What must aircraft crews ensure when performing operations in icing conditions?

In icing conditions, it is critical for aircraft crews to ensure that all flight controls are operable and free of ice because ice accumulation can significantly impair the aerodynamic performance and control of the aircraft. Icing can affect the surfaces of the wings, tail, and other control surfaces, leading to reduced lift, increased drag, and potentially causing loss of control. Ensuring that these flight control surfaces are free of ice is essential for maintaining safe flight operations, as any impediment caused by ice can compromise the aircraft's response to pilot inputs.

Furthermore, while other options may address important aspects of flight operations, the direct relationship between ice accumulation on flight controls and safety makes this choice imperative in icing conditions. Proper management of ice on flight controls is fundamental to ensure that the aircraft maintains its intended flight path and handling characteristics.