Intercept Loc Outbound

[aterpster]

BOAC:

The concept of a 'back course' without a 'front course' is one I will pass on.
A bit like having a backing group with no 'star' up front or a back-up power supply with no primary

Your points would be well taken if the installation were for an approach procedure. But, this is a special case to provide correct sensing for missed approach and departure procedures. When this was installed, RNAV was a limited concept (pre-GPS) so there was no other way to get the course guidance needed to avoid the higher terrain to the southwest of the airport.

[PBL]

Cute SID. Glad I don't have to fly around there.

I am with BOAC on this one: the "back course" is misnamed.

A *course* is directional, both in common speech and in (European) aviation. Both a front course and a back course are flown *towards* the antenna, in the normal meaning of the terms. The non-directional concept can be denoted by the term "course line".

According to those meanings, the SARDD ONE SID requires that one fly the *reciprocal of a back course*.

But maybe for the FAA a "course" sometimes a course line, without direction. Who are we to argue (although we may smirk)? That means the two available courses (in the above meaning) would be called "back course outbound" and "back course inbound". Indeed, here is the quote from the AIM (at http://www.faa.gov/air_traffic/publi...1/aim0101.html):

Originally Posted by AIM 1-1-9 (b)

2. The approach course of the localizer is called the front course and is used with other functional parts, e.g., glide slope, marker beacons, etc. The localizer signal is transmitted at the far end of the runway. It is adjusted for a course width of (full scale fly-left to a full scale fly-right) of 700 feet at the runway threshold.

3. The course line along the extended centerline of a runway, in the opposite direction to the front course is called the back course.

So a "front course" is a course, but a "back course" is a course line, not a course. So be it.

This kind of mild confusion doesn't often matter for regular local airspace users, but such things do get one into grave difficulties sometimes. I just wrote a paper on critical verbal communication in major accidents (rail and air) for the Handbook of Technical Communication (ed. Gibbon and Mehler, Mouton-de Gruyter, Berlin, forthcoming 2011). The air accidents I consider are Cali and Überlingen.

PBL

[SNS3Guppy]

I am with BOAC on this one: the "back course" is misnamed.

Explain that to those who correctly named the facility per convention and in accordance with TERPS.

Both a front course and a back course are flown *towards* the antenna, in the normal meaning of the terms. The non-directional concept can be denoted by the term "course line".

According to those meanings, the SARDD ONE SID requires that one fly the *reciprocal of a back course*.

No, the SARDD ONE requires that one fly outbound on the backcourse.

I realize that you have a real thing for arguing, but you understand that you're arguing the official title of the components of the procedure, so designated per convention, appropriately according to the facility, by the people who designed the procedure. I really do believe that you'd argue that black is white just to make an argument.

Both a front course and a back course are flown *towards* the antenna, in the normal meaning of the terms. The non-directional concept can be denoted by the term "course line".

This kind of mild confusion doesn't often matter for regular local airspace users, but such things do get one into grave difficulties sometimes.

Not in this case. The facility is correctly named and identified. The procedure for it's use is clear and well known, and in full conformance with the prescribed terminal procedures criteria. There is nothing ambiguous about the procedure or it's naming convention, nor is there anything difficult, grave, or otherwise, regarding the procedure's use, the design or function of the facility, or it's name.

You're attempting to argue and be difficult where there is no argument, nor grave difficulty.

[aterpster]

The old time fixed card indicator. This is all still valid:

[PBL]

Originally Posted by PBL

This kind of mild confusion doesn't often matter for regular local airspace users, but such things do get one into grave difficulties sometimes.

Originally Posted by Guppy

Not in this case. The facility is correctly named and identified. The procedure for it's use is clear and well known, and in full conformance with the prescribed terminal procedures criteria.

As I said, fine for regular local airspace users.

Check out the Cali situation, in which the ROZO ONE arrival was named after the endpoint, fully in accordance with local procedures and regulations. But it demonstrably confused the US pilots, who were apparently assuming that ROZO was the commencement of the arrival. And they didn't arrive. AG RVS - Comments on Confusing Conversation at Cali.

Or check out the GOL-Legacy collision, where ATC (and, apparently, almost the entire Brazilian public) was expecting Legacy to change Flight Level without a communication, because it had that change of FL on its flight plan. That's apparently what you do according to local procedure and regulation.

Originally Posted by Guppy

You're attempting to argue and be difficult where there is no argument, nor grave difficulty.

Well, I accept that you don't see one. But that's the thing with these matters. No one saw a problem at Cali, either. Neither did anyone see a problem with having another NDB with the same ID and FREQ 200nm east. I mean, why would you ever tune it in from so high up? But they did.

