Difference between VOR and VOR/DME approach

[John777]

I have been looking up for the difference between those two approaches, and while looing at approach charts, something grabbed my attention.

I will post the link for the two approach charts at different airports:-
http://155.178.201.160/d-tpp/1612/00110V16.PDF
http://155.178.201.160/d-tpp/1612/00483VD23.PDF

I understand, the only difference between the chart is the FAF being identified either by VOR or Fix from VOR.

Is there other difference I do not see here?

And also for VOR16 at KDAB,
http://155.178.201.160/d-tpp/1612/00110V16.PDF
It is using VOR only, even though it is a VORTAC and still able to receive the dme information, why FAA publishes VDP in terms of DME distance if it is VOR approach?
MAP can be well identified by timing from FAF though...

John.

 

[flyingron]

The DAB VOR RWY 16 uses the VOR itself as the IAF and the FAF, while it gives you DME fixes for the VDP and the MAP, DME isn't required. The MAP is otherwise determined by timing from the FAF.
In the DED VOR/DME 23, you the FAF is a DME fix. You need that. There is no other way to determine it. Since you need the DME for the FAF, they go ahead and give you that as the only way to find the MAP as well. No VDP on this approach.

The VDP is advisory. No matter how it's determined, it doesn't change the approach. Sometimes, they don't even give you a fix at the VDP. It's just put out there at a known distance from the runway for you to figure out.

 

[TRocket]

^^ What he said

 

[luvflyin]

Not much for notes on the DAB approach. Other than non standard alternate minimums and there are takeoff minimums and/or departure procedures there is only ASR. I haven't seen ASR in the notes box before. There are no Radar Approaches there that I can see. I thought it might mean there is a Diverse Vector Area but there doesn't seem to be one there. Anyone know what's up with the ASR in the notes box?

 

[flyingron]

It is supposed to mean that there are radar minimums published for this airport.
Oddly, at least in the SE-3 book I have, it does not.

 

[jaybee]

As Ron said the A in the triangle means there are radar approach minimums published - if you ask for a no-gyro this is what you use

640' and 1 Mile for KDAB 16 in my SE-3 page N1 ? ( I do have an outdated copy...)

 

[flyingron]

Ron didn't say anything of the sort.

Triangle-A says there are non-standard ALTERNATE minimums.

The "ASR" notation in the notes block should indicate published radar minimums. The current book, page N-1 shows only KNIP and KEYW. If an older book, shows 600-1 for KDAB, then it looks like either the new book inadvertantly omitted KDAB -OR- they failed to remove the ASR designation from the plate.

 

[jaybee]

Easy killer.

You are correct. The A is for Alternates and ASR is for radar mins. My mistake.

 

[flyingron]

Anyhow the book is in error. I fired a inquiry off the the FAA charting guys. We'll see what they say.

 

[RussR]

Sometimes, they don't even give you a fix at the VDP. It's just put out there at a known distance from the runway for you to figure out.

There is never a (named) [added on edit] fix at the VDP. All VDPs are unnamed.

Reference: FAAO 8260.19G, para 2-10-5a:
(1) Fixes not to be named.
(a) VDPs.

However, there is always a way to determine it, whether it is DME (for non-RNAV procedures) or ATD (Along-track-distance) from the MAP (for RNAV procedures). For a non-RNAV procedure, if there is no DME available, no VDP will be published.

Reference: FAAO 8260.3C, para 2-6-5:

c. Marking VDP location.
(1) For Non-RNAV procedures, mark the VDP location with a DME fix. The DME source must be the same as for other DME fixes in the final segment. If suitable DME is not available, do not publish a VDP. Maximum fix error is ± 0.5 NM.
(2) For RNAV procedures, mark the VDP location with an along track distance (ATD) fix to the MAP. Maximum fix error is  0.5 NM.

 

[luvflyin]

Anyhow the book is in error. I fired a inquiry off the the FAA charting guys. We'll see what they say.

Good. Let us know what they say. ASR and or PAR usually appears on the next row of boxes below, all the way to the right

 

[flyingron]

There is never a fix at the VDP. All VDPs are unnamed.

Your own post and the procedure in the original post proves you wrong. I never said the fix was named, but VDPs very much can be provided as DME fixes. They're just a certain DME from the navaid.

