Positive Separation

Don Desfosse

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Positive Separation
« on: June 10, 2016, 08:07:07 AM »
Cross-posting an excellent description of Positive Separation as written by Christopher Coon on the VATSIM Forums:

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We have a requirement called "positive separation" that in the radar/IFR/class B world anyway means you never have two aircraft in your airspace that require separation that are in possible future conflict. They could be 100 miles apart but if you allow that aircraft into your airspace in future conflict with another, in real world anyway you could be written up for a "box 1" and decertified, washed out or even fired despite not actually losing separation.

I see positive separation violated a lot here so I don't think it's being taught to controllers. I had an instructor level controller working me level at 290 with a crossing restriction at 15,000. Then a couple minutes later somebody went underneath me at 27,000. I asked him why he cleared me down to 15 when there was traffic at 270 and he said "you were two thousand feet above him, we only need 1,000." That's not how separation works. Or another C-level controller who had me on a converging course, same altitude with another aircraft he was working. He descended me before losing actual separation, but we should have never been in that conflict in the first place. When I asked him, he didn't understand his failure to provide positive separation. That's why I don't think it's being taught here.

Positive separation is not about keeping aircraft X miles apart or Y feet vertically, it's about not allowing them into possible conflict in the first place. You should never clear an aircraft into possible conflict with another in your airspace, or allow an aircraft into your airspace if it's in possible conflict with one of yours (you have to resolve the conflict before taking the handoff). In my crossing restriction example, I should have been given no lower than 280 until there was lateral separation ensured with the other traffic. In the converging same-altitude example the controller should have told the previous controller to turn or climb/descend the traffic prior to taking the handoff.

That's positive separation. Converging course with 12 descending to 4 is not separated from someone at 12 descending to 5 whether or not you lose actual separation. If controllers aren't taught positive separation, I don't see how they'll know the proper way to apply visual separation. They need to be positively separated both before and after, before you can use visual separation (7-2-1 of the 7110.65).

Positive separation also means aircraft converging at the same altitude that look like they might lose lateral separation later are not separated from each other even though they're 50 or 100 miles apart. There's no such thing as "I'll turn them away or change altitudes before they get too close" -- if you've allowed that situation to occur in your airspace or between two aircraft in your control, you've failed to provide positive separation and could be disciplined (in real-world, anyway). It's a fundamental part of the job I'd like to see VATSIM teach its controllers before worrying so much about procedures and the other mundane parts of ATC.

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And adding some additional words of wisdom from Wes Miles:

...but for clarification I would add Positive control/separation isn't necessarily ensuring you never have two aircraft in possible future conflict, but recognizing those possible conflicts during your scan, taking corrective action where needed, and being ready to pull the trigger on plans B-D in advance time to where separation is never questioned. I've seen an FAA supervisor apply SUPER-positive separation during a relatively busy day and it ended up causing them WAY too much work (and nearly 3 airspace violations). Try telling controllers at N90 or C90 they should never allow aircraft in their airspace that could be a potential future conflict. In the words of a wise instructor I once had who retired out of D10: "You have RADAR. Use what the taxpayers paid for."
« Last Edit: June 13, 2016, 01:21:53 PM by Don Desfosse »
Don Desfosse
Vice President, Operations, VATSIM (VATGOV2)
Division Director Emeritus, VATUSA

Mark Hubbert

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Re: Positive Separation
« Reply #1 on: June 12, 2016, 09:09:26 AM »
Excellent Post.  I hope that all T/A's and ATM's will read this post and implement this concept into their training programs.
Mark Hubbert
Division Director VATUSA Retired

Ryan Parry

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Re: Positive Separation
« Reply #2 on: June 12, 2016, 11:09:44 AM »
I admire that this was brought up, and I also admire the fact that it appears Division is giving it a stamp of approval. It is something I think we can all work on doing a better job of teaching and practicing.

Sadly, I've seen many instances of hand offs being initiated from a neighboring facility that are already a loss of positive separation. We can't refuse the hand off because a SUP will come along and yell at us (in some cases worse). We can't ask them to turn/ climb/ descend an aircraft because initiating a hand off right over the common boundary (and subsequently busting the airspace) has become the acceptable norm, and complaints about it go unanswered as if it is no big deal. If we can do a better job of teaching all of the fundamentals, positive separation, basic hand off procedures, etc, I think it would greatly benefit the entire Division.

