So the article suggests power loss due to either recirculation or vortex ring (the American term settling with power). Or the latter caused by the former. Still not sure an 18 foot high wall would cause recirculation if they were at roping height, ie well above the level of the wall. Hell, what do I know , I only comment on what is already speculation.
Last edited by high spirits; 7th May 2011 at 06:24.