 

[John777]

Thanks everyone,
AIM states that we area not allowed to descend below MDA by VDP even though we have visual reference acquired.
AIM is non-regulatory in nature and have not seen any regulation for VDP under part 91 as well.

Does VDP really provide required obstacle clearance and if yes, why part 91 does not mandate not descending below MDA by VDP?
Also, I see VDA on some of the charts, most of time 3degree glide path or more, anyone know about how FAA establish VDA?

 

[jaybee]

Thanks everyone,
AIM states that we area not allowed to descend below MDA by VDP even though we have visual reference acquired.

huh ? it says you must have visual reference.

no worries its easy to make mistake, see my above post it serves as a good reminder though, its easy to overlook small details on instrument procedures


f. Visual Descent Points (VDPs) are being incorporated in nonprecision approach procedures.
The VDP is a defined point on the final approach course of a nonprecision straight−in approach procedure from which normal descent from the MDA to the runway touchdown point may be commenced, provided visual reference required by 14 CFR Section 91.175(c)(3) is established. The VDP will normally be identified by DME on VOR and LOC 4/3/14 AIM Arrival Procedures 5−4−19 procedures and by along−track distance to the next waypoint for RNAV procedures. The VDP is identified on the profile view of the approach chart by the symbol: V.
1. VDPs are intended to provide additional guidance where they are implemented. No special technique is required to fly a procedure with a VDP. The pilot should not descend below the MDA prior to reaching the VDP and acquiring the necessary visual reference.
2. Pilots not equipped to receive the VDP should fly the approach procedure as though no VDP had been provided.

 

[RussR]

Your own post and the procedure in the original post proves you wrong. I never said the fix was named, but VDPs very much can be provided as DME fixes. They're just a certain DME from the navaid.

I did (sadly and confusingly) mistype in my post, I have now edited it to say "there is never a named fix at the VDP", which is correct and in accordance with FAA criteria.

The procedures in the OP do not have named VDPs. "Named" means assigned a 5-letter identifier. "OMN 5.2 DME" is not a named fix.

You didn't say they were, but just to clarify.

You did, however, say that "Sometimes, they don't even give you a fix at the VDP. It's just put out there at a known distance from the runway for you to figure out."

This is incorrect. All VDPs are fixes. They are not named fixes, but they are fixes, either DME fixes or ATD fixes depending on non-RNAV or RNAV.

If you can find an example of a VDP that isn't identified by one of these two types of fixes I would be interested to see it.

 

[John777]

huh ? it says you must have visual reference.

no worries its easy to make mistake, see my above post it serves as a good reminder though, its easy to overlook small details on instrument procedures


f. Visual Descent Points (VDPs) are being incorporated in nonprecision approach procedures.
The VDP is a defined point on the final approach course of a nonprecision straight−in approach procedure from which normal descent from the MDA to the runway touchdown point may be commenced, provided visual reference required by 14 CFR Section 91.175(c)(3) is established. The VDP will normally be identified by DME on VOR and LOC 4/3/14 AIM Arrival Procedures 5−4−19 procedures and by along−track distance to the next waypoint for RNAV procedures. The VDP is identified on the profile view of the approach chart by the symbol: V.
1. VDPs are intended to provide additional guidance where they are implemented. No special technique is required to fly a procedure with a VDP. The pilot should not descend below the MDA prior to reaching the VDP and acquiring the necessary visual reference.
2. Pilots not equipped to receive the VDP should fly the approach procedure as though no VDP had been provided.

I have looked into AIM and saw above text as well.
So do you mean that we have to comply with VDP if we are so equipped and able to identify the fix?
Does VDP count for obstacle clearance according to FAA design criteria?

 

[John777]

The DAB VOR RWY 16 uses the VOR itself as the IAF and the FAF, while it gives you DME fixes for the VDP and the MAP, DME isn't required. The MAP is otherwise determined by timing from the FAF.
In the DED VOR/DME 23, you the FAF is a DME fix. You need that. There is no other way to determine it. Since you need the DME for the FAF, they go ahead and give you that as the only way to find the MAP as well. No VDP on this approach.

The VDP is advisory. No matter how it's determined, it doesn't change the approach. Sometimes, they don't even give you a fix at the VDP. It's just put out there at a known distance from the runway for you to figure out.

