PA.XI.A.K5

From the FAA library

• Pilot's Handbook of Aeronautical Knowledgep. 17-22
  Chapter 17: Aeromedical Factors › Vision in Flight › Night Blind Spot

  Night Vision There are many good reasons to fly at night, but pilots must keep in mind that the risks of night flying are different than during the day and often times higher. [Figure 17-16] Pilots who are cautious ... educated on night-flying techniques can mitigate those risks and become very comfortable and proficient in the task. Night Blind Spot It is estimated that once fully adapted to darkness, the rods are 10,000 times more sensitive to light…

• Airplane Flying Handbookp. 11-3
  Chapter 11: Night Operations › Night Vision › Night Blind Spot

  Occurs at dawn, dusk, or under full moonlight levels and is characterized by decreasing visual acuity and color vision. Under these conditions, a combination of central (foveal cones) and peripheral (rods)vision is required to maintain appropriate visual performance. Scotopic ... Vision. During nighttime, partial moonlight, or low intensity artificial illumination conditions, central vision (foveal cones) becomes ineffective to maintain visual acuity and color perception. Under these conditions, if looking directly at an object for more than a few seconds…

• Pilot's Handbook of Aeronautical Knowledgep. 17-24
  Chapter 17: Aeromedical Factors › Vision in Flight › Night Vision Protection

  This precaution increases the rate of dark adaptation at night and improves night visual sensitivity. Oxygen Supply Unaided night vision depends on optimum function and sensitivity of the rods of the retina. Lack of oxygen to the rods (hypoxia) significantly ... reduces their sensitivity. Sharp clear vision (with the best being equal to 20–20 vision) requires significant oxygen especially at night. Without supplemental oxygen, an individual’s night vision declines measurably at pressure altitudes above 4,000 feet. As altitude…

• Airplane Flying Handbookp. 11-3
  Chapter 11: Night Operations › Night Vision › Vision Under Dim and Bright Illumination

  Vision Under Dim and Bright Illumination The eye’s adaptation to darkness is another important aspect of night vision. When a dark room is entered, it is difficult to see anything until the eyes become adjusted to the darkness. Almost ... everyone experiences this when entering a darkened movie theater. In darkness, vision gradually becomes more sensitive to light. Maximum dark adaptation can take up to 30 minutes. Exposure to aircraft anti-collision lights does not impair night vision adaptation because…

• Pilot's Handbook of Aeronautical Knowledgep. 17-23
  Chapter 17: Aeromedical Factors › Vision in Flight › Scanning Techniques

  Figure 17-18. Scanning techniques. Off-center viewing is another type of scan that pilots can use during night flying. It is a technique that requires an object be viewed by looking 10° above, below, or to either side ... object. [Figure 17-19] In this manner, the peripheral vision can maintain contact with an object. With off-center vision, the images of an object viewed longer than 2 to 3 seconds will disappear. This occurs because the rods reach…

• Airplane Flying Handbookp. 11-2
  Chapter 11: Night Operations › Night Vision › Anatomy of the Eye

  Rods are used for low light intensity or night vision and are involved with peripheral vision to detect position references, including objects (fixed and moving) in shades of gray, but cannot be used to detect detail or to perceive color ... Although there is not a clear-cut division of function, the rods make night vision possible. The rods and cones function in daylight and in moonlight, but in the absence of normal light, the process of night vision is placed…