I'm curious what Airbus' definition of a "fully developed" VRS is. I doubt very many instructors would let it get all the way to the 6000 fpm descent rate, which would be a fully developed VRS according to the books. The ones I have done were all recovered at the onset of the shutter/increased vibration and a continuously increasing rate of descent despite collective pull. So are they concerned with the increased vibrations that develop at the onset or the actual full blown thing with a 6k fpm drop rate?