ATC 'Maintain present heading' instruction

[Stephen]

Can someone explain me why sometimes ATC orders you to 'maintain heading' after being cleared to a certain waypoint - sometimes 1 hour flighttime or even more further down the route?

E.g. ATC clears you direct BLBLA and asks you to report your heading once established inbound BLBLA. Once established inbound BLBLA, you report your heading and ATC orders you to 'maintain that heading'

Has it something to do with different lateral separation requirements for aircraft flying 'own navigation' and for aircraft flying on an assigned heading?

I understand that ATC requires you to fly headings in during descent and approach in terminal areas, but a lot of times it also happens enroute at high levels.

Thanks for yor reply!
Stephen

[Arkady]

ATC will give you the best direct routing available most of the time. If you are then told to maintain the heading it will be to separate you against other traffic at or going through your level. The lateral separation limits don't change whether you are on a heading or not but when Radar Separation is applied separation has to be ensured, hence the use of headings. If you are given a direct and immediately afterward told to continue on the heading it will be for the same reason but the controller has decided to let you pick the optimal heading to your way point rather than estimate it him or herself. It’s a good method if the waypoint is a long way off or there is a strong wind playing havoc with the holding headings. Often the traffic you are on a heading against is not on (or not yet on) the same frequency, so it will not be obvious to the flight deck what is going on.

[Bumz_Rush]

how long would YOU maintain the heading, until you realised you were no longer on RT.
assuming a reasonable difference in track made good and track required.....just to keep us thinking along the same lines....Bumz

[DtyCln]

The reason we send you direct then ask you to "maintain heading" is exactly for the reasons you describe.

Where an aircraft is overflying a sector i.e. flying direct to a waypoint an hour down the line, we lock you on that heading if we have aircraft above you to descend down to an underlying airfield or aircraft departing from airfields beneath that have to climb up through you. Generally we will lock the overflight on a heading and vector the climbers or descenders around your heading as the overflying aircraft.

There are no set parameters about lateral distance apart for climbing or descending aircraft through others but the CAA merely insists that we 'ensure' separation. For example Airbus aircraft 'anticipate' turning at reporting points on autopilot and sometimes turn before you expect them to. As a very general rule, I expect some colleague flak here!, I would say roughly 15 miles lateral on head-on routes, maybe slightly less on similar direction routes would require us to use headings for climb/descend throughs.

As regards R/T fail or loss of contact the procedures are quite clear. In the Area Control environment if you are unable to get 2 way R/T with an appropriate sector, you maintain the heading for a period of 3 mins from the time it was issued then squawk R/T fail and fly the shortest possible route to rejoin your flight plan. The rules are slightly different in the TMA or SID STAR environment.

Hope this helps.

DC

[Spuds McKenzie]

For example Airbus aircraft 'anticipate' turning at reporting points on autopilot and sometimes turn before you expect them to
The infamous "fly by". A pain in the neck and potentially dangerous too.

:mad:

[duece19]

For example Airbus aircraft 'anticipate' turning at reporting points on autopilot and sometimes turn before you expect them to.

And so does the Boeings. I know you can create "Overfly" waypoints in the bus. Still havent seen it in a Boeing, maybe someone can enlighten me.

duece

[Spuds McKenzie]

Compared to the 'bus, the Boeings do it on a neglectable scale, hardly noticeable on Radar.
Even when flying towards an obtuse angle, the 'bus will turn (depending on angle and speed) several miles before the waypoint to "catch" the next track.
When it gets really annoying is when the angle between tracks is acute, then the turn can "happen" up to 15NM before the waypoint. Not good and safe enough!

[duece19]

wow, I thought boeings were bad with a mile and a half or so. But 15 miles??? Can it really be that much?


duece

[Evil J]

Very minor point and not related to the thread, but I'm sure I was taught you "maintian" a level and "continue" on a heading?? I stand to be corrected if I'm wrong...

[DFC]

With regard to the comms failure - when being radar vectored according to the rules we wait 3 minutes and then return to the flight planned route. (UK local requirement).

However, we have been sent to a point on our flight planned route whatever miles ahead. This suits us and suits ATC. One could argue that we are not being radar vectored we are simply agreeing with ATC that we will maintain the heading that is currently taking us to that reporting point. Thus we would in effect maintain the heading for 3 minutes after R/T fail and then if necessary adjust heading to maintainn the track to that reporting point and thereafter follow the filed route.

As for the problem with fly-by waypoints. There is nothing new there. It is not only modern aircraft that can take advantage of that - old steam driven aircraft can also (and have done also) in enroute airspace.

Remember that when enroute we navigate to RNP5 - we must remain within 5nm of the route centerline. Thus the aircraft can at any time be up to 5nm to one side of the ATS route and still be considdered to be navigating to the required accuracy. When at a turn point (intersection or beacon) it is perfectly allowed for the aircraft to "cut the corner" or "anticipate the turn" or whatever one likes to call it provided that the flight remains within the requirement of RNP5. Imagine leaving a 90deg turn overhead a VOR until the VOR indicates station passage as say M.80 and FL350 - how far would that put the aircraft off track initially!!!!

I believe that is one of the reasons why radar controllers lock aircraft on headings to ensure radar separation.

Regards,

DFC

[Spuds McKenzie]

RNP5 is an entirely theoretical value. A deviation of 5NM to the left or right of track in reality does not happen. In fact the tracking of a BRNAV equipped acft is exact to the mile.
As for the fly by, it makes a huge difference if an acft such as the Airbus does it extensively as described above or only on a minor scale as also described above. It is a safety issue.

[PPRuNe Radar]

The infamous "fly by". A pain in the neck and potentially dangerous too.

Of course if you knew ANYTHING about procedure design, you'd realise what a stupid statement that was :rolleyes:

Go read the definitions for 'fly by' and 'fly over' :)

Only potentially dangerous if you don't know wtfwhn ;)

Remember that when enroute we navigate to RNP5 - we must remain within 5nm of the route centerline. Thus the aircraft can at any time be up to 5nm to one side of the ATS route and still be considdered to be navigating to the required accuracy.

Which means that you remain within 5NM for 95% of your route ..... sometimes (for 5%) you could actually be MORE than 5NM off track (legally ;) )

[Spuds McKenzie]

Pprune Radar,

When was the last time you worked in front of a Radar screen and noticed that the Airbus turns considerably earlier than any other type of acft?
That it is the issue here and not fly by as such.
Of course I know that a waypoint can't be overflown on the spot in every circumstance, but it still makes a difference when it is 10NM before (Airbus) or 2NM before (Boeing).
And BTW I'm not claiming to carry the ultimate wisdom re ATC (must be a NATS thing...).

Spuds (non-NATS and non-UK ATCO, yes, ATC is being done elsewhere too...)

[ferris]

I'm unsure how locking an a/c on a heading assures separation. I've heard some arguments which were factually incorrect, and am yet to be convinced. If an a/c is tracking somewhere, and you want him to keep doing that, why say anything at all?

[Barry Cuda]

Ferris, try and picture a square with points marked a & b across the bottom, and c & d across the top...

c . . . . d


a . . . . b



Now aircraft No 1 is flying from a to d, and aircraft No 2 is flying from b to a. No 1 is at FL 380, No 2 at 400 descending 360...

Still with me?

If I tell No1 and No2 to "continue present heading" then I can prove my separation because both aircraft were under my direct control and, assuming the headings were providing the required distance (5miles), would not hit each other...

If I leave both aircraft on own nav then the possibility exists that either aircraft may have an intermediate point on the route that would erode the separation and I would therefore not have PROVED it.

I hope that makes sense, next week intermediate Nuclear physics for the retired hostie!!!:cool:

[ferris]

That is exactly what I am talking about. Your example doesn't "prove" separation. It's a furphy.

Continue present heading will not guarantee to keep the aircraft apart laterally. If the wind is different at any of the levels between and including FL370- FL390, then the possibilty exists that the aircraft will drift closer together until they experience the exact same wind at the exact same level (FL380). Lateral sep could be lost within those levels before vert exists.

If, however, the aircraft are told to "track direct to d" and " track direct to a" respectively, that guarantees they will remain on set paths (which is what you are seeing on the radar) despite moving air masses, and therefore known distances apart. Aircraft told to "track direct XXXXX" don't have mysterious intermediate points in their route, unless not following the clearance.

I imagine that this is an old-fashioned technique from pre-RNAV days, when headings were probably more accurate than 'own nav'.

[Evil J]

I think the point is that ATC have control over the aircraft's direction, rather than the pilot's, ergo "proven" separation.

That said, where I work aircraft on the SID's are deemed to be on "known tracks" and lateral separation can be used as if they were on headings.

[DFC]

PPRune Radar,

I prefer to think it more in the terms of in 100,000 flying hours, the flight with be within 5nm of the centerline 95% of the time - we'll be long retired before we get to the 95,000 mark! :)

However, while we can in theory cut corners (and the UK CAA IR flight test required it for commercial expediency there is one requirement that prevents one from pushing it..............remaining within the airway (controlled airspace) at all times.

Isn't turn anticipation for a fly-by waypoint changed if the angle of bank limitation is set to a low level? i.e. limiting the bank angle changes the turn radius requiring the turn to be started earlier to achieve the correct intercept of the outbound track!

Regards,

DFC

[ukatco_535]

Ferris,

Methinks you are being a little pedantic. If I have two a/c in proximity to each other and they are on their own nav, they can turn unexpectedly and come into confliction. If they are maintaining level separation, then this is not a factor. 'Track direct' is not a recognised technique, nor does it ensure separation, however nice the idea may be.

If I want to do a climb through, I will instruct them to fly or continue a present heading as a radar heading thus locking them on to a 'virutally' non deviating track.

We are not stupid, we know winds change, what we are doing is locking a/c onto a resultant track. Any Atco that did this to ensure the minimum 3 miles separation would either be very skilfull, or very silly. The A/c in question may pass each other with ten miles separation in the end, but if they are crossing tracks at oblique angles, a 15 degree heading change by one or the other may make a comfortable situation become sticky. Hence the locking of headings. It also means that a busy ATCO can get on with the other controlling tasks without constantly monitoring the climb through.

If, whilst locking A/c onto headings we can give one a direct routeing to a waypoint, then it's a win win situation for us and the pilot, who gets more direct routeing and an earlier climb/descent to final level.

Working in the London TMA, we have to use headings to achieve what we need to do. Whether these are controller chosen headings or 'locked on' pilot headings is a moot point if it is providing the required separation.

[ferris]

More twaddle.

I don't think I'm being pedantic- quite the opposite. I think I am questioning other pedants who are certain locking a/c on headings makes things safer. I am questioning that (something that doesn't go down very well in this industry). Stuff likeIf I have two a/c in proximity to each other and they are on their own nav, they can turn unexpectedly and come into confliction How? Mysterious intermediate waypoints? Wx avoidance? Or some other random departure from clearance?

Sure, I can think of lots of examples where using headings is useful (do it every day {btw "Working in the London TMA, we have to use headings to achieve what we need to do"- well guess what: In the eleven-and-a-half-thousand movements per-man per-year UAE, we use headings to achieve what we do, too.:rolleyes: }). But this thread was about the practice of using headings to somehow assure route-following (and therefore separation). Something I question. With good reason if you believewhat we are doing is locking a/c onto a resultant track

[DFC]

Ferris,

In the old days of VOR-VOR-NDB-MARKER navigation your comments regarding flights suddenly veering off to some unknown place held some truth - you tracked beacon to beacon and every beacon was identified prior to use and the system ensured that you could never receive two VORs/NDBs with the same ident even up to 50,000ft.

The same can not be said today in the world of FMS and GPS databases...........direct to say DUB could take the aircraft towards a place near you or direct to Ireland...........Thus an aircraft in your area of the world passing a intersection and then the FMS being told to go direct to DUB..........the tired pilot misses the fact that there are two DUBs in the database, the aircraft may suddenly head 30deg right of the expected course............just when you are on the phone and not watching the screen..........before you know it.........that flight is getting toooooooo close to another climbing throught it'slevel and you could have prevented it.

You sould have a read of Attachment A and B to Annex 11.

In annex A, the spacing for parallel routes defined by VORs is basically 18nm with a reduction to 16.5nm for traffic going in the same direction on both.

In annex B, the separation for traffic on RNP5 routes is 10 to 15nm.

There is more involved. However, taking the lowest of the above figures - traffic has to be atleast 10nm parallel and radar monitored to continue on own nav at the same level............try that round Europe and the movement rate would halve or worse.