And no one in Brazil was apparently expecting Legacy to adhere to ICAO norms rather than local ones when radio contact was lost.

And we won't mention the problems US pilots have flying runway heading in the UK when instructed to do so by ATC. Or will we?

Language is a big deal.

PBL

[BOAC]

Well, hoping not to get dragged into yet another session of slanging, here!

Why on earth was the procedure not constructed on a 'front course' of 120? The g/a then back-tracks this localiser a 'course' set of 120, as in many other procedures. I am assuming, of course, that there is no requirement for a 'front course' of 300 in any procedures there, in which case I think this has all been made with unnecessarily complicated?

Apart from keeping everything 'standard', there is a distinct advantage in this solution, namely the course needs only to be twiddled from 148 to 120 for the g/a, instead of all the way round to 300. One less thing to do when surrounded by cumulo-granitus.

Originally Posted by aterp

so there was no other way to get the course guidance needed to avoid the higher terrain to the southwest of the airport.

- have I not just done exactly that? I am unconvinced that just because it 'fits' with some notion of naming in TERPS that it is correct!

[SR71]

I realize that you have a real thing for arguing, but you understand that you're arguing the official title of the components of the procedure, so designated per convention, appropriately according to the facility, by the people who designed the procedure. I really do believe that you'd argue that black is white just to make an argument.

One wonders how it was possible the Titanic ever sank?



I think there is no provision for back-course approaches in the UK, and I have no experience whatsoever in these types of approaches even flying around Europe in the capacity I do, but the give away for me is the "NB" on the chart.

Surely an explicit acknowledgement by Jepperson that the chance of ambiguity exists?

Even then I still find the note ambiguous. Is it normal sensing when you've dialled up "300" or normal sensing when you've dialled up "120"?

Is that claim to "normality" contingent on the fact you've called it a "back-course"?

What does "normal" mean if this is a "non-normal" approach for you? I haven't flown a back-course approach in at least the last 4000...

And if the sensing depends on what instrumet you're using, the note isn't very helpful anyway....

The semantics is hugely important.

[aterpster]

PBL:

Well, I accept that you don't see one. But that's the thing with these matters. No one saw a problem at Cali, either. Neither did anyone see a problem with having another NDB with the same ID and FREQ 200nm east. I mean, why would you ever tune it in from so high up? But they did.

Those guys were both "radar babies" and "children of the magenta line."

First, they tried to get a short-cut in to a procedure in a mountainous area in a non-radar environment, and in South America no less. That flunks IFR Flying 101 right there.

Second, when the aircraft started its big wild-a** turn to try to go to the wrong beacon, a passing grade in IFR Flying 101 would required disconnecting LNAV and using the heading mode to get back on track now. Instead, they became passengers, continuing a wild spoiler-aided descent while letting mis-programmed LNAV take them to neverland.

It was a ground-based combined arrival/IAP procedure they were attempting to fly with RNAV. For those with clues in 1995, there would have been more than a modicum of wariness.

[aterpster]

BOAC:

- have I not just done exactly that? I am unconvinced that just because it 'fits' with some notion of naming in TERPS that it is correct!

No, you have not. You are presuming an HSI where the card is rotated (thus changing the orientation of the CDI) by changing the value in the course window; i.e., set the inbound front course to have to-the-needle sensing on a back course.

Fix cards cannot be rotated. That is the purpose of my illustration above. This installation at ASE was done many years ago, to accommodate the lowest common denominator. There was, and is, no "notion of naming in TERPs" that drove this installation.

[BOAC]

Fix cards cannot be rotated. That is the purpose of my illustration above..

- I think your picture is not one of those! It looks like a museum piece Narco OBS to me.

Quite honestly fiddling around to allow for fixed card aircraft is a waste of time! Anyone using it should be able to work out their displacement from a line or should not fly IFR. Otherwise how on earth would they cope with tracking a localiser outbound or track away from an NDB?

[aterpster]

BOAC:

- I think your picture is not one of those! It looks like a museum piece Narco OBS to me.

I wouldn't argue about its status as a museum piece. Nonetheless, it still meets specs and could be used today. My point in posting it was to show the blue-yellow markings below the course deviation indicator. The "twistable" analog course values at the bottom of the indicator is the selection made by the OBS knob. The OBS selection only affects VOR, not LOC. This indeed is a VOR/LOC navigation indicator with CDI, compliant scaling, OBS selector, and OBS indicator. In more modern displays, such as an HSI, the course selector serves both to position the card and when selected to a VOR facility, it also serves as an OBS.

