op, you're flying along, straight and level at 60kts and you want to reduce speed to zero. What do you do? You ease back on the cyclic to adopt a deccelerative attitude, and maintain height with collective as you slow down. If you don't change the aircraft attitude, you will maintain speed. If you enter a turn at 60kts, as long as you maintain that 60kt attitude, then your speed will remain the same, regardless of the windspeed/groundspeed.