Transcript 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 ...
Yeah … it’s
Objective
darker than a
Man … it’s
dark Bryan
sack of aholes!
Hey, get
your hand
off my leg!
References
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TC 1-204
Fm 1-301
Topics Covered
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Eye Anatomy
Blind Spots
Vision Types And Problems
Dark Adaptation
Night Vision Protection
Scanning Techniques
Distance Estimation And Depth
Perception
Eye Anatomy

The eye is similar to a cameraThe 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.
Eye Anatomy Contd...

Cones- Cone cells are used
primarily for day or highintensity 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.
Eye Anatomy Contd…

Rods- are used for night or lowintensity 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.
Eye Anatomy Contd…
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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.
Blind Spot (Night)
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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.
Blind Spot (Day)
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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.
Eyeball
Vision Types (PMS)

Photopic, Mesopic, Scotopic
Types of
vision used
Light
level
Photopic
high
Technique
Color
of viewing perception
Mesopic medium/low
Scotopic
low
Receptors
used
Acuity
best
Blind
spot
central
good
cones
20/20
day
both
some
cones/rods
varies
day/night
scanning
none
rods
20/200
day/night
Vision Problems
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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.
Vision Problems Contd...
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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.
Dark Adaptation
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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.
Dark Adaptation Contd...
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The lower the starting level of
illumination, the more rapid
complete dark adaptation is
achieved.
Night Vision Protection
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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<
Night Vision Protection
Contd...
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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.
Night Vision Protection
Contd...
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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.
Night Vision Protection
Contd...
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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.
Night Vision Protection
Contd...
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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.
Night Vision Protection
Contd...
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High intensity lighting (STAFF)• Flashes from weapons- use short
bursts of fire, closing one eye will
also help.
Scanning Techniques
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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.
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).
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.
Distance Estimation And
Depth Perception
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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.
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
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.
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)
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.
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.
Questions, Comments,
Better Ideas?
• For additional help refer to the references
listed above or ask your local IP!