Cruising one day in the B47-KH4 in the NT of OZ. Had no door on the RH Side (as usual) and fortunately was at about 1800 agl. Not a cloud in the sky when without any prior indication the aircraft was slammed up vertically coming instantanously to a stop. The collective was driven out of my hand to full pitch, my feet came off the pedals and my knees up to my ears. Everything in the cabin floated momentarily as it swapped sides and the quacker rolled over the vertical to the RHS. Returning to the controls I naturally dumped collective and recovered the rapidly decending RRPM, unusual attitude and A/S. The VSI was in excess of 2000ft/min as we dropped sideways and the heart was maxed out. Everything was covered in dust that had once lived on the floor and passing 500 AGL I accessed that I still had cyclic and engine so tentatively added some collective and it flew out of the decent.
What happened? A local phenomenon called a Willie Willie. The yanks call it a dust devil and generally it is a mini cyclone. Typically you see a smattering of leaves to indicate that you are approaching one but not on this occaision.
I packed myself but you should've seen the colour of the surveyor face who was sitting beside the open door. Thank God his belt was done up tight....