The use of the blue-yellow indicator was quite common when I first got involved with instrument flying in 1957.

Quite honestly fiddling around to allow for fixed card aircraft is a waste of time! Anyone using it should be able to work out their displacement from a line or should not fly IFR. Otherwise how on earth would they cope with tracking a localiser outbound or track away from an NDB?

Perhaps it was all a waste of time. Unlike you I am open on that. I do know they could not achieve the clearance from very high terrain to the southwest for the missed approach procedures unless they used a localizer.

[Zeffy]

My point in posting it was to show the blue-yellow markings below the course deviation indicator.

Thread hijack alert.

Blue/Yellow LOC references were included in early jet transport avionics systems.

The FD mode selection and feedback loop were central to the investigation of a DC-9 accident at Boston July 1973.

In the report, one can find references to a "Blue Left" Sperry Flight Director mode:



As aterpster has noted, the CDI is turned upside-down by an HSI to provide proper orientation for the crew.

The BC (nee "Blue Left") FD mode is necessary to obtain correct steering from the FD.

[SNS3Guppy]

And we won't mention the problems US pilots have flying runway heading in the UK when instructed to do so by ATC. Or will we?

We won't, because I've never found that to be the case. That is, where such isolated cases may exist, these are pilots failing to follow an established ATC direction, not a language ambiguity. It also has no bearing on the Aspen localizer back course, which is correctly labeled, with clear directions on use and application.

The Cali case wasn't an issue of a mislabled procedure, it was a case of a crew failing to obtain clarification, failing to identify, loss of situational awareness, failure to stow speed brakes, failure to verify terrain, failure to identify, and yes, miscommunication (including limited controller vocabulary). You already know this. That has no relationship to the correctly labled back course at Aspen.

One wonders how it was possible the Titanic ever sank?

An iceberg, bad metalurgy, and a failed design that allowed a single stress riser to separate the hull, but that's not important right now. Neither is the loss of the Titanic relevant to a correctly named navaid and course, procedure, and chart, flying into Aspen, Colorado.

Why on earth was the procedure not constructed on a 'front course' of 120? The g/a then back-tracks this localiser a 'course' set of 120, as in many other procedures. I am assuming, of course, that there is no requirement for a 'front course' of 300 in any procedures there, in which case I think this has all been made with unnecessarily complicated?

Because the KASE procedure, as published, eliminates reverse sensing while flying outbound.

I think there is no provision for back-course approaches in the UK, and I have no experience whatsoever in these types of approaches even flying around Europe in the capacity I do, but the give away for me is the "NB" on the chart.

Surely an explicit acknowledgement by Jepperson that the chance of ambiguity exists?

"NB?" Whether one has experience flying a back course or not, it's one basic type of instrument procedure, and if one has an instrument rating or ATP, one should understand it. The instructions on the chart are quite clear. The procedure has been designed to eliminate ambiguity errors by eliminating reverse sensing issues which might lead to disorientation. In the event one is operating with an HSI, which is nearly universally the case today, the matter is largely a non-event.

Is that claim to "normality" contingent on the fact you've called it a "back-course"?

What does "normal sensing" mean in the context of flying a localizer or back course approach? You don't understand this, or you're trying to cloud the issue? We're not talking normal psychology, here. We're not talking normal child development. We're not talking normal schools. We're talking in context about a back course facility (which the I-PKN facility is) with normal sensing.

If you're familiar at all with the concept of a back course procedure (you've stated you've got at least 4,000 hours of flight experience, and apparently you're instrument-rated, so this shouldn't come as any great shock), you'll understand the difference between normal sensing and reverse sensing. If one is instructed that one can anticipate normal sensing when flying outbound on the back course, one knows that given there are only two options (normal sensing vs. reverse sensing), the matter is made clear. One doesn't need to attempt to apply the word "normal" out of context or consider it's higher philosophical implications. Normal sensing when flying a localizer and back course means that when the little needle goes left, you follow it and go left too. (Reverse sensing, of course, means that when the needle goes left, you go right, hence the term "reverse sensing"). This procedure utilizes the back course to provide normal sensing to the pilot, and explicitly states this on the procedure chart, as well as giving only ONE course value (300 degrees) to avoid confusion. Put in 300 degrees, and all is well, one has normal sensing, and one is free to move on to live a life of religious fulfillment.

It's called a "back course" because it is indeed (get ready for it, drum-roll, please) a back course facility, and one is flying outbound on a back course (which, as every instrument student knows, provides normal sensing, as opposed to flying inbound on a back course, which provides reverse sensing).

