Under what condition are brakes considered to be hot?

Brakes are considered to be hot when they exceed a specific operational threshold that indicates they are becoming overly heated due to extensive use or friction. In this context, the correct condition for determining when brakes are categorized as hot is when they exceed 8.1 million foot-pounds of energy. This threshold reflects the amount of energy transferred to the brakes, which can lead to increased temperatures and potential degradation of brake performance.

Understanding this energy threshold is crucial for safety and performance. Brakes that exceed this limit can experience reduced effectiveness, longer stopping distances, and may even lead to brake failure if not managed properly. Monitoring brake energy is an essential aspect of operating aircraft safely, especially in high-stress situations where excessive use of the brakes is expected.

The other conditions presented do not accurately define when brakes are considered hot. Specifically, exceeding 10 million foot-pounds is beyond the defined limit of 8.1 million foot-pounds, making it excessive for the context. Meanwhile, a brake energy value below 8.1 million foot-pounds does not indicate a hot condition, and simply referencing temperature without specific energy metrics lacks the precision needed to assess brake performance.