What atmospheric conditions require a tactile check?

A tactile check is essential in certain atmospheric conditions to ensure safety and aircraft performance. The correct choice emphasizes the significance of performing a tactile check when conditions have been conducive to frost formation. This is crucial because frost can significantly impact the aerodynamic properties of an aircraft, leading to undesirable performance changes during takeoff and landing.

Frost may not always be visually obvious and can develop under conditions often associated with low temperatures and high humidity. When pilots are aware of the potential for frost buildup, they can perform the necessary tactile checks to ensure that critical surfaces such as wings and control surfaces are free of frost before flight. This precaution helps prevent incidents related to reduced lift and control issues due to ice or frost accumulation.

Other options, while related to temperature and potential precipitation, do not specifically address the direct concern regarding frost. In particular, the presence of frost necessitates tactile checks due to its direct impact on flight safety.