Positive Separation

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Brayden Manzella
Joined:Thu Aug 22, 2013 7:53 pm
Positive Separation

Post by Brayden Manzella » Sun Jun 12, 2016 2:46 pm

Cross posting from the VATSIM Forums. Good reading material here...


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.
Brayden Manzella
Team Development Manager

Mike Fries
ZSE Controller
ZSE Controller
Joined:Sat Dec 24, 2005 11:02 am
Location:San Jose, CA

Re: Positive Separation

Post by Mike Fries » Thu Aug 01, 2019 8:46 am

I'm sorry but there is no reason to turn someone because their paths might cross in 100 miles. RW controllers can't get fired for this.

Chris Brettrager
Joined:Thu Dec 20, 2007 12:14 pm

Re: Positive Separation

Post by Chris Brettrager » Thu Aug 01, 2019 10:12 am

Definitely agree Mike, very over dramatic note, separation is a common sense topic, at least for me. If I give a guy "descend via" and see that another aircraft may cross his path, I will monitor the situation and restrict the aircraft as needed as they converge, usually requiring no changes as legal lateral separation was guaranteed. Aircraft ground speeds can change greatly over 100 miles dipping in and out of a Jetstream making any predictions subject to great change.

I think this is a good bump in some respects as although the post is over dramatic, there definitely is a need for being aware of ones airspace and not allowing aircraft to climb/descend into arrival/departure paths. It happens more times then I'd like to see. Also, aircraft on opposite base turns should always have 1000ft or more of separation as a form of "positive separation" unless visual separation is applied. This is a topic me and Frank would like to train others on in regards to management of finals sectors.
The Don - I've been here for too long...
"He who stands a top the mountain for everyone to see, does not lead. He who finds a way to move the mountain, he is the one who leads." - Christian Brettrager

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