Wake Turbulence (simplified)

travelingcutie Junior Member Portland, Oregon

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 Trusted Member

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.

polo708 Epic Member tower

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

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.)

polo708 Epic Member tower

Its a mandatory 2-minute hold

duranme Trusted Contributor San Diego (SCT)

i always click on these threads hoping for a radar question... but its ALWAYS f*cking tower sh!t...

atcguruaf Rico Suave AZ

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.

GLF5 Senior Member

I laughed at this.

JosueZQ8 Trusted Member Akron, OH

God I hope I get picked for enroute...LOL

duranme Trusted Contributor San Diego (SCT)

No, you want Tracon... thats fun radar...