ILS intercept question

[Fokker-Jock]

Hi Guys!

After flying professionally for 6 years I recently came over an episode wich caused an argument between myself and my captain. (On ground afterwards of course).

The case was:
We were cleared direct a beacon that was positioned appx. on 8 mile final to the active RWY along the ILS centerline. The clearance was issued with the intention of giving us a visual approach later on. Upon approaching the beacon appx 5 miles from it at an altitude above MSA we still didn't have the field in sight and I suggested to request "maneuver space" in order to intercept the ILS final approach track ourselves before the beacon and thereby below the ILS GS. The captain stated immediately that that was not allowed and requested vectors for ILS instead which we got. We then completed the ILS approach for landing. Afterwards the discussion came up why or why not this was not allowed. My captain argued that we are only allowed to follow published procedures to intercept the ILS, either from an arrival procedure or from a fix designed as an IAF and in our case the only correct procedure would be to start a racetrack entry at the beacon ahead. I argued that it was not neccessary as we were above the MSA and could thereby fly in anywhat direction we wanted as long as our clearance allowed us to, also to intercept the ILS LLZ and later the GP from below, as long as we had other means of determening our position, either from a QDM from tower, beacon or radial. We agreed that we disagreed and that we should seek an answer to this. After asking another captain who argued the same as myself I decided to ask the question on this forum.

So if there are any Pans-ops and JAR-ops guru's out there that could give me a correct answer it would be highly appreciated!
I would like to point out that both the suggested procedures for approach are safe in my opinion. So the question is more what is legally correct ?

[JABBARA]

It seems reasonable to ask a maneuvering space from ATC to align with ILS LOC course at MSA. However in Jeppesen Introduction section (of course this is an extraction from ICAO or FAA document) MSA is described as "FOR EMERGENCY USE ONLY"

That implies unless you have an emergency, you cannot use airspace as you wish even the altitude is at or above MSA.

Conclusion: I think technically captain is correct


Regards

[Fokker-Jock]

Thanks for the reply!

However I think you misunderstand my question. Once cleared "maneuvering space" for ILS intercept I will still argue that the controller has given you permission to fly at own discression in order to make a safe LLZ intercept.

My question is more related to wether or not you are allowed to make such an intercept on your own without the backup of vectors from the controller and without performing a racetrack at the beacon.

To simplify: Are you allowed to position yourself, if cleared to by the controller, on the LLZ centerline and to perform a direct approach without going through a time consuming racetrack procedure ?

[swh]

FJ,

Of course you are !

Some places in the world you can join an ILS outside radar and controlled airspace. Many precision and non-precision approaches have an IAF which allows a "straight in" entry into the approach.

MSA, manoeuvre as required (in the sector if it has one) to join the approach, if cleared to do so in CTA, or as you desire OCTA, providing you know you position in the MSA.

:ok:

[caniplaywithmadness]

I'm not sure about doing it in a non radar environment, but with radar monitoring and positive descent control from ATC it is perfectly allowable and I permit it on a daily basis.

The crew position the flight to wherever they want to intercept the loc and I give descent to an appropriate safe level.

The only time I've ever done it in a non radar environment was after the radar failed and the particular a/c was on a base leg and was happy to self position to intercept at their current level. If they hadn't been then it weould be all the extra miles to the beacon and then the procedure.

[Capt Claret]

Fokker-Jock,

Several ILS procedures here in Aus have a note to the effect that "aircaft may be vectored to intercept the LLZ at ....

Your interpretation seems acceptable to me.

[bookworm]

FJ

Can you let us know which airport and which approach please? It would help to see a picture.

"Maneuvering space" is not a meaningful term for procedures. You either fly the published procedure from an IAF, or you are radar vectored on to the LLZ for the approach. There's nothing to stop you suggesting headings to the controller, however, which may end up being the equivalent.

What I don't follow is why your self-positioning manoeuvre was more expedient than getting radar vectors for the approach in the first place.

[OzExpat]

I've been a Pans Ops procedure designer for 20 years now and have never before heard the expression "maneuver space". It has no meaning in Pans Ops. The thing that would be of most help is a reproduction of the chart because, maybe, the only thing you really need is an interpretation of the lead-in to the approach procedure, from a designer's perspective.

[Fokker-Jock]

Thanks alot for all your replies!

The approach in question is at ENCN. Kristiansand Kjevik, Norway, ILS 22. The clearance was direct BN beacon.

But the same situation applies for many other airports as well.
The thing that makes this so special is that the initial approach altitude is 200' below the Minimum Sector Altitude. Therefore it is possible to get established on the localizer and when established, descend the 200' down to intercept the glideslope.

