Final answer:
The TERR pb on the overhead panel should be switched off in the Approach environment when the pilot has established visual contact with the runway or is on the final approach to land. the TERR pb should be switched off when visual conditions are sufficient for the pilot to safely navigate and land.
Step-by-step explanation:
In the approach environment, the TERR pb (Terrain display panel) should be switched off when the pilot has established visual contact with the runway or when the aircraft is on the final approach to land. This is because the Terrain display is primarily used for situational awareness during non-visual flight situations, such as in poor visibility or unfamiliar areas.
Once the pilot has visual reference with the runway, it is no longer necessary to rely on the Terrain display for navigation. In fact, keeping it on during visual approaches can sometimes be distracting and may divert attention from other important tasks, such as monitoring the aircraft's speed, altitude, and alignment with the runway. Therefore, to prioritize the most relevant information and reduce workload during the approach, the TERR pb should be switched off when visual conditions are sufficient for the pilot to safely navigate and land.