What does the term "fading" indicate in the context of air brakes?

The term "fading" in the context of air brakes refers specifically to the reduction in braking power due to overheating. When brakes are applied repeatedly or held for extended periods, the friction generated can cause the brake components, such as the brake shoes and linings, to heat up significantly. This heat buildup can diminish the effectiveness of the brakes, leading to a situation where they provide less stopping power than expected. Fading is a critical factor in braking performance, especially in situations that require multiple or prolonged stops, as it can lead to a safety hazard if not properly managed.

Understanding this concept is essential for safe operations, as it underscores the importance of monitoring brake temperatures and recognizing the signs of fading to prevent accidents. The other options don't accurately capture this phenomenon. For instance, an increase in braking power refers to enhanced braking efficiency, which contradicts the idea of fading, while loss of airflow pertains to system integrity rather than performance under heat. Lastly, adjustments of brake shoes relate to mechanical alignment rather than temperature-related performance issues.