Radar Separation Minima

[NW3]

Hello All,

I was just wondering if an Area controller somewhere out there could give me a quick pointer in the right direction.

Because I clearly don't have enough to do, I was looking for something in our Jeppy Text Manual the other day... (skip long and boring bit) ... so in other words, in the Horizontal Separation bit, I could see lots of stuff about longitudinal separation (based on time, DME, MNo etc.) but there were two bits I couldn't find.

1) Ignoring radar for a second, are there any lateral limits (i.e. could I be flying along an airway with someone 'on my wing' 20 miles away.

2) What are the minima for Radar control - how close can I be vectored to another aircraft.

Many thanks for any help,

NW3

[Carbide Finger]

Have a look at this document for the UK:

http://www.caa.co.uk/application.aspx?categoryid=33&pagetype=65&applicationid=11&mode=detail&id=222

1) Yes there are.

2) Depends where you are. 5 Miles or 1000 ft is the usual

[Spitoon]

Carbide has pointed you at the UK controller's book of rules. When you read it - or even the bits that are of interest right now - for the first time it might not make much sense! Many bits of it are dependent on other bits to put in into context and this certainly applies to separations. You also need to know that, in the UK but also elsewhere, variations to the national rules can be permitted and are written into documents (MATS Part 2) that are not available on-line. This applies to area as welll as aerodrome ATC units. Some of the local variations that will affect pilots are published in the AIP but quite possibly not everything that that might interest the inquisitive.....or bored.....mind.

Your questions do not have generally applicable answers and sometimes will vary for reasons that are not immediately apparent. Just one example, although 5 miles horizontal separation is the norm, as you go further from a radar head the picture becomes less accurate and suddenly the 5 miles can become 8 miles just because you cross an imaginary line where the calculations of position accuracy exceed a particular value. In most cases there is more than one radar source available and the combined plot accuracy
is OK for normal ops but if one of those sources is out of service....

Hope this helps.

[BDiONU]

2) Depends where you are. 5 Miles or 1000 ft is the usual
Or 15NM for the scarebus 380!!! :yuk:

BD

[Pierre Argh]

Depends where you are. 5 Miles or 1000 ft is the usual yes it is for area (which i note is the direction of your question), however if you're working a Brit Mil radar Unit you can find yourself with 3nms and 500ft (although the reduced vert sep requires agreement from a civil pilot).

DEVILS ADVOCATE MODE ON One has to ask why is it OK to reduce the separation... and if it is justifiable why eveyone doesn't use that as standard?

[HEATHROW DIRECTOR]

In busy terminal areas, approaches to airfields, etc., separation may be 3nm... and even 2.5nm on final approach between certain types of aircraft.

[NW3]

So is it about fair to say that when flying around in the cruise, the horizontal separation (assuming no vertical separation) will be somewhere in the region of 5 - 10 nm (depending on a number of factors), with this decreasing to the normal separations on final that one would find on your bog standard glideslope?

Many thanks for the answers,

NW3

[eyeinthesky]

For convenience (one might argue), some airways are what is called 'deemed separated' which means that aircraft on them at the same level do not have to be on radar headings to prove separation. There are conditions associated with this, one of which is that if they are not on their own navigation exactly on the route they are supposed to be put on a radar heading. But it is inconsistent, for example:

UL602 and UY70 westbound across the North Sea in UK airspace are 12nm apart. Provided traffic at the same level and going in the same direction is following the route on its own navigation, it is deemed separated under radar monitoring. If both of them are, say 1 nm north of the route, they are no longer separated (though still 12nm laterally apart) and they must be on radar headings if at or passing through each other's level. They are also both under the control of the same controller. OK so far?

Now consider the area around LAM. Traffic from the East running into LAM is being controlled by one controller, who may well be using radar headings against his other traffic heading in the same direction. Another controller will be controlling traffic climbing out of the London area heading East which will, in some cases, pass 6 or so miles north of the westbound traffic passing through each other's level with no radar headings, coordination or other contact between the two controllers. :eek: That's Ok too.