What does "normal" mean if this is a "non-normal" approach for you?

Again, if you'll leave the procedural note in context, as it's written in plain-english, you'll understand. The procedural note says nothing about a normal approach, or abnormal approach. It specifically states "The I-PKN back course outbound is normal sensing." Again, to belabor the point, normal sensing, vs. reverse sensing. One must consider the context, and read. One can't simply see the word "normal," and apply it to any other use of the word "normal" in the English language (it isn't a normal surgery procedure, normal child, normal pet, or normal pizza, but normal sensing, exactly as it's written).

Even then I still find the note ambiguous. Is it normal sensing when you've dialled up "300" or normal sensing when you've dialled up "120"?

Where do you find "120" in the procedure? You don't. It's 300 degrees, which works whether one has a simple fixed-card CDI, or whether one is using an EHSI display. You don't need to figure out sensing, ambiguity (another one of those terms that you're throwing around out of context, here: ambiguity is a proper term when dealing with the procedure and indications thereof). You have normal sensing available, and clearly are flying outbound on a localizer back course.

The semantics is hugely important.

The semantics are important, which is why the procedure is correctly labled, accurate, and spelled out, and which is why the user is specifically given only one course value to insert, along with a clear notation that normal sensing will be available as one is flying the back course outbound. Go figure.

[Denti]

"NB?" Whether one has experience flying a back course or not, it's one basic type of instrument procedure, and if one has an instrument rating or ATP, one should understand it.

Nope, if you narrow that down to a US ATP you are right, outside of the US a backcourse is very rarely used if at all. In fact, my company tells us quite clearly that using back course procedures is prohibited as we do not train it. I learned how to fly as i did my training in the US, but haven't flown any kind of backcourse procedure since, and of course it was not a topic during my ATPL tests.

[aterpster]

Denti:

Nope, if you narrow that down to a US ATP you are right, outside of the US a backcourse is very rarely used if at all.

Thus, the reason the missed approach LDA at ASE was configured as a back course, so when using it as intended (and it would be difficult to use it not as intended) you get normal sensing.

[SR71]

Guppy,

You can holler all you like about the merits of the procedure and how it is TERPS this and TERPS that, but I, as a pilot prohibited by my airline from shooting back-course procedures like Denti (Why is that?), living in a country where there is no provision for them (Why is that?), and having not done one in at least the last 4000 approaches (not flight hours - go figure the difference) found it, initially, could be interpreted, by myself, as ambiguous.

That being the case, I surmised, perhaps erroneously, that I might not be the only one who felt that way. Of course, the fact that previous contributors alerted me to that fact clouds the issue of causality.

So I went away and looked at some notes. Now I feel better and philosophically disabused.

However, I would suggest that the ambiguity of the plate is contingent on far more than your ability to mount a vociferous defence in its favour.

To this end try and understand my analogy(s) a little less literally.

[SNS3Guppy]

You can holler all you like about the merits of the procedure and how it is TERPS this and TERPS that, but I, as a pilot prohibited by my airline from shooting back-course procedures like Denti (Why is that?), living in a country where there is no provision for them (Why is that?), and having not done one in at least the last 4000 approaches (not flight hours - go figure the difference) found it, initially, could be interpreted, by myself, as ambiguous.

I can't really figure the difference, whereas you've given no indication of your typical leg length or frequency of approaches/landings. Given that you appear to be indicating that your experience is confined to Europe, the legs must be very short, so perhaps there's some rough correlation between the number of approaches and the number of hours. I don't really care, nor is it germane to the conversation; I point this out because you brought it up.

You've been insistent on proper terminology. You don't like the name of the approach, you don't like the naming convention, either. Never the less, whereas ambiguity is an important, precise term with regard to flying VHF navigation, you're happy to confuse ambiguity and ambiguous.

Perhaps you mean nebulous, or perhaps you mean confusing. Who knows?

I don't know why your employer prohibits you from flying back course approaches. Perhaps your employer insists on a lower standard of training. Perhaps there aren't any to be hand, and you visit such a small area that it's not a problem for you. Perhaps you're operating to a very limited number of runways, all served by nice, comfy ILS's. Who knows? You asked, but given the lack of information, the only proper response is "who knows?"

I'm betting you do, and perhaps you'll even share the reason. It may change the speed at which the world rotates, so don't delay.

However, I would suggest that the ambiguity of the plate is contingent on far more than your ability to mount a vociferous defence in its favour.