Even though it is safe, no questions about that. Is it allowed seen from a Pans-ops point of view ?

Bookworm: I definately see your point, and you are right. The amout of time spent on a vector in comparison to self-maneuvering is marginal. However I'm not always impressed by the effectiveness of ATC vectors, and when flying in controlled airspace with only one A/C present, I would like to do the manevering myself in order to be as effective as possible. But the question still remains; Am I allowed to do so if above the MSA ?

OzExpat: The term "maneuver space" is a communication term not a Pans-ops term as you clearly stated. I sometimes use it in airspace with low traffic volume in order to gain lateral playroom to position the aircraft. ("Playroom" ? Pardon my english)

As the example I mentioned in my first post. The beacon is situated closer to the airport than the position of GS intercept from initial approach altitude. Therefore if you fly direct that beacon, there is no way you could do the approach directly since you would be some 300 feet above the glideslope.

Instead of flying directly to the beacon I would request maneuver space in order to intercept the LLZ at a point before the GS intercept. The only reason I would argue that this is possible is that you are above MSA and therfore don\'t have a terrain conflict. But the question remains, can I do this on my own or do I need vectors from the controller ?

[swh]

A non operational version of the chart can be downloaded here (ftp://djay.myftp.org/aipmap/encn503-fs.pdf)

:ok:

[keithl]

I can't resist an ILS Intercept question!

All the answers so far have looked at the question from a terrain avoidance angle or a PANSOPS angle. Because I am involved with many Procedural approaches - that is, no radar available - I would like to mention another aspect. Although I can't see anything wrong with "self position for the LLZ" while maintaining above MSA, there is the sequencing question to consider.

Someone ahead of you may have started from the IAF and is following the full (in this case Racetrack) procedure. If you join the ILS at some random point, you could mess up the controller's procedurally established separation plan.

I agree, you didn't suggest you'd do this without talking to ATC, but it is one reason why not following a full procedure can cause problems.

[bookworm]

The thing that makes this so special is that the initial approach altitude is 200' below the Minimum Sector Altitude. Therefore it is possible to get established on the localizer and when established, descend the 200' down to intercept the glideslope.

But you're not "entitled" to do that on a procedural approach. You have to fly to the IAF, then commence your descent at the IAF from your cleared altitude. You haven't told us what your cleared level was at the BN beacon (the IAF) but presumably it was more than 3000 ft or there wouldn't be a problem. So you have to fly to the BN at your cleared level, then fly the procedure. That will require you to fly the racetrack. You're not permitted to descend even from 3200 ft (MSA) to 3000 ft just because you happen to be on the localizer.

However if you look at the RVA chart, there's a significant area well to the north east of the BN in which the controller can descend you to 2500. That avoids the problem.

There's another minor twist. On the real chart the GS intercept point is some half a mile outside the BN. So if you maintain even 3000 to the BN, you'll be about 150 ft above the glide. There is no direct arrival from the north east. Thus strictly speaking, even if you arrive on the feeder route from SKI at 3000 ft, you still have to go around the race track, even though SKI-BN is tantalizingly close to the localiser track.

So I think the way to fly it is to work out your desired intercept heading and make a request, when about 15 miles from the field, to take up that radar vector for the ILS 22 with a descent to 2500 ft.

Thus from a procedural point of view, I believe your captain was correct. This might seem pedantic because practically speaking, as long as you're on top of the situation, you can fly your own "radar vectors" to intercept. It probably would have seemed pedantic to the guys that put a 757 in the side of a mountain trying to get to Cali, too. :(

[Fokker-Jock]

Bookworm: Let's for the sake of argument say that our clearance was 3200' direct BN for later visual approach. 5 miles from the beacon the controller has not yet recieved our "Field in sight". Instead he issues a clearance for the ILS 22. We then request "maneuver space" in order to position ourselves for a direct approach well outside BN and also well outside the ILS GS intercept point.

I would then say that since we are cleared for the ILS, that would imply that as soon you are established on the LLZ you may descend to 3000' (Initial approach altitude) and perform a straight in ILS 22, if your position after establishment can be confirmed either by other navaids or by ATC radar.

How can this be illegal ?

Pedantic or not. I would like to hear every aspect of the case..

[OzExpat]

My thanks to swh for the "Non-operational chart". If this chart is an accurate representation of the real one, I can make a few comments. My apologies in advance for the lengthy nature of this post.

