Why is it necessary to use sunshades in the aircraft windshield?

Using sunshades in the aircraft windshield is crucial primarily to prevent interior damage from sunlight. Sunlight can cause various materials inside the aircraft, such as plastics, fabrics, and electronic components, to degrade over time. Prolonged exposure to UV rays can lead to fading, warping, or cracking of these materials, which could compromise their integrity and longevity. By utilizing sunshades, the internal cabin environment is protected from harmful solar radiation, ensuring that the aircraft remains in better condition over time and ultimately prolonging its lifespan.

The other contexts provided do not fully address the primary purpose of sunshades. While visibility and temperature control may have some relevance in terms of comfort or operational considerations, the essential function of protecting the aircraft's interior is paramount.