Tim,
In response to the OP's query, there are two calendar photos from December 2005 which illustrate helicopter vortices quite well. The first, an R44, is quite a light aircraft:
whilst the Puma, of course, is another kettle of fish!
When the Sea King entered service with the RN we were in the habit of hover taxiing everywhere, and gave no thought to not continuing the practice with the King Dipper. RNAS Culdrose had (has?) an area of grass leading down to the bomb dump which was used for slope landings, adjacent to a taxiway: one lonely Hiller 12E was thus occupied with a stude Midshipman when one of us trundled past in a Sea King and casually blew the Hiller base over apex.
That wouldn't have been so bad in itself, but the incident went unnoticed by all until the Tower spotted a bedraggled pilot hobbling across the runway back toward 705's dispersal. Said pilot was a tearful Middie who had extracted himself from the wreckage and spent 10 minutes waiting to be rescued before giving up and seeking solace in the ACRB
The Sea King downwash was re-assessed to be of sufficient magnitude as to require ground taxiing from then on
