Visual Separation and You: Dos and Don'ts

Dhruv Kalra

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Visual Separation and You: Dos and Don'ts
« on: December 29, 2018, 09:36:50 pm »
Figured I'd jump in and throw another topic up for discussion here. The concept of how to solicit and apply visual separation. Unfortunately, throughout the process of flying under the control of a number of facilities as well as training controllers within my own, I've found that visual separation is a often misunderstood and misapplied concept. Key examples of this include, but are not limited to:

  • Attempting to apply visual separation in the flight levels

First, in order to establish some definitions, let's look at 7110.65 7-2-1, which states:

Quote from: JO 7110.65X 7-2-1 a. (Terminal) and b. (Enroute)
Visual separation may be used up to but not including FL 180

Yep. Can't use it in Class A airspace. Have to have lateral, vertical, and/or wake turbulence separation. no exceptions.

About the only exception to applying visual separation in the flight levels is to climb or descend through traffic below Class A airspace. For example, if you have a climbing aircraft with traffic above him at 17,000, an aircraft is allowed to climb into Class A airspace after visually separating from an aircraft no higher than 17,000 feet MSL. The reasoning is the instant before the aircraft breaks the plane into Class A airspace visual is no longer being applied and “separation after” will exist. An aircraft at FL 180 is also allowed to transition out of Class A airspace using visual separation if the visual maneuver will be a descent through the altitude of another aircraft at or below 17,000 feet MSL. The reasoning is that separation exists before the aircraft descends and visual is not applied until the descent starts. At that instant, the aircraft will also be out of Class A airspace.

It's important to note that if altimeters are below 29.92, meaning FL 180 is not an assignable altitude and FL 190 or above is usable, any visual separation maneuver out of FL 190 or above would begin in Class A airspace. This is not an allowable application, therefore nullifying transition out of Class A airspace. The reasoning is that FL 180 is still a discernible altitude just not an assignable altitude.

  • Attempting to apply visual separation between aircraft between which a loss of radar separation has already occured
  • Not establishing a form of prescribed separation both before and after the application of visual

These two basically go hand in hand. Visual separation is meant to be used as a tool to expedite traffic which is already separated by another form of legal separation. If you're using it to try and save a deal, tough luck:

Quote from: JO 7110.65X 7-2-1
Visual separation may be applied when other approved separation is assured before and after the application of visual separation. To ensure that other separation will exist, consider aircraft performance, wake turbulence, closure rate, routes of flight, known weather conditions, and aircraft position. Weather conditions must allow the aircraft to remain within sight until other separation exists. Visual separation is not authorized when the lead aircraft is a super.

In a nutshell, when using visual separation to climb or descend through traffic, the aircraft must be positively separated (typically assigned vertically separated altitudes) prior to the use of visual separation. Separation after is then ensured by the assignment of altitudes to both aircraft that will ensure vertical separation, or by headings/courses that will diverge to minimum lateral separation.

You can also use it to waive wake turbulence separation when operating underneath or behind large/heavy aircraft (NOT Supers). When applying this on successive arrivals to the same runway, this effectively means that your "separation after" the application of visual is runway separation appropriate to the categories of aircraft involved.

Either way, it's a tool, not a crutch. Use it wisely and proactively. It goes hand in hand with ensuring positive separation of your traffic!

  • Advising VFR aircraft to maintain visual separation with other aircraft (not used outside of Class B/C and for a very specific use case at the tower level)

Remember that within Class B airspace, VFR aircraft are radar separated from all IFR and VFR aircraft by either target resolution/500 ft vertical (from aircraft weighing 19,000lb or less) or by 1.5 miles/500 feet vertical (from turbojet aircraft and aircraft weighing >19,000lb). In Class C airspace, VFR aircraft are radar separated from IFR aircraft only by target resolution/500 ft vertical.

You can use visual separation to your advantage in these airspace strata to expedite VFR traffic movement, but all too often, I hear it being applied in the pattern at Class D towers. The only time visual separation would apply within Class D airspace would be in a case when you're faced with a Small weight class aircraft (< 41,000lb) performing a touch/go or stop/go after a departing Small+, Large, or Heavy aircraft.