As a pilot being on a vector or locked on a heading is no big problem........unless I am being taken all over the place - which route direct and continue the headig when established is definitely not.

Regards,

DFC

[ferris]

DFC.

Once again, I beg to differ. I think in the pre-RNAV days, the tracking of aircraft would've been less accurate (scalloping etc), than with the dead-on multiple GPS gismos today. Perhaps you should have a read of your own post, in that RNP5 separation quoted is less than for VORs.
If you are trying to say that pilot error is the negating factor, then that applies equally to any instruction (such as flying a heading). We are talking about a specific situation; where the instruction has been issued to track to direct to somewhere. If the controller doesn't check the tracking, before basing sep on it, what's the difference to issuing a heading and not checking the a/c is approximating that?

As for all the stuff about route separation....I'll bear that in mind if the radar fails. I'll give you a tip; just because an aircraft is left on it's own nav, on it's route, radar separation doesn't stop applying.

[ukatco_535]

This is verging on the ridiculous now, and getting very tedious.

If a/c are on own nav, of course radar separation continues to apply, as it does if they are on radar headings... it's all about the degree of monitoring. If a pilot is on his own nav, he can turn to avoid weather etc (by the way - route direct to you may mean one thing, but to a pilot, following company policy it may mean another - they may have to go via certain waypoints etc (this is stretching it a bit far I know but when we are talking about pilots with different first languages, continue heading or fly heading is unambiguous))... if he has been instructed to fly a heading, he is more likely to ask before he turns - it's basic human nature.

and before more pedantry prevails regarding the fact that the pilot should always ask before making a heading change in CAS. we know this and pilots know this, but the fact of the matter remains; if a pilot is on his own nav, he is more likely to deviate first then ask later than if he had an assigned RADAR HEADING.

and just to cover my back a bit better (and this does not apply to you DFC - you, at least, sound like you have a modicum of common sense), most pilots will understand without having to be told in the most minute detail, that if they are on a radar heading, it is for a reason and will therefore have a bit more savvy about them regarding turning on their own whim.

:D

[ferris]

if he has been instructed to fly a heading, he is more likely to ask before he turns - it's basic human nature It's where this usually ends. An assumption.
You have absolutely no evidence of this, it's just your opinion. In my experience, it makes no difference. A/c have a no higher rate of compliance whether on own nav, or on an assigned heading ( radar heading- you guys crack me up).

If a pilot is on his own nav, he can turn to avoid weather Tedious, to me, is having to apply techniques that have no relevence today, that are based on waffle, assumption and other baseless dogma.

Cheers.

[Bern Oulli]

Let's put it this way. When training radar controllers of the Approach incination, any student who failed to lock aircraft on headings to prove the separation, would be taken outside and given a serious slap with a wet fish. In an exam situation, the student would be almost certainly failed. Whether this is logical, sensible or totally over the top I care not. It is what was taught, and in the few months since I retired I doubt anything has changed.

[ferris]

on headings to prove the separation My point is very well demonstrated by your post. Thanks Bern.
If you were failing students because they weren't applying what they were taught to do, then that's one thing. But if you were actually failing them for failing to prove separation, then you may want to rethink your position, because as yet no-one seems to be able to state how this technique proves anything. Other than how popular herd mentality is......Whether this is logical, sensible or totally over the top I care not. It is what was taught Thinking is just not encouraged, is it? Probably why we end up with the managers we do.

[Bern Oulli]

ferris, you have two aircraft opposite direction. For simplicity's sake they are flying on separate airways that run parallel and actually join at the edges, each delineated by VORs. Effectively then we have a chunk of CAS, say 17 miles wide, with two parallel tracks 7 miles apart. Our two aircraft are on their own nav, one requiring climb ('cos it is a departure) and one requiring descent ('cos it is an inbound). At some point their levels will cross and all other things being equal they will be 7 miles apart laterally.

I grant you the arguement that before altering heading away from own nav the pilot should inform/ask ATC. I grant you also that if you had told both aircraft to "route direct" to whatever VOR marked the end of that airway then everything should be OK. However, in aviation we all know that things don't always go according to plan. Congested frequency, CBs, first language not English, nav-aid failure (a/c or ground), misheard call-sign, you name it. The only sure way of proving you did everything to ensure separation is to lock both aircraft on headings, and of course, listen to the read-backs. It may well be the headings you use are the ones they were already on - great. That makes "resume own nav" dead easy when the crisis, sorry, confliction is past.


Whether this is logical, sensible or totally over the top I care not. It is what was taught

When I wrote this I was trying to separate (pun unintended) the rationale of the method from the immediate reason why it is used. It is used because controllers are taught it.
The rationale as to why it is taught is as above. Leaving pilots to do their own thing proves nothing, other than the controller has "assumed" that all will be well. He has done nothing to "ensure" separation. And at the subsequent Court of Enquiry, if you did not prove the separation then the possibility of a manslaughter charge is on the cards. The cynical but realistic person could describe it as an arse-covering exercise. Experience teaches to watch your six o'clock because no-one else will.

Oh, and by the way ferris, I never was a manager - I thought too much!

[ferris]

Bern, an excellent post. I agree with almost everything you say, except that 'locking on headings proves separation'. I went thru why in earlier posts, so I won't go over and over it. Suffice to say that at that subsequent court of enquiry, you would have a hard time proving that locking on headings is safer than a perfectly servicable modern a/c flying on it's own nav (IMHO). It's exactly the sort of thing clever lawyers get you with.
I can argue that every single thing you name as a reason for why you lock them on headings, is not neccesarily right. eg

Freq congestion: A great reason not to add to RT loading with instructions that are a waste of time (headings). How congestions is a problem for a/c on their own nav, I'm not sure.

CBs. In my experience, a/c approaching CBs will deviate whether on an assigned heading, or not. If (by issuing headings) we have fostered the belief that it's OK to deviate if on your own nav, then that's our fault and needs correcting.

First language not English: In my experience (and we have a lot of non-native speakers around these parts!), "track direct to XXXXX" is as equally well understood as "continue on present heading" or "fly heading XXX"

Nav failure. This is probably the best reason you give. However, if someone actually did some research, I'd reckon that nav equip failure, in modern a/c, would be about as common as altimeter or transponder failure, yet we take no special precautions against these failures (which involve the a/c actually being much closer together). Ground aids aren't even required these days (witness the approach of ADS-B).

Mis-heard callsign. I would say that actually works against your argument, as the 'locking heading' technique involves more RT than saying nothing.

So, as you see, I disagree with the basic premise that this technique proves anything.

[Euroc5175]

Precision Area Navigation (P-RNAV) is being introduced as the standard to use throughout ECAC Terminal Airspace, if you wish to introduce RNAV routes. The option of conventional procedures is retained.

P-RNAV is predicated upon a lateral track accuracy of 1NM for 95% of the time. There are detailed design criteria to be followed for P-RNAV routes that are published in a Eurocontrol document. However, fly-by turns are required to be used for most procedure designs when using P-RNAV. The design criteria contains a multitude of formulae and tables that let the procedure designer determine when aircraft will start to turn prior to a fly-by waypoint. Factors such as the speed of the aircraft, turn angle, bank angle are taken into account. A minimum distance between successive waypoints is required for stabilisation. This minimum distance also varies depending on speed, bank angle, turn angle, etc. The point is that P-RNAV enables procedure designers to determine when an aircraft will start to turn prior to a fly-by waypoint. All aircraft, if flying P-RNAV, should turn so as to remain within 1NM of the published track. There are several rules for P-RNAV design. One such rule is that no single turn should exceed 120 degrees. This is to avoid aircraft having to initiate the turn, even in Terminal Airspace, at a substantial distance prior to a fly-by waypoint.

Work is currently on-going to determine the required spacing that should be provided be P-RNAV routes. Initial noises from the CAA suggest that 5NM is an appropriate distance to apply between P-RNAV routes. This is presumably based on the fact that aircraft fly within 1NM of published track, and allows for a 3NM separation criteria even if both aircraft are at the edge of their respective 1NM tolerances.

It is also being suggested that in the near future the CAA will look favourably upon separation criteria such as Aircraft A on a P-RNAV route, being separated by xNM from Aircraft B that is on a radar heading. Historically in the UK both aircraft A & B would have been provided with headings to fly (or be 'locked' on).

P-RNAV is likely to be introduced on a more widespread basis as new runways, requiring revisions or additions to SIDs, STARs and new airspace come into effect in the UK. Work is on-going to ensure that P-RNAV is introduced in such a way as to ensure a safe and efficient operation continues to exist in UK Terminal Airspace.

[Bern Oulli]

ferris, we may have to disagree on this one. However I will take you up on one small point. You said you would have a hard time proving that locking on headings is safer than a perfectly servicable modern a/c flying on it's own nav . What I actually said was The only sure way of proving you did everything to ensure separation is to lock both aircraft on headings, (my italics). There is a difference. All I would have to prove in court is that I did what has been, until now, the accepted (and SRG approved) way of ensuring lateral separation. I would contend that if I could not prove this, then I am in trouble.

Frequency congestion and CBs. If an aircraft has been told "route direct XYZ", the pilot does not know if this is for separation purposes or the ATCO is being nice today. He wishes to avoid a build-up ahead, the frequency is humming, he is, in his mind, on his own nav. He deviates from track and tells ATC when he can get a word in sideways. Ooops! On the other hand, if told to "fly heading XXX" it should suggest that it is for a reason, probably separation. Heading deviation without clearance is far less likely IMO.

Nav aid failure. Well I suppose it depends what airspace you are in and what traffic you get. Not everyone has super-duper modern aircraft with fancy glass cockpits and all the gizmos. The system has to cater for the poor sods at the bottom if the IFR food chain i.e. the lowest common denominator surely?

First language not English. We obviously have different experiences of this!

So, some disagreement but hey, that's life.

[ferris]

All I would have to prove in court is that I did what has been, until now, the accepted (and SRG approved) way of ensuring lateral separation That would get you off the hook (actions of a reasonable man), but if you were executing instructions handed down from SRG, then they would have to explain themselves. It doesn't make the technique right, or safer.

Agree to disagree (as long as you're not checking me;) ).

[Guy D'ageradar]

Ferris, what planet did you actually manage to pass a licence exam on? (Or is it simply that you're best buddies with a certain S'african!)

I would love to know if anyone out there can calculate the required change in windspeed through a 2000ft climbthrough to erode separation between two aircraft that have been locked on parallel headings with, let's say, 7 miles initial separation to give a bit of a margin to see just how far out Ferris's theory of drift is.

At the 7 units in 3 countries (Abu Dhabi included) where I have been Valid, I have never, ever heard of even a proposal of "Track to " separation. Has anyone else?
Funnily enough, parallel headings were accepted at all. Funny thing that, isn't it?:yuk:

[ferris]

This is the sort of entrenched thinking that I am talking about. Put up one decent argument, just one, and I might reconsider my position.
Perhaps you haven't read the thread thru. Just because a technique has been perpetuated since the 1950s, doesn't mean it has any relevence today. Regardless of how many countries perpetuate it.:zzz:
I am not proposing a "track to" standard (although obviously you haven't been valid in the UK- or you would realise that "track to" separation is being applied at aerodromes there right now {read the thread:hmm: }). I am merely questioning the technique described by the thread starter. The standard is a radar standard, and the query surrounds that standard's assurance. I am not even querying 'parallel headings' ( a technique that is still very useful in certain situations).

You can't even work out the drift in order to argue. You just assume and use derision. The old "my positions right, and anyone who questions it is a fool" routine.
Funny? Yep.

[Guy D'ageradar]

Sorry Ferris, wrong again - multiple previous validations in the Uk albeit before any "track to " separation was acceptable. (maybe I'm getting too old!)

