Can I shoot a VOR / DME-A approach without a VOR?

[dtuuri]

The note says you can't use GPS for "lateral guidance" on the final approach segment. It doesn't say anything about the "primary navaid."

Do you really think the bureaucrats who penned that were thinking about the MTN approach? It would be more likely, to me, they were concerned with remaining within the proven obstacle protection area of TERPS that are predicated on the performance of the primary NAVAID, GPS being unproven without criteria at the time.

Also, aren't you required to have lateral guidance on a CDI display in order to use a GPS to fly an approach? What if the GPS won't do that on this approach?

To "use" a GPS? As an "alternate" means of navigation you mean? While monitoring the underlying NAVAID? I think, since it must be a "suitable" GPS, the answer is yes. If the GPS is replacing the DME as an authorized "substitute" it's no different than any other DME arc, IMO. Of course, this is NOT a GPS approach.

BTW, I have recently added a couple of GPS tutorials to my website. Any feedback is appreciated.

Introduction to GPS (avclicks.com)

Gulfport_RNAV_(GPS)_RWY_14 (avclicks.com)​

 

[Palmpilot]

Do you really think the bureaucrats who penned that were thinking about the MTN approach? It would be more likely, to me, they were concerned with remaining within the proven obstacle protection area of TERPS that are predicated on the performance of the primary NAVAID, GPS being unproven without criteria at the time.

I don't, but if they had meant the substitution exclusion to apply only to the specific navaids listed, they wouldn't have used the words "for example."

To "use" a GPS? As an "alternate" means of navigation you mean? While monitoring the underlying NAVAID?

The note uses the word "substitute." If you have an operable DME on board, there's no need for substitution, so the note becomes irrelevant.

I think, since it must be a "suitable" GPS, the answer is yes. If the GPS is replacing the DME as an authorized "substitute" it's no different than any other DME arc, IMO. Of course, this is NOT a GPS approach.

It's no different from any other DME arc if you have an operating DME, but if you don't then you need to substitute GPS for it, and the note says you can't do that on the final approach segment.

 

[Palmpilot]

Is DME really a "NAVAID"? The P/CG says a NAVAID provides "point to point" navigation, doesn't it? Does a DME? I think a DME can only take you back where you began and won't even tell you when you arrive.

According to the FAA Web site, "NAVAIDs include Distance Measuring Equipment (DME), Non-Directional Beacons (NDB), Tactical Air Navigation (TACAN) systems, Very High Frequency (VHF) Omni-Directional Range (VOR) systems, VOR Test Facilities (VOT), and certain combinations of these systems."

https://www.faa.gov/air_traffic/flight_info/aeronav/aero_data/7900.2D-NAVAID/

Also, if you look at the table of contents of the AIM, DME is listed in Chapter 1, Section 1, which has the title "Navigation Aids."

Doesn't a VOR provide guidance on the MTN approach too? How will you know when to descend to the next lower MDA if the DME is welded on 14.7 all of time unless you're guided by the VOR? Looking at the plan view—the stepdown fixes are laterally separated just like the on a VOR approach. I think I'm a gonna go with Ryan.

The note says "lateral guidance," not just "guidance." The FAA uses the term "lateral guidance" to mean guidance that gives your lateral position, i.e., whether you are left of course, on course, or right of course. The VOR portion of the VORTAC on the MTN approach is used to tell you your along-track position. It cannot tell you whether you are on course or not.

 

[RussR]

According to the FAA Web site, "NAVAIDs include Distance Measuring Equipment (DME), Non-Directional Beacons (NDB), Tactical Air Navigation (TACAN) systems, Very High Frequency (VHF) Omni-Directional Range (VOR) systems, VOR Test Facilities (VOT), and certain combinations of these systems."

https://www.faa.gov/air_traffic/flight_info/aeronav/aero_data/7900.2D-NAVAID/

Also, if you look at the table of contents of the AIM, DME is listed in Chapter 1, Section 1, which has the title "Navigation Aids."

