ATC 'Maintain present heading' instruction

[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

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
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. Because

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

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.

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...

[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.

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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.

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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.