We try to teach this as a "common sense" practice at ZOA, but I think we'll write up something in the Wiki or our CBT's on this. Thanks for sharing this Don!
« Last Edit: June 12, 2016, 11:28:09 AM by Ryan Parry »
Ryan Parry - 965346
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Re: Positive Separation
« Reply #3 on: June 13, 2016, 12:04:22 AM »
I'm sure Don will weigh in, Ryan, but I would love to see a wallop for a controller refusing a handoff because another is setting them up badly.  It would be a great teaching moment.  I've never seen a wallop from a controller about a handoff being refused.  As far as the norms of handoffs and it being ignored, I would like to see it being taken up with that facility's staff and the ATD.  I'm sure the ATDs will be happy to intervene and help address this issue if it is really an issue.

Ryan Geckler

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Re: Positive Separation
« Reply #4 on: June 13, 2016, 04:45:12 AM »
If you get walloped for refusing a handoff with valid reasons, please email me.
Ryan Geckler - GK
VATUSA9 | Traffic Management Unit Director
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David Stone

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Re: Positive Separation
« Reply #5 on: June 13, 2016, 08:42:26 PM »
I'll chime in and say I have to be with Wes on this one. The controller needs to be 'in control' of his airspace, know what is currently going on, what is coming up, and have a plan formulated as to how he is going to deal with it. Another point I noticed while reading is that although he stated his source for 'visual separation' (7-2-1), he failed to provide his source for the remainder of his position. I am always open to discussion and even constructive criticism, and if I am wrong I'll be the first to admit it, not afraid of a little humble pie. But come prepared to prove your point, state your source not your opinion or the opinion you have been taught. There is local policy and there is published policy.
David Stone

Steve Galasso

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Re: Positive Separation
« Reply #6 on: September 21, 2016, 11:36:31 PM »
There is a giant difference between giving someone a crossing restriction and then having an aircraft fly underneath said crossing restriction.  That is definitely not positive separation.  However, to stretch positive separation into saying you can't take a handoff on two aircraft that are in conflict 100 miles out is absurd.  The real concern should be how much time until the conflict.  A conflict 100 miles away with one aircraft on a 090 heading and the other on a 080 heading and they're still 20 miles lateral is going to be a while.  Opposite direction...not so much. 

Dhruv Kalra

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Re: Positive Separation
« Reply #7 on: September 23, 2016, 08:46:12 PM »
There is a giant difference between giving someone a crossing restriction and then having an aircraft fly underneath said crossing restriction.  That is definitely not positive separation.  However, to stretch positive separation into saying you can't take a handoff on two aircraft that are in conflict 100 miles out is absurd.  The real concern should be how much time until the conflict.  A conflict 100 miles away with one aircraft on a 090 heading and the other on a 080 heading and they're still 20 miles lateral is going to be a while.  Opposite direction...not so much.

Also, different techniques apply to enroute vs terminal in this case. Center guys find 20 minutes finding where the problem is and 20 seconds fixing it, whereas guys take 20 seconds finding each 'problem' (because everyone in the terminal environment usually needs something done to keep them separated). It's definitely a tactical vs. grind process.
Dhruv Kalra
ZMP ATM | Instructor | Grumpy Old Man

Brad Littlejohn

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Re: Positive Separation
« Reply #8 on: September 26, 2016, 12:40:10 PM »

Question to everyone here, including the (d)ATMs who may read this.

For those who have noticed this issue, have you noticed if any controllers are asking pilots to maintain visual separation when incidents like this occur?

I ask because I personally remember getting dinged on this by my instructor/mentors back when I was starting at the CTR position. I was promptly reminded that not only is visual separation not applicable in Class A airspace, but it is up the the controller to maintain positive separation in that airspace.

That was 15 years ago. So I wonder if this issue is something that was taught, but simply has been lost between then and now, and like we all agree, a refresher/reminder is needed for all of us, instructors included.

BL.

Rick Rump

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Re: Positive Separation
« Reply #9 on: September 26, 2016, 01:19:45 PM »
"Maintain visual separation" in class A is something I have been hearing more and more as of late (Anecdotally of course). It is one thing we grind in to our guys when they start radar training (As we have some TRACONs that stretch up into the A). Like most of the "toolbox items", bringing it up early and often tends to reduce the occurrence later on.

As an aside, we have definitely taken this overall topic of positive separation to task and I am glad it was brought up. Instead of merely mentioning it and looking out for it in problems, we have purposefully designed problems that actually result in positive, and eventually actual separation and we try to bring it up if we notice it before the first happens to drive the importance of it home. As per usual, sometimes you do not notice you are glossing over or not training something right until it gets brought to your attention (either directly or you realize it from something like this).
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