The major point missed by colgans submision is that the pilots (both of them) did not fly the aircraft corectly for the conditions and configuration the aircraft was in.
The captain flew by numbers - at x dme flap 5, at y dme gear down, at z dme flap 15 reduce speed to vref etc etc. It would have worked had the increase ref switch not been on.
Does that make the switch the killer? NO.
What it does mean is that he did not know how to corectly fly the aircraft in icing conditions and more importantly from icing on aproach to non icing on finals and landing.
That and his reaction to the stick shake is a result of training. That is down to Colgan and the FAA.
For those that are unaware the action of selecting incr ref on is matched by a manual increase in the Vref and of any V climb or Vga depending on company sops. The increase ref switch should be on for entering iceing conditions and when residual ice is on the airframe ( increase speeds). It can be switched of for approach only if there is no residual ice ( when normal speeds can be used). If in doubt leave them on and increase speeds.
In addition he was still manouvering in iceing conditions so should have had an increase to the minimum manouver speed for his flap setting (5 in this case).
There is a bloody great red tape that should have alerted him to something being wrong (like maybe too slow?) but that obviously did not fit into his mental model which required him to reduce speed towards Vref so he could be stable for the aproach. To those that say he leveled out and did not apply power - wrong. He maintained level flight prior to Loc intercept and even made corections to maintain speed. He deliberatly reduced speed in order to be at Vref. (the wrong one)
Training is the key because both of them failed to spot the error and both of them reacted very badly to the stick shake. Yes the aircraft will pitch up dramatically when the AP disconects and yes it will pitch up even more when the power is applied - but he killed them when he Pulled back. She helped by not knowing what the F**K was going on and raising flap.
TRAINING.
(the aircraft does warn you when you have set too low a Vref - it produces a red tape that goes higher than your selected speed. To have any other warning is stupid - Q what hapens if you set the bugs in the cruise as part of the brief for non iceing airport but are in IMC with the ref switch on? A the alarm will go off - thats usefull.)