3 minutes separation, Longitudinal or Radar

[GroundBound]

Many moons ago, when I learnt ATC separation standards the distinction between procedural and radar separation was much clearer, and I thought (!) I understood longitudinal separation.

My understanding is that longitudinal separation is a time based separation, relative to a point which can be easily identified by aircraft flights (e.g. VOR, NDB or way point with today's wizmos). Effectively, it is based on position reports, pilot and ground-based estimates, and can be applied without radar. Nowadays, there seems to be some blurring of understanding.

For example, if a Letter of Agreement between 2 units defines something like 20nm or 3 minutes, I believe that 3 minutes is still a procedural separation, even though it may be dependent on having radar confirmation of the flights' positions (rather than relying on pilot reports or ground based calculation of estimates)? In other words the radar confirms the accuracy of the flights' positions, which allows a reduced longitudinal separation of 3 minutes (procedural) to be applied.

My understanding of radar separation is that it is horizontal distance separation, based upon the displayed position of flights on an electronic device (e.g. 3/5/10 n.m).

This raises the question whether a 3 minute separation being applied at a boundary point between two units, in accordance with the Letter of Agreement) is radar separtion or procedural separation.

Anyone care to comment?

[Plazbot]

I would say neither. It sounds more like a traffic management tool.

[Duke of Burgundy]

Grounbound - I would say that your "letter of agreement" would probably say something to the effect that 3 minutes longitudinal separation is permitted provided that both aircraft are continuously radar monitored and the actual distance between them is never less than 20 miles rather than saying that either 3 minutes or 20 miles is acceptable.

In the UK 3 minutes separation is permissible with similar caveats and it is definitely a procedural separation.

[GroundBound]

D of B

yes indeed, that is very much what is stated - perhaps my original text was a bit short-handed :o .

The significant point for me is that 3 minutes is a procedural separation, albeit requiring radar monitoring to ensure accurate aircraft positions (and thus allowing reduction from 5 or 10 minutes).

However, I have encountered experienced controllers telling me that it is a radar separation - which I find a little troubling - hence my post :)

[5milesbaby]

To me the 3 minutes is longitudinal separation as it is used solely for planning purposes, so that the right levels are sent by the ACT message appropriately.

The radar separation is the 20nm bit, monitored, and in areas permitted to be further reduced to either 15 or 10 nm in trail, or as much as 5nm on headings subject to approval.

However the terms and conditions will most probably state that reduced longitudinal separation may only be used provided that;
1: the direct dial phonelines between units are available,
2: a/c are displaying correct discrete 4 digit code,
3: SSR available at both units,
4: the radars at both units are fully serviceable.

Can you have a longitudinal separation based on radar????? :confused:

[GroundBound]

5M

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Can you have a longitudinal separation based on radar?????
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Well, I think that's where the blurring comes into play.

As I see it, your list of conditions are there to ensure that radar is used (on both sides of the divide) and that the controllers can speak to each other. The key point being that the aircrafts' positions have been accurately determined (radar) rather than being reported (position reports) or computed (estimate calculation). These latter 2 methods being subject to a fair amount of imprecision.

Indeed, the radar has to be there, but that does not make the 3-minutes a radar separation. It remains a procedural separation, employing radar to confirm the accuracy of the estimates.

The intersting consequence is of course, if it is a procedural separation and not a radar separation, can you apply it if you do not have a procedural rating?

[Numpo-Nigit]

"" The intersting consequence is of course, if it is a procedural separation and not a radar separation, can you apply it if you do not have a procedural rating? ""

I know that the definitions of licence ratings are being "re-aligned", allegedly in the interests of European harmonisation, but surely you cannot have a radar rating without the equivalent procedural rating? Otherwise, what do you do if the radar fails - just say "oops" and do nothing to make the situation safe? Of course not!!!

So, the three-minute, radar-monitored, procedural separation is OK for a radar controller to provide where the local instructions permit.

[DFC]

IMHO, it is a procedural separation.

The way that I see it is that say London ACC uses radar to set up aircraft 3 minutes appart and having confirmed that separation, transfers them to say Maastricht.

In the period between the aircraft leaving the London frequency and after establishing communication with and being identified by the Maastricht controller, nobody is providing radar separation. Thus the separation being provided is procedural.

If radar separation is being used at the point of transfer say 5nm parallel or 10nm in trail then a radar handover (transfer of radar control) is required.

It all comes down to the difference between radar monitored and radar separated.

Numpo, NATS controllers at many airfields hold approach radar ratings but no approach procedural ratings.

DFC

[VectorLine]

The 3 minute separation is a procedural separation, used for planning purposes. The requirement for radar and telephone serviceability does not change that. The requirement only allows the 3 minutes to be used.

When we were at LATCC, ATSA's planned levels based on the 3 minute separation. It cannot therefore require a radar validation.