No inconsistency there, then!

WRT the original question, there must be some limit set for air routes to be separated without radar (and not the 60nm across the pond). What is it?

[Lon More]

there must be some limit set for air routes to be separated without radar
The old "prescribed separation" (IIRC filled a huge board above Sector 24 back at Redbrae) based on angle and distance from VOR/NDB.

BTW UA34 tracks just parallel to the Dutch-London/Scottish UIR boundary. At one time UK radar coverage was minimal, so was this deemed separated from traffic operating to the east of the boundary? Always puzzled me and never got a satisfactory answer

[camisa10]

there must be some limit set for air routes to be separated without radar
You'll find something about that topic in ICAO annex 11 :
Attachment A- Material relating to a method of establishing ATS routes defined by VOR
Attachment B- Method of establishing ATS routes for use by RNAV equipped aircraft
According to attachment B-minimum spacing between parallel tracks or between parallel RNAV route centre lines based on RNP type 5 (in non-radar environment) should be:
-16.5 NM in a unidirectional system
-18 NM in a bi-directional system
cheers

[safety case]

OK so far most people agree the norm can vary from 3nm or 5nm or 1000'.:)
What about when A/C are on reciprocal tracks and information is received from radar that the A/c have passed, so a climb or descent can commence before the required 3nm separation is acheived :8 and before everyone says you're mixing and matching , I use Radar, but levels for inbound and outbound A/C are generally assigned on a procedural basis.:p
Discuss

[Spitoon]

Discuss. What's to discuss?

There are all sorts of separation - procedural, radar, deemed (i.e. in a unit manual). The ATC game is to make sure that you have one of them all the time!

[Gonzo]

Spitoon, you're forgetting window pane separation (frequently used in the tower......not so much in a centre!) and of course frequency separation.

Eh? What do you mean they're not real ones?????? :confused:

[safety case]

Discuss. What's to discuss?

There are all sorts of separation - procedural, radar, deemed (i.e. in a unit manual). The ATC game is to make sure that you have one of them all the time!


So the point is what is Radar separation:ugh:

[radarman]

Gonzo,
On a par with frequency separation is my old mil area radar trick: when separation gets a bit tight just drop the radar down a range scale. Hey presto! The blips suddenly get further apart :D

[Spitoon]

Gonzo, I wasn't forgetting the one where I look out the window - I'm a TWR/APC man so it's daily business.......but you're right it's just one more separation that is available if the circumstances are right.

safety case asks what is the point of radar separation. Well, I'll treat this as a serious question but I'm conscious that I might be being suckered in here!

Each of the different separations has rules and conditions associated with it. Some separation standards are more efficient (i.e. you can put the aircraft closer together whist complying with the rules). As an illustration, and these are paraphrased and simplified, here are some examples.

With nothing but a stopwatch and radio two aircraft at the same level on the same route have to be 10 minutes apart - that's quite a long way if they're 737s. Have both the aircraft on tracks split by 30 degrees outbound from an NDB and they only need to be 4 minutes apart. It's all to do with how much confidence you have in the relative positions of the aircraft. With radar you can put two aircraft as little as 2.5 miles apart given the right radar equipment and circumstances (remember I said these were simplified examples) - because you know far more accurately where the aircraft are. Before I move on from radar though, one more point - don't be misled into thinking that what you might see on a radar is completely accurate, every radar picture suffers inaccuracies for a variety of reasons. Finally there's the window separation - or reduced separation in the vicinity of the aerodrome to give it its proper title. Here if the pilots or the controller can see what's going on and can make sure the two aircraft don't collide then they're separated. I believe this is the origin of the expression "a miss is as good as three miles".

Like I said before, the controller's job is to make sure that one of these separations exists between two IFR aircraft - which one the controller chooses is determined by the circumstances that pertain at the time. There endeth just about everything I know about the black art that pays my mortgage.