Firstly, maybe I'm missing something, but I don't see an IAF marked anywhere on the chart. This is probably a minor point, but makes me wonder exactly where the approach starts. After all, it's only the precision segment that starts at GP intercept and there has to be a way to get there. In absence of any other information, I believe that the holding pattern at BN is a racetrack procedure and, therefore, BN is the IAF.

I am not accustomed to seeing an initial segment indicated by a dotted line such as those used to indicate feeder routes and the racetrack at BN. Thus, I'm also trying to come to grips with the way things are depicted on this chart, so that I don't confuse the issue by thinking in terms of our own depictions.

The first extremely relevant point is that the GP angle appears to be 3.6 degrees, which I note is 0.1 degrees above the maximum angle for which Pans Ops provides OAS data. Such an angle will not be used unless there's a significant obstacle problem, so my first comment is that this is not a procedure where one should take too many liberties.

Anyway, it occurs to me that, if you happen to be tracking 220 degrees toward BN, you certainly are quite close to the LLZ track of 217. Depending on what your AIP says about pilot tracking tolerances, you may actually be allowed to slide across from the 220 track to the 217 track.

That would certainly be the case where I am because there will be an overlap between the tracking tolerances for the NDB and those for the LLZ. Given that there seems to be no other information on that chart, I would venture to suggest that the "slide-over" is the way that one is intended to intercept the LLZ.

This would also mean that it would be possible to descend to 3000 feet during the "slide-over" manoeuvre from one track to the other. The problem is that you must know the outer limit of the protection on the 220 track to BN. This is because the 3000 feet limitation seems to be available only within the racetrack. There is no indication on the chart of the DME distance at which one could descend from 3200 to 3000.

The result of this lengthy ramble is that, without radar vectors, it would seem that one must maintain the MSA until reaching GP intercept. The only other issue would seem to be whether or not your AIP allows routine use of the MSA, as we do here, or whether it is only available in an emergency.

To me, therefore, it seems that you are required to go around the racetrack to take advantage of the descent to 3000 feet. Then, having turned inbound 220 to BN and within tracking tolerances of the LLZ, diverge right just enough to make the intercept of the LLZ - hopefully prior to GP intercept.

Given the circumstances, therefore, I think that the captain was probably correct on this occasion.

[bookworm]

I would then say that since we are cleared for the ILS, that would imply that as soon you are established on the LLZ you may descend to 3000' (Initial approach altitude) and perform a straight in ILS 22, if your position after establishment can be confirmed either by other navaids or by ATC radar.

There are two sorts of approach: procedural approaches and radar vectored approaches.

For a procedural approach, you fly from an IAF proceding from point to point on prescribed tracks and/or arcs (I'll call them "legs"). The protection from terrain is guaranteed by making sure that if you fly those legs as depicted, you won't hit anything. You don't need to know where you are on the legs, as they just link waypoints at which altitude changes may occur -- you know you may descend to the next level when you have reached the next point. The procedure is 1-dimensional in that you fly along prescribed legs.

A radar vectored approach offers its protection in a different way. The controller has an RVA chart and can permit you to descend to a level consistent with the minimum altitude for your 2-dimensional position. It obviously offers more flexibility.

There is no halfway house. Procedural approaches do not permit the crew arbitrarily to say "looks like I'm now in an area where the terrain would permit a descent to 3000 ft, so down we go". Descents are only permitted on the legs of the approach as you pass points that signify altitude changes.

So when you've intercepted the LLZ on your straight in, how do you know that you can descend to 3000 ft rather than the 3200 ft MSA?

What you want to say is "well I'm pretty sure from other navaids I'm within a few miles of the BN so that nasty terrain that I might hit below 3200 ft is well behind me. Let's go down to 3000 ft."

But that's not the way the procedural approach game is played. Only when you reach the BN can you be sure that a descent to 3000 ft is safe, and only then on a particular track, the racetrack -- because that's the start of the approach. Otherwise, how do you know how far out you are? As far as the procedure designer is concerned, you might be 30 miles NE of the BN when you intercept the localizer (given VOR tolerances that's not unlikely if you're coming in from SKI). So the procedure has to say, "you can descend when you get to BN, and not before".

(That's a long way of saying what OzExpat said, "There is no indication on the chart of the DME distance at which one could descend from 3200 to 3000".)

In a radar environment, you're at liberty to ask the controller for you "maneuver space", wiggle your way onto the LLZ at 2500 ft (if authorised) and come straight in. But the guarantee of terrain separation comes from the controller knowing where you are in 2 dimensions. Make no mistake, if you're asking for "maneuver space" below the MSA, you are asking for a radar vectored approach, not a procedural one.

