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]

A) Serious question, have you worked at tower in Class C and had pattern traffic? I have. And worked pattern traffic at it almost every day I was in the tower.

No, you’re the only one. Also My dad can beat up your dad.

B) Where in "Class C Services" does it say "radar"?

If they are in the pattern at a Class C airport, they are receiving radar Class C services

yeah I cited a shitty source, sorry

Pilot applied visual separation satisfies 5-5-4 wake turbulence minima, as well as not operating directly behind the lead landing "wake generating" aircraft.

If they are in the pattern at a Class C airport, they are receiving radar Class C services, and that arrival needs wake separation with the heavy or large in the pattern.

how do you meet that requirement? would it be by radar identifying an aircraft so you can provide that radar separation, per chance?

You think DAB is radar IDing the 18 Riddle aircraft in their pattern after every touch and go??

they Have a scope to positively correlate an aircraft position to its target, so yes.


After_Victor your post was spot on

 

[rhombus]

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.

If you consider runways airspace would you also consider taxiways airspace? How would you go about applying Class B or Class C airspace separation to two taxiing aircraft?

 

[AlphaLima@]

Runways are part of the earth and are not considered or included in airspace
View attachment 8629

“from the surface” not “including the surface”

From

/frəm/
preposition
1.
indicating the point in space at which a journey, motion, or action starts.
"she began to walk away from him"
2.
indicating the point in time at which a particular process, event, or activity starts.
"the show will run from 10 to 2"

 

[ManBearPig]

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

No.

 

[Termine]

Yah the center or tracon applies radar before the tower takes over visually

We're talking about Class C pattern traffic here. A VFR departs and is in the pattern; they fly a tight downwind for whatever reason and their target gets close to the target of an IFR guy short final.

Class C services include separation between the IFR and the VFR. If someone asks LC "what separation were you using" of course they will say "tower visual." Again, visual separation (tower or pilot) requires the assurance of other separation before and after the visual separation. What separation was LC using before visual? Target resolution. Target resolution is a form of radar separation and requires that both aircraft are (or are about to be) be radar identified. How was the VFR pattern traffic identified? The TRACON sure as hell didn't identify them using 5-3-2a because the TRACON never received a rolling call. So LC has to have identified them somehow.

 

[Termine]

Tower applied visual separation does not require a radar ID.

False. False false false. "Visual separation may be applied when other approved separation is assured before and after the application of visual separation." If you don't have radar ID, you don't have visual separation (unless you can make it work using Chapter 6 rules).

You think DAB is radar IDing the 18 Riddle aircraft in their pattern after every touch and go??

Yes. I don't think they're issuing the "radar contact" phraseology, but if LC is radar certified (which they should be) then the aircraft are radar identified by application of 5-3-2a. Or heck, 5-3-2c and the crosswind turn.

 

[Termine]

Why do we say "radar contact" to everyone in approach if we don't have too????

We do have to. But there are rules and there are rules. If I allow separation to decrease to 2NM—that's a loss. If I tell someone leaving the ramp to "Taxi via C" instead of "Taxi via B, C"—that isn't a loss. I am sorry that management got their undies in a bundle about you not saying it.

Curious how you handle aircraft on an IFR flight plan, in the tower pattern.

The same way I treat VFRs, right? I ensure approved separation. Except VFR-IFR is 500', target resolution, or visual; IFR-IFR is 1000', 3NM, or visual. So hell yes, if I don't have the inbound in sight then I keep them 3 miles apart. If I do have the inbound in sight then I don't have to, provided that I ensured other approved separation existed before I got them in sight. Just the same as in the VFR-IFR scenario.

And what separation did I ensure existed? Radar separation.
How was it legal for me to apply radar separation? Because I identified both aircraft.

 

[HammerHead]

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.

Approaches OR directly behind. Directly Behind is defined as following flight path of the lead aircraft over the surface of the earth. The cautionary from 3-10-3 is in addition to this.

 

[tmdarlan]

Im still stuck on the no wake turb in deltas… my facility is gona have some heated convos this week…

How are we getting around 3-9-6 and the arrival version? Deltas can still use time. And i argue if you got a certified tower display you can still use miles. Thats the whole point of it.

 

[HammerHead]

If the small is just landing, it's a caution WT. Approving a touch and go would require visual and caution (3-9-7 b3). In the unlikely scenario you can't get visual, then you just need 3 minutes (3-9-7 a2) since a touch and go is considered an intersection departure.

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.