How does a DME work when used with an ILS/Loc Approach?

[ajstoner21]

(I am an instrument student. Am not instrument rated yet)

This is probably a very typical approach, however, I have not seen an ILS with a DME before. The airport I typically fly from does not use DME and the airplane I fly most does not have DME.

Its a little confusing to me. I am used to seeing Outer Marker beacons and Middle Marker beacons, however, on the "ILS or LOC/DME RW 34" into Arlington Municipal (GKY) threw me a curve ball haha.

Can someone explain this approach to me? How do you identify the missed approach point for the Loc/DME?

DME is only required for the localizer approach correct? If that is true, how do you tell the tower where you are if you do not have DME? For example, I'm used to telling the tower that I'm over the outer marker.

I know that when DME is listed in the title, its required for the approach, but is it required for the ILS when its in the "or LOC" part?

 

[taters]

The DME works automatically when you enter in the ILS freq.
You identify the missed approach point by looking where the bold line turns into a dashed line in profile or plan view on the approach plate. For example, ILS 31 in DSM
the missed approach point is at MM or 0.6 dme from the end of the runway.
Some Loc approached have a OM, Locater Marker, Vor radial fix etc.... my understanding that DME not required unless its says so with some exceptions.

 

[BillTIZ]

Many DME recievers can be slaved to NAV 1 or NAV 2 or operate independently.

Las Vegas ILS Rwy 25L, The DME portion of the approach is from the VORTAC, so you need to tune your ILS Receiver (normally NAV 1) to the ILS Freq and tune your DME receiver or NAV 2) to the VORTAC for the DME portion and slave the DME to NAV 2.

Las Vegas ILS Rwy 1L, the DME is on the ILS freq, so tune NAV1 to the ILS and slave the DME to NAV 1. Put LAS VORTAC in NAV 2 for back up.

As to the other part of your question... it's the "OR", you can fly the ILS, or you can fly the LOC/DME.. you cannot fly the LOC without the DME because you have no timing to determine the MAP. And because the DME points are defined as "I-GKY", the DME is on the LOC frequency.

There is no OM or MM, they are DME fixes, you'll also note you cannot fly the approach without ATC Radar (Radar Required), there are no IFR transitions to the final approach course. ATC will vector you to final. You would report postion to tower based on DME or call the FAF (Final Appch Fix) from the DME or Glide Slope Intercept. 2000MSL on glideslope.

The missed approach for the ILS is called at DH (Decision Height, 820MSL), the missed approach for the LOC/DME is based on 1.1DME (I-GKY).

The missed approach hold is based on the Maverick (TTT) VOR, so you would want at least your NAV2 tuned to TTT or the freq loaded in back up on NAV 1 or NAV2 for a quick one switch retune on the missed and turn up the volume to check the ID, without DME you would also need to tune MQP on the other NAV for the crossing radial to identify the holding intersection TILLA.

 

[gismo]

The DME works automatically when you enter in the ILS freq.

Not necessarily. Many DMEs have a way to enter the frequency directly, and some can do that as well as let you choose to load the frequency from either of two Nav receivers. Also on some LOC approaches the DME must be tuned to a different frequency such as a nearby VOR.

You identify the missed approach point by looking where the bold line turns into a dashed line in profile or plan view on the approach plate. For example, ILS 31 in DSM
the missed approach point is at MM or 0.6 dme from the end of the runway.

Not quite. That's the point where the GS intercepts the ILS DA. The LOC MAP on the DSM-ILS31 is the runway end or 4.9 nm from the FAF and is identified by timing (or with an IFR GPS).

Some Loc approached have a OM, Locater Marker, Vor radial fix etc.... my understanding that DME not required unless its says so with some exceptions.

DME is required if it's in the title or there's a "DME required" note on the plan view. Sometimes DME is required for the LOC and not the ILS, which is the case for the GKY-ILS or LOC/DME RW 34. If you're flying the ILS, the FAF is the point where you intercept the GS and start down and the "MAP" (there's no actual MAP on an ILS) is where you hit the DA (decision altitude) while on the GS. DME is required to fly the LOC approach so you can identify the FAF (where you drop from 2000 to the MDA) and the MAP.

And FWIW, the Terps manual (specs for designing approaches) says DME is never required for an ILS but I've seen exceptions to that.

 

[BillTIZ]

The DME works automatically when you enter in the ILS freq.
You identify the missed approach point by looking where the bold line turns into a dashed line in profile or plan view on the approach plate. For example, ILS 31 in DSM
the missed approach point is at MM or 0.6 dme from the end of the runway.
Some Loc approached have a OM, Locater Marker, Vor radial fix etc.... my understanding that DME not required unless its says so with some exceptions.

Read the OP.. he may not have DME on the airplane he flies so it would not tune automatically. The approach he referred to does not have OM or MM, just DME points. The DME is required on the approach he referred to, it is ILS "or" LOC/DME.. so if he has no glide slope, he must execute the LOC and then he needs DME.

