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