But their airspeed indicator was telling them that they were going to fast. My hubby thinks that when the autopilot kicked off the plane was beginning to enter a stall, with an “aft CG” situation-the plane stalled and then the plane entered a spin. Large T-CAT aircraft are not designed nor tested for recovery from spins. My hubby thinks that prolly by the time they noticed the altimeter “unwinding” they were already into a spin and outa control. Ok. Enough aerodynamics for one evening....
The Auto Pilot and Auto Thurst both kicked off when the Pitot Tubes iced over. Since the computer no longer had a way to verify air speed both systems shut off. The warning buzzer sounded to let the copilots take over.
It is my understanding that they then thought they were in a stall or were trying to gain some altitude to go over the storm. Trying to get some clearer air. The kept pulling nose up increasing the AOA (angle of attack). That eventually put them in to a stall and it was pretty much over from there.
It is very easy to get disoriented especially in a larger aircraft and with all kinds of weather and at night. That's why you HAVE to trust your instruments. You can't fly a plane like that at that speed and altitude by the seat of your pants. As someone up thread said they should have seen the altimeter unspooling as it would have still been working and taken remedial action. The action in that circumstance, according to the manual, would have been to increase speed and push the stick forward to gain lift.
I can't understand why the pilot who had come back to the cockpit didn't sit down and take over. He had over 10,000 hours flight time. Greater than both of his co pilots combined.