I will grant you that I jumped the thread a bit - screaming kids in the background tend to be a bit distracting. However, I beg to differ on who's showing entrenched thinking here. I suggest that you re-read Bern Oulli's two previous posts, he's much more eloquent than I am but I think is trying to express the same idea. ie, we are not only required to provide separation but to ASSURE it. Big difference. As we all know and BO (unfortunate that) has already stated, there are any number of reason that an aircraft may change track while on "own Nav", the risks of which are greatly diminished by the use of parallel headings. I know which I prefer to stake my licence on.

p.s. very disappointed to see the old US of A's lazy spelling methods have reached the rest of the colonies!! Thru :*

[ferris]

Apology accepted.
Now...
there are any number of reason that an aircraft may change track while on "own Nav", the risks of which are greatly diminished by the use of parallel headings Who was talking about parallel headings? The example was a/c on own nav (laterally separated) being put on headings to "assure" sep. You see, I don't think you can support that position with any actual evidence . Prove it. All I ever get in reply is "well, it's common sense". Where is it stated anywhere that a/c on own nav can divert around wx, track to mysterious intermediate waypoints etc etc? The pilots aren't handflying anymore. If they are told to track direct XXXXX, then they push buttons and the a/c does it. Doing anything else requires intervention. As I have stated over and over, I have seen just as many a/c divert around wx while on own nav, as on an assigned heading. If you are under the misapprehension that an a/c on an assigned heading will not divert, then you are setting yourself up for a fall. As I previously said, if pilots are under the misapprehension that if on own nav, they can divert, then that is something that ATC has probably fostered and needs correction.
If you are going to argue that the a/c may not track to XXXXX due to database errors, pilot error, etc etc, it's no different to an assigned heading error. If you don't check the tracking before 'setting and forgetting', it's the same as assigning a heading and not checking.
we are not only required to provide separation but to ASSURE it Furthermore, if a/c are changing level, I don't think you can assure anything with headings. See earlier posts. You even acknowledge that you don't know how much wind shear would be required for you to lose separation in your example (and it would depend on the time involved ie rate of level change). More to the point, we don't plan/buffer for failure of altimeters or transponders, and the a/c are far closer together there. Why do it for 7nm lateral sep (that the a/c will achieve without our intervention)?
As I said, times have changed.multiple previous validations in the Uk albeit before any "track to " separation was acceptable. (maybe I'm getting too old!) Maybe it's time to rethink some of these techniques. Alas, I find many minds are closed on the subject (except maybe the people writing those "track sep" procedures in the UK you aren't aware of, Guy ;) ).

[ukatco_535]

Ferris - the amount of difference in wind speed/direction required to make putting a/c a dangerous proposition would be immense and unheard of within close band levels.

You talk about people not being able to do the calculations to work out how much wind would be required to move the aircraft in question; so what???

I assume you do not know how to work it out either, or you would realise that it would be too complicated, and would need additional information from the pilot to work it out rapidly when controlling aircraft.

However, whether you know how to go about working it out or not is a moot point - though I would be interested in watching any ATCO performing such an in depth geometric calculation whilst on radar - the fact is, the difference in wind being experienced by two a/c in such proximity needed to create such a phenomenon would be akin to divine intervention. And if that happened, we may as well hang up our headsets and let the ethereal beings get on with it.

[ferris]

difference in wind speed/direction required to make putting a/c a dangerous proposition would be immense and unheard of within close band levels You need to get out more. We are working here right now in the Gulf with wind speed changes of 100kts or more over a 3000' interval. In other places I have worked where jetstreams are prevalent, you can get 120kt wind speed changes within 2000' feet or less.You talk about people not being able to do the calculations to work out how much wind would be required to move the aircraft in question; so what??? The point I am making is that is that it is too complicated to work out for each situation, yet to use the technique to provide assurance , surely you would have to work it out? It's the people making the argument for using headings who need to know. That's why. You can't sit there and argue for the use of a technique if you can't even assess it's risk.the difference in wind being experienced by two a/c in such proximity needed to create such a phenomenon would be akin to divine intervention Obviously the big guy is in action every day- you are just too ignorant to realise it.

Now as a very basic example, lets work thru one (just so you get the idea.:hmm: ). In the example used earlier in the thread, we have a square a b

---------------------c ------ d

Aircraft 1 is tracking c to d, a B738 FL230, and a/c 2 is tracking b to c, an A345 climbing from FL200 to FL380and will pass each other at the roughly the midpoint by roughly 7-8 nm. Assuming the controller is comfortable with this margin he locks the headings. The wind at FL200 is 300/30, the wind at FL230 is 300/120, and at FL380 is 300/140. As the wind speed increases as a/c2 climbs, the FMS would normally adjust heading to the right to make good the track from b to c. But with the heading locked, a/c 2 begins to drift left, at potentially 90kts, as he climbs into the stronger wind. As a/c 2 is an A340, so may take up to 3 hours to climb over the 738:hmm: , the drift could be enormous (and in the example may take as little as 2 minutes to lose sep, depending on the wind gradient). Even worse, this drift will not be immediately apparent. Only if you keep monitoring the situation will it become so.

You think this sort of wind would be divine? Well, in the Gulf we work with this sort of wind for about 3 months of the year (now).

Just trying to get people to think about something often considered 'gospel':rolleyes:

[Guy D'ageradar]

I'll keep this quick since I'm on a break at work.

1. Ferris, in the climbthrough you just mentioned, the level change takes place between FL220 and FL 240, therefore, wind speeds at FL 380 are irrelevant.

2. Fact. Pilots are on own Nav have been known to "deviate" the odd mile or so around weather etc. without mentioning it.

3. Fact. Pilots are required to advise any deviation from an assigned heading.

4. Fact. Pilots are required to advise a rate of climb below a pre determined level, according "local" AIP - often 1000fpm.

I have to say that in my experience, pilots are much more likely to advise a change of assigned heading than a small deviation while on own nav. Let's face it, they're not really stupid and don't tend to have a death wish so most recognize that if we assign headings, it's for a reason.

You seem very keen to quote extreme examples of winds etc. and to assume that, knowing of the existence of such winds, we would all choose to ignore them when allocating headings. We're not all stupid either. It's not too difficult to apply a rate of climb or a slightly different heading to acheive the desired result. Going by previous posts, I think I am correct in saying that most of those here in most normal situations would use a heading to do so. To make no allowances in extreme situations would be nothing short of reckless.

Have a pint of black for me next time you're in Dubliners. Cheers

:cool:

[DFC]

Ferris,

You seem to have missed the whole idea of issuing a heading to an aircraft..........i.e. for the controller to position that aircraft where the controller chooses and not rely on the pilot hopefully positioning the aircraft where the controller hopes it will go.

Note the frequent use of "hope" in the above.........not good to say after........."I had hoped the pilot would.....".

What would you say the equivalent RNP for an experienced controller in enroute airspace under moderate traffic load is........i.e. when they put aircraft on headings, how close will they keep the aircraft to the desired track for 95% of the time? (assume an area where 5nm separation is permitted)

I would guess that it is about RNP2.........i.e. controllers frequently vector aircraft along one side of the airway 2 miles from the edge without going outside. Provided that the resultant radar returns or responses do not get closer than the required minimum radar separation (say 5nm) then the required separation has been acheived in a compact piece of airspace.

Compare this theoretical RNP2 figure to the figures I quoted earlier for traffic on own navigation.

As for calculating the drift it is not hard at all.........we simple pilots do it day in day out even when we are half asleep!

Simply put - at 420 Kt for every 7 Kt of crosswind there will be 1 degree of drift.

Each degree of drift puts the aircraft 1nm off track in 60nm

However here comes the crunch - being a good controller and aware of the upper winds you will momnitor the actual tracking of the aircraft atleast every minute or two and issue a correction to the heading. So the most the aircraft is going to get off track is 2nm 95 % of the time provided you do your job properly.

You quoted an extreme case but provided you take charge of the situation and you do you job well the only person who can be blamed for a loss of separation is you.

Note the frequent use of "you" in the above situation.

If you did loose separation, the question I would ask is why knowing the wind situation did you not climb to 1000ft below initially to check that separation was being ensured?

Finally you seem to base all your assumptions regarding tracking on the aircraft's ability to automatically follow a track accurately.

Never assume.

We can quite happily fly the aircraft in heading mode- we change the heading to try and acheive the required tracking or we can even manually fly the aircraft as accurately as we can (wandering over the sky if the winds are shifting and the bumps are hard!). What is important is that we do not have to tell you how we are flying the aircraft provided we acheive the required RNP.

Do you not think that a large part of controller workload in busy enroute airspace comes from having to vector aircraft? If so then do you not also think that moves would have been made to increase capacity (reduce workload) by reducing the requirement for vectors?..........The answer lies in the Eurpean study from where I got those separation figures for parallel tracks earlier.

Regards,

DFC

PS as Captain I don't trust you to save my licence - that's my job.............don't expect me to do anything to save yours! ;)

[ferris]

Guy
Once again...
Fact. Pilots are required to advise of any deviation from track.
Fact. Pilots have been known to deviate a mile or two when on an assigned heading, as well.
So does that make you more right?
The windspeed at FL380 was mentioned just to indicate that the windspeed is increasing with altitude.

It is really irrelevent what rate the a/c climbs at (the time the risk is experienced will be the same whatever the technique). The point being that 'locking headings' has just as much, if not more, inherent risk than saying nothing and leaving a/c on their own nav. You seem very keen to quote extreme examples of winds No, I wasn't. But it became apparent that people holding entrenched views don't believe they could be wrong. Hence the verbosity. All this talk of proving or assuring separation. Just trying to demonstrate that it isn't neccessarly the case.

Cheers, except that I don't drink.:cool:

edited because DFC slipped his post in ...
DFC.
A long post, full once, again, of waffle.
If you had followed the thread properly, you would've read that the original question was why lock a/c on headings they are already doing.
There are many reasons why controllers vector a/c, I just happen to disagree with one of them- the one this thread is about. It is a technique that I have thought about long and hard, and has nothing to do with 90% of your post. I don't expect you to understand, as you are not a controller, but nor do I expect to receive advice on my job from you. The piloting aspects of what happens when we do certain things, sure, I would welcome your input, but I just cringe when you have NFI about what is being discussed.Finally you seem to base all your assumptions regarding tracking on the aircraft's ability to automatically follow a track accurately Yep, with todays modern a/c, I believe they can track at least as accurately, in the situation described, as a controller locking headings.
As mentioned by someone else earlier, this technique is supposed to be a 'set-and-forget' thing, allowing the controller to move his attention to other things. This is one reason why it has always been touted as superior to leaving a/c on own nav. Alleged sep assurance.

BTW- would you deviate around a cell, or fly thru it, if you were flying an assigned heading?
Don't you agree that we are wasting everybody's time by applying this technique, when the a/c are so far apart, and the real risk of collision is so small, yet we take no preacautions about other lapses/failures, which involve the a/c being much physically closer together?
Personally, I am quite happy to front an interview about a loss of sep, armed with the excuse "the pilot deviated from track without informing me". No different to a level bust. Why do we treat it as such?

[ukatco_535]

Ferris

A - I am sure DFC does not appreciate the fact you say he will not understand as he is a pilot and indeed that you think hes has NFI - you are incredibly pompous, arrogant and basically, an A**e!! DFC is obviously a customer, whether of yours or not, but he does use ATC services. His input IS valuable and two-way converation is essential in this business. To simply dismiss someone because they are a pilot as opposed to controller merely highlights your shortcomings.

B - You say that it is a waste of time to use this technique when A/C are so far apart - maybe that is so in en-route sectors, but a heck of a lot of us on Pprune work in the TMA environment, some of our sectors are 35-40 miles wide with a hell of a lot of movements. If we did not apply this technique, we would come to a standstill. Not just me saying this - it is a FACT.

Your arguments have some merits, but as DFC above explained - RNP standards are resultant standards - how you get that result is another matter (manual flying/autopilot). However, I have filed on A/C before because glitches in the software have meant that they climbed above SID levels if a pilot inputs a new heading (an Airbus A/C 6 months ago) - resulting in a change of operations by the company.

What you have to realise - but I'm afraid that you never will, is that other people on this thread (the other 98%) have valid arguments as well.


DFC - As an ex-mil aviator, I understand the drift equation and you are entirely correct, but to calculate it whilst on Radar is a little difficult and time consuming because we would need near enough exact readouts of wind, the pilots true heading, the TAS or RAS, The temperature (if we are being really picky). We would also then need the exact Closest Point of Approach of the A/C then use the 1 in 60 rule. I only mentioned it because I wanted to point out to Ferris what was involved before he started his tirade on people. I say the word exact above several times because if I was being entirely pedantic in the manner of Ferris, I would want these calculations to be as accurate as possible! I do however say the above without having any reserve on endorsing all that you have put in your post.

And I am sure I can speak for the rest of the controllers on Pprune in saying that we value very much a pilots perspective.


:D :D

[DFC]

Ukatco_535,

Absolutely, the mental calculation of drift is a bit much for use at radar especially considering the multitude of tracks, levels and speeds. However you guys seem to get a good feel for the wind after a time at the dispaly and if I remember correctly, on handover the previous controller should have given you an indication of the "heading of the day" and any significant winds.