I agree. Especially with VOR/DMEs having the VOR portion being decommissioned and leaving the DME portion, such as below, to support DME/DME/IRU RNAV systems, what else would you call a DME but a NAVAID?




The PCG was quoted before. From a different part of it:



Pretty clear to me.

 

[dtuuri]

The PCG was quoted before. From a different part of it:

View attachment 92014

Pretty clear to me.

That can be read, "...from the DME's navaid." I wouldn't burn them in hell for not using an apostrophe 's'. I think the business about "lateral" is due to ground-based navaid's having angular obstacle protection vs. GPS having linear deviation. With the MTN approach, the arc is like other arcs and uses linear protection, so I think "lateral" notes and restrictions shouldn't apply—it's the same as GPS. But you're an expert at this, so I'll defer to you. I'm just stirring the pot.

 

[Ryan F.]

It's no different from any other DME arc if you have an operating DME, but if you don't then you need to substitute GPS for it, and the note says you can't do that on the final approach segment.

Problem is, you've got yourself a game of whack-a-mole.

• (c)4 says you may use a suitable RNAV system to "Fly an arc based upon DME." Great!
• But Note 4 says "Pilots may not substitute for the NAVAID (for example, a VOR or NDB) providing lateral guidance for the final approach segment." Well, shucks. That adds an element of confusion.
• Well, where does that lateral guidance come from?
• It comes from BAL, a VOR-DME.
• Palmpilot says "Well, you have to have DME, then!"
• Okay, let's assume for a moment that's true and whack that particular mole. So that would lead us to believe that the underlying "navaid" in this case in fact DME... not VOR. So you may fly the final segment of this VOR approach without monitoring the VOR, then. Surely that can't be right?
• Palmpilot says, "Well, I think maybe so! Look at Note 5! 'Use of a suitable RNAV system as a means to navigate on the final approach segment of an instrument approach procedure based on a VOR, TACAN or NDB signal, is allowable.' It doesn't say DME, guys!"
• But Note 6 says "For the purpose of paragraph c, “VOR” includes VOR, VOR/DME, and VORTAC facilities and “compass locator” includes locator outer marker and locator middle marker."
• "But this isn't really a VOR approach, it's basically a DME approach," says Palmpilot. (RussR nods quietly in the background)
• Well, that's just not true. It's a "VOR or TACAN" approach per the approach title. Note 4 states "This restriction does not refer to instrument approach procedures with “or GPS” in the title when using GPS or WAAS." So the approach title is significant as to equipment requirements, obviously.
• ...
• The underlying navaid is a VOR-DME...
• ...
• We can monitor that navaid...
• Palmpilot interjects "No way, lateral guidance is from DME. There's no way you can do it with just the VOR. You have to have DME!"
• And we get that DME from the underlying NAVAID... a VOR-DME. Note 6 specifically lists this navaid by name.
• ...
• ... which is why this is a "VOR or TACAN" approach and DME is required equipment. Going back to (c)4, we can use an IFR GPS to fly a DME arc. Going back to note 1, "The allowances described in this section apply even when a facility is identified as required on a procedure (for example, “Note ADF required”)."

You can go 'round and 'round like this for a while.

The interplay between Note 4, 5 and 6 is almost enough to come to a sensible conclusion, but TBL 1-1-6 is the last piece of the puzzle.

This approach (and its brother at WAL) is an outlier. Most likely 1-2-3 and 1-1-17 never considered their existence in the first place. But TBL 1-1-6 is what allows an aircraft owner to fly straight to the avionics shop and ask for his ADF and DME to be removed. In the United States, in terms of instrument approach procedures, there is nothing you can't do with a hard-installed DME which can't be replaced by an IFR GPS. That was always the intention... a universal replacement across the board. Could the AIM be modified to be more precise for just this unique instance of "lateral guidance on the final segment?" Possibly. But you're hung up on lateral guidance and its specific source. I say, it's a VOR approach and DME is required equipment. VOR is the underlying navaid, and Note 6 makes it clear that VOR-DME is synonymous.

