Defining the MAP during a nonprecision approach

[jrh]

Here's a question for the instrument gurus here...

Suppose you have a non-precision IAP that does *not* use DME distance or a crossing radial to define the MAP. The only method published for defining the MAP is time. For example, an approach like this:

http://204.108.4.16/d-tpp/1104/05540VA.PDF

May a pilot use an IFR certified GPS to determine the MAP, rather than time?

Or must time be the determining factor, even if the GPS indicates otherwise?

Now, here's the challenge...whatever you say, back it up with solid, written references. "My instructor," "My examiner," "My local FSDO inspector," etc. don't count.

 

[SurferLucas]

According to AIM Section 1-1-19, Subsection C (Use of FPS for IFR Oceanic, Domestic Enroute, and Terminal Area Operations), number 3 says: (cliff notes)

The GPS Approach Overlay Program can only be used if the IAP has "or GPS" in the title. If it does not have "or GPS" in the title, the database may contain information about the nonoverlay approach procedure that is intended to be used for enhanced positional orientation, generally providing a map, while flying these approaches using conventional NAVAIDS. These approaches should not be confused with a GPS overlay approach.

So in this case, you would still fly the approach based off of VOR and time for the missed approach point. The GPS can only be used for positional awareness and not to determine the MAP.

 

[A150K]

I believe so. AIM 1-2-3 is pretty clear on what you can do with an IFR GPS, however it fails to mention MAPs--I'll try to find something more specific.

 

[SurferLucas]

If the MAP is defined by a DME and you're using the GPS to substitute for DME, you can use the GPS to define the MAP.

In order to fly the approach in GPS mode, it has to say "or GPS" in the title of the approach. (this for example:http://204.108.4.16/d-tpp/1104/05385VDG7.PDF)

If it does not say "or GPS" in the title (as your example states), you can only fly the approach in VOR (or NAV mode) and use the GPS for positional awareness. The MAP would be defined by the time after crossing the FAF.

 

[A150K]

If the MAP is defined by a DME and you're using the GPS to substitute for DME, you can use the GPS to define the MAP.

In order to fly the approach in GPS mode, it has to say "or GPS" in the title of the approach. (this for example:http://204.108.4.16/d-tpp/1104/05385VDG7.PDF)

If it does not say "or GPS" in the title (as your example states), you can only fly the approach in VOR (or NAV mode) and use the GPS for positional awareness. The MAP would be defined by the time after crossing the FAF.

I don't think we're talking about using the GPS for course guidance, you have to use the VOR as your primary nav source unless it can be flown as an overlay ,we're talking about defining the MAP. I'm not finding anything that says you can't, but I'm also not finding anything that says you can. Personally, I still time it even if it's loaded in the 430--might as well have all of the situational awareness you can.

 

[SurferLucas]

I don't think we're talking about using the GPS for course guidance, you have to use the VOR as your primary nav source unless it can be flown as an overlay ,we're talking about defining the MAP. I'm not finding anything that says you can't, but I'm also not finding anything that says you can. Personally, I still time it even if it's loaded in the 430--might as well have all of the situational awareness you can.

From what I'm understanding, even if it's in the GPS to allow for positional awareness, you can't use to define any part of the IAP (IAF/FAF/MAP). I know in the Garmin when you load the approach for a VOR (non-or GPS), it tells you that you can only use it for positional awareness and not for navigation.

I think if you were to be standing in front of the FAA during a hearing, they would use that to "hang you" so to speak.

Also, in 1-1-19, subpart J (waypoints), number 4, the MAWP may have a 5 letter ident, or RW##. If the MAWP is not located at the threshold, it will have a a 5 letter ident. Since this approach does not have an ident for the MAWP (not located on the threshold), one shouldn't show up in the database and you wouldn't have any clue how to ident the MAWP other than time.

 

[Ajax]

Logically you would think that you could identify it more accurately than with time alone. However, since it isn't a /DME approach or an "or GPS" approach then I don't think you can, but I'm going to keep reading to see if I can find something concrete.

 

[A150K]

From what I'm understanding, even if it's in the GPS to allow for positional awareness, you can't use to define any part of the IAP (IAF/FAF/MAP). I know in the Garmin when you load the approach for a VOR (non-or GPS), it tells you that you can only use it for positional awareness and not for navigation.

I think if you were to be standing in front of the FAA during a hearing, they would use that to "hang you" so to speak.

Also, in 1-1-19, subpart J (waypoints), number 4, the MAWP may have a 5 letter ident, or RW##. If the MAWP is not located at the threshold, it will have a a 5 letter ident. Since this approach does not have an ident for the MAWP (not located on the threshold), one shouldn't show up in the database and you wouldn't have any clue how to ident the MAWP other than time.