PS - safety case, please tell me you're not a controller!!!!

[Lon More]

two aircraft at the same level on the same route have to be 10 minutes apart Pedant mode on. ICAO standard is 15 minutes.

[Spitoon]

Good point Lon, but, of course, NW3 is from London so I just went into UK mode (believe that and I've got a nice little runner you might be interested in, one lady owner....).

An important point here is that the standards are sometimes varied by different States and some are open to a teensy weensy bit of interpretation.

But if that was the only thing I got wrong I feel chuffed - as I wrote it I felt like I was doing a validation board (and that will give an idea of how long I've been doing ATC - and when I started I used loads of those old fashioned procedural separations!).

[safety case]

safety case asks what is the point of radar separation. Well, I'll treat this as a serious question but I'm conscious that I might be being suckered in here!

Yep:D

PS - safety case, please tell me you're not a controller!!!!

Why ?:hmm:

[5milesbaby]

safety case, even though an awful lot of controlling these days is done with radar, it doesn't mean that a controller has to use radar separation all the time, there are other forms of separation that can be employed even if radar is available which is more expedicious which is all the answers you have above.

Basically, radar in the UK is normally 5 nm. This is extended to 10 nm where the airspace is deemed this is needed due to the distance from the radar heads. In the TMA's this can be reduced to 3nm if within 40nm of a radar head supplying the radar feed (think that's still correct?). However, we don't always achieve this. Radar separation is much closer than nearly any other form of separation so is used when available to gain the optimum for the a/c concerned. Simple?

[SM4 Pirate]

One mile between aircraft when visual separation does not apply (ignoring the vertical plane and wake turbulance)...

Radar, procedural, 'deemed' etc, is all about proving the minimum separation standard exists; that is one mile, laterally, and longitudinally...

All the standards used have a buffer or tollerance built in; but essentially they all achieve the same standard, which is one mile separation.

[Scott Voigt]

One of my favorites over here that I haven't seen mentioned is diverging courses... We got to use that here in the approach control facilities where they are using a single site radar... You get two aircraft that are diverging by at least 15 degrees and you get target resolution (there is space between the two radar targets <we call it green between>.) and we can then discontinue vertical separation, so you can see someone a half mile off your wing come blasting through your altitudes as they pry away from you <G>...

Wish we could use that enroute <sigh>...

regards

Scott

[Spitoon]

PS - safety case, please tell me you're not a controller!!!!
Why ?:hmm:Just in case you're on the other end of the phone and I have to start explaining it then!

[safety case]

Spitoon and 5miles baby

Jesus you two lighten up if people actually read what was posted and not what they think they have read perhaps these forums would be put to better use, instead of just a chat room for the self important and self opinionated :mad:

[ILS 119.5]

So here is a question for all you ATCO's out there. What is the separation between an a/c flying in class a airspace working area control whose standard separation is 5 miles and an a/c working approach control in class d airspace which ajoins the class a airspace but its minimum separation is 3 miles. Is the separation between adjoining airspace 3 or 5 miles?

[eyeinthesky]

Without knowing the exact details of your unit...

I seem to remember that the ability to use 3 miles separation required details already highlighted, such as distance from radar head and so on, but also:

Both aircraft under the control of one controller or co-located controllers where direct coordination was possible (or some-such MATS-speak).

In the case you mention, these criteria would not seem to apply, so 5 miles required. Which makes sense, using the worst case is better than hoping for the best!

[ATCO2]

ILS 119.5 (http://www.pprune.org/forums/member.php?u=76271)

Radar separation is normaly 5 NM, can be more, depends on national regulations. It can be reduced to 3 NM as well and to 2,5 NM on the final approach but within 10 NM only. Radar separation from the next sector is normaly half of radar separation of that one you apply, it is valid also for the next sector to apply the same rule and you are radar separated.

I hope it helps,