So, even though the timing from the FAF to MAP is given on VOR/DME approach, we cannot use the timing in order to identify MAP correct?

 

[tsts4]

So, even though the timing from the FAF to MAP is given on VOR/DME approach, we cannot use the timing in order to identify MAP correct?

No--you can use timing but Dustance is way easier. Dude seriously--enroll in an instrument ground school.

For part 91 VDPs are advisory only.

 

[John777]

No--you can use timing but Dustance is way easier. Dude seriously--enroll in an instrument ground school.

For part 91 VDPs are advisory only.

Seriously, I was enrolled in a ground school, and I was taught not to descend below MDA until VDP.
I do not know why they teach this way even thought we operate under part 91, my question is if VDP provides additional feature such as obstacle clearance.

 

[tsts4]

A VDP has nothing to do with obstacles-- it's only used in visual conditions. Technically you can descend below the MDA once you have the runway environment in sight regardless of where you are in relation to a VDP.

Another way to look at a VDP is it is the optimum point along the final approach segment from which to descend from the MDA if the required criteria for a descent are met.

 

[jaybee]

I have looked into AIM and saw above text as well.
So do you mean that we have to comply with VDP if we are so equipped and able to identify the fix?
Does VDP count for obstacle clearance according to FAA design criteria?

VDP is advisory only part 91

In order to comply with 91.175 (c)(1) while operating under 121 or 135 you wouldn't be able to make a "normal" landing in the touchdown zone if you didn't start your descent at the VDP

No, once you are visual you are responsible for maintaining obstacle clearance.

 

[jaybee]

Seriously, I was enrolled in a ground school, and I was taught not to descend below MDA until VDP.
I do not know why they teach this way even thought we operate under part 91, my question is if VDP provides additional feature such as obstacle clearance.

Technically, you can "dive and drive" however the FAA is trying to get away from that way of thinking and preaching stabilized approach which utilizing a VDP will give you. So, they are teaching that way as it a "safer" way of doing it and consistent with current FAA guidance

 

[denverpilot]

I just saw a plate the other day with an interesting note... where was it...

Ahh that's it. KSNY VOR/DME 13.

Hadn't seen something invalidate a VDP before in the notes. Maybe just never noticed it.

Makes sense though. You might not be at the AGL altitude you think you are, when using the Kimball altimeter setting.

I wonder if this VDP invalidation note is boilerplate on any VOR approach that allows the use of an altimeter setting from somewhere else.

 

[RussR]

A VDP has nothing to do with obstacles

Not quite correct. The presence of a VDP indicates that what's known as the 20:1 visual area is clear of obstacles. If it is not clear, then a VDP is not published. So, if you wait until the VDP to begin descent, you are supposedly assured of obstacle clearance.

Technically you can descend below the MDA once you have the runway environment in sight regardless of where you are in relation to a VDP.

While that is correct, there is an argument to be made for the opposite. 91.175 prevents you from descending below MDA unless descent "can be made at a normal rate of descent using normal maneuvers". While we generally think of this as preventing unusually steep or other crazy descents, it could be argued that it also applies to abnormally shallow descents. If the VDP is based on a 3 degree glidepath, and you start descending early, you are descending at less than a 3 degree glidepath. Since 3 degrees is considered de-facto "normal", then anything less could be considered abnormal.

Another way to look at a VDP is it is the optimum point along the final approach segment from which to descend from the MDA if the required criteria for a descent are met.

Exactly. That's all it is!

KSNY VOR/DME 13.

Hadn't seen something invalidate a VDP before in the notes. Maybe just never noticed it.

Makes sense though. You might not be at the AGL altitude you think you are, when using the Kimball altimeter setting.

I wonder if this VDP invalidation note is boilerplate on any VOR approach that allows the use of an altimeter setting from somewhere else.

Yes, this is boilerplate. VDPs are not published when a remote altimeter setting is used, and if one is used as a backup, then you get the "VDP NA when using xxx altimeter setting" note.

 

[RussR]

Since there are so many questions about VDP, I figured it would be helpful to post the complete "decision tree" in FAAO 8260.3C used by procedure developers. It's fairly straightforward as far as these things go.