You are good to go with an IFR GPS providing DME on this approach.

 

[Ryan F.]

BTW, I have recently added a couple of GPS tutorials to my website. Any feedback is appreciated.

Introduction to GPS (avclicks.com)

Gulfport_RNAV_(GPS)_RWY_14 (avclicks.com)​

Hey, that's pretty good. You kept me entertained for a while.

I like the method by which this works. It's engaging and simple, and keeps the user motoring along.

Nicely done!

 

[Palmpilot]

Problem is, you've got yourself a game of whack-a-mole.

• (c)4 says you may use a suitable RNAV system to "Fly an arc based upon DME." Great!
• But Note 4 says "Pilots may not substitute for the NAVAID (for example, a VOR or NDB) providing lateral guidance for the final approach segment." Well, shucks. That adds an element of confusion.
• Well, where does that lateral guidance come from?
• It comes from BAL, a VOR-DME.
• Palmpilot says "Well, you have to have DME, then!"
• Okay, let's assume for a moment that's true and whack that particular mole. So that would lead us to believe that the underlying "navaid" in this case in fact DME... not VOR. So you may fly the final segment of this VOR approach without monitoring the VOR, then. Surely that can't be right?
• Palmpilot says, "Well, I think maybe so! Look at Note 5! 'Use of a suitable RNAV system as a means to navigate on the final approach segment of an instrument approach procedure based on a VOR, TACAN or NDB signal, is allowable.' It doesn't say DME, guys!"
• But Note 6 says "For the purpose of paragraph c, “VOR” includes VOR, VOR/DME, and VORTAC facilities and “compass locator” includes locator outer marker and locator middle marker."
• "But this isn't really a VOR approach, it's basically a DME approach," says Palmpilot. (RussR nods quietly in the background)
• Well, that's just not true. It's a "VOR or TACAN" approach per the approach title. Note 4 states "This restriction does not refer to instrument approach procedures with “or GPS” in the title when using GPS or WAAS." So the approach title is significant as to equipment requirements, obviously.
• ...
• The underlying navaid is a VOR-DME...
• ...
• We can monitor that navaid...
• Palmpilot interjects "No way, lateral guidance is from DME. There's no way you can do it with just the VOR. You have to have DME!"
• And we get that DME from the underlying NAVAID... a VOR-DME. Note 6 specifically lists this navaid by name.
• ...
• ... which is why this is a "VOR or TACAN" approach and DME is required equipment. Going back to (c)4, we can use an IFR GPS to fly a DME arc. Going back to note 1, "The allowances described in this section apply even when a facility is identified as required on a procedure (for example, “Note ADF required”)."

You can go 'round and 'round like this for a while.

The interplay between Note 4, 5 and 6 is almost enough to come to a sensible conclusion, but TBL 1-1-6 is the last piece of the puzzle.

This approach (and its brother at WAL) is an outlier. Most likely 1-2-3 and 1-1-17 never considered their existence in the first place. But TBL 1-1-6 is what allows an aircraft owner to fly straight to the avionics shop and ask for his ADF and DME to be removed. In the United States, in terms of instrument approach procedures, there is nothing you can't do with a hard-installed DME which can't be replaced by an IFR GPS. That was always the intention... a universal replacement across the board. Could the AIM be modified to be more precise for just this unique instance of "lateral guidance on the final segment?" Possibly. But you're hung up on lateral guidance and its specific source. I say, it's a VOR approach and DME is required equipment. VOR is the underlying navaid, and Note 6 makes it clear that VOR-DME is synonymous.

You are good to go with an IFR GPS providing DME on this approach.

Actually, it's a VORTAC, not a VOR-DME.

Beyond that, you have attributed some statements to me that I did not make.