However, if you take the example of S18 (Seaford!), there is also an allowance for silent radar handovers when there is 10miles in trail (constant or increasing) between 2 aircraft at the same level. This allows the 3 minutes procedural separation to be changed to 10miles radar separation by the controller.

In trail is of course longitudinal. So in answer to 5MB: you can have longitudinal, horizontal or level separation based on radar.

To finish - the question now arises: Since, at LACC, level planning is carried out by a planner using radar, is there now any need for the 3 minute separation in the letter of agreement? I would say not, since if the radar was not available, then 3 mins could not be applied anyway.

just my tuppence worth

[Numpo-Nigit]

DFC

We're drifting slightly away from the original topic, I know, but it's a long, long time since I did approach or approach radar. Am I correct in assuming that the system still generally works with a procedural approach controller (who takes releases and allocates stack levels, etc) and an approach radar controller sitting side-by-side? If that is so then, in the event of a radar failure, there will always be a suitably-qualified procedural controller "in the loop".

I must confess that, rather parochially, my earlier response was geared to the en-route environment where the old concept of A, D and radar controllers has long-since vanished. In the current tactical/planner or executive/support controller environment the radar controller must be qualified to issue "procedural" clearances, if only to provide emergency separation, if/when the radar fails. However, I do concede that the vast majority of current en-route radar controllers, at least in the UK, are out of practice with "real" procedural control. That is certainly the view of SRG, who have specifically restricted the options of controllers in the Lands End sector if the Burrington and Mount Gabriel radars fail, leaving us without cover in the south-west. They insist that, after any "emergency" separation is effected, that only vertical or ten minutes longitudinal separation is permitted as controllers are unfamiliar with the application of other procedural separation standards. Let's just hope that the radars keep working, at least in the westbound/eastbound rush!!! ;)

NN

[Scott Voigt]

I'm glad that someone started this thread... This has been very interesting reading for me...

regards

Scott

[Chilli Monster]

Numpo
Am I correct in assuming that the system still generally works with a procedural approach controller (who takes releases and allocates stack levels, etc) and an approach radar controller sitting side-by-side?
Current practice is 1 Controller and 1 ATSA. If the radar goes down either the ATCO will also hold a procedural rating or, if they don't, then they have enough 'get you out of trouble' training to cope.

CM

[GroundBound]

Numpo

Unfortunately it is not the case (any more) that a controller providing radar services has a procedural control rating. It is assumed that in the event of radar failure, emergency separation must be provided. However "emergency separation" does not imply full procedural control - it means take some action to stop 'em colliding, until the radar comes back, or you get rid of them to the next unit. It also means stop anybody else entering your airspace while the radar is U/S - which might be from 2 minutes to 5 hours!

Also, your interesting comment
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I know that the definitions of licence ratings are being "re-aligned", allegedly in the interests of European harmonisation, but surely you cannot have a radar rating without the equivalent procedural rating?
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This does indeed raise a critical question. With the extended use of radar over the years, the procedural separation techniques have more or less disappeared, but residual elements remain, such as this 3 min or 20nm situation. It is clear that a "radar" rating is needed, but it is no longer clear that a procedural rating is needed .

Unfortunately, it is not entirely clear what the re-aligned ratings of the European alleged harmonisation entitle you to do. It appears you can do what you have been trained to do. So, if the training for an Area Control Surveillance (with radar endorsement rating) does not include procedural separation of aircraft, then presumably you cannot provide a 3 minute separation at the boundary, even if it is in the letter of agreement. That would mean either removing the separation from the LoA, or receiving the "full procedural" training for an Area Procedural rating, not much liked because of lengthy training, expensive, difficult etc. .

Your second remark ...
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the vast majority of current en-route radar controllers, at least in the UK, are out of practice with "real" procedural control. That is certainly the view of SRG, who have specifically restricted the options of controllers in the Lands End sector
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Although I think SRG are right, I don't think they being right enough! An ATC rating entitles a controller to practice certain types of ATC. Those types of ATC and the separtions used are well defined by ICAO. Also, it is imperative that a controller's skills are constantly maintained - hence the various rules that are applied stating absences of more than a certain period (e.g. 3 months) will remove a controller's validity to practice at a given position/sector. Thus, if in the regular operation those skills are not being exercised (e.g. procedural control techniques), then it would seem they can not be relied upon in emergency or downgraded system situations. In other words, if you don't use it - you lose it!

VectorLine

I think radar separation is properly described as horizontal separation, which encompasses both longitudinal and lateral separation. Radar separation relies on accurate display of an aircraft's position on a Plan Position Indicator (PPI), (note PLAN position), and requires a minimum fixed distance between aircraft.