If this procedure were to be used regularly in a non-radar environment, it would make sense to establish a direct arrival procedure. US style would be, I think, to establish a waypoint say 5 miles NE of the BN on the LLZ as an intersection with a feeder route from the SKI. You could also route direct to that point with RNAV. That would become an IAF for a direct (no PT) arrival and you'd be free to descend from 3200 to 3000 after that point. UK style would be to establish a DME arc say 5 miles outside the BN (since there's no TDME it would have to be on the SVA I guess) and allow you to join the arc to intercept the LLZ either at 3000 ft, or if that didn't work at 3200 ft with further descent once established.

I hope that's consistent with the contribution above from OzExpat (who has forgotten more about procedure design than I will ever know). He doesn't have the benefit of the real chart (EN_AD_2_ENCN_5-3 which is on the EAD (www.ead.eurocontrol.int) if you have the patience required to access it -- they've put it in the wrong section there in that it's under AD rather than Charts). The only substantial difference appears to be the recognition that at 3000 ft the GP intercept point is actually 0.5 mile outside BN.

Hope that makes sense.

[Tinstaafl]

I must be missing something? Providing that routine use of the MSA is allowed in that region - as can be done in Oz & PNG - and not just for emergencies then why can't the a/c stay at or above the MSA, manoeuvre to intercept the LOC a couple of miles from BN, then once on the LOC and the GS is intercepted descend with the GS?

Surely the a/c *must* be within the holding protected airspace then? And able to descend *using GS guidance* to no lower than 3000' until crossing BN? It's still possible to check GS vs position & altitude crossing BN.

[BOAC]

Tin - I cannot see any safety issues in that, but I guess the whole thing hangs on the 'clearance'? A procedural 'clear for ILS R22 via the BN' implies route TO the BN at which point the 'procedure' should begin - either the teardrop or the hold entry to the ILS. I would have thought that a simple call to ATC asking for 'selfposition' would have cracked the problem?

Incidentally, if the chart is accurate?? the BN is not 'on' the localiser.

[bookworm]

why can't the a/c stay at or above the MSA, manoeuvre to intercept the LOC a couple of miles from BN, then once on the LOC and the GS is intercepted descend with the GS?

So effectively you'd be using the glideslope intercept to substitute for a DME measurement to tell you that you were close enough to the BN to leave 3000 ft for 3200 ft? You could also do something similar with a simple DME indication, to determine that you're closer to the BN than the 1 min racetrack would take you anyway, so if it's safe to be at 3000 ft on the racetrack inbound, it must be safe to be at 3000 ft on the LLZ.

In terms of risk management, providing everyone is on top of the situation, I can't see a problem with that. The only issue is that procedures are intended to be flown as depicted, and as soon as you start taking liberties with that, you start to bet that you're capable of seeing all the failure modes of the home-made procedure. For the one time in 100 that the procedure is flown without radar, I'm not sure it's worth the stress.

[Fokker-Jock]

Tinstaafl: My point exactly. There is no safety issues there by doing it that way, and that is probably the reason so many other pilots in my company does it this way, myself included.

As to both Bookworm and OZexpat: Your point are well taken, and definately valid ones! Thanks both for clearing up any misunderstandings I may have had to this subject. I guess we now can agree that it is procedurally incorrect to perform such an approach, but well safe to do so.

Captain - F.O 1-0

[OzExpat]

Bookworm... thanks for the reference to the real chart. Sadly, I've been having MANY more problems than usual with my internet connection from this backwater of the world, so I haven't even attempted to download it. However, I see what you're saying and agree that it makes little difference to the overall synopsis.

I'm sure that, if I've actually forgotten more than you'll know, I run the risk of not knowing enough. I do, however, try to put myself in the situations that I create, to see what sort of problems it creates. If that had been my procedure, I'd have moved Heaven and Earth to install a LLZ/DME fix to show when descent from 3200 to 3000 is possible.

I guess that, for all practical purposes, one could invent a DME distance that equates to about 4 miles NE of the BN beacon and use that for the descent to 3000 feet. However, there's no way of knowing whether or not the designer considered that and, if so, why it was not incorporated.

In any event, I would never even consider creating a procedure in Controlled Airspace without close collaboration with ATC. It is entirely possible that this particular procedure has been based on some very specific ATC requirements. These requirements need not be specified on the chart, but there would be a set of instructions available to the ATCOs to assist them to manage the approach.

FJ... there's no shame in losing an argument. Quite the contrary in fact because there is great shame in not having that argument in the first place. In practice, when all else fails, I have always survived by erring on the side of safety. It might not always be the most efficient way, but there's a better than even chance that it will keep your butt safe.