RE: Which plane would an instructor fear the most?
Way back when I was 2nd flight instructor for the club. You get to see all sorts of things come to the field.
I did teach a guy to fly with a Goldberg Chipmunk. It does handle well at slow speeds. I had the dual rates up and lots of expo for him. He did take his time in learning. Took him about 4 months to do his first take off. He flew that plane until it was a sponge. It was so fuel soaked, the covering had blisters.
I had a big problem with a club member who would tech people with a 86 inch old timer that flew at about 4 mph. It was a Quaker Flash type of plane. Yes it flew great. Nice and slow and easy for the student to fly. Problem was, they thought they could fly anything after soloing on it. The next plane they brought would be a War bird, KAOS, Extra, or some other responsive plane and promptly plant it after about 5 seconds of air time.
Favorite trainer has to be the Falcon 56, any of them, mark I, mark II or the mark III. I have taught a bunch with the Tower Trainer 60.
Worst plane I have seen some one bring to the field to be trained on, a Quickie 500. He said he got a good deal on it. We had fun flying it. We showed him how fast it went. He understood he needed something with a little less speed.
Dru.