What is necessary to revert the engine to mechanical controls during power fluctuations?

To revert the engine to mechanical controls during power fluctuations, the second step of the BOLDFACE procedure is necessary. The BOLDFACE steps are critical actions that must be performed quickly in response to specific emergency situations, and they provide a structured approach for pilots to follow in order to ensure safety and stability of the aircraft.

In the context of engine power fluctuations, this step typically instructs pilots on how to disconnect electric or automated control systems and restore manual control, which is vital for managing the situation effectively. The BOLDFACE procedures are designed to mitigate the impacts of unexpected conditions quickly, thus enhancing the pilot's ability to maintain control of the aircraft.

The other options listed—throttle adjustment, control surface reset, and initiating emergency protocol—do not directly address the immediate need for reverting to mechanical controls in response to engine power fluctuations. While they may be relevant in other emergency contexts, they do not provide the same direct solution required for this specific scenario involving the restoration of mechanical control.