What PBY said! What's amazing to me is the industry has known about this problem for 20 years and they give it lip service in manuals but then have procedures as ridiculous as making it a no-no to turn off a FD. One step forward and two steps back.
Best 25 minutes one can spend on this subject....a 20 year old video that unfortunately isn't outdated (like it should be by now):
http://youtu.be/pN41LvuSz10