Speaking of some approach radar people I have "been a customer of", it is nice to see them being able to put us on the centerline of an SRA with a single heading in a 40Kt crosswind............RNP measured in metres!! :)

---

Ferris,

Overall I made two important points previously -

When separation is your responsibility then you must take responsibility.

Do not expect to keep us on our own navigation and then after a loss of separation try to shift blame from you to the pilot. Separation is your responsibility and part of the service you are contracted to provide.

You ask - do we ask before diverting round a cell when on a radar heading.

The answer is absolutely yes. We will never change heading without asking when you are navigating the aircraft.

However when on our own navigation..........we can alter heading as much as we like provided we do not get too far from track.

I have been flying during the period when one of the comets was visible (about 10 years back) - the co-pilot was an astro buff and during the cruise we had a great view. After briefing the cabin we turned off the lights and zig-zaged with gentle banks so that people could get a nice view from the windows..........All in the middle of Europe during the evening.......we never were more than 2 miles off track or so and ATC never said anything.

As for weather........well if I am 90nm from a VOR on a non-RNAV route then I can go to half scale deflection to get round without asking ATC.

Go away and find out how far half scale deflection is for a VOR at 90nm allowing for all the possible errors.

If it was a acceptable practice then controller workload in Europe would be halved and thus capacity increased.

Ferris to head one sky ;)

Regards,

DFC

[PPRuNe Radar]

What more can I add to DFC's post ?? ;) :ok:

[ferris]

ukatco_535
If you want to lower the thread to name-calling, fine. It usually happens when people run out of valid argument. I also tend to find the proponents of this technique to be the pompous ar$e-types. As for the rest of your sycophantic outburst (customers:zzz: ), I quite clearly stated that pilot input was valuable, I took issue with the how-to-do-your-job advice.What you have to realise - but I'm afraid that you never will, is that other people on this thread (the other 98%) have valid arguments as well Well, where are they?

If we did not apply this technique, we would come to a standstill. Not just me saying this - it is a FACT. I assume you work in the UK. It seems, from reading this thread, that there are TMAs in the UK already using a/c tracking as sep assurance. Maybe where you work is a little behind.before he started his tirade on people What tirade? I thought I was sticking to the discussion quite well.And I am sure I can speak for the rest of the controllers on Pprune in saying that we value very much a pilots perspective So do I (as stated). I don't need pilot's telling me how to do my job.

DFC
Great waffle, but your argument sucks.When separation is your responsibility then you must take responsibility No abrogation of responsiblity has been suggested.Separation is your responsibility and part of the service you are contracted to provide That contract is predicated on you following the instructions issued (your part of the contract). If you are told to "track direct XXXXX", then go on comet-watching jaunts etc, how dare you attempt to suggest that it's the controller's who carry the can. If I have determined that by you following your track, then you are separated, your part in that contract is to follow your track.We will never change heading without asking when you are navigating That simply isn't true. I have had, on several occasions, a/c change their assigned heading without advising me (usually due to freq congestion). There was a pprune thread on the middle east forum about one such occasion (titled 'a night to remember').we never were more than 2 miles off track or so and ATC never said anything Clearly the mistaken belief that you can wander around when on own nav needs to be addressed. As mentioned, the UK seem to already be at the point of basing sep assurance on it at some locations. Despite what you say, you cannot legally alter heading when on own nav, unless for track-keeping.

As for your attempt at muddying the waters with half scale deflections etc.... I thought it was axiomatic that we were discussing RNAV here.If it was a acceptable practice then controller workload in Europe would be halved and thus capacity increased I can only assume you are talking about some method of doing away with all vectoring. Not what this thread is about. But I do have an open mind- unlike most.:hmm:

[Roger Standby]

Starting to get a little heated here! Obviously different strokes for different folks. Different techniques and theories in different parts of the world. I think along the same lines as Ferris and I'm sure it's to do with way the training is done/perceived. What works for you, works for you. I think if you sat in either environment and observed for awhile, you couldn't pick one and say it was wrong.

What I can't understand with the bulk of the responses is that in modern aircraft tracking direct to a point has to be more accurate than flying a heading (I believe the tolerances are built into the standards to allow for errors/limitations of equipment, not to go flying all over the sky at your leisure. Any deviation from track must be advised according to my books.) Blah, blah, blah about the limited impact on changing winds, the fact is, a heading is NO guarantee that the track will be maintained as required by the controller, therefore where's the assurance?

R-S.

[TrafficTraffic]

A good friend of mine (they do exist!) pointed me in the direction of this thread. I have read the thread and re-read it and I would love to have a go at Ferris and call him names and dispute his posts and theories but I am afraid I do not have a clue what this thread is about (which is actually a similar outcome to whenever London try and coordinate something).

Ferris was quite obviously beaten as a child or dropped on his head (or should have been)

He is also a little upset by the beating the US peso has taken quite recently.

Don't you agree that we are wasting everybody's time by applying this technique, when the a/c are so far apart, and the real risk of collision is so small, yet we take no preacautions about other lapses/failures, which involve the a/c being much physically closer together?

As I am sure one of your heroines(sp?) would say "PLEASE EXPLAIN?"

I agree with you Ferris u saucy minx, It is silly to waste everybody's time when the aircraft are so far apart - by that do you mean 100 miles or 5 miles? (Of course we all know that the actually separation standard is 1 mile the other 4 is just for worry warts) .

I would love to stay and chat more with Ferris but the swimming pool is calling my name...after all talking with Ferris is like Charity Work... wonder if I can claim my PPrune account back on tax ??

TTFN TT

BTW DD please pm me

[DFC]

Clearly the mistaken belief that you can wander around when on own nav needs to be addressed. As mentioned, the UK seem to already be at the point of basing sep assurance on it at some locations. Despite what you say, you cannot legally alter heading when on own nav, unless for track-keeping

I can wander round as much as I like on own nav provided that I remain within the required tracking requirements which are in the case of VOR - half scale deflection.

This means that I can go from half scale deflection right to half scale deflection left and back to half scale deflection right as many times as I like. If you don't like that wiggle across your display then lock us on a heading and you take care of the tracking.

RNAV or not RNAV makes little difference unless you are delaing with routes where the VORs are more than 120nm appart.

ICAO has published the figures I quoted for separation of aircraft on their own navigation with radar monitoring. If you want to use figures less than what ICAO specify then you better have a good safety case.

What is your minimum horizontal separation for opposite direction flights on own navigation at the same level?

What is your minimum separation of the same flights when on headings issued by you (being vectored)?

I can only assume you are talking about some method of doing away with all vectoring. Not what this thread is about

No we are all talking about controllers issuing headings in the enroute environment to acheive separation between flights.

Regards,

DFC

[ferris]

DFC
Why keep referring to half-scale deflection nonsense? I refer you to ICAO Rules Of The Air, Annexe 2, Chapter 3.6.2.1.1 Track-keeping. Do you not fly RNAV (and especially RNP5) aircraft? Even in the Gulf, it's RNP5 only now. I am sure the people in the UK responsible for the 'track separation assurance' would be most interested in your posts. Keep babbling about situations we are not talking about, by all means, but don't expect further responses. Clearly I am not talking about DC3s flying VOR to VOR in 1960. What is your minimum horizontal separation for opposite direction flights on own navigation at the same level?
What is your minimum separation of the same flights when on headings issued by you (being vectored)? In both cases, the applicable radar standard (which, where I work, is 5nm). There is no difference. I think it's important you appreciate this.No we are all talking about controllers issuing headings in the enroute environment to acheive separation between flights. Good try, but not quite. I am talking about specific cases where 2 a/c, based on their cleared routes, are judged to miss by an amount that the controller is happy with- say 7nm (one or both is climbing/descending). A technique often espoused by some people is to ask the a/c their headings, and lock the a/c on those headings, thereby somehow gaining separation assurance. I disagree with the assurance angle of this technique, believing that it provides no assurance, can actually cause as many problems as it relieves, and is a waste of R/T.

TT. Thanks for your input. Most valuable. I am dazzled by the luminosity that is your intelligence, shining like a beacon from your tower of golden Euros.
Good to see the pilots keeping up better than you.

[LostThePicture]

What is your minimum horizontal separation for opposite direction flights on own navigation at the same level?
What is your minimum separation of the same flights when on headings issued by you (being vectored)?
To answer the second question first, the minimum is 5 miles, where I work. The first question could throw up a multitude of answers, but on specified radar-monitored routes, the minimum is 12 miles, where I work. The wording in italics is from the manual at my unit, and to me it means the following:

1) If the aircraft's track does not appear to be following the centreline of the airway or UAR, then I will lock any aircraft at the same level on radar headings. (This is in fact a requirement if track-keeping is not satisfactory, and is stated as such in the manual).
2) If my radar fails, and I am working procedurally, then I cannot have two aircraft on the two different airways at the same level.

ferris, you say in your post that your unit requires aircraft to conform to RNP5. Therefore, an aircraft can be on its own navigation, in airspace controlled by you, and be up to 5 miles away from its "correct" track - or what appears to be correct from your perspective, looking at your radar. This traffic is conforming to the required standard in your FIR. Just because modern aircraft are CAPABLE of much better navigational performance is not the point. By your own admission, an aircraft in your sector could fly 4.9 miles left or right of track and the pilot need not tell you. As someone else said earlier, if the aircraft is not a modern glass-cockpit jet, then the pilot may not even know he's 5 miles off track.

What's my point? Well, say you have two aircraft. You want to climb one through the other. Whether they are running parallel, opposite direction, or on crossing tracks does not matter. You judge they are going to miss by, say, 9 miles. So you do the climb through without using headings. Now, the fact is that both aircraft can be conforming to the minimum navigational requirements in your FIR and have an airmiss, or worse still, hit each other. At the subsequent board of enquiry, the pilots are found to have been conforming - do you think that you would be entirely exonerated from blame?
Alternatively, you could lock the aircraft on headings. Because you're such a professional controller and have checked today's upper wind forecasts, you know all about that nasty 100kt change in windpeed in a 2000ft band of air (!!), and can therefore correct for it in your headings. So you do the climb-through on headings and the two aircraft still have an airmiss. This time, at the subsequent board of enquiry, it is found that the pilots of each aircraft turned slightly into one another to avoid weather.
In the first scenario, the airmiss is ENTIRELY your fault. In the second, the pilots have turned away from an assigned radar heading without asking, which is not permitted and they must therefore take the majority of the blame. However, you will probably still be chided for not periodically monitoring your radar headings. Such is life for a controller with responsibilities.

I grant you that my scenario is somewhat unlikely with modern aircraft, but that won't stand up in a court of law. By your own admission your state requires RNP5. Until it requires RNP2 or better, you should start using radar headings a bit more.

I'd love to be a fly on the wall at your competency exam after you've allowed two aircraft to whistle past each other on their own navigation at the same level. Suffice to say, you wouldn't have validated at my unit controlling like that (and I DO work in the UK).

LTP

[ferris]

It's good, I think, to get all this stuff out in the open.
LTP, I think you've made a good attempt, and I think where you are coming from is exactly where the proponents of this technique reside.
You are, however, sadly mistaken in the nuts and bolts side of several issues.
Firstly, if an a/c appears to be not track-keeping, you would be an idiot to allow it to continue on own nav. Why even mention such stuff? Lets raise the level of the argument a bit, please.
Therefore, an aircraft can be on its own navigation, in airspace controlled by you, and be up to 5 miles away from its "correct" track This, to me, is your biggest misapprehension. It is simply not true. I suggest you find out exactly what RNP means. RNP5 aircraft are extremely accurate at track-keepeing (ops normal). In particular, look at the rate a conforming a/c can drift, and you will find it is significantly less than that possible with wind and headings. It, to me, is why the "lock heading" technique is a waste of time.By your own admission, an aircraft in your sector could fly 4.9 miles left or right of track and the pilot need not tell you Not true. At no time have I "admitted" that. See above. As someone else said earlier, if the aircraft is not a modern glass-cockpit jet, then the pilot may not even know he's 5 miles off track. Not unless there is a malfunction. Not if he is RNP5 regardless of glass cockpit. Even oceanic.I grant you that my scenario is somewhat unlikely with modern aircraft, but that won't stand up in a court of law. By your own admission your state requires RNP5. Until it requires RNP2 or better, you should start using radar headings a bit more No, your scenario is not unlikely, it's impossible (barring system failure).At the subsequent board of enquiry, the pilots are found to have been conforming You see, you do not understand this bit. They couldn't have been. Your scenario is a waste of words. Suggest you do some research.
Suffice to say, you wouldn't have validated at my unit controlling like that Like I said, maybe it's time to rethink some of these 1950s techniques, with the modern technology at our disposal. The entrenched 'old-school' is hard to shake.

