Lift dependent drag is proportional to the inverse square of TAS, whereas zero lift drag increases with the square of TAS.
So the reduction in vortex magnitude is certainly 'speed related', I would venture to suggest.
Regarding the F4 landing technique, I agree with how Rob Prest described it in his book F4 Phantom:
'100 feet ... 50 feet ... a slight tension now ... the neccessity to fine down the movements, hold it steady in the groove ... the earth flattens and expands, but life is still graceful, relaxed as my eyes tell my brain to tell my hands (don't ask me how) that the time is right to make a little backwards movement to check our rate of descent slightly (the purist never crashes the Phantom onto the ground as the QFIs taught us to do at OCU Conversion) and at the moment critique, draw back the throttles and settle the main wheels ... feather soft and belying our 170 mph onwards race ... onto the damp runway ... easy.'
Last edited by BEagle; 11th Jan 2007 at 19:10.