Narvik: Valkhenza is a phenomenon caused by airframe asymmetries in early production Mig-15s which were due to poor manufacturing practices. At transonic speed it resulted in the aircraft entering a dangerous aerodynamic mode, which was difficult to escape from due to increasing stick forces and decreased elevator responsiveness due to air flow separation. It is a vastly different situation to that of the Fokker E3 which had poor roll sensitivity due to its primitive wing warping.
We fixed the roll rate last night by decreasing the control sensitivity significantly.