The reason for the use of visual separation in this case is that once the landing portion of the touch/go or stop/go is complete, the Small aircraft effectively transitions from being an arrival to being an intersection departure. We're required to have 3 minutes of wake turbulence separation for a Smal intersection departure following a Small+ or greater full length departure. Advising the Small aircraft to maintain visual separation with the departing larger aircraft is the "out" in this case. The phraseology for this is as follows:

Quote
N12345, report the departing B737 in sight.
Departing B737 in sight, N12345.
N12345, maintain visual separation with the departing B737, caution wake turbulence, runway 1, cleared (touch and go/stop and go/for the option)

We see so little pattern work on VATSIM that this one probably won't come up very often, but it's pretty much the only time you'd hear a controller at a Class D tower issue visual separation, which is why I bring it up.

Hopefully the explanations above give you guys some insight into how and when visual separation can be properly used to help run your traffic flow more efficiently while still maintaining legal separation throughout the process. There are a few other cases where visual separation can be used (successive departures being the most notable) that some of the other r/w guys who work in towers can probably shed some light upon, but these are the ones that I wanted to hit on based on my time spent flying, controlling, and training on the network.
Dhruv Kalra
ZMP ATM | Instructor | VATSIM Network Supervisor

Matt Bromback

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Re: Visual Separation and You: Dos and Don'ts
« Reply #1 on: December 30, 2018, 07:33:46 am »
Hopefully the explanations above give you guys some insight into how and when visual separation can be properly used to help run your traffic flow more efficiently while still maintaining legal separation throughout the process. There are a few other cases where visual separation can be used (successive departures being the most notable) that some of the other r/w guys who work in towers can probably shed some light upon, but these are the ones that I wanted to hit on based on my time spent flying, controlling, and training on the network.

Good post Dhruv!

I was going to ask this specific question about successive departures. I have flown out of MSP many times where they ask "are you able to maintain visual separation with departing B737?" If pilot responds affirmative they provide visual separation in takeoff clearance (and from looking at TCAS we are in the air about 1.5 to 2.0nm behind aircraft) I am assuming they can only do it to aircraft not going to same departure route/gate. I found this in the 7110.65 but wondering if anyone can provide a little more insight as I am curious to this:

Quote
1. Tower-applied visual separation.
(a) Maintain communication with at least one
of the aircraft involved or ensure there is an ability to
communicate immediately with applicable military
aircraft as prescribed in Paragraph 3−9−3, Departure
Control Instructions, subpara a2.
(b) The tower visually observes the aircraft,
issues timely traffic advisories, and provides visual
separation between the aircraft.
(c) Issue control instructions as necessary to
ensure continued separation between the applicable
aircraft.
(d) Do not apply visual separation between
successive departures when departure routes and/or
aircraft performance preclude maintaining separation.
(e) The use of tower-applied visual separation
is not authorized when wake turbulence separation is
required

This is common practice at airports like MSP where they are effectively running single runway ops (arrivals/departures to same runway). Just wondering if divergent headings are required, or can same heading be issued and its up to Departure to separate??
Matt Bromback

Toby Rice

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Re: Visual Separation and You: Dos and Don'ts
« Reply #2 on: December 30, 2018, 09:38:35 am »
Great post, Dhruv.

Good question, Matt. Correct me if I’m wrong, but tower-applied visual separation effectively removes (where allowed) all other separation requirements (except your 3000, 4500, 6000, and intersections, etc.) and simply leaves the tower entirely responsible to ensure the aircraft don’t get within an unsafe proximity.

