When should the helmet visor be down, according to the procedures?

The correct answer indicates that the helmet visor should be down anytime the canopy is closed. This practice is important for safety reasons. When the canopy is closed, the visor protects the pilot's eyes from debris and potential hazards, especially during takeoff, landing, or adverse weather conditions. Additionally, having the visor down helps to maintain the integrity of the cockpit environment, as it minimizes glare and distractions that could impact the pilot's focus and visibility.

The other options, while relevant in certain contexts, do not encapsulate the comprehensive safety protocol involving the visor. For example, stating that the visor should be down only when aircraft seats are occupied neglects situations where the canopy could be closed without complete occupancy. Similarly, restricting the visor’s use to daytime flights or flights above 10,000 feet does not account for scenarios where visibility could be compromised, thereby underscoring the necessity for consistent visor usage whenever the canopy is closed.