Wing tip vortices (wake turbulence/jet wash) visible due to fog
I’m often asked about wingtip vortices. First I’ll spare you any math, so what are they? Basically when a wing produces lift it also produces drag. This type of drag is called induced drag. A by product of it are swirls of air coming off of the wing tips. These circular rotating winds are biggest when a large, heavy aircraft is low and slow.
The video of a landing A-340 is shot on a foggy night that allows you see them; things to note:
1. Size, as it forms compare it to the size of the wide body A-340. Imagine a narrow body airliner or small civil aircraft flying into it.
2. The rate of rotation.
3. How long it stays over the runway.
4. Multiple vortices; more of a cork screw then a single event, look at time 25 and you can clearly see it.
5. Duration/Size; look how large it still is when a car drives by some 25 seconds later.
This is why we wait 2 minutes or until a wide body is 5 miles away before we follow it on take off. In the Navy we just called it jet wash. It could give you a bump or two when you flew through it while chasing a Bogey.