For example, ATL in real life on a visual approach day will let the IFR to IFR guys on the visual approach compress all the way down to 2 NM of separation at the threshold (provided the 3 to 2.5 for Radar is ensured prior to Tower handoff) by using tower-applied separation to make sure the guys don’t touch. They don’t go usually go less than 2 miles because by the time the lead aircraft exits the runway, the trailing aircraft is pretty darn close to the threshold, which if crossed would be a separation bust.
Toby Rice
ATC Instructor (I1)
Jacksonville ARTCC
VATUSA ACE Team | CFI/CFII | Former HCF ATM
toby.rice@zjxartcc.org


Matt Bromback

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Re: Visual Separation and You: Dos and Don'ts
« Reply #3 on: December 30, 2018, 11:37:48 am »
Great post, Dhruv.

Good question, Matt. Correct me if I’m wrong, but tower-applied visual separation effectively removes (where allowed) all other separation requirements (except your 3000, 4500, 6000, and intersections, etc.) and simply leaves the tower entirely responsible to ensure the aircraft don’t get within an unsafe proximity.

For example, ATL in real life on a visual approach day will let the IFR to IFR guys on the visual approach compress all the way down to 2 NM of separation at the threshold (provided the 3 to 2.5 for Radar is ensured prior to Tower handoff) by using tower-applied separation to make sure the guys don’t touch. They don’t go usually go less than 2 miles because by the time the lead aircraft exits the runway, the trailing aircraft is pretty darn close to the threshold, which if crossed would be a separation bust.

Toby,

I believe your correct in terms of arrival traffic, basically its the whole one aircraft on a runway at a time rule. I have been as close as 1 to 1.5nm from threshold and traffic is still on the runway. That is when you usually hear on the radio "expedite exit traffic short final" :) I have been sent around before particularly when heavy aircraft don't clear the tail over the hold short line, that is always fun :)

Matt Bromback

Shane VanHoven

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Re: Visual Separation and You: Dos and Don'ts
« Reply #4 on: December 30, 2018, 10:26:33 pm »
Great post, Dhruv.

Good question, Matt. Correct me if I’m wrong, but tower-applied visual separation effectively removes (where allowed) all other separation requirements (except your 3000, 4500, 6000, and intersections, etc.) and simply leaves the tower entirely responsible to ensure the aircraft don’t get within an unsafe proximity.

Almost. It’s important to note that you cannot use tower applied visual separation if some sort of wake turbulence standard is required. Example. If you have a small departing behind a heavy, you cannot have less than 5 miles by applying tower visual. You must always have the wake sep, unless you use plane to plane visual.
Shane VanHoven
Minneapolis ARTCC, VATUSA ACE Team | Instructor
Private pilot, Instrument, ASEL
FAA Air Traffic Developmental, Terminal

Shane VanHoven

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Re: Visual Separation and You: Dos and Don'ts
« Reply #5 on: December 30, 2018, 10:41:58 pm »
Hopefully the explanations above give you guys some insight into how and when visual separation can be properly used to help run your traffic flow more efficiently while still maintaining legal separation throughout the process. There are a few other cases where visual separation can be used (successive departures being the most notable) that some of the other r/w guys who work in towers can probably shed some light upon, but these are the ones that I wanted to hit on based on my time spent flying, controlling, and training on the network.

Good post Dhruv!

I was going to ask this specific question about successive departures. I have flown out of MSP many times where they ask "are you able to maintain visual separation with departing B737?" If pilot responds affirmative they provide visual separation in takeoff clearance (and from looking at TCAS we are in the air about 1.5 to 2.0nm behind aircraft) I am assuming they can only do it to aircraft not going to same departure route/gate. I found this in the 7110.65 but wondering if anyone can provide a little more insight as I am curious to this:

Quote
1. Tower-applied visual separation.
(a) Maintain communication with at least one
of the aircraft involved or ensure there is an ability to
communicate immediately with applicable military
aircraft as prescribed in Paragraph 3−9−3, Departure
Control Instructions, subpara a2.
(b) The tower visually observes the aircraft,
issues timely traffic advisories, and provides visual
separation between the aircraft.
(c) Issue control instructions as necessary to
ensure continued separation between the applicable
aircraft.
(d) Do not apply visual separation between
successive departures when departure routes and/or
aircraft performance preclude maintaining separation.
(e) The use of tower-applied visual separation
is not authorized when wake turbulence separation is
required

This is common practice at airports like MSP where they are effectively running single runway ops (arrivals/departures to same runway). Just wondering if divergent headings are required, or can same heading be issued and its up to Departure to separate??

