Wake turbulence with pattern traffic

[creepstreets]

We had a scenario come up, and there was a bit of a debate regarding wake turbulence for an aircraft in the pattern.

We had a large that was on a visual approach to the runway on right downwind. At the same time, we had a small on left downwind in the pattern. The large turned base, and we pointed out the traffic to the small so that he could follow the large in to the runway. If the small did NOT get the large in sight, would the small require the 4 miles in trail behind the large in 7110.65 5.5.4I?

 

[MJ]

Can you point to where the book says that?

I mean obviously you do it, I do it, we all do it. We provide same-runway sep because we have to and I'm not saying we shouldn't... but what's the textual justification for providing SRS between two VFRs at a Delta? Putting the pieces together, same-runway separation is a kind of separation. It's right there in the name. And according to the pilot/controller glossary, at a Delta there is no separation service provided between VFRs.

Just one of those things that they haven't gotten around to spelling out in the book because nobody has been annoying enough to force them to, I guess.

There are services provided defined by airspace requirements, and services that are provided that are not defined by airspace requirements. Runway sep is a requirement regardless of airspace, and the "no separation service" you're referencing is in regards to airspace requirements.

 

[Somenewguy]

Runways are part of the earth and are not considered or included in airspace
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“from the surface” not “including the surface”

This argument doesnt really hold up to scrutiny.

If you're 2000' from the runway threshold and airborne in a class delta, you are no longer on the surface, so I can land a 747 behind that Cessna right?

Or to put it another way, a landing aircraft can cross the runway threshold with another aircraft on the runway but as long as it's airborne I don't have to apply any separation?


Everyone claims the 7110 was written by lawyers but it was mostly written by a bunch of FAA management/staff support types who "fixed" problems haphazardly as they arose. It is written with the assumption that the person reading it can infer quite a bit of the practical application aspect and avoid using rules in situations where it would compromise safety. Unfortunately most people are kind of stupid so they find new ways to fuck things up while still thinking that theyre following the rules. As a consequence the rule book has to get bigger every year because it doesn't explicitly say what to do in every situation.

 

[rhombus]

I didn't say runways are airspace. I said your explanation of how things are doesn't make sense because same runway separation DOES include airborne aircraft.

All runway separation is based on markings or landmarks on the ground. The ground is the reference point. It doesn’t matter if one of the aircraft involved is airborne. Runway separation or lack thereof occurs on the ground

 

[rhombus]

I know this is a year old, but I am debating it right now at my facility. If you have a small departing behind a large, same runway at an intersection, paragraph b3 allows you to depart the small with no time interval provided the small has the large in sight and maintains visual separation.

Or is it only in the air. If the small is following a large doing touch and go’s or the large is departing. Not if both are departing.

b3 only applies to two aircraft in the pattern or one departure/one in the pattern. For two departures originating on the ground apply a1-4. Pilots can waive the wake interval if they fall into the parameters in a1 or a2

 

[A2J]

The large is an arrival not a departure. What you mention applies specifically to a intersection departure behind a departing aircraft.

5-5-4 H, is what applies to this situation. You would need 4 miles of separation if the succeeding aircraft comes within 2500 feet (directly behind) of the preceding aircrafts flight path.

99% of the time you are going to use pilot applied visual. As far as the rule goes he has to be directly behind (2500 feet of flight path). So base him once the large is over threshold. Even though the wake doesn't disappear, the separation requirement does.

You're right, that section I referenced was for a departing large.

I wanna say that 4-mile rule is for approaches though right? In 3-10-3 b2 just says throw a "caution WT" in there when it's same or parallel runways 2.5 or less for a small behind an arriving/departing B757/Large. That 4-mile rule is for approaches if I am not mistaken. It's in 5-5-4 g1. For sequencing purposes.

 

[Acquired Taste]

I stand corrected. I never realized those notes were in there to apply to 5-5-4 minima but that's pretty dumb. Let's take a look at DAB for example. You think when they have 10 in the pattern on 25L and a large is coming in on 25R, they just extend everyone so to next arrival after the large is 4 miles in trail? They are a class C and the runways are approx 1600 ft apart.

 

[rhombus]

I stand corrected. I never realized those notes were in there to apply to 5-5-4 minima but that's pretty dumb. Let's take a look at DAB for example. You think when they have 10 in the pattern on 25L and a large is coming in on 25R, they just extend everyone so to next arrival after the large is 4 miles in trail? They are a class C and the runways are approx 1600 ft apart.

