I used to operate the Metro III, it had a SAS (stall avoidance system) which consisted of a stalling warning horn, light and stick pusher.... there was a very good reason for having such a system on this type, it had nasty wing tip stall characteristics, placarded in front of my seat was the message 'Do not stall this aircraft'.
Now as it happens I have been in this aircraft in a stall and it wasn't pleasant. We carried out an airtest at 18000', all was well. Engineers had asked us to check the SAS operation in flight as spurious SAS fault lights had been seen. Very experienced Captain was handling, however as we approached the stall speed our speed crept back perhaps just a little quicker that the required 1kt/sec, just as we felt the first bit of buffet, the SAS fault light illuminated and a wing tip stalled, I remember it vividly as the nose dropped through the horizon and the wing dropped giving a bank angle of 90 to 100 degrees. Full opposite rudder was applied, the power left at idle, we eventually recovered wings level (rudder very ineffective for good few seconds) and eased out of about a 15 to 20 degree dive recovering by approx 13000' (if my memory serves me correctly, this was about 8 years ago).
That airtest scared the s**t out of me, I flew the aircraft for a few more years, but boy did I respect its characteristics!