I'll stand by to be flayed by those who know more than me, but the recovery technique in the C150 POH has exactly what Centaurus is saying NOT to do. And that's what I was taught as well. When practicing stalls, especially with power & flap, in the event of a wing drop (ie incipient spin), the recovery is :-
- Close throttle
- Ailerons neutral
- Full opposite rudder to stop yaw
- Controls forward to break the stall
- Roll wings level, recover from dive etc etc
So which part of that is incorrect..?
Regarding descending, I think Sir Instrucalot has it right, in that pulling the throttle back, or lets call it reducing power, is the correct thing to do, just not TOO far back, which it seems happened here due to leaving their descent too late. When commencing a descent, its poor airmanship to leave the cruise power setting and simply 'shove' the nose down in a fixed pitch prop C150, you'll end up with the ASI in the yellow arc most likely. Better to reduce power to say 2000RPM, lower the nose slightly and set up a descent rate between 300-500fpm. Of course if you've left your descent too late....well...you'll be needing a lower power setting which will put you past the green arc on the tacho, so best you pull the carby heat knob out!
I agree with Flyer517 regarding mixture control and instruction in its use. Its not taught very well at all in a lot of schools, especially in basic aircraft like C152/172, PA28's etc. I was taught very early on in my nav training that you should in fact go full rich before changing altitude, including starting a descent. The reason given, was that as we descended the mixture could become so lean, we would risk all sorts of nasty things happening to the engine! A lot of nonsense but oh well, you live & learn!