What condition must be met for the landing light and taxi light to illuminate?

The correct condition for the landing light and taxi light to illuminate is that the switch must be on and the gear must be down and locked. This ensures that both safety and operational readiness are maintained during critical phases of flight.

When the gear is down and locked, it indicates that the aircraft is in a state appropriate for landing or taxiing, where visibility is crucial. The landing and taxi lights are designed to provide additional illumination during these phases to help pilots navigate and make the aircraft more visible to others. If the landing gear were not down and locked, the aircraft could be in a position where activating these lights would be inappropriate or could indicate a state of emergency.

Thus, for the lights to function correctly, the switch must be on, confirming that the pilot intends to use them, along with the gear being down and locked, signaling that the aircraft is safely configured for landing or taxiing operations.