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Comment by cr4ig_ | Hacker News Reader

I was looking at FlightRadar24 and listening to ATC while an A380 took off from Dulles near DC. Not only did they warn for wake turbulence when the plane was already well away, they held other aircraft for a runway inspection after the plane took off. I'd imagine that kind of wake could kick up some significant debris on the ground as well.

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I believe warning of wake turbulence is very common after take off of any large and heavy aircraft.

Wingtip vorticies can sit over a runway (or even drift over to parallel runways) for minutes after a takeoff. They are very dangerous to smaller aircrafts.

The key to avoiding vorticies is to take off at a point earlier than the previous aircraft and to climb at a steeper angle (vorticies travel behind and downwards from the aircraft that made them).

Example: http://www.boldmethod.com/images/learn-to-fly/aerodynamics/a...

Helicopters can also produce serious turbulence as well!

Helicopters. Indeed - there is a state known as "settling with power" https://en.wikipedia.org/wiki/Vortex_ring_state where a helicopter is sitting inside its own vortex, and is incapable of climbing straight up with full power.

Super interesting! Never knew this about helicopters. Thanks.

Another point related to its size: the 747 has thrust reversers on all four engines. The A380 only has them on the two innermost engines, because the wingspan is so wide those engines aren't always over the runway and have a higher chance of kicking up debris with reverse thrust.

The same would happen with any widebody, the displacement is enormous and it's one very good reason to nail down everything close to the ground in the path of these planes very well.

Which is also why, as you might know, they explicitly call them heavy and super respectively.

https://en.wikipedia.org/wiki/Heavy_(aeronautics)

https://www.youtube.com/watch?v=iI6avay9w4g

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