[DtyCln]

Ferris, despite some good arguements , you are beginning to sound like a K**b!

There are several airlines who fly through the UK every day, some UK based some foreign, who regularly use all 10 miles of their airways whilst flying under their 'own nav'. Some of the routes that transit overhead London have 'kinks' in them at BPK,CPT, LAM etc. Air2000 as was, would regularly fly 4.9 miles to the right/left of track if it straightened out the kink. Their arguement is that they are 'own nav' in the airway that they filed to fly along! It continues today.

I personally use headings where I think they are needed. Like I said on page 1 of this thread about 15 miles lateral opposite direction, slightly less same direction. The majority of level headed responses on this thread appear to be in the same ballpark. As to why?

Aircraft entering orbits at reporting points due to incorrect FMS inputs. A/C turning at reporting points going off down routes they thought they were on and company filed them a different way. A/C turning for weather and unable to report it due to the R/T being too busy. Own nav'ving an A/C which was transferred on a radar heading from Maastricht with another 15 miles abeam at the same level, only for the A/C to commence a turn back towards Holland to a previous (undeleted) FMS fix. etc etc the list is endless.

As one of your UAE colleagues texted me the other day, "we don't need headings 'cos we don't have any conflicts!"

Ciao

[vector4fun]

I can't speak to the enroute portion of the debate, having spent my entire career in the Terminal option. However, I must weigh in that during the transition from radar vectors to pilot nav via one of the published DPs, I've observed MANY strange things on a radar scope, and it has seemed the more advanced the equipment, the stranger they are. Differend FMS systems behave differently in regard to sequencing waypoints, errors are made in programming the route, and errors are made in setting the correct nav mode.

One example, I've seen multiple occurances where the crew turned out a "radial" from the airport, rather than the VOR as published. Another example, when releasing a crew to resume own nav, it's a fair bet which fix the FMS is actually going to turn towards. The named fix closest to present heading is NOT always the FMS's first choice.

The fact is, to most controllers I know, headings are, (rightly or wrongly), a more reliable method of insuring lateral separation. In fact, the FAA allows us to use less than 3 miles separation between aircraft on diverging Headings. After 25 years, I plan to continue dancing with what brung me for the last few...

:cool:

[DFC]

Hey Ferris,

What is all this super new equipment you have at your disposal. Have you a new ACC? New equipment that the rest of the ATC world would love to have perhaps so that they can stop using headings to provide separation?

Let's say I am on your frequency and you expect me to track due east 090 along an airway. You base separation on that but later discover that I am drifting off track to the south towards the other aircraft which is now at the same level...........what are you going to do?

Regards,

DFC

[ferris]

Ferris, despite some good arguements , you are beginning to sound like a K**b! Fair enough. If the facts are getting too hard, I'll give up. Just because people don't like those facts coming to light, doesn't make them less factual. Unless I missed some of your reasoning? Oh, there isn't any.
You base your dismissal on crews making errors. Therefore there is no merit in my argument, right?
How simple is this? If the aircraft doesn't begin tracking where you expect, when you say "track direct XXXXX", then you don't base sep on this. How friggin basic do I have to make this? Faaarrrck. If the aircraft busts his level, do you use level separation? geeez.The majority of level headed responses on this thread appear to be in the same ballpark. As to why? It's called "convergent thinking".As one of your UAE colleagues texted me the other day, "we don't need headings 'cos we don't have any conflicts If you want to make stuff up, great.:hmm:
VFF
errors are made in setting the correct nav mode I'd bet if you did the research, mode errors would crop up far more often due to radar vectoring. Telling an a/c to "track direct XXXXX" is pretty simple really, and dismisses the errors you are alluding to.
The fact is, to most controllers I know, headings are, (rightly or wrongly), a more reliable method of insuring lateral separation Something I am asking you to question. After all, it's not necessarily a fact , it's a perception .

Ahh, DFC. Embarrassed, and trying a different tack?What is all this super new equipment you have at your disposal It's called RNAV and RNP.equipment that the rest of the ATC world would love to have perhaps so that they can stop using headings to provide separation? They have it. In fact, in the UK, apparently they are doing so as we speak. Whether they know it or not is another thing. Re-read the thread. Obviously there is a massive gap in knowledge between what is happening at various places.Let's say I am on your frequency and you expect me to track due east 090 along an airway. You base separation on that but later discover that I am drifting off track to the south towards the other aircraft which is now at the same level...........what are you going to do? Since your track-keeping is inadequate, I would apply another form of separation, most probably radar vectors- as the most efficient form of a/c nav (own nav)is no longer available to me, I would have to assume responsiblity for nav. I would enquire as to whether you thought ops were normal (in case the crew were engaged in some illegal activity that could be rectified, such as a comet-watching jaunt). I would also be obliged to co-ordinate with the next agency, to see if they would accept an a/c with faulty nav. I would then take steps to have you grounded, so that your navigation equipment could be repaired. Your point?

[Guy D'ageradar]

It appears to me that so far, the only two in favour of using "track to " as a form of separation are both aussies. Must be either the VB or all that time spent upside down!!!

Bon Journée!
:cool:

[AirNoServicesAustralia]

Bottom line is you lock an aircraft on present heading, you in no way ensure they stay on present track. If you aren't ensuring they stay on present track, how can you say you have separation assurance.

You will find a lot of Aussies whether in Oz or working overseas, do use own nav separation, because we have realised that aircraft can navigate more accurately and allow for extremely large wind shifts in flight (as we have in abundance in Oz with the whopping jet streams, and also here in the Middle East) and still stay on track. On too many occasions have I been on the recieving end of a hand off from a perfectly well trained pom, where two aircraft on supposedly parrallel locked headings come to me 6.5 NM abeam and rapidly converging. Each time when the annoyed call is made to the Pom, there is a great deal of head scratching made on their part and they just can't fathom how their separation assurance didn't assure separation.

I know us colonists are just little upstarts who know nothing and could never teach you anything, but maybe just once you could all have a look at the calender, see that is is 2005, and move with the times.

Finally aircraft everywhere have been known to deviate around that little cell of weather without asking, whether on heading or on their own Nav. Both practices are illegal and should be reported as such.

Again finally one point I would like to make, is the number of times I have been given aircraft that were told to maintain present heading, which was at the time the same as their own nav track, and were subsequently forgotten about. Yes, the controller should not transfer them still on that heading and the pilot should report they are on that heading on first contact with the next sector, but in alot of cases neither of these things are done. The result is the aircraft flys through the next waypoint doesn't turn and the poo can hit the fan big time. The alternative is the aircraft is on their own nav and they get the to the waypoint and make the turn as flight planned. This whole heading thing creates workload, and increases risk.

[PPRuNe Radar]

Just for the avoidance of doubt, can those who use 'own nav' track separation advise what RNP they have in force and what the minimum distance is between the tracks they are advocating separate themselves without any ATC intervention ??

Just interested to see if your figures tie up with those laid down by ICAO when deeming routes are 'separated' ;)

Until we also get enhanced downlinked parameters which show the FMC activated route and what mode the aircraft is being flown in, ATC can't be 100% sure where an aircraft on it's 'own navigation' will be going - just the same as when it is on a heading.

[ferris]

We have RNP5 here.

The reason behind your question intrigues me, and I think may be one source of the reluctance discussed. Do you misunderstand ICAO, I wonder, when you talk about recommendations for sep for a/c under their own nav (as DFC did)?without any ATC intervention ?? This is the key bit. I gather you consider "ATC intervention" to be taking control of the headings? I think you are missing the fact that radar identified a/c are separated BY THE RADAR STANDARD, regardless of who is doing what. RADAR is the ATC intervention. If 2 a/c are on their own nav, the RADAR STANDARD doesn't cease to apply, or conversely, the a/c do not have to be on assigned headings in order to use the radar standard. Not anywhere I've worked, and not according to ICAO. The "route standards" you allude to, apply to procedural control . Also, if you have vectored an a/c off the airway, then you tell him to "track direct XXXXX" to regain his planned route, what standard applies while he is off the airway? Radar, of course.

Your last paragraph takes the cake.Until we also get enhanced downlinked parameters which show the FMC activated route and what mode the aircraft is being flown in, ATC can't be 100% sure where an aircraft on it's 'own navigation' will be going - just the same as when it is on a heading Without these 'downlinks', you are prepared to give the pilot an instruction (either headings or levels) which you will rely on for separation, based on his readback (and radar monitoring). Why, then, is that safer than having him readback "track direct to XXXXX" (and radar monitoring)?
If you acknowledge that headings are no safer (as you appear to do by your last sentance) why do people waste their breath with them? To me, the fact that the a/c are asked their headings, before being locked on them, says it all.

The world is moving towards more control from the cockpit (not neccesarily the pilot) with ADS-B, flex- tracking etc etc. The change-resistance shown here is significant. And doomed.

[PPRuNe Radar]

One day Ferris may just answer a question with a straight answer ? How far apart are aircraft when you are monitoring them on their own tracks and are happy to do so ?? Clue .. the answer should be a number of miles ;)

I'll answer your other details when I have more time.

Incident statistics in the UK prove that 'monitoring' radar separation, rather than taking steps to ensure it (however that is achieved), is quite high on the list of causal factors in ATC culpable losses of separation. Ask the Safety Regulation Group of the CAA

Distraction, workload, complexity of other tasks .... a whole host of things can take your eyes of the ball for a period of time.

Might be fine in quieter airspace but keeping your eye on everyone when it is busy and immediately picking up errors which might erode separation when it is already close to the minimum has proven that humans are not too hot at monitoring compliance. Unless you're an Ozzie it seems :ok:

[Nomorecrap]

Aw Gee,

Did we have to play the Aussie bashing card so early in the piece?

Letting that one through to the keeper (b. Warne c. Gilchrist), I will answer PPrune Radars question from my own viewpoint:

Just for the avoidance of doubt, can those who use 'own nav' track separation advise what RNP they have in force and what the minimum distance is between the tracks they are advocating separate themselves without any ATC intervention ??

I don't care - neccessarily know or need to know, if the separation standard is Radar. (Is that not the point Ferris is making?)


Just interested to see if your figures tie up with those laid down by ICAO when deeming routes are 'separated'


You are talking route tolerances for procedural separation surely. (Love that word 'deemed' separated. How ambiguous. How ICAO!)

Until we also get enhanced downlinked parameters which show the FMC activated route and what mode the aircraft is being flown in, ATC can't be 100% sure where an aircraft on it's 'own navigation' will be going - just the same as when it is on a heading.

Scuse me? Then WHY are headings being advocated if this is the case?

Radar is used where higher densities of traffic require closer/lesser separation standards than can be provided by procedural standards - the argument about ensuring separation assurance by considering the tolerances of the stated RNAV or terrestrial NAVAID tracking seems to totally negate the advantage of the Radar in the first place, no?

What distance am I happy to monitor? greater than 3 miles, with a trend to remain greater, be that through diverging tracks, diverging or parallel headings at held Altitudes, diverging headings or tracks at level changes.

Perhaps in the interest of understanding the counter argument I should pose the following question:

At same altitudes, under what criteria / minima would you allow aircraft on own navigation to be left on own navigation? What about aircraft crossing levels?

[ferris]

Personally (to answer your question) if a/c will miss by 7 NM or more making good their present track, then I won't vector them further apart. We actually have automatic acceptance between international units where some tracks (routes) are as little as 8nm apart (silent handovers).
rather than taking steps to ensure it (however that is achieved), is quite high on the list of causal factors in ATC culpable losses of separation Have you forgotten that this debate centres on whether putting a/c on vectors (that simulate the a/c's track) actually provides any separation assurance? You just keep taking it as read that it does!picking up errors which might erode separation when it is already close to the minimum has proven that humans are not too hot at monitoring compliance. Monitoring a radar vector that you have set up is monitoring compliance , and arguably a compliance that is less accurate than own-nav.Might be fine in quieter airspace I gather you are intimating that you have quieter airspace where you work, making your technique more acceptable? Especially considering the extra R/T it involves?

[DFC]

What a joke.

