Trans-sonic piccy
 

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What's happening to the surrounding air on the bottom piccy then?:ooh:

Someone will come up with a more technical answer, but it's to do with the shockwave causing the moisture in the air to condense out, giving the effect you see.

It is a very good picture, which reminds us that everything happens in three dimensions. Most of the diagrams you see which deal with subsonic, transonic and supersonic flight show a side view of an aircraft (usually Concorde!) and a diagrammatic representation of the shockwaves extending backwards above and below the aircraft. This picture shows the fact that they extend all around the aircraft and make it much clearer.

Another good picture for making things clear is that one of a Citation climbing out of a layer of stratus, and leaving a couple of perfect wingtip vortices in the cloud deck behind. (Or to see one in motion, watch the end of the 'Die Hard' movie based at an airport ('Die Hard 2?). Right at the end our hero is out on the runway helping everyone to land lined up on the flames from the baddies' aircraft and an aircraft flies through a smoke plume. Perfect wingtip vortex results.) :8

eyeinthesky

Thanks for the answer - I was actually trying never to watch that film again but I suppose I'll have to have another look now!

There's a good example of a helicopter vortex (thru' smoke) in 'Apocalypse Now' too. (hehe....double :8 :8)