What is the requirement for operating below MDA/DH?

Operating below Minimum Descent Altitude (MDA) or Decision Height (DH) is primarily contingent upon the visibility conditions required for the approach being executed. The requirement for minimum visibility ensures that pilots can safely identify the runway environment and determine that they are in a position to land or execute a go-around if necessary.

Visibility is crucial because it affects the pilot's ability to visually reference the runway and assess the landing conditions. If visibility is below the required minimum, the pilot must not descend below MDA or DH, as this increases the risk of controlled flight into terrain or other obstacles.

The other options, while important in various operational contexts, do not specifically pertain to the legal and safety requirements for descending below MDA or DH. Therefore, ensuring that visibility meets regulatory minimums is the key factor for safe operations in this scenario.