I would suggest you determine the meaning of ambiguity in the context of VHF navigation. It has nothing to do with my defense (that's defense, with an "s). Vociferous is a big, aggressive sounding word, so like a strange do, we'll leave it aside.

Given that you think you mean that the approach chart is ambiguous (as opposed to the proper term ambiguity, when considering VHF navigation...your choice to harp on the correctness of the terminology here, remember), what exactly do you find ambiguous about the plain-english rendering of "The I-PKN back course outbound is normal sensing?"

We've already determined, early in the thread, that flying toward the nav facility is inbound, and flying away from it is outbound. Therefore, given that you're told it's a back course, you're told it's the outbound course, you're given the oubound course value (300) only (with no other numbers to confuse you), and you're told that it's normal sensing (as opposed to the standard expectation when flying a back course: reverse sensing), then it's really, really hard to see the information on the chart as ambiguous, unclear, improper, inaccurate, or wrong.

To this end try and understand my analogy(s) a little less literally.

A little less literally, you say, but you also told us that semantics are important. Let's be precise, you say. Okay; that's the point of this tangent the thread has taken, anyway. People are upset that the procedure doesn't appear proper, doesn't appear to be accurate, so let's be precise. You tell us semantics are important, yet you tell us not to follow along so literally. You must decide (but don't do it with ambiguity...)

The semantics is hugely important.

Indeed.

[Turbine D]

aterpster

I believe you to be correct at ASE. The airport is in a "box canyon" so to speak. There are two instrument approaches into the single runway:
1. A LOC/DME-E direct in approach.
2. A VOR/DME or GPS-C direct in approach that requires dual VHF navigational receivers.
There is a Roaring Fork Visual RWY15 for day use only with cloud deck and visual minimums.
There are four departures, three use the so called "Back Course":
1. LINDZ SIX requires a climb rate of 465 ft per NM to 10,000 and a left turn to intercept the 300° back course.
2. PITKIN TWO (RNAV) (same route as above)
3. SARDD ONE (OBSTACLE) requires a climb out to 9100 ft, a climbing turn to 270° to intercept the 300° back course. This is used to commence a holding pattern at LINDZ from which one can then proceed east or north when released by ATC.

The fourth departure is a straight out visual departure with cloud deck and visual minimums and can not be used at night.

The so called Back Course is used for missed approaches by turning right and intercepting the 300° back course. It is the only safe way out of the canyon as you are landing into the mountains with mountains on both sides at an elevation of 7820 feet.
At this time of the year you can never count on arriving or departing when you want to due to snow and gusty winds (white-out conditions), it is a very tricky airport.

As for the debate on the "Back Course" terminology, I leave that to the experts.

Turbine D

[PBL]

Terpster and Guppy,

I don't want to sidetrack the thread any more than necessary, but your comments on Cali suggest I need to clarify.

Everybody seems to want to select their favorite causal factors for a given accident, and say "it was *really* this". Analysts such as myself list and discuss all of them. If we want to prioritise some for some reason, we then provide our criteria and perform the selection. The paper which I referenced considers broadly speaking the language issues. It does not consider the others (for that, see our full analysis).

The NTSB letter on the accident to the FAA mentions the very issues that Gibbon and I discussed in the short paper I referenced. There is a reason for that.

Concerning "runway heading",

Originally Posted by PBL

....the problems US pilots have flying runway heading in the UK when instructed to do so by ATC......

Originally Posted by Guppy

.....I've never found that to be the case. That is, where such isolated cases may exist, these are pilots failing to follow an established ATC direction, not a language ambiguity

Mistaken analysis. It is controllers not following established phraseology. The appropriate response as a pilot is to query the clearance.

And the reason it is no longer established phraseology is ..... ??

Language is an issue.

For example, people here have surmised that hiren.bhingradia is a low-time insufficiently-trained newby, or maybe a simmer, simply on the basis that heshe is not using terminology we consider appropriate. No one has yet considered whether the terminology heshe uses might be what is commonly used in hisher environment. (If so, of course, there is yet another language issue to be sorted!)

PBL

[SR71]

Guppy,

You're hot on the bandwidth, I'll give you that.

You and I both know why Jepperson do not include the note "If you fly around randomly below MSA IMC, you'll bump into something" on their ASPEN plate.

You and I both know why Jepperson include the note "I-PKN backcourse is normal sensing outbound" on their plates.

I do not feel the need to respond to the rest of your commentary for 2 reasons, one far more important than the other:

1) It adds nothing further to the discussion.
2) Judging by your existing conduct on this thread (and many others) you wouldn't afford it any respect anyway, so I won't bother.

Enjoy.