Longitudinal separation , as described by ICAO, is a time based separation, normally 10 minutes between succeding flights - although less may be permitted in certain circumstances.

I believe you need a procedural control rating to apply procedural control separations, and that 3 mins longitudinal is a procedural separation (most would seem to agree with this last bit). It bothers me that a number of people (beyond this forum) believe you can provide such a separation with only a radar rating.

[zkdli]

numpo,

The truth about enroute controllers in the UK is that for at least the last nine years these controllers have held what is called an area control centre rating. This has an element of procedural control training in the rating but does not count as a procedural rating. You are right, SRG considers it enough to get you out of trouble in an emergency situation but nothing more. If any UK radar controller says they have an area procedural validation or can control enroute procedurally SRG are only too happy for you to show them in the sim or on live traffic!!!!;)
The current crop of enroute controllers coming out of the college are only going through a very abbreviated procedural course that is in effect a strip moving and recognising a confliction by ten minutes on crossing or following tracks course.

The powers that be say we cannot do our job with out radar, so they are working on the assumption that we will always have radar. :D

[Scott Voigt]

This sounds amazing... If I understand this correctly, you have a radar rating and then one for non-radar??? Did I get that right? Now I think I understand better why you have had to shut down some sectors...

Over here, you are certified radar/nonradar on every position that you work. The assistant or D-side as we call them is the procedural person and that is where you get your first training, you are also to assist the radar person with the radar too...

regards

Scott

[5milesbaby]

Scott, nowadays in NATS all you have is radar controllers who have had an element of non-radar taught to them during training, normally at the college. If the radars ever failed for any period of time, our task is to attempt a 'clear the skies' method procedurally, and then leave the building.

At Swanwick the setup is now we have one controller in full control of the RTf, another sat alongside listening in, fielding the phonecalls and co-ordinations (the planner), providing some advice if necessary or requested, and then our assistant (not to be confused with your definitions) who puts our trusty strips out, and aids with the phone calls when asked.

TC (West Drayton) only differs in the fact they don't have the planner controller, but instead a co-ordinator who can be monitoring several positions at any one time, and doesn't listen in on any RTf directly.

DFC, on most of my sectors going down to 10nm in trail has already been approved and is not subject to a radar handover, as neither is headings to and from a couple of centres.

[TrafficTraffic]

Scott, nowadays in NATS all you have is radar controllers who have had an element of non-radar taught to them

Are you it isn't.....
procedural controllers who have been taught a small element of radar......?

:eek:

[Scott Voigt]

Five Miles;

Thanks for that... I understand most of the set up as I have been able to sit in on the old LATCC. I just didn't know that you couldn't work non-radar in the event a sensor went out...

regards

Scott

[GroundBound]

Scott,

this is the crux of the issue, and the reason I triggered the post.

Because of the shift to radar control, and that some areas have complete radar coverage (sometimes triple coverage), the use of procedural control has effectively disappeared, and the requirement to have a procedural control rating has also disappeared with it. The radar failure situation being covered by emergency separation until the system is emptied.

However, some separation standards remain, as in LoAs between units, and maybe even between sectors, which define procedural separation (such as this 3 minute case). It is my contention that this is wrong, and must either be removed from the LoA, or the controllers must have a full procedural rating - note "just enough of a of a rating for specific cases", as seems to be the case exposed in the UK is not (to me) acceptable.

The problem is raised because a new directive has been issued requiring a harmonisation of ATC ratings, within Europe, which are not compliant with ICAO. It is therefore necessary to determine what a controller is entitled to do under the new ratings, and what he is not.

Unfortunately the directive is not sufficiently explicit. However, it defines a training program and content, referred to as Common Core Content (CCC). It seems to follow, then, that you can do what you are trained for within the CCC. Within the rating training for the new Area Control Surveillance (Radar) rating, there is no training to cover procedural control separation - thus my contention that a controller with such a rating cannot apply a 3 minute separation at a boundary. If of course, some people consider it to be a radar separation, then I suppose you could. :)

[Scott Voigt]

Thanks GroundBound;

Here in the enroute environment, we all come out trained in non-radar. It isn't as exhaustive as it once was, but you still must take your problems when training and show that you can keep them apart with a pencil a strip and a clock <G>...

regards

Scott

[GroundBound]

Scott,

I agree with you. However, there are more and more among us who don't understand what you mean - therein lies the dilemma :confused:

[VectorLine]

5MB

Where does it say that we have to leave the building if we lose radar? What would we be running away from?

Now, if the building was on fire or a terrorist threat....that would be a different matter!

[5milesbaby]

If you think I'm gonna stay sitting in a hot/cold drab boring stuffy ops room while bods fly around trying to work out what the hell happenned then you got some thinking to do, I'll definately be leaving the building. If the radars have gone, there will be a serious reason, and I don't want to know what'll be next.