We do a similar thing at my little tower in Southern California. All of our departures fly the same heading for our 2 main SIDs. One goes north and the other goes east. If we have two successive departures that go out the same gate, we’ll give the tracon standard separation because they don’t have a ton of room to pry them apart. But if we have two departures with one going north and the other going east, we’ll launch them 6000 and airborne because all the tracon has to do is turn them on course and they’ll diverge.

This is why ground controls job is more than just taxiing airplanes. At big airports with a lot of airplanes and SIDs, you can make or break the operation by putting 5 of the same SIDs in a row instead of fanning them out.

But to answer your question, you need diverging headings OR visual. You don’t need to use both (That’s what we call over-separating)!
Shane VanHoven
Minneapolis ARTCC, VATUSA ACE Team | Instructor
Private pilot, Instrument, ASEL
FAA Air Traffic Developmental, Terminal

Frank Miller

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Re: Visual Separation and You: Dos and Don'ts
« Reply #6 on: January 06, 2019, 12:48:06 pm »
A question for the experts:   I’ve heard on occasion in real-world, tower ask if a second departure has visual on a rolling first departure (typically same wake class).  Once acknowledge, the second departure is given “maintain vis sep from that a/c, cleared for takeoff”).  I’ve always assumed that is done where they don’t have diverging headings for the two a/c but expect they will turn-out in different directions once with Departure, so the vis sep allows a quicker launch for second a/c.  From this thread, I’m not clear whether this is a correct interpretation of what is happening, though.   Maybe the first a/c was VFR.

Thoughts?

Frank
Frank Miller
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Brad Littlejohn

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Re: Visual Separation and You: Dos and Don'ts
« Reply #7 on: January 07, 2019, 11:59:59 am »
Figured I'd jump in and throw another topic up for discussion here. The concept of how to solicit and apply visual separation. Unfortunately, throughout the process of flying under the control of a number of facilities as well as training controllers within my own, I've found that visual separation is a often misunderstood and misapplied concept. Key examples of this include, but are not limited to:

  • Attempting to apply visual separation in the flight levels

First, in order to establish some definitions, let's look at 7110.65 7-2-1, which states:

Quote from: JO 7110.65X 7-2-1 a. (Terminal) and b. (Enroute)
Visual separation may be used up to but not including FL 180

Yep. Can't use it in Class A airspace. Have to have lateral, vertical, and/or wake turbulence separation. no exceptions.


Great post here, Dhruv, and one that definitely needs to be either pinned here or taught as a refresher to each individual sector (not that the instructors at those sectors don't do a great job; but just as a reminder of what we at the TRACON and En Route facilities can use as a tool).

However, while I know this answer, I would love to see how you would extend this to any VFR-on-top operations, where they can operate at FL+500ft. I know that for the most, the same lateral/horizontal/wake separation standards would still apply, but the +500ft throws that off a lot of people's games when it comes to Class A airspace.

For example. Say you have 3 aircraft that are laterally separated but geographically converging at a given point. One is VFR at 17500, one descending through FL180, and one VFR on top at 18500. Here you would be applying different methods of separation, including visual. How would you think that should be handled?

BL.

Rick Rump

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Re: Visual Separation and You: Dos and Don'ts
« Reply #8 on: January 07, 2019, 01:07:40 pm »
one that definitely needs to be either pinned here or taught as a refresher to each individual sector

Oh the list :)
These sorts of topics are going to get merged into CBTs I am hoping.
Deputy Training Director
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Ryan Geckler

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Re: Visual Separation and You: Dos and Don'ts
« Reply #9 on: January 07, 2019, 02:02:02 pm »
.

For example. Say you have 3 aircraft that are laterally separated but geographically converging at a given point. One is VFR at 17500, one descending through FL180, and one VFR on top at 18500. Here you would be applying different methods of separation, including visual. How would you think that should be handled?

BL.

