How well can you see at night? A pilot, flying at night, must scan the sky steadily; focusing on his or her peripheral vision in order to avoid common night-flying hazards, such as a central blind spot, night illusions, and adjustment to bright lights.
Significance of Night Vision in Aviation
Night vision is of particular importance to pilots operating aircraft at night. According to the American Optometric Association, “Visual acuity may be reduced to 20/200 or less, color vision is lost, blue-green lights will appear brighter while red lights will appear dimmer, problems may occur with night myopia, depth perception is degraded, glare is a factor, and a central blind spot is present.” These effects are common participants in the formation of night illusions.
Illusions in Night Flying
Certain illusions, such as the following, occur during the night, which can make night flying dangerous.
- Distant stationary lights can be mistaken for stars, or aircraft, in clear night conditions.
- When a pilot approaches a well-lit field to land, with no other lighting in the surrounding terrain, the black-hole approach illusion occurs, due to a lack of peripheral visual cues.
- When bright runway and approach lighting systems coincide with few lights illuminating the surrounding terrain, the illusion of a shorter distance to the runway than actually exists may occur.
In most cases, complex navigational instruments and other aids that depict aircraft orientation and position to the surface of the earth compensate or errors of judgement of distance during the night, visual autokinesis, confusion of stationary lights, other illusions, and the central blind spot.
What is the Central Blind Spot?
When looking directly ahead from the cockpit at night, the pilot experiences a central blind spot. When there is an airplane or other object approaching head-on, if it is within the exact center of the pilot’s visual field, the incoming object will go undetected – which can result in a collision. Why does this happen? It’s due to the arrangement of light-sensitive “rods” and “cones” in the back of the pilot’s eye. Rods, which are primarily concerned with night vision, are not highly concentrated directly behind the pupil – which means that it is easier to see objects in the dark when they are viewed through peripheral vision.