Wake Turbulence (simplified)

travelingcutie

Senior Member
Dec 13, 2008
170
1
18
Atlanta
I've always found wake tubulence to be a bit confusing, but this article greatly helped. The following is from the flying penguin:

The best way I've found to describe Wake Turbulence is as a logic puzzle. It's a seemingly endless combination of "If A = B then B = C... but does C = A?" puzzles that just become a little mind-numbing. There's a lot of factors to take into account, from aircraft size to the departure point on the runway.

The problem is that, as dry as it is, it is absolutely vital to successfully passing this course. You will be making a ton of "HOLD FOR WAKE TURBULENCE" and "CAUTION WAKE TURBULENCE" calls throughout your training. You need to know it well enough that it will just roll off your tongue without a thought, because when you're getting busy you can't stop and think about anything.

However, I think I've broken it down to its essence. The packet we were being taught from was pretty lengthy and it went into a lot of unnecessary detail and repetition. I like things simple, and I think I managed to simplify it enough to put it into a few basic rules.

To start, there's three common factors for each Wake Turbulence rule:

Holding time
Can it be waived?
Is it measured from when the aircraft begins its takeoff roll, or from when it rotates and leaves ground?

And from there, we go on:

3 Minute Holds (Non-waiverable / Timed from Aircraft Rotation):

Anything at an intersection behind a Heavy/Boeing 757.
All departures in the opposite direction of a departing Heavy/Boeing 757.

Simplified: If you're taking off behind a Heavy/B757 from anywhere other than the Heavy's end of the runway, you're getting 3 minutes.


3 Minute Holds (Waiverable / Timed from Aircraft Rotation):

Small behind a Large or Small behind a Small-Plus at an intersection - same or opposite direction.
Small departure from opposite direction behind Large departure or Large low/missed approach.

Simplified: If you're taking off after a Small or Large from anywhere other than the other aircraft's end of the runway, you're getting 3 minutes... but you can waive it.


2 Minute Holds (Non-waiverable / Timed from start of Takeoff Roll):

Anything (Small, Large, Heavy) behind a Heavy/Boeing 757 that's departing from the same runway end the Heavy started its takeoff roll from.

Parallel runway departures where the flight path of a departing aircraft will take it through the flight path of a Heavy/Boeing 757 departing ahead of it from the parallel runway.
Departure from intersecting runways following a Heavy/Boeing 757 if the Heavy's runway intersects the departure's runway.

Simplified: If you're taking off after a Heavy, or your path will intersect with a Heavy - either in the air or on the ground - you're getting a non-waiverable 2 minute hold.

Situations that do NOT need Wake Turbulence separation:
These can all be cleared for immediate takeoff.

Small behind a Small (duh).
Small behind a Small-Plus
Small behind a Large
Small-Plus behind a Large
Large behind a Small
Large behind a Small-Plus
Large behind a Large
 

FM_Weasel

Senior Analyst
Dec 9, 2008
991
7
18
To further simplify the start time and waiverable/non waiverable you can also remember:

2 minutes = always from start of roll
3 minutes = always from rotation

Heavy/757 = Never waiverable
All others = Waiverable.

These are all mentioned in your post, just thought I'd chime in with some pointers that helped me grasp the wake turbulence concept.
 

The Heatles

Loving Life
Jun 15, 2008
2,172
24
38
Miami, FL
Simplified: If you're taking off after a Small or Large from anywhere other than the other aircraft's end of the runway, you're getting 3 minutes... but you can waive it.
No disrespect but the original creator of this(Flying Penguin) is a RADAR trainee... not a certified tower controller. This statement is wrong... maybe he meant small plus to make that statement correct, but this "simplification" is assuming that ALL scenarios involve a small aircraft as the 2nd aircraft. For example, a large departing an intersection after a large from the end will have no wake turbulence. Anything following a small departure will never have wake turbulence. For the record I love his blog so please no hate mail, lol.


This may be simplifying things for someone, but there are plenty of left out situations and the wording he uses is a bit confusing to even me. I was lucky enough to start out at a cargo base with a vast variety of airframes and a heavy operation every 5 minutes.
 

dtblaser

Newcomer
Oct 22, 2009
23
0
1
Just to clarify using a situation:

A Skyhawk 172 is holding short for a full length departure on runway 9. A heavy 767 is making a low or missed approach on runway 9. Does the 172 have to hold for wake or can it go since it is not the opposite direction of takeoff?

