What preparation should a pilot make to adapt the eyes for night flying?

• A. Open all cabin lights to maximize visibility
• B. Avoid bright white lights at least 30 minutes before flight
• C. Turn on all exterior lights just before takeoff
• D. Increase cockpit brightness to maintain night vision

Answer: (B)

Night vision relies on the eyes adjusting to darkness, a process that mainly uses the rods in the retina. Those cells take time to become sensitive in low light, and they are easily throttled by bright illumination. To let dark adaptation occur, you want to minimize exposure to bright light before you fly. Avoiding bright white lights for at least 30 minutes before takeoff gives the rods a chance to regenerate rhodopsin and switch your eyes into a night-ready state, improving your ability to see dim lights and contrast once you're airborne. Using bright cabin or exterior lights would keep the eyes in a light-adapted state and hinder night vision; if illumination is necessary, red lighting is preferred because it has a smaller effect on night adaptation.