ATC Separation for Wake Turbulence

Source: www.pilotworkshop.com, Featuring John Krug

Subscriber Question:

"You are taxiing for takeoff at a busy multi-use airport. Reaching the runway you see that you are following a Boeing 737, and several planes are now behind you in the lineup. The tower is launching departures as fast as they can. You are worried about wake turbulence separation. How do you handle this situation?" - Colin B.

John Krug:

"Because of the possible effects of wake turbulence, ATC is required to provide certain separation minima between aircraft of different weight classes. The separation used depends upon the aircraft involved and relative positions.

A 3-minute interval will be provided when a small aircraft (less than 12,500 pounds) will take off from an intersection on the same runway.

A 2-minute interval is provided when the previous departure is a heavy jet or B757 and the small aircraft is departing from the same threshold.

In the situation that you describe, a small aircraft following a large, ATC is only required to provide the small aircraft a cautionary advisory for wake turbulence.

You may request additional separation for wake turbulence if you feel that you need it. This request should be made as soon as practicable on the ground control frequency and at least before taxing on the runway.

The controller may juggle the departure sequence to minimize the delay. For example, if there are 2 or more light aircraft, they may be sequenced together to avoid excessive delays.

You may also request an early turn to avoid flying in the path of the departure. Make sure the turn is on the upwind side. Try to liftoff prior to the large aircraft to avoid wake turbulence."