You can't be VFR on top in Class A airspace.

In the case of the other two, there is no requirement to separate the two planes, but you would stop the IFR aircraft above until clear or they have the 17500 guy in sight.
Ryan Geckler - GK
Former VATUSA3 | Division Training Director
Minneapolis ARTCC | RW Miami ARTCC

Matthew Kosmoski

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Re: Visual Separation and You: Dos and Don'ts
« Reply #10 on: January 07, 2019, 03:21:05 pm »
You can't be VFR on top in Class A airspace.

Why not?

91.179 (IFR cruising altitudes) permits for VFR on top above 18k, referencing requirements of 91.159 (VFR cruising altitudes), which actually permits for VFR in Class A, just requiring pilots to maintain altitude as assigned.  I've heard this regularly being done with gliders, but that's really the only time I've heard it actually used.

Quote
91.176(a) In controlled airspace. Each person operating an aircraft under IFR in level cruising flight in controlled airspace shall maintain the altitude or flight level assigned that aircraft by ATC. However, if the ATC clearance assigns “VFR conditions on-top,” that person shall maintain an altitude or flight level as prescribed by §91.159.

Quote
91.159(b) When operating above 18,000 feet MSL, maintain the altitude or flight level assigned by ATC.

While the AIM 4-4-7 says ATC won't authorize it, the law permits for it, and we know what authority the AIM actually has.
Matthew Kosmoski
Air Traffic Manager | ZHU ARTCC
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Ryan Geckler

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Re: Visual Separation and You: Dos and Don'ts
« Reply #11 on: January 07, 2019, 04:59:20 pm »
Let's take a look at 7110.65, shall we?

Quote
7−1−1. CLASS A AIRSPACE RESTRICTIONS

Do not apply visual separation or issue VFR or
“VFR-on-top” clearances in Class A airspace.


Gliders usually operate in accordance with a LOA and the facility/agency will block airspace (i.e ATCAA).
Ryan Geckler - GK
Former VATUSA3 | Division Training Director
Minneapolis ARTCC | RW Miami ARTCC

Shane VanHoven

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Re: Visual Separation and You: Dos and Don'ts
« Reply #12 on: January 07, 2019, 07:39:05 pm »
...and we know what authority the AIM actually has.

From one of the first few pages in the AIM:

"This publication, while not regulatory, provides information which reflects examples of operating techniques and procedures which may be requirements in other federal publications or regulations. It is made available solely to assist pilots in executing their responsibilities required by other publications."

No authority. The AIM has no authority.
Shane VanHoven
Minneapolis ARTCC, VATUSA ACE Team | Instructor
Private pilot, Instrument, ASEL
FAA Air Traffic Developmental, Terminal

Shane VanHoven

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Re: Visual Separation and You: Dos and Don'ts
« Reply #13 on: January 07, 2019, 07:41:17 pm »
I’ve always assumed that is done where they don’t have diverging headings for the two a/c but expect they will turn-out in different directions once with Departure, so the vis sep allows a quicker launch for second a/c.  From this thread, I’m not clear whether this is a correct interpretation of what is happening, though.   Maybe the first a/c was VFR.

Thoughts?

Frank

You are correct. This is how we handle it at work. You don't need visual separation if you'll have 15 degrees divergence within 1 mile after departure. It's either/or. Using visual AND a diverging heading is over separating.
Shane VanHoven
Minneapolis ARTCC, VATUSA ACE Team | Instructor
Private pilot, Instrument, ASEL
FAA Air Traffic Developmental, Terminal

Shane VanHoven

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Re: Visual Separation and You: Dos and Don'ts
« Reply #14 on: January 07, 2019, 07:42:39 pm »
I was really hoping that this was obvious, but according to my experiences this evening online, it isn't and I will add this to Dhruv's original post:

Visual separation is only for aircraft in the AIR. You do not use visual separation on the ground.

That is all.
Shane VanHoven
Minneapolis ARTCC, VATUSA ACE Team | Instructor
Private pilot, Instrument, ASEL
FAA Air Traffic Developmental, Terminal