Yesterday just after take off in an A320, once the plane levelled after the initial climb out we were hit by a massive shudder of turbulence - very violent. Most people near me cried out - me included. A few overhead bins opened.

Pilot was almost instantly on to say "don't worry we just hit the wake vortex of the previous plane to depart" - which I think was a Virgin A340-600 (Four big engines).

I've heard about wake vortexes - though never hit one before. Scary.