What is the function of Flight Level (FL) Law?

The function of Flight Level (FL) Law is indeed to maintain a low cabin altitude of approximately 1,000 feet until the aircraft reaches an altitude of 22,000 feet. This approach is crucial for passenger comfort and safety. By keeping the cabin at a lower altitude during ascent, passengers experience reduced physiological stress, minimizing the risk of hypoxia, which can occur in higher altitudes where the air pressure is significantly lower.

The system operates by continuously monitoring the cabin altitude as the aircraft climbs, ensuring that it does not exceed the set threshold until a safe cruising altitude is reached. This function is especially important as it allows passengers to acclimatize gradually to the thinning air at higher elevations, thereby maintaining a comfortable environment.

In contrast, the other options do not accurately represent the primary role of Flight Level Law. Maintaining cabin pressure at sea level doesn't align with the operational purpose of FL Law. Emergency landing procedures involve different systems and protocols that are unrelated to maintaining cabin altitude. Lastly, regulating cabin temperature is managed by separate environmental control systems, which focus on heating, cooling, and airflow rather than altitude management.