PA.XI.A.K8FAA-S-ACS-6C · Nov 2023Knowledge
Visual illusions at night.
Visual illusions at night.
Bottom line
Many different types of visual illusions commonly occur at night, and anticipating and maintaining awareness of them is usually the best way to avoid them. Some illusions experienced in flight can lead to spatial disorientation, and others can lead to landing errors. All pilots are susceptible to false sensory illusions while flying at night or in certain weather conditions.
Key numbers
| Number | What it means |
|---|---|
| about 8 to 10 seconds | Autokinesis onset |
| no more than 10 seconds | Stare limit |
| 4 to 20 cycles per second | Flicker vertigo |
| less than 3 miles visibility | Instrument training |
FAA references
- PHAK ch. 17 (p. 17-26) — FAA-H-8083-25C (2023)
- AIM 8-1-5 (Illusions in Flight) — AIM Basic 2/20/25 w/ Change 1 (8/7/25) & Change 2 (1/22/26)
- AFH ch. 5, Human Factors (p. 5-3) — FAA-H-8083-3C
- PHAK ch. 17 (p. 17-27) — FAA-H-8083-25C (2023)
- PHAK ch. 17 (p. 17-9) — FAA-H-8083-25C (2023)
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