I see what you're talking about, however you can use GPS as your primary nav until established inbound and still outside of the FAF (a good rule of thumb is to switch nav modes when turning inbound. Whether that be from an arc or a PT). For instance on the ILS/LOC to my home field, The GNS430 will automatically switch me to VLOC once inside CIBVU : http://204.108.4.16/d-tpp/1104/00548IL2.PDF. Personally, I switch when turning inbound from the arc. If one couldn't use GPS nav inside of an IAF on a non GPS IAP, then how would they fly an arc without actual DME (1-2-3 says you can fly an arc with GPS)? I can also use the 430 in lieu of ADF to ID the LOM (DOMAN) and use it to fly the miss. I'm pretty sure by "navigation" Garmin means actual course guidance given by a LOC or VOR, not id'ing specific points on an approach.

 

[SurferLucas]

I see what you're talking about, however you can use GPS as your primary nav until established inbound and still outside of the FAF (a good rule of thumb is to switch nav modes when turning inbound. Whether that be from an arc or a PT). For instance on the ILS/LOC to my home field, The GNS430 will automatically switch me to VLOC once inside CIBVU : http://204.108.4.16/d-tpp/1104/00548IL2.PDF. Personally, I switch when turning inbound from the arc. If one couldn't use GPS nav inside of an IAF on a non GPS IAP, then how would they fly an arc without actual DME (1-2-3 says you can fly an arc with GPS)? I can also use the 430 in lieu of ADF to ID the LOM (DOMAN) and use it to fly the miss. I'm pretty sure by "navigation" Garmin means actual course guidance given by a LOC or VOR, not id'ing specific points on an approach.

You're right there, I was typing faster than the brain was processing what was being typed.

I think in this example though, without having a 5 letter ident for a MAWP, then you'd be forced to use time to identify the MAWP.

 

[MidlifeFlyer]

This question comes into my personal category of "don't ask, don't tell, don't care."

In doing the CBF VOR-A, will I rely on the situational awareness provided by
(a) my calculation of guestimated winds (estimated winds aloft, maybe actual winds below), calculated GS based on those guestimated winds and my timer; or
(b) even a non-ifr-certified handheld that can show me when I'm at the runway threshhold or 5.3 NM from the VOR.

To me the answer is obvious. Just as obvious as if you asked whether I can use 5.3 DME to identify the MAP even though it's an aproach that doesn't require DME.

In fact, if you're interesting in researching the question in a formal way, I think that's the inquiry - I'll take the WAG that timing is not mandatory. The box in this approach shows both a DME distance and a time as a way to identify the MAP. The fact that it's not a DME approach just means that you are not required to have DME in order to fly it., not that you can't use DME. You use the equipment you have that will identify it in the most reliable way. If you have DME, that will be with DME, not with guesses about timing. If you have an IFR GPS box, you use the GPS as a substitute for DME. If you have a non-IFR GPS, well, I'd say that the official answer is that you time the approach and use your GPS for "situational awareness." (And if there are rocks past the MAP, if the 396 says I'm there but my closk says I have 2 minutes to go, I know which one I'd believe).

 

[Ayork62493]

Oh the VOR-A into CBF...
Anyways, if I had a GPS available I would tiem the approach as well as use the GPS to aid in the correction of my timing. (Changes in Ground speed mainly)
Luckily for me, the planes I do my instrument work in lack a GPS so I go by timing and estimate everything.

 

[A150K]

Oh the VOR-A into CBF...
Anyways, if I had a GPS available I would tiem the approach as well as use the GPS to aid in the correction of my timing. (Changes in Ground speed mainly)
Luckily for me, the planes I do my instrument work in lack a GPS so I go by timing and estimate everything.

Do they have DME? If I was flying a VOR approach in an airplane without GPS, but with DME then I would use the DME to determine the VDP and time to determine the MAP. It eliminates alot of guessing when you know you have to have the runway by the VDP and will start the climbing portion of the miss there and the turning at the MAP if going missed becomes necessary.

 

[Jflyer]

This might be a silly question, but is there a difference in legality of using DME if the number isn't published as DME (in the box-like thing on the NOS charts)? I'm assuming maybe that's only on approaches that are actually .../DME.

Personally, I'm using the GPS (or DME) to help with situational awareness if I have that option. You're wasting resources if you don't. (I remember having a "discussion" during an instructor meeting at a former flight school about the same thing.) But if I'm in front of the FAA, and they're asking me how I "officially" figured out the MAP, based on the approach plate, I'm going with "time."