In most airplanes (other than those GARMIN models).. the DME is a seperate receiver and must be either slaved to NAV1 or NAV2 or tuned independently.

 

[ajstoner21]

Makes sense.

What would an initial call to the tower sound like when handed off from Center (on a practice approach?)?

"Arlington Tower, Cessna 1234 on LOC/DME Rwy 34 approach at Esike"
or
"Arlington Tower, Cessna 1234 on LOC/DME Rwy 34 approach at 11.4 DME"
or
"Arlington Tower, Cessna 1234 on ILS Rwy 34 approach at Esike"
...?

 

[SCCutler]

Makes sense.

What would an initial call to the tower sound like when handed off from Center?

"Arlington Tower, Cessna 1234 on LOC/DME Rwy 34 approach at Esike"
or
"Arlington Tower, Cessna 1234 on LOC/DME Rwy 34 approach at 11.4 DME"
or
"Arlington Tower, Cessna 1234 on ILS Rwy 34 approach at Esike"
...?

well.

It'll be Regional Approach, not Center- Center will have handed you off to Approach way out.

The call-up to tower would be "Arlington Tower, Cessna 1234, Localizer three four."

You don't need to tell them a fix unless they ask you.

 

[taters]

(there's no actual MAP on an ILS)

Your Right,
But you still supposed to fly to this "place" laterally speaking before going missed. and there is no DH on a loc.

 

[Doggtyred]

(I am an instrument student. Am not instrument rated yet)

This is probably a very typical approach, however, I have not seen an ILS with a DME before. The airport I typically fly from does not use DME and the airplane I fly most does not have DME.

As others have said, if your stack is wired together properly, the DME is slaved to the VOR/LOC receiver. When the VOR/LOC is tuned, the DME auto-tunes to the discrete paired DME frequency for the VOR/LOC freq. You can also manually tune in the VOR/LOC freq used into the DME device in some cases (which really tunes the discrete paired frequency for that VOR/LOC freq... something that is transparent to the end user/pilot)

Its a little confusing to me. I am used to seeing Outer Marker beacons and Middle Marker beacons, however, on the "ILS or LOC/DME RW 34" into Arlington Municipal (GKY) threw me a curve ball haha.

In this case you only need DME if you are doing a localizer approach..

Can someone explain this approach to me? How do you identify the missed approach point for the Loc/DME?

DME 1.1 (edited to correct from VDP of DME 2.4)

DME is only required for the localizer approach correct? If that is true, how do you tell the tower where you are if you do not have DME? For example, I'm used to telling the tower that I'm over the outer marker.

Radar is required.. so ATC has to have radar to allow the approach {presumably to vector you to the FAF} (not necessarily radar in the tower cab though).. but instead of outer marker you can say "final approach fix inbound". Flying a real approach in real conditions, Regional Approach will hand you off to tower once you are established on the approach path.


If you dont have a DME, and dont have an APPROVED gps that can substitute for a DME, then you cannot legally fly the localizer only approach, and either must fly the ILS with glideslope, or use another approach there or elsewhere.

I know that when DME is listed in the title, its required for the approach, but is it required for the ILS when its in the "or LOC" part?

If the approach chart title said ILS/DME then it would be required for ILS. The DME is only required for LOC approach, and in this case, so you can identify your stepdown fix from 2000 ft to 1040 or 1080 feet (straight or circling, respectively) and your MAP. On the ILS you will use the altimeter and glideslope to determine those points (2000 ft MSL glideslope intercept, 820 ft MSL MAP)

Make sense now?

 

[ajstoner21]

Can someone explain this approach to me? How do you identify the missed approach point for the Loc/DME?

DME 2.4

Why is DME 2.4 the MAP for the LOC/DME? What would indicate that?

 

[taters]

I posted the wrong plate earlier ILS 31

 

[taters]

Why is DME 2.4 the MAP for the LOC/DME? What would indicate that?

2.4 I-GKY is the VDP (Visual Decent Point)

1.1 dme I-GKY is the MAP for the loc (end of the runway)

In theory if there was a nearby VOR radial or something else to define the MAP then you wouldn't need dme.
This is why DME at a minimum is required for the loc. The dme transmitter itself is located at the opposite end of the runway in this case. (thats why its says 1.1 not 0) The only other possible way is via a helpful ATC calling the fix and a clock (timed approach) that could get you close.

