Night Flying

Night Physiology

• Cones are concentrated in the fovea (center of vision). They handle color and fine detail, but require strong light. They become inactive in low light.
• Rods are concentrated around the periphery. They are the primary night-vision receptors. There are virtually no rods at the center of the eye — creating a night blind spot at the fovea.
• Cones adapt to darkness in 5–10 minutes (~100× more sensitive). Rods take ~30 minutes to fully adapt (~100,000× more sensitive than in light).
• Bright lights destroy dark adaptation in seconds. Dim cockpit lighting and avoid white lights once adapted.

Hypoxia at Night

Vision is one of the first faculties affected by hypoxia. Cabin altitudes as low as 5,000 ft MSL begin to noticeably degrade night vision. Use of supplemental oxygen above 5,000 MSL at night is recommended even though regulations don't require it until 12,500 MSL.

• Avoid self-imposed stressors that worsen night vision: tobacco use, alcohol, low blood sugar, fatigue, dehydration
• Hyperventilation can mimic hypoxia — stay aware of your breathing during high workload

Scanning Techniques

• Use regularly spaced eye movements — small, deliberate scans rather than wide sweeps
• Off-center viewing: Look 5°–10° off the object you want to see. This places its image on the rod-rich periphery rather than the cone-only fovea (the night blind spot).
• Keep eyes moving — staring at a single point causes the image to fade
• Refocus often if flying through clouds or featureless terrain to prevent empty field myopia (eyes default to a focal length of 10–30 ft when there's nothing to focus on)

Airport Beacon Colors

Rotating beacons identify lighted airports at night. Color combinations distinguish airport types:

• Civil land airport: Alternating white and green
• Water airport: Alternating white and yellow
• Heliport: Green, yellow, white
• Military airport: White / white / green — but with dual peaked (two quick) white flashes followed by green, distinguishing it from civil

Use a well-lit runway with a VASI or PAPI for night approaches whenever available — the visual glide slope replaces depth perception that's degraded at night.

Night Visual Illusions — ICEFLAGGS

The mnemonic for the eight major somatogyral and visual illusions. Memorize them — and trust the instruments, not your inner ear.

• I — Inversion: Climb to straight-and-level produces a feeling of tumbling backward
• C — Coriolis: Head movements during prolonged turns trigger a violent sensation of rolling, pitching, and yawing simultaneously. Avoid sharp head movements in turns.
• E — Elevator: An updraft or downdraft creates a sensation of pitching up or down even when level
• F — False horizons: Sloping cloud lines, terrain, ground lights mistaken for stars — pilot tries to align with the wrong reference
• L — Leans: Sustained banking turn entered slowly is not perceived; rolling out feels like banking the other way
• A — Autokinesis: A stationary light stared at for 6–12 seconds appears to move. Common cause of fixating on isolated lights.
• G — Graveyard spiral: Pilot in a constant-rate turn loses awareness of the turn; descent goes uncorrected; recovering by pulling back tightens the spiral
• G — Graveyard spin: Pilot recovers from a spin but the inner ear interprets the recovery as a new spin in the opposite direction; pilot re-enters the original spin
• S — Somatogravic: Rapid acceleration feels like pitch up; rapid deceleration feels like pitch down. Common on takeoff over water or featureless terrain.

Other Illusions

• Relative motion illusion: A car or aircraft moving in your peripheral vision can give the false sensation that you are moving — common at stops or in formation flight
• Reversible perspective: At night, an aircraft in the distance may appear to be moving away when it is actually approaching. Verify with running lights and trend over time.
• Flicker vertigo: Not strictly an illusion — viewing a flickering light (anti-collision strobe, propeller through the sun) can be distracting and, in rare cases, induce nausea or seizure
• Empty field myopia: Without focal targets, eyes relax to a 10–30 ft focal length, missing distant traffic. Force focal changes by scanning to wing tips, instruments, and back outside.

14 CFR Part 61 Night Currency

• For Part 61 passenger-carrying purposes, "night" means 1 hour after sunset to 1 hour before sunrise
• To carry passengers at night, a pilot must have made 3 takeoffs and 3 full-stop landings at night within the preceding 90 days
• FAR 1.1 defines night more strictly (end of evening civil twilight to beginning of morning civil twilight) — used for logging night flight time
• FAR 1.1 night ≠ FAR 61 night. Know the difference.