 

[jrh]

This question comes into my personal category of "don't ask, don't tell, don't care."

In doing the CBF VOR-A, will I rely on the situational awareness provided by
(a) my calculation of guestimated winds (estimated winds aloft, maybe actual winds below), calculated GS based on those guestimated winds and my timer; or
(b) even a non-ifr-certified handheld that can show me when I'm at the runway threshhold or 5.3 NM from the VOR.

To me the answer is obvious. Just as obvious as if you asked whether I can use 5.3 DME to identify the MAP even though it's an aproach that doesn't require DME.

In fact, if you're interesting in researching the question in a formal way, I think that's the inquiry - I'll take the WAG that timing is not mandatory. The box in this approach shows both a DME distance and a time as a way to identify the MAP. The fact that it's not a DME approach just means that you are not required to have DME in order to fly it., not that you can't use DME. You use the equipment you have that will identify it in the most reliable way. If you have DME, that will be with DME, not with guesses about timing. If you have an IFR GPS box, you use the GPS as a substitute for DME. If you have a non-IFR GPS, well, I'd say that the official answer is that you time the approach and use your GPS for "situational awareness." (And if there are rocks past the MAP, if the 396 says I'm there but my closk says I have 2 minutes to go, I know which one I'd believe).

As usual, your post is spot on. This sums up my beliefs on the whole issue.

I got in to a debate about this topic with another instructor recently. He was insisting that a person MUST time the approach and use it to determine the MAP.

My question to him was, "So you're going to disregard the GPS and go missed based on time, when an IFR certified GPS is in the panel next to the clock?"

"No, I'd probably use the GPS to decide to go missed," was his answer.

"Ok, me too. Then why are you doing something (starting a timer) with the full knowledge that you're going to immediately disregard it?" The whole thought process is messed up, IMO. I teach to go missed based off the GPS. Start a timer, if you can remember it, and use it as a backup to make sure your GPS is giving you reasonable information.

The other instructor was getting caught up in what the FAA's stance would be, or what the examiner's stance would be during a checkride. I say to forget the FAA and checkrides and fly the safest way possible. I'm trying to keep people from hitting the side of a hill.

I started this thread to see how far into left field my thinking is.

 

[SurferLucas]

If I were conducting an Instrument Progress or Stage Check for your student, and they didn't start their time after the had station passage on this approach, it would be a failure. (and I have 3 years experience giving Stage Checks/Progress Checks for instrument ratings)

The reason being, you cannot define the MAWP unless you have time. The GPS does not matter because even though it says "5.3 NM", that is not a GPS fix (5 Letter or RW##) and because it's not DME Fix either, you can not use the GPS for NAVAID substitution. You're only allowed to use the GPS for DME substitution for a define DME Fix on an approach, which this approach does not have. Since the Approach Title does not have "or GPS", you can only use the GPS for situational awareness.

According to the Instrument Flying Handbook: (Chapter 8)

"The MAP varies depending upon the approach flown. For the ILS, the MAP is at the decision altitude/decision height (DA/DH). For nonprecision procedures, the pilot determine the MAP by timing from FAF when the approach aid is away from the airport, by a fix or NAVAID when the navigation facility is located on the field, or by waypoints as defined by GPS or VOR/DME RNAV. The pilot may execute the MAP early, but pilots should, unless otherwise cleared by ATC, fly the IAP as specified on the approach plate to the MAP at or above the MDA or DA/DH before executing a turning maneuver."

I also refer you to Figure 8-16 in the Instrument Flying Handbook, the top example is for a Localizer Approach but is the same as this VOR approach in terms of identifying the MAP.

Since the approach does not have any waypoints defined by GPS or VOR/DME RNAV, the only way to determine the MAP is time, period.

 

[MidlifeFlyer]

Since the approach does not have any waypoints defined by GPS or VOR/DME RNAV, the only way to determine the MAP is time, period.

In the real world, you're welcome to fly the approach in the soup by guesses. I'll go with equipment that measures or identifies it with some degree of certainty.

But I'd also fail the student that didn't start the timer. It's a good backup

It's sort of like flying an NDB approach with a GPS. In either case you say you flew the "official" way and use the more reliable way for situational awareness.
Of course, they can always tell with an NDB approach, especially where the NDB is off airport - if you ended up in from t of the runway, you obviously used the GPS.

But seriously, I still don't know the answer to one question. Maybe you do: That little box has both a distance and times. Do you have a reference that makes measuring the time mandatory and measuring the distance forbidden?