Here are the ICAO minimum ats route lateral separation figures for aircraft on their own nav;

1. Procedural;

RNP 20 - 100nm
RNP 12.6 - 60nm
RNP 10 - 50nm
RNP 5 or RNP4 or better - 16.5nm unidirectional, 18nm bi-directional

2. Radar;

RNP 4 - 8 to 12nm
RNP5 - 10 to 15nm

All of the above must have safety evaluations and controller workload evaluations plus other work to prove that safety will be ensured.

Basically - if you can apply one of the above separations it will be in your operations manual. It is not a tactical day to day issue!

So - provided that the ATS routes have been "deemed separated" because they are 10nm appart and the flights are all RNP5...........that still is;

10 miles separation; and
Aircraft must be on two different published ATS routes!!!

Can't see it catching on in Europe or the US much except perhaps for 1 or 2 quiet hours at night!

-----

Ferris,

RNAV and RNP5 equipment is at my disposal - not yours! You still have decades old radar technology and nothing more!

Regards,

DFC

[TrafficTraffic]

OMFG Chicken little the Sky is Falling the Sky is Falling....

I am going to have to agree with Radar And DFC here on this ....

The enroute radar separation standard is 5 miles - so as long as that is acheived you have separation - it doesnt matter if the acft are on own nav, vectors or tracks. What I am looking at here is how you ensure(assure?) that separation.

I accept Tracks

I accept Headings (Dont crap on about 120kt jetstreams and think that is something special)

I dont accept own navigation for a number of reasons.

Ferris u suggest that by telling an acft to track direct to ABC you are establishing the fact that he will continue inbound on the present track (that he was already doing - so I have no Idea how you would clear an acft to do something that he was already doing - but you are the expert on RT aren't you!)

What I am missing is if you have two acft crossing with a predicted min distance of 7 nm you fix it by telling them to keep doing what they are doing? (Im not even being sarcastic here just correct me if I am wrong).

Now under RNP5 Track Keeping these acft could stray by say 2 miles each therefore leaviing you with 3 or 4 miles - is that correct? But if they were locked on headings 5 - 10 minutes before the CPoA notwithstanding atmospheric anomolies, acts of god, or an ERJ 145 in climb the +/- 7 miles would remain.

I am open minded when it comes to this sort of thing F but u may have to convince me a little harder (and a little simpler) of the merits of what you are suggesting.

TT
(Poolside)

[EuroATC]

In response... first.not sure what my location says but i'm now in Montreal Canada. I also have worked in 3 countries, 4 licences and everyone does it different.

FACTS.

1. A direct track to a waypoint is more accurate than a heading.. no one can dispute this. I have seen 30-40 kt wind changes in 2000 ft. I have been burned before by locking headings.

2. Heading or track.. pilots will deviate without telling you, I don't care who you are and where you are from, it has happened to me. Pilot".. oh forgot we were assigned the heading".. Locking a heading assured NOTHING.


The problem here is that ATCO's are resistant to change.. ohhh that's the way it's been done for years and years and years therefore it's correct.. Well times are changing. Out with the old and in with the new, use technology to our advantage. Once we understand how these aircraft systems work, let's use them to seperate airplanes. Keep pilots in the picture of what we're dong in the radar room..."ie. cleared direct to xyz.... i'll be descending traffic 5 miles off your left side.."

And for Guy d'age... Go work above FL 290.. you'll see the differences in wind!!! hahahaha.. you low level guys :)

[Spuds McKenzie]

At least Guy won't have to move to Aix-en-Provence once the French decide that they won't support Geneva being the location of the FBA Alps... ;)

[DFC]

Traffic,

You have hit on a very important point.

In a modern aircraft on our display we can have a readout of;

a) Magnetic Heading - what we use most.

b) True Heading

c) Track

Now when told to fly on a heading we will flay on that heading and if we diverge then we are in the worng.

What we can also do is change our display and when requested fly on a particular track. If we diverge again it is our fault but beware of the ICAO limitations.

Bothy of the above effectively mean that we put in a 3 digit figure and maintain that - no waypoints, no turnpoints, no chance of entering DUB for Dublin when we are in Ferris' play area!

This use of track must be done in conditions which allow for the pilot's/ the navigation system's ability to maintain that track....basically is the pilot and aircraft combination able to maintain an assigned track as well as a controller using radar vectors?

So perhaps we could have;

ABC123 report your track.............track is 090 abc123.........abc123 track 095 until advised.

Nothing much different there from the well known system of giving heading instructions and I believe that it could be safer

Provided

that the procedure is accepted and published by ICAO and/or in AIPs and when the following happens;

ABC123 report your track.............track is 090 abc123.........abc123 track 090 until advised

The pilots must take the aircraft out of the normal navigation sequencing mode and place it on a track i.e. the same way we do it when assigned a heading - put it on the bug!

Now that could work - if it is implemented. Not until then though cause confusion will abound and safety is not assured.

Regards,

DFC

[ferris]

DFC
Can we get a reference please for your quoted figures. Because lets face it, do they make any sense to you? According to you, an RNP5 a/c can be 5nm off track, but if you are flying down an airway 10nm laterally from another airway, on which there could be another a/c 5nm off track, ICAO says that's OK? Fat lot of good all that garbage is. Either you are using the radar, or you are not. How you are using it is a different issue, and hopefully what this discussion is about.
According to the ICAO Navigation Systems Panel (responsible for DOC9613) the lateral error for satellite updated INS RNP a/c is 100 metres (and if you read the documents there is actually a lot of fat in that), leading to the Sep2004 recommendations for RNP1 and PRNAV. This error is for a/c up to and including RNP20.
If you want to really get down to it- the way that a/c nav system manufacturers achieve RNP5, actually means they are achieving far greater accuracy. You would have to "dumb-down" or "intentionally cause" an RNP5 nav system to actually achieve such poor performence as the RNP5 theoretical figure. As yet, there is no known system that achieves the RNP5 standard, that is not incredibly accurate. Even if one existed, the RATE of drift allowed is miniscule.

TrafficTraffic
What I am missing is if you have two acft crossing with a predicted min distance of 7 nm you fix it by telling them to keep doing what they are doing? That is a technique espoused by various people, both where I work and on this thread, as sep assurance. It what this thread is about. Is the weight of your wallet cutting off the blood to your brain? Hopefully after 5 pages you've caught up. Now under RNP5 Track Keeping these acft could stray by say 2 miles Well, no they can't, not in the time-frame we are talking about. The RATE at which RNP5 a/c can drift, is far smaller than that which a/c on radar vectors can drift. I disagree that locking headings is as safe or safer than allowing a/c that would miss by 7nm or more, to continue on own nav.

edit (becaue DFC slipped his post in). DFC. I still don't see the advantage of telling you to do something you are doing, whether that's track or heading. I agree that telling you to continue to make good your present track is safer than saying "continue present heading"- but why would we do it? As stated by someone before- nav tolerances are not there for you to exploit. It is incumbant upon you to track as best you can, at all times. Not even for comet-watching:rolleyes: unless you seek prior approval. Such is IFR life.

[LostThePicture]

Well this is fun isn't it? Really flogging this one to death aren't we?!

ferris
I suggest you find out exactly what RNP means.I know exactly what RNP means. In the case of RNP-5, which we both use, any given aircraft would be expected to be within 5 nautical miles of their intended track for 95% of their flying time. Kindly let me know if you disagree.

Now like it or not, if we operate in RNP-5 airspace, we should separate all aircraft as if they were RNP-5. Yes, we both know that the vast majority of aircraft can do much better. That's not the point. Until ICAO, or our respective aviation authorities, come to our respective workplaces and decree the airspace to be RNP-1, your argument holds no water.


EuroATC
The problem here is that ATCO's are resistant to change.. Not exactly, no. The problem is that those who prescribe our separation standards are resistant to change. The cogs of bureaucracy grind painfully slowly. Until the Required Navigation Performance Level in my airspace is improved, I'll keep doing my job the way that my organisation requires it to be done.

DFC has kindly furnished us with the ICAO minimum lateral separation requirements for aircraft on their own navigation on prescribed routes. For RNP-5 airspace, this is "10 to 15 nm". Note that these are radar monitored routes.

Back to ferris:
According to you {DFC}, an RNP5 a/c can be 5nm off track, but if you are flying down an airway 10nm laterally from another airway, on which there could be another a/c 5nm off track, ICAO says that's OK? Fat lot of good all that garbage is. Either you are using the radar, or you are not. Oh dear, oh dear. Your almost total lack of understanding is exposed for all to see. Part of the above is correct. Technically, two RNP-5 aircraft flying on two airways, 10 miles separated, could fly over each other in the middle of the two routes, and still be more than complying with RNP-5. See my first paragraph above. These routes, however, are radar-monitored, so if the aircraft are not on the centrelines of the airways, you either ensure separation using headings, or you use vertical separation. You are "using the radar" to ensure that the aircraft are following the routes! The UK CAA actually requires radar-monitored routes to be at least 12nm apart, so one could be watching a DVD or reading a book, and hopefully the worst case scenario is that the aircraft will still miss by 2 miles. 95% of the time anyway! ;)

I'm willing to admit that locking an aircraft on its present track, rather than its present heading, would be a better way of ensuring separation. But this is not in my procedures, so I'll keep using headings. More than likely because not all aircraft that fly in our airspace are capable of flying a given track accurately.

I don't dispute that two modern jet airliners are probably better left alone on their own nav if they're going to miss by 7 miles. But my unit's procedures, together with the fact that my airspace is ICAO RNP-5, mean that I can't do that and say that I've ensured separation. Such is life.

LTP

[divingduck]

Ahh, robust debate.

Guys, both neither side is definitively right or wrong...there are many ways of skinning a cat.

Here in Muscat, we are able to use "continue present track" Just as we can do the heading thing.
For the info of anyone flying through our patch...we have airways that are parallel exactly 8nm apart, 3 of them entering UAE (Ferris's) patch to the south east of Dubai. If we attempted to lock them all on headings the airspace would be a complete shambles. BTW two of those tracks are for descending aircraft, the middle one for overflying stuff.
regardless of how much or little traffic you are working, you simply cannot do it here. No room, no time, too much metal flogging through.

I have seen the lock on headings go horribly wrong, in Perth of all places. An examiner who had this "you must lock them on headings if going within 10 miles" rule did just that. Guys going north came out of a 40 knot easterly into a 150knot westerly, the one descending did the opposite. result? about one mile and some angst. The examiner got busy with an emergency and didn't see the track crossing over.
one of the ex PATCO guys in Perth had a far simpler solution... "don't wander off track without talking to me first!" Great phrase, and no one ever did!

BTW TT pm in your inbox!

cheers all, corners out, ring the bell, next round....

[ukatco_535]

Ferris

To paraphrase you, 'if a/c tracks will provide you with 7 miles separation, you will not vector them apart'

So if you are going to get say 7.5 miles, you will use vectors??

What is to stop these vectors from resulting in less than standard separation, bearing in mind the winds you experience?

Any answer to the above question will validate the arguments for locking a/c on headings.

:D

[AirNoServicesAustralia]

Hey Diving Duck, having worked the super big chunk of airspace down south of Oz, I can attest to those wind shifts. For that reason, locking aircraft on headings is dangerous.

UKatco, I don't know about you but when I go to vector, whether for separation or sequencing, I don't go for parallel tracks, I decisively turn the aircraft so the windshift is irrelevant.

BTW, in response to all those "well it must be because you have more time there", and "well it's because your airspace is bigger", or " it's because you are quieter there" comments, check up on some movement figures boys, and compare that to number of controllers moving the metal, and see who is really quiet and who is really earning their money.

And also for the guy who keeps making the point that there is the danger that you will be cleared to Dubai and put in DUB (as in Dublin) and as such flying under own nav is fraught with danger. First off... Yeh right??!!!!??, but second of all, if you are landing in Dubai, you will never be cleared direct to Dubai, but instead at best to the final approach fix, and if you are overflying you will never be cleared to Dubai, as it is on none of the airways, Sharjah (ie. SHJ) is the crossing point for all the airways.

So try again.

