Control tabs are used to move flight controls in the event of what?

Control tabs are employed to facilitate the movement of flight controls during manual reversion. This situation typically arises when the primary electronic or hydraulic systems that generally control the aircraft's flight surfaces become inoperative, necessitating a secondary method to operate those controls.

In manual reversion, pilot inputs are redirected through a mechanical or simplified system, allowing the crew to maintain operational control even when the primary systems fail. Control tabs serve as assistive devices to enhance the pilot's ability to manipulate the control surfaces effectively, providing necessary aerodynamic feedback and reducing control forces required to move the primary flight controls. This allows the aircraft to remain maneuverable and responsive during flight, critical for safety.

In contrast, power failure refers to a broader operational loss, and unexpected turbulence relates to environmental conditions that do not necessarily involve failure of the control systems. Altitude adjustment also pertains to routine flight operations under normal conditions, rather than emergency controls. Thus, manual reversion is the only situation specifically associated with the need for control tabs for effective control surface management.