What does Minimum Descent Altitude (MDA) refer to?

Minimum Descent Altitude (MDA) specifically refers to the lowest altitude that an aircraft is allowed to descend to during the final approach phase of an instrument approach procedure when not in a position to make a landing. This altitude is critical for maintaining safe navigation and clearance over obstacles in the vicinity of the runway.

When pilots approach an airport under instrument flight rules (IFR), the MDA provides a safety buffer, ensuring that if they do not have visual reference to the runway environment, they are still at a height that prevents collisions with terrain and obstacles. The MDA is determined based on the specifics of the instrument approach procedure and the surrounding geography, which helps ensure the safety of the aircraft and its occupants during descent when transitioning from an IFR condition to visual flight conditions.

In contrast, the other options do not accurately describe the MDA: the total altitude to be maintained in cruise and the altitude necessary for takeoff relate to different phases of flight, while the maximum altitude before landing does not reflect the regulatory functions of the MDA.