I would hope not. Just establish pilot applied visual and they can get as close as they want

 

[Acquired Taste]

If they are in the pattern, and can't get pilot applied, it's time for them to full stop.

I would hope not. Just establish pilot applied visual and they can get as close as they want

Ahh I forgot about that part of the question. It's time for bed.

 

[MJ]

radar separation section which is synonymous with

They are not synonymous. Radar sep is a type of IFR sep.

do you provide that separation between IFR aircraft or TO an IFR aircraft

Separation service is always provided to an IFR aircraft. What those services are are dependent on things like airspace class and facility capability.

 

[HammerHead]

They are not synonymous. Radar sep is a type of IFR sep.


Separation service is always provided to an IFR aircraft. What those services are are dependent on things like airspace class and facility capability.

Ok I clearly don't know what synonymous means lmao that's not what I meant at all.

What I was mostly getting at with that is, in other than class B/C(I now know to specify), we supposedly do not have to provide wake turbulence separation to IFR if the preceding aircraft is VFR. Is this correct?

I'm generally asking because at this point I'm not sure.

 

[creepstreets]

It really depends what class of airspace you're working. Class B and C you would apply 5-5-4. Class D issue a wake advisory and just don't have a deal on the runway.

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This was the exact answer I was hoping for. Thanks! It IS still weird to me that in a class D, it just goes away and is fixed with a cautionary, but oh well!

 

[BDUB]

If you have a Large departing and a small on an instrument approach to the same runway and that small reports the large in sight on a 1 mile final can you give the spiel and give T & G clearance even though they can’t really mitigate their wake turbulence because they’re flying a established approach?

 

[SharDiNae]

If you have a Large departing and a small on an instrument approach to the same runway and that small reports the large in sight on a 1 mile final can you give the spiel and give T & G clearance even though they can’t really mitigate their wake turbulence because they’re flying a established approach?

If hes at 1 mile final id probably just hold the large and depart him after the small is gone. I have this same question though for if he was say 2/3/4 miles out. Maybe they give the small a missed heading to fly over the turbs. Can always say "go around" to take it in your own hands.

 

[MJ]

Ok I clearly don't know what synonymous means lmao that's not what I meant at all.

What I was mostly getting at with that is, in other than class B/C(I now know to specify), we supposedly do not have to provide wake turbulence separation to IFR if the preceding aircraft is VFR. Is this correct?

I'm generally asking because at this point I'm not sure.

It's not that you don't have to provide it, it's more like you can't provide it.

To exaggerate the point, think of an uncontrolled field. Do you have ANY idea of what's going on in that pattern where you would be able to provide separation to an IFR arrival? Same idea for a D tower. Towers' only separation responsibility for arrivals is the runway. Strip that tower down to it's basic function/capability and it's easy to see why it can't provide any sep.

And it's also a type of VFR sep, in those situations/airspaces where VFRs are provided separation.

 

[Acquired Taste]

It's not that you don't have to provide it, it's more like you can't provide it.

To exaggerate the point, think of an uncontrolled field. Do you have ANY idea of what's going on in that pattern where you would be able to provide separation to an IFR arrival? Same idea for a D tower. Towers' only separation responsibility for arrivals is the runway. Strip that tower down to it's basic function/capability and it's easy to see why it can't provide any sep.

I've never worked a class C but if someone is doing pattern work at a Class C airport, are they radar identified?

 

[darthmoses]

No D towers have a radar, they have certified tower displays.

Not all of us have radar. Speaking as a controller at one of the 2 FAA towers in the NAS that don’t. No traffic displays of any kind.

 

[rhombus]

No D towers have a radar, they have certified tower displays.

A tower in a C* provides radar services, so yeah they are positively id'd.

*there are exceptions, where the tower is within a C airspace but is a D surface area, so they don't provide radar services. pretty sure all usaf towers w/ approaches are like that

It might be the only one in the nation but Teterboro provides radar services

 

[AZNLUVR69]

No D towers have a radar, they have certified tower displays.

A tower in a C* provides radar services, so yeah they are positively id'd.

*there are exceptions, where the tower is within a C airspace but is a D surface area, so they don't provide radar services. pretty sure all usaf towers w/ approaches are like that

What if they departed from the the C airport to remain in the pattern? How are they radar identified? Can a tower only Class C controller radar identify aircraft?

 

[rhombus]

What if they departed from the the C airport to remain in the pattern? How are they radar identified? Can a tower only Class C controller radar identify aircraft?

You don't need a radar ticket to radar ID aircraft. Class B controllers do it every day.

I would only radar ID someone in a C if I were applying 5-5-4 for wake reasons