When is it permissible to descend below MDA/DA?

Descending below Minimum Descent Altitude (MDA) or Decision Altitude (DA) is permissible only when the required visual references have been established. This rule is critical for ensuring the safety of the aircraft as it guarantees that the pilot has sufficient visual cues to navigate safely and ultimately land the aircraft.

The required visual references typically include seeing the runway environment, which may consist of elements like the runway itself, approach lights, or any other recognizable features of the runway that confirm it can be safely reached. This guideline helps to ensure that the descent is conducted under conditions where the pilot can effectively manage the landing process, thereby reducing the risk of controlled flight into terrain.

In contrast, descending below MDA/DA solely based on ATC clearance without visual references does not guarantee that the pilot can physically see and safely navigate to the runway. Similarly, visual flight rules suggest maintaining visual reference during flight, but descending below MDA/DA should not depend on being in visual flight conditions alone. Additionally, operating under stratus conditions typically entails low visibility, further complicating the judgment on whether it is safe to descend. Thus, only when the necessary visual references are clearly established is it safe to continue the descent.