Which is a key requirement before takeoff regarding frozen contaminants?

A key requirement before takeoff regarding frozen contaminants is that they must be eliminated from critical surfaces. This is crucial because any ice, snow, or frost accumulation on the wings and other critical surfaces of an aircraft can significantly impair its aerodynamic performance. Frozen contaminants can disrupt the airflow over the wings and tail, leading to reduced lift, increased drag, and potential control issues during flight. Ensuring that these surfaces are clear from any contaminants is essential for maintaining safety and performance standards in aviation.

While it may seem that frozen contaminants only on the wings could be acceptable under certain situations, the reality is that any contamination affects the critical aerodynamic surfaces directly tied to the aircraft's lift and control. Similarly, in cold weather, frozen contaminants are far from irrelevant; they pose a substantial risk if not properly managed. It's also not sufficient for contaminants to be away from the control surfaces; their presence anywhere on critical surfaces could lead to dangerous flying conditions. Therefore, the removal of any frozen contaminants from critical surfaces is not just a best practice, but a necessary protocol before takeoff.