Night operations — physiology, equipment, and visual illusions
**Physiological considerations:** the retina has ~6.5M cones (color, daylight, central vision) and ~125M rods (low-light, peripheral). Rods require 20–30 minutes for full dark adaptation and are most sensitive off-center — at night, **look slightly to the side** of an object to see it better (off-center viewing).
Night vision degrades with hypoxia. Above 5,000 ft MSL at night (even though supplemental oxygen isn't required until 12,500 ft per 14 CFR 91.211), consider oxygen use.
**14 CFR 91.205(c) — night VFR equipment:** position lights, anti-collision light system, adequate source of electrical energy (alternator/generator), spare fuses (or three of each kind required), landing light (only if for hire).
**14 CFR 61.57(b) — night currency:** to carry passengers at night (defined as 1 hour after sunset to 1 hour before sunrise), the pilot must have made 3 takeoffs and 3 landings to a full stop within the preceding 90 days, at night.
**Visual illusions at night:**
• **Black-hole approach** — approach to a lighted runway over unlit terrain/water creates the illusion of being higher than actual; pilots tend to fly too low.
• **Featureless-terrain illusion** — same effect on approach over snow, water, or desert.
• **False-horizon** — sloping cloud tops or ground lights mimicking stars create false attitude reference.
• **Autokinesis** — a stationary light stared at for 6–12 seconds appears to move. Counter with a moving scan.