assistance is not provided, I disagree with the AOPA... until I hear their explanation otherwise.

* Update: found the reference I was thinking of in 91.175(k)

(k) ILS components. The basic ground components of an ILS are the localizer, glide slope, outer marker, middle marker, and, when installed for use with Category II or Category III instrument approach procedures, an inner marker. A compass locator or precision radar may be substituted for the outer or middle marker. DME, VOR, or nondirectional beacon fixes authorized in the standard instrument approach procedure or surveillance radar may be substituted for the outer marker. Applicability of, and substitution for, the inner marker for Category II or III approaches is determined by the appropriate part 97 approach procedure, letter of authorization, or operations specification pertinent to the operations.​
Click to expand...

First off thank you all for the responses, I like that there are people on both sides of this. I think from a practicality standpoint I wonder why can't I fly this approach without DME, do I really need to know that I am over JUGBA, can't I just use glideslope intercept? AOPA's explanation is pretty much the same reasoning that jeflies uses, that it is an ILS or LOC/DME chart, and therefore the approach is to be thought of as either an ILS or a LOC/DME and not an ILS/DME & LOC/DME.
 
durind said:
First off thank you all for the responses, I like that there are people on both sides of this. I think from a practicality standpoint I wonder why can't I fly this approach without DME, do I really need to know that I am over JUGBA, can't I just use glideslope intercept? AOPA's explanation is pretty much the same reasoning that jeflies uses, that it is an ILS or LOC/DME chart, and therefore the approach is to be thought of as either an ILS or a LOC/DME and not an ILS/DME & LOC/DME.
Click to expand...

Yeah that's what I've got my head wrapped around. The notes do say you must receive simultaneously the LOC and the VORs DME. I'm wrong on my initial answer and would not shoot this without DME.

Reason you want to know your at the FAF (with the DME) glide slope intercept is so you can double check the GS intercept altitude. False glides slopes and altimeter errors can be found here instead of at the DA when you go smush.




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durind said:
AOPA's explanation is pretty much the same reasoning that jeflies uses, that it is an ILS or LOC/DME chart, and therefore the approach is to be thought of as either an ILS or a LOC/DME and not an ILS/DME & LOC/DME.
Click to expand...

They would be absolutely correct... IF the marker beacon transmitters worked.
 
jeflies said:
Yeah that's what I've got my head wrapped around. The notes do say you must receive simultaneously the LOC and the VORs DME. I'm wrong on my initial answer and would not shoot this without DME.

Reason you want to know your at the FAF (with the DME) glide slope intercept is so you can double check the GS intercept altitude. False glides slopes and altimeter errors can be found here instead of at the DA when you go smush.




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Click to expand...

Yeah this is the explanation I give my students when I tell them why DME is required. I feel like there should be some sort of notation of the chart though that DME is required, not just simultaneous reception of I-PAE & PAE VOR DME is required. That isn't really clear enough. I guess you have to infer that since JUGBA is only defined by a DME fix you must need DME to identify it. Thanks for the replies, I am sort of relieved I haven't been teaching this wrong for the past few months.
 
rframe said:
They would be absolutely correct... IF the marker beacon transmitters worked.
Click to expand...

Yeah AOPA is referencing a different chart so, I think the idea would be that the marker beacons work on the approach for which the question is based around- the approach to bakersfield or something, but different when I tried to draw a parallel to the local approach in my area at KPAE, the only confusion lies in that there really isn't any clear notation on either chart that there are marker beacons, whether they work, or that DME is required at all with reference to the ILS approach.
 
durind said:
Yeah AOPA is referencing a different chart so, I think the idea would be that the marker beacons work on the approach for which the question is based around- the approach to bakersfield or something, but different when I tried to draw a parallel to the local approach in my area at KPAE, the only confusion lies in that there really isn't any clear notation on either chart that there are marker beacons, whether they work, or that DME is required at all with reference to the ILS approach.
Click to expand...
You would have to check the NOTAMS about the market being out.... although I'm still not 100% convinced in either direction yet. Going to do some reading myself now.
 
durind said:
There are no notams, the marker beacons have not been in operation for a long time. At least for the local approach: http://155.178.201.160/d-tpp/1301/00142ILDZ16R.PDF
Click to expand...
I see that(I just did check the notams for PAE).
According to that approach plate, I should be able to fly up there in a /U airplane and be just fine shooting the ILS. If that's not the case, there's a problem. I also wish I had a jepp plate in front of me instead. I swear whenever there's confusion on an approach a 1/2 second look at a jepp fixes any confusion.
 
When an approach plate states ILS or LOC/DME, DME is required for both the ILS and the LOC approach.

About 10 years ago the FAA changed chart titles for such approaches from ILS/DME or LOC/DME to ILS or LOC/DME.

Also, if you look at the chart DME is the only means to identify the FAF.

Finally, I was asked this question at a US Air interview and the answer was indeed DME required for both.
 
JetDrvr said:
When an approach plate states ILS or LOC/DME, DME is required for both the ILS and the LOC approach.

About 10 years ago the FAA changed chart titles for such approaches from ILS/DME or LOC/DME to ILS or LOC/DME.

Also, if you look at the chart DME is the only means to identify the FAF.

Finally, I was asked this question at a US Air interview and the answer was indeed DME required for both.
Click to expand...

For an ILS shouldn't glideslope intercept be enough to count as the final approach fix? It just happens to be the same as the localizer FAF in this case.
 
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