Perhaps I should have rephrased that. I didn't mean all the time, but sometimes it can be useful to have a student 'think out loud' while going through the steps of a forced landing exercise or something similar. I certainly hope I'm somewhere north of half-decent as a FI (I may be wrong there of course), but that doesn't guarantee the same level of instruction to the topic starter. I wanted to explain that there are more situations during flying training where a stutter may be a hindrance. I've had students go mute when faced with a bit of decision making while flying the aircraft and looking out for the next waypoint, and they didn't start out with a speech impediment.