What is the required flight altitude to which an aircraft must be able to make an emergency descent within four minutes when operating at or below Flight Level 250?

The requirement for an aircraft to be able to perform an emergency descent within four minutes when operating at or below Flight Level 250 is based on regulatory standards that ensure safety during altitude loss. The correct altitude is 14,000 feet because it provides an adequate margin for descent within the specified time frame, taking into account the rate of descent and operational safety.

When performing an emergency descent, pilots typically aim for a descent rate that allows them to reach a safe altitude quickly, usually around 1,500 to 2,000 feet per minute or more, depending on the aircraft's design and operational procedures. By planning to descend from higher altitudes, such as 14,000 feet, pilots can ensure that they have enough altitude to descend safely and effectively navigate to a lower altitude or safely recover from an emergency situation.

The choices set at lower altitudes, such as 10,000 feet, 12,000 feet, and 16,000 feet do not meet the requirements properly. Descending from anything lower than 14,000 feet would not maintain adequate safety, while 16,000 feet surpasses the operational limits for the scenario given (Flight Level 250), making 14,000 feet the most appropriate and compliant choice.