[ferris]

LTP
Your almost total lack of understanding is exposed for all to see Yeah, right. I just love the attitude; I agree with what you are saying, but until 'someone' tells me to do it differently, I'll keep doing it the old way. And in the meantime, you're wrong.:yuk: I'm willing to admit that locking an aircraft on its present track, rather than its present heading, would be a better way of ensuring separation Ever heard the expression "fat, dumb and happy"?

ukatco_535
So if you are going to get say 7.5 miles, you will use vectors No, the opposite. If I am going to get more than 7nm, I won't turn them off track, further away from each other. If I am going to get less than 7nm, I will use vectors to turn them away from each other. I am not saying you should never use vectors (use them all day every day). This was discussed earlier. I just disagree with locking headings to somehow assure a separation that was going to happen (if a/c continued on their present track). As for monitoring those vectors- of course, you must monitor your vectors to ensure the required result is being achieved (an increase in lateral spacing).
What is to stop these vectors from going wrong? Well, without explaining vectoring 101, hopefully I would've picked headings that turn the a/c out from each other (a "decisive vector" as ANSA put it). If I need to, then adjust the vector. Vectoring increases workload, no doubt about it, and is one of my major beefs with this heading lock thing. Locking a/c on their present heading is not necessarily increasing spacing, nor is it done to increase spacing- it's proponents argue it just assures the present spacing. I have been attempting to argue that it does no such thing.Any answer to the above question will validate the arguments for locking a/c on headings I think not.

BTW. DD et al. Did you like the comment earlier in thread about it being quiet here with no conflicts?:p

[Guy D'ageradar]

EuroATC - still haven't figured out how to change your name then!! More importantly, I'm not so much resistant to change (at least not THAT much) as resistant to adopting unapproved procedures which may well be detrimental to my licence.

Spuds - don't start that - we're still waiting for the "you're all moving to Zurich" bombshell! :ok:

Ferris - have you had etisalat hardwired or what?

must go - another 6 inches of fresh!:cool:

[PPRuNe Radar]

The non serious stuff out the way first ....

Nomorecrap

Aw Gee, Did we have to play the Aussie bashing card so early in the piece?

So early ?? It was at least 11 hours after this Pom bashing comment. Ironic humour, such a British thing don't you think, but you have mastered it well :ok: ;)

You know us colonists are just little upstarts who know nothing and could never teach you anything, but maybe just once you could all have a look at the calender, see that is is 2005, and move with the times.

Now back to the issues.

Ferris

The reason behind your question intrigues me, and I think may be one source of the reluctance discussed. Do you misunderstand ICAO, I wonder, when you talk about recommendations for sep for a/c under their own nav (as DFC did)?

Not at all. The European Region of ICAO has done the safety assessment work through Eurocontrol, and published its guidance for RNAV operations, including separation 'standards' which States might wish to adopt. ICAO EUR DOC 001 RNAV/5 is the name of that document. If any other ICAO Region is also using 'reduced separation standards' from those in the core ICAO documentation, then I would expect them to have assured themselves of the safety and publish their findings as Europe has done. Then there is a logical basis for people to use RNAV for separation purposes, rather than just what they think is personally safe.

This is the key bit. I gather you consider "ATC intervention" to be taking control of the headings? I think you are missing the fact that radar identified a/c are separated BY THE RADAR STANDARD, regardless of who is doing what. RADAR is the ATC intervention. If 2 a/c are on their own nav, the RADAR STANDARD doesn't cease to apply, or conversely, the a/c do not have to be on assigned headings in order to use the radar standard. Not anywhere I've worked, and not according to ICAO. The "route standards" you allude to, apply to procedural control . Also, if you have vectored an a/c off the airway, then you tell him to "track direct XXXXX" to regain his planned route, what standard applies while he is off the airway? Radar, of course.

Some of what you say is correct. The standard being applied is Radar Separation, but unless you have documentation that shows that aircraft operating on tracks separated by X miles meets the Target Level of Safety, then under what basis are you allowing them to have a free rein without any intervention ? Gut feeling ? Or close monitoring, which like own nav (or headings) is not infallible. The route standards I am referring to are ones which require radar and several other non procedural requirements, all detailed in the guidance material - the generic ICAO procedural ones are so far apart that using radar as the separation tool is overkill.

Why, then, is that safer than having him readback "track direct to XXXXX" (and radar monitoring)? If you acknowledge that headings are no safer (as you appear to do by your last sentance) why do people waste their breath with them?

In terms of adherence to a heading, then there is a reduction in the level of system errors which can be experienced when compared to RNAV operations. That is not to say that headings will give a more accurate and predictable track most of the time, it will depend to a large extent on the skill of the controller and the pilot. The controller will have to take account of the wind changes, bear in mind the accuracy which headings need to be flown to by qualified pilots, and of course be aware of the Flight Technical Errors which can occur (incorrect readback, mode selection, etc). Under RNP-5, the 10NM wide swathe of the flights permitted performance (allowing for the errors within the MASPS) would be potentially a lot wider than that for a given heading which the controller is issuing.

To me, the fact that the a/c are asked their headings, before being locked on them, says it all.

Who uses that technique ? Not I, since it will result in 4 transmissions when 2 will do.

The world is moving towards more control from the cockpit (not neccesarily the pilot) with ADS-B, flex- tracking etc etc. The change-resistance shown here is significant. And doomed.

I agree with the first part of your statement. There are numerous workstreams taking place in the European and North Atlantic ICAO Regions, as well as a lot of other Regions too, looking at precisely these concepts. They all come under the ICAO FANS Committee. Change resistance is always present in humans, especially at shop floor level, but ultimately such change does come about and people make things work to provide a benefit. Many of the future airspace and navigation changes will go through exactly the same problems that we have seen and faced in the past.

Nomorecrap

I don't care - neccessarily know or need to know, if the separation standard is Radar. (Is that not the point Ferris is making?)

So you don't need to know whether the distance you are happy to let people wander about in close proximity to each other by whilst on their own navigation meets the Target Level of Safety or not ?? And don't care that there are errors which could easilly turn your good day in to a bad one. Your choice of course .. and your licence.

You are talking route tolerances for procedural separation surely. (Love that word 'deemed' separated. How ambiguous. How ICAO!)

Surely I am not .... I am talking about the tolerances for RNAV tracks which are using radar and controller interventions, in other words those which are NON procedural. ICAO Europe and the North Atlantic publish these, presumably other Regions who have done the work and assured themselves of the safety do so also.

Radar is used where higher densities of traffic require closer/lesser separation standards than can be provided by procedural standards - the argument about ensuring separation assurance by considering the tolerances of the stated RNAV or terrestrial NAVAID tracking seems to totally negate the advantage of the Radar in the first place, no?

No one is talking about procedural separations apart from yourself. ICAO has studied how the availability of radar and RNP RNAV operations can meet its stated Target Levels of Safety and what the 'separation' standards might be for flights on RNAV routes when all these things come together. It is on the basis of what they publish that controllers might like to base their actions on, unless they directly use another technique to reduce sepration even further (headings perhaps ?? :p )

What distance am I happy to monitor? greater than 3 miles, with a trend to remain greater, be that through diverging tracks, diverging or parallel headings at held Altitudes, diverging headings or tracks at level changes.

Monitoring 3NM or slightly greater on RNAV tracks is very brave in RNP-5 airspace, at least if you believe the mathematicians.

At same altitudes, under what criteria / minima would you allow aircraft on own navigation to be left on own navigation?

Personally, if they are same direction going to waypoints with tracks which are diverging by at least 15 degrees and are at least 7NM apart (and the trend is increasing), then I am happy to monitor them on their own navigation. For opposite direction, it would be 12NM in accordance with the instructions laid down by my ATC Regulator.

What about aircraft crossing levels?

See above, why would it be different ? Or did you mean crossing tracks ??

Ferris

Personally (to answer your question) if a/c will miss by 7 NM or more making good their present track, then I won't vector them further apart.

Our philosphies are not all that different ;) However, if the aircraft were crossing tracks then I would want a bit more.

Have you forgotten that this debate centres on whether putting a/c on vectors (that simulate the a/c's track) actually provides any separation assurance? You just keep taking it as read that it does!

We would be as well agreeing that nothing ATC can do will ASSURE separation. In which case, why are we needed :)

Monitoring a radar vector that you have set up is monitoring compliance , and arguably a compliance that is less accurate than own-nav.

ICAO accepts that the vast majority of aircraft operating under RNP-5 will exhibit accuracy which is more in keeping with RNP-1 or less ... however, for the mathematical collision models, they have to take a worst case. And there are still aircraft out there, as well as pilots, which when combined will use the full swathe of 'protected' airspace which their RNP allows. If you have one of these aircraft compared to someone on a heading, then the guy on the heading will more likely fly a more predictable path. But neither will match exactly the track you want them to.

I gather you are intimating that you have quieter airspace where you work, making your technique more acceptable? Especially considering the extra R/T it involves?

The ICAO mathematical model includes workload, and makes assumptions on it. I don't see how 2 transmissions to put someone on a heading and get a readback (assuming you have the right 'heading of the day' to start with) increases workload anymore than instructing someone to route direct to a waypoint and get a readback (also 2 transmissions).

EuroATC

1. A direct track to a waypoint is more accurate than a heading.. no one can dispute this. I have seen 30-40 kt wind changes in 2000 ft. I have been burned before by locking headings.

As a generic statement, yes. But you can't say it is a FACT, since own navigation can also experience errors which could be more than those experienced with a well judged heading.

Ferris

Can we get a reference please for your quoted figures. Because lets face it, do they make any sense to you? According to you, an RNP5 a/c can be 5nm off track, but if you are flying down an airway 10nm laterally from another airway, on which there could be another a/c 5nm off track, ICAO says that's OK? Fat lot of good all that garbage is. Either you are using the radar, or you are not. How you are using it is a different issue, and hopefully what this discussion is about.

The procedural and radar monitored own nav 'separations' appear in the EUR RNAV document I mentioned at the beginning. But these are only applicable in the EUR/NAT Region. Other ICAO Regions would have to do their own work (or adapt the EUR stuff) and then publish them in an appropriate Regional supplement. The EUR document points out that reducing to a 10NM distance between RNP-5 RNAV routes results in a greater number of required ATC interventions and so places a higher reliance on ATC monitoring and communications requirements. It also places reliance on the State to make the judgement as to what is acceptable (15NM to 10NM is the suggested distance band) and suggests that they may wish to consider the implementation of ATC Support Tools such as conformance monitoring/track deviation alerting to optimise the ATC intervention capability and help minimise any increase in ATC workload.

If you want to really get down to it- the way that a/c nav system manufacturers achieve RNP5, actually means they are achieving far greater accuracy. You would have to "dumb-down" or "intentionally cause" an RNP5 nav system to actually achieve such poor performence as the RNP5 theoretical figure. As yet, there is no known system that achieves the RNP5 standard, that is not incredibly accurate. Even if one existed, the RATE of drift allowed is miniscule.

Remember though that RNP is not just about the nav system. In addition to nav sensor error and airborne receiver error, it also includes display error and the Flight Technical Error (the humans !!) leading to a Total System Error. I suspect the latter individual error is the one which adds the most to the RNP figure.

divingduck

For the info of anyone flying through our patch...we have airways that are parallel exactly 8nm apart, 3 of them entering UAE (Ferris\'s) patch to the south east of Dubai.

RNP-1 airspace I hope ;) Or if not, can you point me to the ICAO Regional document which details the safety analysis if it is RNP-5. We could use it in Europe too :ok:




If any insomniacs want to see information on how the EUR/NAT document arrives at its Target Levels of Safety and how it works out the various rates of ATC intervention based on RNP equippage and the route spacing, and hence its recommendations, I can publish a summary on here. Or do a google for the \'Reich model\'

[Spuds McKenzie]

Guy - if any of the units (UAC or TCG) move to ZRH, I'll walk to GVA naked, in winter! ;)

[DFC]

OK, lets change the direction slightly.

Ferris,

When handing over traffic to an adjacent ACC in a situation where you both have radar and direct telephone communications, what is the minimum in trail separation for aircraft at the same level on own navigation on the same route?

Do you put aircraft which have filed the same speed 5 or 6nm in trail and rely on the requirement for pilots not to change speed without telling you to ensure that gap does not get smaller?

or

Does your procedures require such flights to be 10nm (or some other figure) in trail unless some specific conditionsd are met?

regards,

DFC

[ferris]

PPRuNe Radar.
I'll get back to you in due course.

