Term
| Dark adaptation is impaired by: |
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Definition
- Cabin pressure altitudes above 5000 feet
- Carbon monoxide (inhaled while smoking)
- Vitamin A deficient diet
- Prolonged exposure to bright sunlight
- Viewing bright light
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Term
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Definition
| Color sensors, used in high light levels, provide detail. Concentrated in center of field of vision, particularly fovea, so look directly at object to use cones. Adapt to light level changes quickly. |
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Term
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Definition
| Low light and motion receptors, cannot sense color, distributed away from center of field of vision, so look away (averted vision) to use rods. Slow to react to light level changes. No cones near fovea so "blind spot" there in low light. |
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Term
| Dark adaptation for night flight is achieved by: |
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Definition
- Avoiding bright light for 30 minutes
- Moderate dark adaptation in 20 minutes in dim red light
- If bright light encountered close one sys to preserve night vision
- Keep cockpit lights at a minimum
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Term
| Describe night scanning techniques |
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Definition
- Scan like daytime in 10 degree sections except:
- Use averted vision
- Use small circular eye movements to avoid fading
- Move eyes slowly to avoid blurring (allow time to focus)
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Term
| What steps should be taken to cope with illusions created by various lighting conditions? |
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Definition
| Spatial disorientation from illusions can be prevented only by visual reference to reliable fixed points on the ground or to flight instruments. |
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Term
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Definition
| While looking at a point of light against a dark background, the light will appear to move. To prevent it, use scanning to limit time on target. |
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Term
| What is night myopia and how can you prevent it? |
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Definition
- Night induced nearsightedness, similar to empty-field
- With nothing to focus on, the eyes focus at rest on a point slightly ahead of the aircraft
- Prevented by searching out and focusing on distant light sources
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Term
| What is empty-field myopia and how can you prevent it? |
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Definition
- With nothing to focus on, the eyes focus at rest on a point slightly ahead of the aircraft
- Usually occurs when flying in haze and/or above clouds
- Looking without seeing
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Term
| What is a false horizon and how may it be caused? |
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Definition
- Illusion from lights not aligned with the horizon
- Confusion of linear light pattern for the horizon
- Occurs when horizon is obscured
- Mistake road lights for horizon or city lights
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