On an instrument approach, when may a pilot not operate below the DH or MDA?

A pilot is prohibited from descending below the Decision Height (DH) or Minimum Descent Altitude (MDA) unless specific criteria are met that ensure a safe landing can be made. The correct choice reflects the concept that during an instrument approach, the pilot must maintain a continuous visual reference that allows for a safe landing.

When the pilot is in a position to consistently make a descent to a normal landing on the intended runway, it indicates that visual references are adequate and that the aircraft can be safely maneuvered to complete the approach. This requirement is crucial because not only does it provide safety by assessing the ability to land, but it also aligns with regulations that dictate maintaining minimum visibility and situational awareness during approaches.

While other options mention visibility and the presence of lights, these criteria alone do not encompass the full requirement for safely continuing below DH or MDA. For instance, merely having visibility or lights visible does not assure that the pilot is in a position to land, as there may still be obstacles or other factors that affect the safe landing process. Hence, the continuous ability to make a safe descent is paramount in determining when a pilot may operate below DH or MDA.