(Note, if I were the Skyhawk pilot, I'm waiting 3 minutes whether I have to or not in this situation.)
 

The Heatles

Loving Life
Jun 15, 2008
2,172
24
38
Miami, FL
A Skyhawk 172 is holding short for a full length departure on runway 9. A heavy 767 is making a low or missed approach on runway 9. Does the 172 have to hold for wake or can it go since it is not the opposite direction of takeoff?
Its a mandatory 2-minute hold
 

duranme

Senior Analyst
Nov 3, 2009
920
13
18
BUR
i always click on these threads hoping for a radar question... but its ALWAYS f*cking tower sh!t...
 

atcguruaf

Rico Suave
Jan 4, 2009
1,377
0
36
Right here
You know, I think by re-thinking wake turbulence, you're actually making it more difficult. As stated by a few others, the "simplified" versions do not cover all scenarios, as it leads the reader to believe. So, now, instead of just saying "SWA1242, runway (xx) line up and wait, caution wake turbulence" and waiting the required 5 miles (or even 2 minutes from departure roll from the previous heavy), you're thinking "okay, SWA is a B737, which is a large. Departing behind a heavy, so I need 2 minutes."

I feel those little placards they gave us simplifies it enough. I don't want to say it's easy, because I know it's something to learn. But just like with ANY OTHER THING you have to learn (like phraseology, or other separation requirements), it takes time and practice.

By trying to "simplify," it's making things more difficult. Otherwise, instead of people finding loopholes in the "simplified ways", we'd be saying "wow, thanks! That's awesome!" People are either adding to it, or pointing out problems.

My solution - learn it from the .65. Draw out your runway configuration or get a diagram. Play out the scenarios over and over again on the board.

By seeing it on paper, it will help to visualize out the window. Trying to "re" relearn wake turbulence in a simplified way may prove to cause more harm than good. I appreciate the "penguin's" efforts. As controllers, we always work too hard on finding an easier way out, when if we just do it the first time, no matter how much more difficult it seems, we would end up alright.

It's like taking a test. Some students spend so much time trying to figure out how to cheat, or get around to an easy A, that they sometimes spend more time trying to figure that out than if they would have just done it right and studied hard the first time around. I may not be relaying my thoughts in easy to understand terms, but I think most of you get the gist.
 

FM_Weasel

Senior Analyst
Dec 9, 2008
991
7
18
Just to clarify using a situation:

A Skyhawk 172 is holding short for a full length departure on runway 9. A heavy 767 is making a low or missed approach on runway 9. Does the 172 have to hold for wake or can it go since it is not the opposite direction of takeoff?

(Note, if I were the Skyhawk pilot, I'm waiting 3 minutes whether I have to or not in this situation.)
Consider an aircraft conducting a low approach as an arriving aircraft until it crosses the runway threshold, then as a departing aircraft. Your heavy B767 has essentially departed Rwy 9 full length.

Therefore, your C172 has a 2 minute wake turbulence hold, which can not be waived.

atcguraf is absolutely right and reminds me of a conversation I had with a new coworker the other day. You'll get into traps trying to think of clever, abbreviated, ways to remember certain rules. It's much better to fully and completely understand the rule, so you don't get caught unprepared by a situation a particular summarized technique doesn't cover. (not saying you specifically, dtblaser, just in general)

An example I remember clearly being taught at Academy is that "Small+ only exists on the ground, in the air they're all small." It's an oversimplification that can help new students grasp a difficult concept enough to work in a closed environment (academy sims), but doesn't necessarily cover many real world situations that the student may later find confusing if they adhere to the simplified rule.
 
A

atcpookie

Guest
Just to clarify using a situation:

A Skyhawk 172 is holding short for a full length departure on runway 9. A heavy 767 is making a low or missed approach on runway 9. Does the 172 have to hold for wake or can it go since it is not the opposite direction of takeoff?

(Note, if I were the Skyhawk pilot, I'm waiting 3 minutes whether I have to or not in this situation.)
A little bit of a confusing question...... runwy 9 verses runway 9 is not an opposite direction.

