hi， chillie, thanks
i think you did not grasp what i want to ask, the original question is:
in real air traffic control ,as a controller ,do you often use the method of speed control to adjust the progress of the aircraft? may you instrust an aircraft that in approach phase to increase its speed?
in FAA 71110.65 and ICAO doc 4444 ,there are similar statements :
keep speed adjustments to the minimum necessary to achive or maintain required or desired spacing. in 7110.65
speed adjustments should be limited to those necessary to establish and /or maintain a desired separation minimum or spacing.
I come from china, so not well in english, i want to know what does it mean by saying it . not to use the speed control method too frequently or just to limit the amout of speed adjustment to minimum?