Which of the following is NOT a visual illusion?

Which of the following is NOT a visual illusion?

• A. False Horizon
• B. Flicker Vertigo
• C. Relative Motion
• D. Autokinesis Illusion

Answer: (C)

Visual perceptual errors in flight come from how the eyes and brain interpret visual cues when attitude or motion is ambiguous. False horizon is a classic example: if the true horizon is obscured or confusing, your brain can misread your aircraft’s pitch or bank, leading to improper control inputs. Flicker vertigo occurs when rapid flickering lights stimulate the visual system and vestibular inputs, triggering dizziness or disorientation. Autokinesis is the illusion where a stationary light in darkness appears to move, even though it isn’t, due to sustained fixation and eye movements. Relative motion, on the other hand, is not a misperception. It describes the actual motion of one object relative to another because both are moving. In flight, you may see ground features or other objects seem to move relative to your aircraft, but that movement is real relative motion, not a deceptive illusion produced by sensory input.

Visual perceptual errors in flight come from how the eyes and brain interpret visual cues when attitude or motion is ambiguous. False horizon is a classic example: if the true horizon is obscured or confusing, your brain can misread your aircraft’s pitch or bank, leading to improper control inputs. Flicker vertigo occurs when rapid flickering lights stimulate the visual system and vestibular inputs, triggering dizziness or disorientation. Autokinesis is the illusion where a stationary light in darkness appears to move, even though it isn’t, due to sustained fixation and eye movements.

Relative motion, on the other hand, is not a misperception. It describes the actual motion of one object relative to another because both are moving. In flight, you may see ground features or other objects seem to move relative to your aircraft, but that movement is real relative motion, not a deceptive illusion produced by sensory input.