bhall II wrote: ......An aircraft experiences vortex lift when the AoA of a swept wing (or leading-edge extension) is increased to such a degree that the pressure differential between the high- and low-pressure sides is sufficient to pull air flow across the leading edge in the These vortices keep air flow attached to the low-pressure surface. Without them, the pilot in the F-22 below would pull back on the stick to go vertical, and the aircraft would promptly fall out of the sky, because abrupt flow separation would stall the wings.
"Somebody's probably gonna tell me that wouldn't happen. But there's no need to let something silly like 'reality' get in the way of a tremendous point." —probably Donald Trump
Though triggered by increased AoA, the key factors are a high pressure differential to pull air flow from the high-pressure side to the low-pressure side, and a sweep angle that will allow such movement to occur across the wing's leading edge from the root instead of its trailing edge at the tip.
reasons why 'it' wouldn't happen .........
a thinnish section that's (rather) symmetrical is likely to develop full span seperation near the LE with reattachment down-chord - the 'LE bubble'
(the blog seems to wrongly associate this with wing sweep)
ie there's a significant loss of Cl and increased or greatly increased Cd
but Cl doesn't collapse to the extent that textbooks (based on traditional/normal cambered asymmetricalish sections) have in mind
thousands of planes in service or manufacture eg prop commuter airliners are flying with these symmetricalish sections
'it' (Cl collapse) or otherwise non-collapse applies whether straight or swept planform (swept is famously worse of if 'it' happens - ie 'pitch-up')
low aspect ratio rather has anyway the same results as attributed to the LE (root) extensions
but LERX will more strongly make both wings behave the same despite wing:wing differences in AoA from likely factors eg included roll
and will better contain the stability and control issues wrt pitching and/or rolling moments
at high AoA the nose would shed alternating Karmann vortices as did the F-4 (nbg for weapons aim) but the LERX prevent these
so it's handy for the taxpayer
LERX seem for these purposes to have been designed into some straight wing planes eg the Britten-Norman prop 'flies like a jet' advanced trainer
our BAC Lightning could fly continuously at c 30deg AoA (4 min endurance on internal fuel at max thrust)
the X-33? programme lavishly featured 'post-stall manouvreing' that particularly interested the Germans
in short, having in continuous slow and level flight flown various aerobatic planes at AoA 45 - 55+ deg I know the Cl doesn't collapse
