our instructor hopefully emphasized the importance of "if not obtaining performance, I will close both throttles and land ahead"
Probably why so many stall at 20'.
Think about the probable ramifications of drumming that into a pilot short on experience/ judgement.
The aircraft is not performing for whatever reason...the speed is probably bleeding back towards VMCa as the pilot sits there knowing he's about to crash and he suddenly remembers
"Close both throttles and land straight ahead" and does it.
The reduction in thrust, the reduction in lift from the engine blasting air back over a largish portion of wing and the sudden lack of any need for huge rudder input causes a loss of control..and a very hard arrival.
What I used to drum into guys was;
After securing the engine etc.
Nail the speed,
Rudder as required
lift the dead engine up 'a bit'. (you need less rudder)
If the aircraft will
NOT climb
or maintain ht
maintain that speed no matter what...maintain the full thrust no matter what. Find somewhere soft and reduce the power to idle as you round out, flare and touch down, keep the aeroplane straight with rudder. What you are trying to achieve is essentially arriving at 20' at Vyse (minimum ROD) with full power and then bleed off the power as you round out and flare, reducing rudder deflection as you do so (VMCa quickly drops below stall speed as you pull power off) and flare into a fairly normal landing with zero thrust.
Can you see the difference in mindset?
I think it is obvious which method will be more likely to produce a more consistantly survivable forced landing.
When ****s are trumps a pilot will remember what he has had drummed into him at an early stage...particularly innexeperienced ones. You have to be incredibly careful what ingrained habits you put there.