Q400 tailplane stall
I fly Q400s, and we are being told by our company representatives, who have been in close contact with Colgan reps., as well as the NTSB, that the Q400 is NOT susceptible, to tailplane stall. We are emphatically instructed to disregard considerations of tailplane stall in the future, and have even had references to that phenomenon removed from our manuals following the Colgan accident.
The reasons for this change are several. Firstly, the Q400 has a t-tail, specifically designed to remove most of the influence of flap extension on tailplane AOA. Secondly, the tailplane airfoil is supposedly designed to avoid ice accumulation to the extent required to separate the airflow. Thirdly, the tailplane de-icing system is designed in 4 segments, which provides some redundancy, making a failure of the system catastrophic enough to allow excessive ice accumulation very unlikely. Again, these are things we have been told, not necessarily my opinions.
Also, we were told that the stickshaker in this accident activated at 20-30 KIAS above aerodynamic wing stall (due to the 'Ref Speeds' switch being selected to 'INCR,' which was proper procedure in this instance).
Hope this helps.