What is the first action in response to uncommanded power changes?

The first action in response to uncommanded power changes is to set the Power Control Lever (PCL) to mid-range. This action is crucial because it stabilizes the engine's power output while addressing the situation. By placing the PCL in mid-range, the pilot is able to reduce the effect of any uncommanded changes and regain control over the engine’s performance. This helps to prevent further complications that may arise from extreme power outputs, whether too high or too low.

Setting the PCL to mid-range allows for a balance between power and control, which is essential in managing the aircraft's operations safely. In contrast, other options like selecting the PCL to idle, off, or max could lead to either a complete loss of engine power or an increase in power that exacerbates the situation, making the response less stable and potentially more dangerous.