How long may it take for the electrically controlled defog valve to close if it is turned off?

The time it takes for the electrically controlled defog valve to close after being turned off is designed to provide a gradual decrease in airflow, helping to prevent abrupt changes in cabin pressure and temperature. This gradual adjustment is essential for maintaining comfort and visibility in the cockpit.

Specifically, the defog system is engineered to take about 40 seconds to fully close once it is deactivated. This duration is important as it allows for optimal defogging performance during operation and assists in the mitigation of cockpit condensation or fog that can impair visibility during flight. Understanding this timing helps pilots manage cabin conditions effectively, enhancing overall flight safety.

Other time durations provided in the choices do not align with the operational characteristics of the defog system, which is specifically calibrated for a 40-second closure period. This precision is part of the standard training that pilots undergo for ensuring efficient and safe aircraft operation.