It’s easy to be afraid of flying, after all, you can’t just “pull over” in a 300-tonne Airbus A380 flying at 600mph at 40,000ft in the air.

However, one of the most dangerous aspects of flying is something you (mostly) cannot even see. Let me explain.

So What Is Wake Turbulence?

Wake Turbulence refers to the disturbed air left behind an aircraft as it flies through the air. The most important part of this disturbance are pairs of rotating air currents called wingtip vortices.

These vortices form because of how lift is generated.

To understand wake turbulence, we need to first account for lift. Lift is created when there is a pressure difference between the upper and lower side of the wing. Lower pressure above the wing – Higher pressure below the wing. This lift is what creates the upward force that keeps the aircraft in the air.

However, air flows from higher pressure to lower pressure and at the wingtips, air from beneath the wing moves around to the top, which creates the famous swirling motion we see forming on either side of the wings.

Properties of Wake Turbulence

• Their strength depends on aircraft weight
  
  Heavier aircraft produce larger wingtip vortices since they are larger, they require more lift, which means there is a greater pressure difference between the two faces of the wings.

• The speed the aircraft is going
  
  Wake turbulence produced is strongest when an aircraft is flying slowly and at a high angle of attack (I.e. during takeoff and landing, which is also why turbulence is often strongest near airports)

• The way the vortex behaves impacts its strength
  
  After vortexes form, they sink (due to energy loss and being pulled down by gravity), spread outwards and weaken due to air resistance. This means that the vortices are strongest right after they are created. This is also the reason why there are strict spacing guidelines and rules for aircraft taking off and landing to reduce the effects of the vortices, hereby reducing turbulence.

So Why Is Wake Turbulence Dangerous?

Wake turbulence presents risks as it introduces high speed rotating airflow directly into the path of incoming aircraft.

If a smaller aircraft flies into one of these vortices, the rotating air forces one wing up and the other down. This creates a rolling moment that can exceed the roll-control authority (the maximum turning force generated by the pilot’s ailerons). The pilot physically cannot counter the spin, leading to stalling, and worse.

Wake turbulence is most critical during takeoff and landing. During these phases, aircraft fly slowly and at a high angle of attack, which maximizes the pressure differential (meaning there is a large difference in pressure between the different sides of the wing) and makes the vortices as strong as possible