We had a session with a good unreliable speed scenario, the airplane ended up pitching up a lot, speed decaying. PF was unable to arrest the pitch up. This was a 320. When I prompted him to pitch down he said "I can't, I,m trying"
We had lost quite a few thousand feet already, the airplane slowing down and descending, the stall warning all the time. I remembered the Air France and started to use the THS handwheel to pitch the airplane down. Eventually it worked. The TRE told us later that due to some computer, I don't recall which one, the THS had frozen!
We learnt a lot.
By the way I became to two conclusions:
1- the most difficult part is realising that speed is unreliable
2- when speed is unreliable you don't know for how long it has been unreliable, you can be well in overspeed or about to stall, ergo safety is compromised and you should do the memory items, which at high altitude are illogical, but at least you have to disconnect everyithing, level off and fly a reasonable pitch with thrust as required, then troubleshoot