 

[SteveC]

(directed to Lucas)

Why can't you use the 5.3 DME that is listed right there in the timing chart? "5.3 mm FAF to MAP"

edit to add: We are all still talking about the VOR-A at KCBF, aren't we?

 

[SurferLucas]

In the real world, you're welcome to fly the approach in the soup by guesses. I'll go with equipment that measures or identifies it with some degree of certainty.

But I'd also fail the student that didn't start the timer. It's a good backup

It's sort of like flying an NDB approach with a GPS. In either case you say you flew the "official" way and use the more reliable way for situational awareness.
Of course, they can always tell with an NDB approach, especially where the NDB is off airport - if you ended up in from t of the runway, you obviously used the GPS.

But seriously, I still don't know the answer to one question. Maybe you do: That little box has both a distance and times. Do you have a reference that makes measuring the time mandatory and measuring the distance forbidden?

Unfortunately, when you're doing your instrument rating or any training at all, you're not necessarily training for the "real world". In the pass/fail world for checkrides, you can't say "that's the way it works in the real world", especially when you're in front of a DPE/FAA inspector. When it comes to students, you have to give them the set guidelines that they must operate in, if they go outside of it, they fail. We all know in the real world people aren't +100/-0 ft on MDA's, but if my student goes below MDA during training or on a prog check, it's a bust. Simple as that. After they pass the checkride and learn "how things happen in the real world", it will be up to them to answer for any mistakes they make.

As to your other question though, the Instrument Flying Handbook and Instrument Procedures Handbook say:

"Beneath the airport sketch is a time and speed table when applicable. The table provides the distance and the amount of time required to transit the distance from the FAF to the
MAP for selected groundspeed".

The sentence about MAP for Nonprecision: " For nonprecision procedures, the pilot determine the MAP by timing from FAF when the approach aid is away from the airport, by a fix or NAVAID when the navigation facility is located on the field, or by waypoints as defined by GPS or VOR/DME RNAV." You would have to use time because it does not fit the others.

 

[SurferLucas]

(directed to Lucas)

Why can't you use the 5.3 DME that is listed right there in the timing chart? "5.3 mm FAF to MAP"

edit to add: We are all still talking about the VOR-A at KCBF, aren't we?

Yes we are.

This sentence from the Instrument Flying Handbook: "For nonprecision procedures, the pilot determine the MAP by timing from FAF when the approach aid is away from the airport, by a fix or NAVAID when the navigation facility is located on the field, or by waypoints as defined by GPS or VOR/DME RNAV."

Since it doesn't have a VOR/DME Fix depicted by a "D" with 5.3 and the station ident for that DME reading, you cannot use DME to determine a fix that doesn't exist. That 5.3 isn't DME (slant range), it's a true distance from the FAF to the MAP. It only shows distance in the box so you can determine the time to fly for a given groundspeed.

 

[jrh]

Unfortunately, when you're doing your instrument rating or any training at all, you're not necessarily training for the "real world". In the pass/fail world for checkrides, you can't say "that's the way it works in the real world", especially when you're in front of a DPE/FAA inspector. When it comes to students, you have to give them the set guidelines that they must operate in, if they go outside of it, they fail.

You precisely expressed the problem I see with many training institutions today. They get so caught up with technical definitions that they miss what really matters. That might work fine for pilot mills churning out future airline pilots, but it's a lousy approach to training individuals flying for business or pleasure.

I tell people to fly like they train and train like they fly. I *never* want to hear, "This is how you have to do it for your checkride..." coming from an instructor. If a person gets busted for something on a checkride, there are only two possibilities. 1) What they were doing was unsafe and they shouldn't have been doing it that way in either real world ops or a checkride, or 2) the examiner busted them on a stupid technicality and they shouldn't have busted. It's gotta be one or the other.

So with that in mind, maybe you could tell me...if there is a discrepancy between time and GPS, which one do YOU (as in, you personally) follow? I'll gladly tell anyone who asks, I use GPS. If you follow the GPS, why did you bother to start a timer that you're going to completely disregard? If you follow the timer, why are you disregarding a piece of equipment (GPS) that is so clearly more precise? I'm not asking these questions rhetorically, I honestly want to hear your reasoning if you disagree with the way I do it.

Time or GPS, one or the other, a pilot MUST pick a "primary" reference. There has to be a moment during which the throttles get pushed forward and nose pitched up. My decision to take those actions is based on the GPS.

Also, while I respect your experience as a check pilot, I'm equally experienced as an instrument instructor. I've sent numerous clients to checkrides with multiple examiners and never been questioned on this technique. The reason I bring it up here is because another instructor told one of my clients it's a big deal to always start the timer during an approach. I disagree and wanted to see how other instructors teach this area.