Sensory Systems and Illusions
Vision
The primary source of information for pilots ("See and Avoid").
- Retina: Contains Photoreceptors.
- Cones: Central vision (Fovea), detailed, color, require bright light (Photopic).
- Rods: Peripheral vision, movement detection, black & white, sensitive in low light (Scotopic).
- Blind Spots:
- Anatomical: Where the optic nerve exits (no receptors).
- Night Blind Spot: The Fovea (Cones) is blind at night. Pilots must look off-center to use Rods.
- Empty Field Myopia: In featureless skies (blue sky, haze, dark night), the eye tends to focus at a resting distance of ~1-2 meters, making distant traffic detection difficult.
Vestibular System (Balance)
Located in the inner ear.
- Semicircular Canals: Detect angular acceleration (Rotation: Pitch, Roll, Yaw).
- Otoliths (Utricle & Saccule): Detect linear acceleration (Gravity, Speed up/down).
Illusions (Spatial Disorientation)
When visual cues are lost (IMS/night), the vestibular system can mislead.
- The Leans: A slow roll is undetected by the canals (below threshold). A sudden correction feels like a roll in the opposite direction.
- Coriolis: Moving the head during a steady turn stimulates multiple canals, causing unbearable tumbling sensation.
- Somatogravic Illusion:
- Take-off (Acceleration): Otoliths interpret acceleration as a pitch up. Pilot pushes nose down $\rightarrow$ CFIT.
- Deceleration: Interpreted as pitch down. Pilot pulls nose up $\rightarrow$ Stall.
Hearing
- Noise Induced Hearing Loss (NIHL): Prolonged exposure to high decibels (>90 dB) damages the hair cells in the cochlea. High frequencies are lost first.