With these two aircraft; Opposite= 3min Same= 2min
 

dtblaser

Newcomer
Oct 22, 2009
23
0
1
A little bit of a confusing question...... runwy 9 verses runway 9 is not an opposite direction.

With these two aircraft; Opposite= 3min Same= 2min
I know they are not opposite direction, if they were it would be 3 min, we answered this in class later in the day and looking back it was real simple, just was wanting to make sure, thanks for the input.

Low approach considered departure when passing threshold, so 2 min. (unwaiverable since heavy).
 

atcguruaf

Rico Suave
Jan 4, 2009
1,377
0
36
Right here
I know they are not opposite direction, if they were it would be 3 min, we answered this in class later in the day and looking back it was real simple, just was wanting to make sure, thanks for the input.

Low approach considered departure when passing threshold, so 2 min. (unwaiverable since heavy).
2 minutes is never waiverable, so the last part of your statement adds to possible confusion that there may actually be a "2-minute waiverable" rule.
 

j_time41

Senior Analyst
Nov 17, 2008
1,015
9
38
35
Lakeville, MN
Heavy or 757 is never waiveable. So, 2 minutes is never waiveable.

Rule of thumb, if a pilot want to waive ever, just say unable. They love that.


Just kidding on the second part
 

dtblaser

Newcomer
Oct 22, 2009
23
0
1
2 minutes is never waiverable, so the last part of your statement adds to possible confusion that there may actually be a "2-minute waiverable" rule.
Hehe, no, did not mean to imply that, rather the opposite. Since a heavy or B757 is involved in all of the 2 min. rules, all the 2 min. rules are not waiverable, never said you could waive one; it was my attempt to keep it short and not get another repeated answer to my already answered question.

Clearly implied one could never waive a 2 min. rule, since they all involve heavy/B757 and heavy/B757 hold times cannot be waived, which people had already mentioned in this thread if you look back.
 

atcguruaf

Rico Suave
Jan 4, 2009
1,377
0
36
Right here
Hehe, no, did not mean to imply that, rather the opposite. Since a heavy or B757 is involved in all of the 2 min. rules, all the 2 min. rules are not waiverable, never said you could waive one; it was my attempt to keep it short and not get another repeated answer to my already answered question.

Clearly implied one could never waive a 2 min. rule, since they all involve heavy/B757 and heavy/B757 hold times cannot be waived, which people had already mentioned in this thread if you look back.
I don't think you understood my statement. You added to your statement by saying "unwaiverable since heavy". If you wanted to keep it short, you wouldn't have written that. 2 minutes ONLY applies to heavy/B757, so there's no need to add anything to the original statement.

It's like when you apply visual separation. People say maintain visual separation "from that traffic". However, there is no need to say "from that traffic". It adds excess verbiage. If you learn to cut out the excess crap now, before you really start training, you'll be ahead of your peers (if you're not already ahead of them).

I know it's not a big deal, but I'm mentioning it because I believe you misunderstood the point I was trying to make.
 

PorkBarrel

Rookie
Nov 21, 2008
35
0
6
One thing I find confusing is the intersecting flight path rule as it applies to wake turbulence. For example, if a heavy or 757 departs lets say the west side of an airport that is eastbound, and you have traffic waiting to depart off the east side that is eastbound, which rules applies: The two minute intersecting flight path rule or if is it 5 miles if you're a radar facility? If it's the former, is it the point of departure roll or is it rotation? This is one rule that is constantly brought up at my facility whenever this situation arises. There seems to be differing opinions on this.
 

vvatc

Junior Member
Dec 14, 2009
100
0
16
Palmdale, CA
Years ago I had a picture that showed graphics of all different types of aircraft arriving, departing and enroute with wake turbulence rules. Can't seem to find it now...not that it would be accurate anymore. But probably not hard to fix. Anyone remember this picture? Have a copy?
 

mountain_hiking

Newcomer
Mar 8, 2009
2
0
1
SC/OI
2min 3min

S=Same
C=Crossing
O=Opposite
I= Intersection

Only non-waiverable is a heavy or B757. all else is waiverable by the pilot.
This is a very simple way to remember it. I liked the idea about drawing out your airfield layout.