What should you do if the runway environment is not in sight at DA/DH during a PAR approach?

The correct choice is to execute the appropriate missed approach procedure if the runway environment is not in sight at the Decision Altitude (DA) or Decision Height (DH) during a Precision Approach Radar (PAR) approach.

In this scenario, the DA/DH represents a critical point in the approach where you must have the runway or its environment in sight to continue safely landing. If visibility does not meet the requirements by this point, it indicates that continuing the approach could lead to unsafe conditions, including the risk of inadequate separation from the ground or obstacles.

Executing the missed approach is a key safety protocol that ensures the aircraft can safely climb away from the current trajectory and reassess the situation. It provides pilots a structured way to recover from an approach where visibility is inadequate, and this process typically includes established waiting procedures or potential additional navigation to regain situational awareness before attempting another approach.

In contrast, options like continuing the approach without sight of the runway, circling until it's visible, or descending further generally do not adhere to safety protocols and could lead to dangerous situations. It is essential for pilots to adhere strictly to procedures to maintain safety and ensure proper decision-making in low-visibility conditions.