F and S...........
As far as i understand it, and without going to the books (so prepared to be shot down!!), flying at s speed gives you the full flight envelope with which to manouvre, as garuanteed by toulouse. If you go below this without taking flap, you haven't got the full envelope to play with.
This is how it was described to me, i've only just finished my line training, so as ever would welcome any comments.............. clean though please!!