 

[John Collins]

Being a pedant, slaved is not the proper term to use to describe the channeling of the DME. The DME frequencies are paired with VOR/Localizer frequencies, so you select the VOR/Localizer frequency associated with the VOR/Localizer, and this channels the correct DME paired frequency. The charts don't show the actual DME frequency, but only show the paired VOR/Localizer frequency.
DME's come in a variety of configurations, starting from a simple unit without any interface to Nav1/Nav2 where you dial in the paired frequency. An enhancement to this design allows the DME to be channeled by a Nav receiver or integrated into a Nav receiver (KNS80). A hold function on a DME allows the DME to remain channeled to the current Nav pair while freeing the Nav receiver to be re-tuned to another frequency. In some systems, the DME has a remote display and a selector switch enabling Nav1 or Nav2 to be selected, or including a middle position that holds the last channeled paired frequency.

 

[John Collins]

Makes sense.

What would an initial call to the tower sound like when handed off from Center (on a practice approach?)?

"Arlington Tower, Cessna 1234 on LOC/DME Rwy 34 approach at Esike"
or
"Arlington Tower, Cessna 1234 on LOC/DME Rwy 34 approach at 11.4 DME"
or
"Arlington Tower, Cessna 1234 on ILS Rwy 34 approach at Esike"
...?

I would suggest:

"Arlington Tower, Cessna 1234, ILS 34"

You are not required to report your position leaving the FAF when in radar contact, since radar is required for the approach, it is not necessary.

AIM Reference:


5−3−3. Additional Reports

a. The following reports should be made to ATC or FSS facilities without a specific ATC request:​

1.

​

​

At all times.

<snip>

2. When not in radar contact.​

(a)​

​

​

​

​

​

When leaving final approach fix inbound on final approach (nonprecision approach) or when leaving the outer marker or fix used in lieu of the outer marker inbound on final approach (precision approach).​

 

[gismo]

Your Right,
But you still supposed to fly to this "place" laterally speaking before going missed.

How would you know where "this place" is on an ILS if you didn't have DME. I think that you are allowed/required to begin the missed approach procedure from the point where you hit the DA while following the GS and I expect that the procedure takes into account that you might reach that point a little early or late depending on how well you're holding the GS and the accuracy of your altimeter.

This does raise the point that if you don't follow the GS (you're really only required to stay on or above it) for some reason, you wouldn't know when/where to start the miss unless you have an alternate means of identifying that point (e.g. crossing radial, MM, DME, or GPS).

 

[taters]

How would you know where "this place" is on an ILS if you didn't have DME. I think that you are allowed/required to begin the missed approach procedure from the point where you hit the DA while following the GS and I expect that the procedure takes into account that you might reach that point a little early or late depending on how well you're holding the GS and the accuracy of your altimeter.

This does raise the point that if you don't follow the GS (you're really only required to stay on or above it) for some reason, you wouldn't know when/where to start the miss unless you have an alternate means of identifying that point (e.g. crossing radial, MM, DME, or GPS).

By using your I-phone..:wink2:

It is a great question,..and there are times you want to fly the GS high..... so far I can only come up with having ATC call the fix and using a timer against the charted distance (note the times are not published on arlington plate).

 

[Palmpilot]

How would you know where "this place" is on an ILS if you didn't have DME. I think that you are allowed/required to begin the missed approach procedure from the point where you hit the DA while following the GS and I expect that the procedure takes into account that you might reach that point a little early or late depending on how well you're holding the GS and the accuracy of your altimeter.

This does raise the point that if you don't follow the GS (you're really only required to stay on or above it) for some reason, you wouldn't know when/where to start the miss unless you have an alternate means of identifying that point (e.g. crossing radial, MM, DME, or GPS).

I think that the approach procedure designers take into account the fact that there is a tolerance on how well pilots track the glideslope, and that this causes variation in where pilots begin the missed approach. So they presumably take that into account when they do the obstacle assessment. I have heard, for example, that the missed approach course is assessed to a certain width on either side of the desired course (although I don't remember what that width is), so if there are any turns involved, that would allow for some variation in where the missed approach is begun. I do know that the instrument PTS specifies that an applicant for an instrument rating must maintain no more that 3/4-scale deflection on the glideslope. If the needle were pegged, then your position relative to the MAP would be unknown unless you had some other way of determining it.

 

[gismo]

I think that the approach procedure designers take into account the fact that there is a tolerance on how well pilots track the glideslope, and that this causes variation in where pilots begin the missed approach. So they presumably take that into account when they do the obstacle assessment. I have heard, for example, that the missed approach course is assessed to a certain width on either side of the desired course (although I don't remember what that width is), so if there are any turns involved, that would allow for some variation in where the missed approach is begun. I do know that the instrument PTS specifies that an applicant for an instrument rating must maintain no more that 3/4-scale deflection on the glideslope. If the needle were pegged, then your position relative to the MAP would be unknown unless you had some other way of determining it.

You're right about the PTS but AFaIK it's perfectly legal to fly the GS to some altitude above the DA and level out as if that altitude were a MDA (except for certain approaches with a note precluding this). But if the miss involves a turn after reaching some altitude this could result in a plane making that turn earlier than the approach designer intended.

 

[ajstoner21]

what does AFaIK stand for?

Edit: Nevermind....