B757 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Total 17000; Flight Crew Type 612
Aircraft Equipment Problem Less Severe
Flight Crew Diverted; Flight Crew Landed As Precaution
Aircraft
During cruise at FL330 in smooth conditions we experienced several strong and numerous weaker un-commanded yaw inputs. The aircraft tail yawed to the left and then returned to a neutral position to the right. The right auto-pilot was on. During these events the amber 'brake temp' light illuminated and the brake values changed from zero to a different number such as 1; 2; or 3; and a loud hissing sound could be heard that ceased when the yaw ended. Due to the possibility of a flight control malfunction I [advised ATC] and diverted to the nearest suitable airport; and landed without incident.
B757 Captain reported diverting to an alternate after experiencing flight control abnormalities.