Point is, most folk ignore all this and the initial climb out is at increasing speed - which is fine if you take the flap up but its definitely not if you leave the take off flap set. Its grossly incorrect to be doing 190 with flap 20 still selected in the challenger yet thats what my last companies SOP's called for. My old company are happy climbing the challenger with flaps 20 at V2+70 on the way up to 1500 feet. And its utter, utter rubbish! The flaps should go up at (maybe shortly after) V2+20 on a challenger on any take off. The theory is true for any pretty much any aircraft.