Terms:
NPA = Non-Precision Approach
PA = Precision Approach
APV = Approach with Vertical Guidance

2-6-5. Visual Descent Point (VDP). The VDP defines a point on an NPA procedure from which normal descent from the MDA may be commenced provided the required visual references have been acquired.
a. Establish a VDP for all straight-in NPA procedures (to include those combined with a PA/APV procedure), with the following exceptions/limitations:
(1) Do not publish a VDP when the primary altimeter setting comes from a remote source.
(2) Do not publish a VDP located prior to a stepdown fix.
(3) If the VDP is between the MAP and the runway do not publish a VDP.
(4) Do not publish a VDP when the visual area 20:1 surface is penetrated [see section 3-3].
(5) The VDP should be ≥ 1NM from any other final segment fix (for example, MAP, stepdown). When not feasible, the VDP must be at least 0.5 NM from any other final segment fix. If < 0.5 NM and the other fix cannot be relocated, do not publish a VDP. Do not increase the MDA to achieve the ≥ 0.5 NM distance.

 

[flyingron]

I wouldn't say it is optimum. It's perhaps the earliest reasonable place to start the descent, but 3 degrees isn't optimal in a lot of airplanes for a non-precision approach.

 

[John777]

Not quite correct. The presence of a VDP indicates that what's known as the 20:1 visual area is clear of obstacles. If it is not clear, then a VDP is not published. So, if you wait until the VDP to begin descent, you are supposedly assured of obstacle clearance.



While that is correct, there is an argument to be made for the opposite. 91.175 prevents you from descending below MDA unless descent "can be made at a normal rate of descent using normal maneuvers". While we generally think of this as preventing unusually steep or other crazy descents, it could be argued that it also applies to abnormally shallow descents. If the VDP is based on a 3 degree glidepath, and you start descending early, you are descending at less than a 3 degree glidepath. Since 3 degrees is considered de-facto "normal", then anything less could be considered abnormal.



Exactly. That's all it is!



Yes, this is boilerplate. VDPs are not published when a remote altimeter setting is used, and if one is used as a backup, then you get the "VDP NA when using xxx altimeter setting" note.

Thanks, Can you also post the reference you had for 20:1 clear area on VDP?
I think you saw it from FAA Order on TERPS.

 

[RussR]

That's getting into the weeds, but since you like the weeds, here you go:

FAAO 8260.3C, para 3-3-2c(4)(b):
(b) 20:1 OIS. If penetrated, limit visibility to no lower than 5000 RVR or 1 SM, do not publish a VDP, and if the obstacle is unlighted, annotate the chart to deny the approach or the applicable minimums at night.

There is a lot of surrounding information that affects that paragraph, but that's the basic "if 20:1 is penetrated, no VDP" wording.

This is starting to get way beyond anything that is expected of a pilot to know.

 

[denverpilot]

l
This is starting to get way beyond anything that is expected of a pilot to know.

Nah, an aviator should know there's a spec and someone is following it. That's not a bad thing.

I appreciate when you guys and gals share that info. It's interesting and can't hurt to know it, at all.

Granted few will be able to keep it all in their heads -- but that's ok.

 

[flyingron]

OK, I got an email back from the FAA. The RADAR MINIMUMS for KDAB were deleted last March. They're going to remove the ASR mark on the chart.

 

[John777]

OK, I got an email back from the FAA. The RADAR MINIMUMS for KDAB were deleted last March. They're going to remove the ASR mark on the chart.

Do you talk to legal interpretation division for that?

 

[John777]

That's getting into the weeds, but since you like the weeds, here you go:

FAAO 8260.3C, para 3-3-2c(4)(b):
(b) 20:1 OIS. If penetrated, limit visibility to no lower than 5000 RVR or 1 SM, do not publish a VDP, and if the obstacle is unlighted, annotate the chart to deny the approach or the applicable minimums at night.

There is a lot of surrounding information that affects that paragraph, but that's the basic "if 20:1 is penetrated, no VDP" wording.

This is starting to get way beyond anything that is expected of a pilot to know.

So anyway, VDP provides sort of obstacle clearance.... If I am correct...

 

[flyingron]

Do you talk to legal interpretation division for that?

Eh? I talked to the charting folks. It isn't the first error I've found in a chart and they're usually pretty good about it.