DFC.
You are mixing several different concepts here. But to answer your question; we hand off 10nm, to some, and 40nm to one. The main reason being that we use the smallest radar standard (5nm), and the units we hand off to use larger standards (either 8nm or 10nm). The 40nm is too hard to go into. Obviously we can't hand-off smaller standards than the receiving sector uses.
As to relying on flight-planned speed; no, we don't. But nor do I rely on flight-planned route when using own nav. We are required to restate the route clearance on first contact (which eliminates surprise turns if flying a different FMS route to that filed), and/or the instruction to "track direct XXXXX" is a specific instruction, as is the instruction to fly a specific speed. A lot of what we hand off is still climbing, so you are involved in the dynamics of different types, acceleration, WIND etc etc. What I am getting at is the longitudinal situation is a lot more fluid than the lateral one.
So, good try, but no cigar.
That's not to say I never encounter problems with pilots changing speed without telling me (especially when you are running a tight sequence).

[divingduck]

tee hee...

Actually, Ferris and his mates are supposed to hand off 10nm in trail, no closing....this is many times difficult to achieve:E

but one gets used to heavies at F170 with hercs above and in front..:\

irony button to off position:suspect:

[AirNoServicesAustralia]

Ok DD off topic but I'll bite ;)

We over here love the old scenario where both aircraft are pegged to 280 KTs IAS, 0nly problem being that the back guy is 12,000 ft higher and so is closing by 60 KTs. Always is met my stunned surprise when we very ironically thank the Muscat bods for all their stellar help :E

Cheers.

[ADIS5000]

PPrune Radar

Now that's what I call a post!!

(I have nothing constructive to add to this debate!);)

Edited cos I cant spel........doh!

Regards, ADIS

[DFC]

Feris

Quote;

As to relying on flight-planned speed; no, we don't. But nor do I rely on flight-planned route when using own nav.

You said it boy!!

Knew there had to be an ATCO in there somewhere :D

Regards,

DFC

[TinPusher]

Gudday All....

I've followed this debate with some interest and here's my 10cents worth...

For my money (and given I have a family and a mortgage) the key to it is that I want assurance that sep will be maintained.
Over the years I have found an instruction such as 'make no left/right turns for the next x miles' provides me with that assurance without locking aircraft onto headings. Included with that instruction will be traffic information.
I prefer to operate in an environment where I have NO surprises as they are likely to raise my blood pressure and shorten my working life.
The kind of situation I am wary of is where an aircraft suffers a decompression and commences an emergency descent along with a turn (as I understand such a situation would require) into traffic. While in this situation they no doubt would 'miss' I don't like the idea of them turning at each other. As the pilot is in the loop from the outset I would expect them to turn away from traffic.
This technique has saved my bacon only once but once was enough :ok:
Dunno if the above is particularly relevant to the enroute situation... my 10cents worth anyway.
TP

[ferris]

The European Region of ICAO has done the safety assessment work through Eurocontrol, and published its guidance for RNAV operations, including separation 'standards' which States might wish to adopt Alas, the document you refer to is about airpsace design, and has nothing to do with the subject at hand. It makes no comparisons to 'own nav' (as in the heading lock technique) vs vectoring. If you cast your mind back to the first 2 pages of this thread, I questioned whether 'locking headings' achieves anything. There is an enormous assumption out there that it does. I believe that locking headings is often used a mitigation , but is that mitigation sound given the standard of nav these days?
Often quoted here has been the "RNP5 a/c can be 5nm off track" argument. They can be, sure, but they cannot get there in quantum leaps, nor can they get that far off track at a very fast rate at all. In fact, an a/c drifting due wind can drift MUCH faster than an RNP5 a/c on own nav.
If you are trying to use these documents to say what you are, then you are dawing a very long bow, indeed. I could then use other documents (PNAV, for example), to support my case. BecauseThe standard being applied is Radar Separation, but unless you have documentation that shows that aircraft operating on tracks separated by X miles meets the Target Level of Safety, then under what basis are you allowing them to have a free rein without any intervention what constitutes "intervention"? Here is where it gets grey. The 'lock headings' technique appears to exist only in people's minds. I have no documentation available to me which describes this technique, either by definition or function or propagation. IMO, if an analysis was done on the technique for Total Sytem Error, it would be higher than for doing nothing.
Some work must have been done in the UK, as earlier in the thread it was alleged that some airfields there are using 'own nav' as sep assurance. I assume this was vetted etc by SRG, who must have done the work and documentation.Under RNP-5, the 10NM wide swathe of the flights permitted performance (allowing for the errors within the MASPS) would be potentially a lot wider than that for a given heading which the controller is issuing I disagree. See above.Who uses that technique ? Not I, since it will result in 4 transmissions when 2 will do It's what this thread is about. Obviously lots use it (some have responded here). My technique uses no transmissions.We would be as well agreeing that nothing ATC can do will ASSURE separation. In which case, why are we needed Not at all. But there is no point in doing things which assure nothing. Certainly, our days are numbered.Monitoring 3NM or slightly greater on RNAV tracks is very brave in RNP-5 airspace, at least if you believe the mathematicians Only if you mis-use the maths. Drift rates, again.I don't see how 2 transmissions to put someone on a heading and get a readback (assuming you have the right 'heading of the day' to start with) increases workload anymore than instructing someone to route direct to a waypoint and get a readback (also 2 transmissions). Because proponents of the technique would have you make further transmissions to 'assure sep' (the a/c are already tracking XXXXX).In addition to nav sensor error and airborne receiver error, it also includes display error and the Flight Technical Error (the humans !!) leading to a Total System Error And what is the TSP when a/c are taken off their own nav unnessarily (IMO)? Is the solution worse than the thing it is mitigating against?

Cheers.

[TrafficTraffic]

It makes no comparisons to 'own nav' (as in the heading lock technique) vs vectoring.

I am sorry but if I lock an aircraft (or two) on the their present headings - this is vectoring - the aircraft are on a heading this is not own nav - it is vectoring...dont get confused my little Sandpit Crusader.

It's what this thread is about. Obviously lots use it (some have responded here). My technique uses no transmissions.

Thats not quite true is it F? You still give the "Track Direct XXXXX" dont you? Just to be sure?

[ferris]

I am sorry but if I lock an aircraft (or two) on the their present headings - this is vectoring - the aircraft are on a heading this is not own nav - it is vectoring True, but without splitting hairs I believe there is a big difference between actually turning the a/c away from each other as opposed to locking headings. Poor choice of words.You still give the "Track Direct XXXXX" dont you? Just to be sure The track direct has to be issued no matter what (here), so I don't count that. Again, I should've said "no extra words".

[divingduck]

There is an extra transmission in vectoring that no one has mentioned yet... "resume own Nav, track..."

Don't have to do that with own nav.

[TrafficTraffic]

Ferris

I accept your apologies


DD

There is an extra transmission in vectoring that no one has mentioned yet... "resume own Nav, track..."

Thats the same if you say continue present track - isnt it???

I dont mind saying heading or track (despite what F says) but some positive control still needs to be exercised if they are less than the prescribed minima for just monitoring - whenever that distance is specified - (I think for Nerc it must be 50 nm miles ;)).

I still find it strange that if an aircraft was on his own nav to say OSN that you would then say ...track direct OSN.... is that the idea? How do you guys separate climbing traffic opp direction? It just seems funny to tell a pilot to keep doing what he's doing in an effort to assure separation...

[ferris]

How do you guys separate climbing traffic opp direction? It just seems funny to tell a pilot to keep doing what he's doing in an effort to assure separation... I'm not sure what you are getting at. I don't care if they are opp direction, same direction, converging, diverging, whatever. If they will miss laterally by 7nm or more, then I don't believe I need to do anything. Especially asking them their present heading and then telling them to continue on that heading. That is telling them to do something they are already (in a fashion) doing which, IMO, is worse than doing nothing.
If you mean what do we do if they are opp diection and not going to miss laterally, then I'd cut them off or vector them so that I would achieve lateral.
We have a requirement to state the route clearance on first contact. Generally this will mean directly to the end of the FIR (it's pretty small), or may include an intermediate waypoint. IMO, I have aquitted my responsibility for the a/c's tracking. So I would not say "continue present track" as the separation scenario approached. I would say nothing.I dont mind saying heading or track (despite what F says) but some positive control still needs to be exercised if they are less than the prescribed minima for just monitoring Firstly, I would say if the routes are parallel, you may have a point. Purely because ICAO says so (they may change this in the near future). But if the tracks are converging or diverging, it's open to interpretation. Secondly, define "positive control".

[vector4fun]

1. Procedural;

RNP 20 - 100nm
RNP 12.6 - 60nm
RNP 10 - 50nm
RNP 5 or RNP4 or better - 16.5nm unidirectional, 18nm bi-directional

2. Radar;

RNP 4 - 8 to 12nm
RNP5 - 10 to 15nm



Owwwww, now my head hurts. :ugh:

I suppose I'm doomed to a life in a vector sector in the States. Not bright enough to remember all this minutiae. 3 miles or a thousand feet. Less if headings diverge by 15 degrees or more. (20 is a good, safe, round number) I vector aircraft 4-5 miles apart about every 3 minutes on a busy day. And probably have a VFR aircraft somewhere in between them.

One of these days those heathens at ORD, ATL and DFW are going to have to catch up with the rest of the civilized world...:E

[DFC]

vector4fun,

I suppose I'm doomed to a life in a vector sector in the States. Not bright enough to remember all this minutiae

No need to worry, those figures are used by ATS authorities to determine when aircraft on such routes are separated when on their own navigation. If you had such routes, or could use such figures, it would be specified in your local procedures most likely as a single figure.

---

Traffic,

I dont mind saying heading or track (despite what F says) but some positive control still needs to be exercised if they are less than the prescribed minima for just monitoring - whenever that distance is specified - (I think for Nerc it must be 50 nm miles

I travel up and down the Daventry Sectors and through the clacton Sectors on a regular basis. Since we are not always on a heading, the minimum separation must be less than 50nm and closer to the 12nm that someone earlier said. Whenever we are near the middle, we are nearly always on a heading.

---

Ferris,

Based on how accurate you think aircraft navigate using RNP5 or RNP4, provided that they are told to route direct (point), direct (point), direct......, what do you think the minimum lateral separation should be between such aircraft on the North Atlantic where the current lateral separation is 60nm?

I know there is no radar monitoring but if you are happy to use 7nm when radar monitored in RNP5 you must considder that simply icreasing this to 60nm in the absence of radar monitoring extremely excessive.

Furthermore, procedurally when you have aircraft diverging on tracks separated by 45deg you procedurally have lateral separation. Do you with two aircraft overhead an FIR boundary point put them on 45 deg separated tracks and place them at the same level or climb one through another with less than 5nm radar separation?

If you say no then why not.......you have procedural separation?

Perhaps that points out the fact that separation standards must be as laid down by the authorities and not made up by an individual on a day to day basis.

Regards,

DFC

[VectorLine]

Isn't this getting awfully deep and unmeaningful?

It is clear that different techniques and standards are applied at units around the world. But the long and short of it is that ATC endeavour to maintain at least the separation minima set out in their unit MATS part 2/local instructions.

There will always be a certain amount of interpretation in the techniques and rules [PERCEPTION - recent attendees of NATS TRM will see what I did there!], so argument will always rage on.

At LACC, the direct track is used as well as heading assignments. Some airways between certain points are 'deemed separated ' according to MATS part 2.

However, unless using the procedural separations laid out in MATS part 1 all separation is radar monitored and therefore, as Ferris has argued earlier not proven. This phrase seems to have crept into OJTI at some point and although it's meaning is understood by the OJTIs and trainees, it is not used in the literal sense.

Happy tin pushing folks

[ferris]

DFC
I really don't understand what you are on about.
Yes, I do think that 60nm is excessive, especially as you pointed out that ICAO have laid down 18.5nm as the lateral sep for RNP5 a/c in a procedural environment. I don't think anyone is going to care what I think.If you say no then why not.......you have procedural separation? Best you leave the controlling to the controllers. 45 degrees between tracks is not a separation standard- I think you have misunderstood something somewhere. There are lots of variables involved- not the least of which is the distance from the crossing point- however, I won't get into it.
Aside from that; if you are asking would I be happy to use a procedural standard, even though radar was available, and that standard allowed a/c to be closer together than the radar standard, then yes, I would be perfectly happy to use that (if it was allowed at the unit). I have done so in the past (sight and follow is one of the best examples). Perhaps that points out the fact that separation standards must be as laid down by the authorities and not made up by an individual on a day to day basis How you get to this statement, I just don't know. I do agree that individuals shouldn't be making up their own standards, but I am not advocating that. I am questioning a technique , not a standard, which indeed appears to have been made up somewhere along the line and perpetuated thru the years, because I can find no actual definition, reference or official sanction of any kind of that technique in the docs available to me where I work, or have worked in the past.