I've said what I have to say. Do what you want.

 

[Possum]

So just for clarification..... if I am on my IFR checkride and the DPE instructs me to fly a DME arc followed by a VOR-A approach, I do not need to "tune 10 and turn 10" but rather I can fly the magenta line on my Garmin.

 

[RussR]

So just for clarification..... if I am on my IFR checkride and the DPE instructs me to fly a DME arc followed by a VOR-A approach, I do not need to "tune 10 and turn 10" but rather I can fly the magenta line on my Garmin.

You may get some disagreement from examiners on this one, but there is nothing in the ACS about "how" you fly it, just "how well" you fly it - within +/- 1 nm, which I always thought was really, really generous in the planes we generally use for training.

 

[Ryan F.]

So just for clarification..... if I am on my IFR checkride and the DPE instructs me to fly a DME arc followed by a VOR-A approach, I do not need to "tune 10 and turn 10" but rather I can fly the magenta line on my Garmin.

If the procedure can be loaded from the GPS database, nothing prevents you from flying the entire approach (and monitoring the underlying navaid per AIM 1-2-3, as discussed here) on your "suitable RNAV system," i.e. a Garmin 430, GTN 650, Avidyne, etc. That's straightforward.

Our discussion on the equipment requirements for MTN VOR or TACAN RWY 15 approach, above, is beyond any reasonable expectation of applicant knowledge for any practical test. It's more of an interesting discussion between people who like getting into the weeds on very unusual IFR "oddballs."

Scenarios requiring the use of the VOR receiver for guidance are possible. I tend not to do this unless the applicant is heavily reliant on an aircraft with a lot of automation... or if I just want to switch it up, which I am wont to do at times. I'll require something flown "raw data" at some point during an instrument rating practical test, whether it's a hold, navigating on a victor airway, or... a VOR approach!

 

[denverpilot]

So just for clarification..... if I am on my IFR checkride and the DPE instructs me to fly a DME arc followed by a VOR-A approach, I do not need to "tune 10 and turn 10" but rather I can fly the magenta line on my Garmin.

Sounds like an excellent time for the simulated GPS failure. LOL.

 

[Ryan F.]

Hello everyone. Just a followup here. Regarding everyone's favorite VOR approach at MTN, I received confirmation from AFS-400 that "the reason for the title without the equipment requirement is due to a criteria change," which is exactly what RussR explained earlier in the thread.

Additionally and most importantly, AFS-400's view was stated as "DME on the procedure is providing distance not course guidance." This is in reference to the discussion we had above regarding Note 4, which states "Pilots may not substitute for the NAVAID (for example, a VOR or NDB) providing lateral guidance for the final approach segment." Given that the BAL VORTAC is responsible for course guidance, "actual" DME equipment is not required to fly this approach if a "suitable RNAV system" is installed in the aircraft. I.e., an IFR GPS may be used in lieu of DME on this approach, including the final approach segment.

Regards,

 

[somorris]

My thanks to all of you who have spent your time "arguing" the finer points in this thread. I have read through it all and found it thought provoking and a big help to keep my head in the game. Thanks!

 

[flyingron]

Additionally and most importantly, AFS-400's view was stated as "DME on the procedure is providing distance not course guidance." This is in reference to the discussion we had above regarding Note 4, which states "Pilots may not substitute for the NAVAID (for example, a VOR or NDB) providing lateral guidance for the final approach segment." Given that the BAL VORTAC is responsible for course guidance, "actual" DME equipment is not required to fly this approach if a "suitable RNAV system" is installed in the aircraft. I.e., an IFR GPS may be used in lieu of DME on this approach, including the final approach segment.

This is the dumbest interpretation I've seen come out of the FAA for a long time. What do they think he "TAC" part of the BAL VORTAC is? How does the VOR part provide any lateral guidance when you're always perpendicular to the radials? The rework of this approach plate is similarly ugly.