A few factors could combine in a downwind quickstop to set up the relative airflow into the disc so that it would be coming in from underneath, perhaps leading to the conditions for VRS, I think.
As gedney said, the components of flow relative to the disc would be the important thing, wouldn't they?
Using Nick's figures of needing somewhere between 800 and 2000 fpm coming into the disc from 85 degrees 'below', I wonder if you could get that in a downwind quickstop?
Just crunching a couple of numbers in a scenario, say you were carrying out a quickstop into a pad with 10 kts downwind, got a bit steep (as you probably would) and allowed a rate of descent to develop, how about this - slowing down with about 20 kts groundspeed, subtract the 10 kt downwind leaving you with 10 kts through the air horizontally = 1000 fpm, approx. Add the vector of your descent, say 600 fpm, which gives a relative airflow from about 30 degrees below the horizontal. Also, you're flaring, maybe 40 degrees nose up (?) giving you about 1160 fpm of relative airflow coming in at 70 degrees from below the disc. Slowing down would continue to increase that angle, if you kept the rate of descent on.
As you pulled in power to try and save a very messy situation, you'd then have all the conditions for VRS, wouldn't you? Just a thought.
Last edited by Arm out the window; 2nd Feb 2007 at 23:59.