What should be done to the canopy defog system during takeoff and landing?

During takeoff and landing, it is essential to have clarity in the cockpit and to manage the airflow properly. Turning off the canopy defog system at these critical phases of flight is the correct choice because turning it on could introduce potential distractions or an unwanted airflow that might obscure visibility rather than improve it. The defog system can create turbulence within the cockpit if not managed properly, which could detract from situational awareness when pilots need to be most focused.

Additionally, during these phases of flight, there is often an emphasis on having the systems in the simplest configuration to reduce workload and avoid any unnecessary complexity. By keeping the defog system off, it ensures that all available focus can be concentrated on the aircraft's performance, environmental conditions, and any communication with Air Traffic Control.