Effects on the Human Eye
The most important factor to remember about night flying is the simple reactions of human eyes when attempting to operate at night. Since people are not nocturnal, eyes do not function at complete capacity during a lack of light. Eyes use two types of receptors to detect light: rods and cones. During the daytime, cones are used to see color-sensitive light in a process known as photopic vision. Rods are used in low light conditions in the process of scotopic vision. With scotopic vision, one does not readily see color, impacting the ability of a pilot to see different features while flying.
In order to accomplish the necessary adaptations for proper night flying, the eye needs to make adjustments. First, the pupil allows more light to enter the eye. This increases as the pilot spends more time flying at night. At the same time, the cones cease to function and the rods take over nearly all vision duties using a pigment called rhodopsin, also known as visual purple.
According to research, one of the best things a pilot can do before flying at night is to prepare for duty in an environment with red light.
Although piloting a plane flying at night can be dangerous, many adaptations both physically and technically ensure these situations have the best chances for success. The effects of night flying impact nearly all aspects of aviation procedures, but with proper training and good planning, a flight can be handled with minimal issues.