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Night Flight Considerations

Night Flight Considerations. DET 32 STANDARDS OFFICE. Objective. To provide aircrews a source for night flight information. Objective. Somewhere near Mather … at 0 dark 30 hours. Objective. Man … it’s dark Bryan. Yeah … it’s darker than a sack of a-holes!. Hey, get your hand off my leg!.

gwendolyn-winters
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Night Flight Considerations

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  1. Night Flight Considerations DET 32 STANDARDS OFFICE

  2. Objective • To provide aircrews a source for night flight information.

  3. Objective Somewhere near Mather … at 0 dark 30 hours ...

  4. Objective Man … it’s dark Bryan Yeah … it’s darker than a sack of a-holes! Hey, get your hand off my leg!

  5. References • TC 1-204 • Fm 1-301

  6. Topics Covered • Eye Anatomy • Blind Spots • Vision Types And Problems • Dark Adaptation • Night Vision Protection • Scanning Techniques • Distance Estimation And Depth Perception

  7. Eye Anatomy • The eye is similar to a camera- The cornea, lens, and iris gather and control the amount of light allowed to enter the eye. The image is then focused on the retina. The retina has two types of cells: the rods and the cones.

  8. Eye Anatomy Contd... • Cones- Cone cells are used primarily for day or high-intensity light vision. Concentrated in the central retina (fovea centralis) they permit high visual acuity in high illumination. The chemical iodopsin is always present in the cone cells.

  9. Eye Anatomy Contd… • Rods- are used for night or low-intensity light vision. The peripheral retina is almost exclusively associated with rods. Rhodopsin (visual purple) is the photochemical found in rods. Rods are 1000 times more sensitive to light then cones.

  10. Eye Anatomy Contd… • Rods contd..- The period of highest light sensitivity usually occurs after 30-45 minutes in a dark enviroment. The rod cells may become up to 10,000 times more sensitive than at the start.

  11. Blind Spot (Night) • Night blind spot- 5-10 degrees wide due to the concentration of cones in the Fovea centralis and para fovea, the area immediately surrounding the fovea of the retina.

  12. Blind Spot (Day) • Day blind spot- (physiological) is always present not only during the day. This blind spot results from the position of the optic disk on the retina. The optic disk has no light sensitive receptors. It covers an area approx 5.5 by 7.5 degrees about 15 degrees from the fovea.

  13. Eyeball

  14. Vision Types (PMS) • Photopic, Mesopic, Scotopic

  15. Vision Problems • Presbyopia- Part of the normal aging process, which causes the lens of the eye to harden. • Night Myopia- Myopic or slight nearsighted individuals will experience visual difficulty at night when viewing blue-green light that could cause blurred vision.

  16. Vision Problems Contd... • Astigmatism- Is an irregularity of the shape of the cornea that may cause an out of focus condition. If, for example, an astigmatic person focuses on power poles (vertical), the wires (horizontal) will be out of focus in most cases.

  17. Dark Adaptation • Definition- Dark adaptation is the process by which the eyes increase their sensitivity to low levels of Illumination. Individuals dark-adapt to varying degrees at at different rates. Optimum night visual acuity occurs in 30-45 minutes under minimal light conditions.

  18. Dark Adaptation Contd... • The lower the starting level of illumination, the more rapid complete dark adaptation is achieved.

  19. Night Vision Protection • Remember ROSPH • Red lens goggles- if worn prior to flight they can start your adaptation at the 5 minute level. They can preserve up to 90% of your adaptation. • Oxygen- w/o oxygen night vision declines measurably @PA 4000<

  20. Night Vision Protection Contd... • Sunglasses- ND-15 sunglasses or equivalent filter lenses should be worn when exposed to bright sunlight. This precaution will increase the rate of dark adaptation at night and improve night visual sensitivity.

  21. Night Vision Protection Contd... • Precautions at airfields (LAMPS) • Lanes for hovering- marked lanes with minimal lighting keep you from having to use landing light. • Airfield lighting- reduced to lowest intensity. • Maintenance personnel- use light discipline with headlights and flashlights.

  22. Night Vision Protection Contd... • Precautions at airfields (LAMPS) • Position the aircraft- position at a part of the airfield where the least amount of lighting exists. • Selection of approach and departure routes- avoid highways and residential areas where illumination can impair night vision.

  23. Night Vision Protection Contd... • High intensity lighting (STAFF)- • Shut one eye- continue to observe with the other. • Turn aircraft away- fly in the periphery of the lighted area. • Avoid built up areas- plan your mission to avoid brightly lit areas. • Flares- maneuver to a position along the edge of the lit area.

  24. Night Vision Protection Contd... • High intensity lighting (STAFF)- • Flashes from weapons- use short bursts of fire, closing one eye will also help.

  25. Scanning Techniques • Remember SOS • Scanning- look from right to left or left to right. Begin scanning at the greatest distance an object can be perceived (top) and move inward toward the aircraft (bottom). Each stop approx. 30 degrees should be scanned. No stop should last longer than 2-3 sec. and overlap the previous FOV by 10 degrees.

  26. Scanning Techniques Contd... • Off-center viewing- This technique requires that an object be viewed by looking 10 degrees above, below, or to either side of the object. Peripheral vision can maintain contact with an object. View no longer than 2-3 secs to avoid photochemical equilibrium (object disappears).

  27. Scanning Techniques Contd... • Shapes or silhouettes- visual acuity is reduced at night, objects must be identified by their shapes or silhouettes. You must be familiar with the architectural design of structures in the area covered by the mission (ex: Churches etc) Features depicted on the map will also aid in recognizing silhouettes.

  28. Distance Estimation And Depth Perception • Remember BM-GRAM • Binocular Cues- Binocular perception is useful only when an object is close enough to make an obvious difference in viewing an angle with both eyes. • Monocular Cues- (GRAM) Geometric perspective, retinal image size, aerial perspective, and motion parallax.

  29. Distance Estimation And Depth Perception Contd. • Geometric perspective- (LAV) An object may appear to have a different shape when viewed at varying distances and from different angles. • Linear perspective- parallel lines, such as runway lights tend to converge as distance from the observer increases. • Apparent foreshortening- true shape of an object or terrain feature appear elliptical when viewed at a distance. • Vertical position in the field- Objects or terrain features farther away appear higher on the horizon than those closer

  30. Distance Estimation And Depth Perception Contd. • Retinal image size (KITO)- The brain perceives the actual size of an object from the size of an image focused on the retina. • Known size of objects- the brain learns to estimate the distance of familiar objects by the size of their retinal images. • Increasing or decreasing size- size decreases, relative distance is increasing and vice versa. • Terrestrial association- determining an objects size by comparing to a known object.

  31. Distance Estimation And Depth Perception Contd. • Terrestrial association- determining an objects size by comparing to a known object. • Overlapping contours- when objects overlap, the overlapped object is farther away. • Aerial perspective- The clarity of an object and the shadow cast by it are perceived by the brain and are clues for estimating distance. (VLP)

  32. Distance Estimation And Depth Perception Contd. • Variations in color or shade- Subtle variations in color or shade are clearer the closer you are to an object. However, as distance increases, these distinctions blur. • Loss of detail or texture- As a person gets farther from an object, discrete details become less apparent. • Position of light source and direction of shadow- if the shadow of an object is toward the observer, the object is closer than the light source.

  33. Distance Estimation And Depth Perception Contd. • Motion parallax- refers to the apparent motion of stationary objects as viewed by an observer moving across the landscape. The rate of apparent movement depends on the distance the observer is from the object.

  34. Questions, Comments, Better Ideas? • For additional help refer to the references listed above or ask your local IP!

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