Night Flashcards
How heavy can counter weights be
0-22oz
Are counter weights required
no
How long does peak dark adaptation take to occur
Starts at 5 min, takes 30-45 minutes
What does the ABC do
Automatic brightness control
ABC for me
Controls brightness of output, slows flow of electrons
What does the BSP do?
Bright source protection
BSP for the NVG
It limits photocathode from taking in too much light, protects goggles
What causes a green monochromatic viewing image
the phosphor screen
When do rods work
They are always working, but work best at night
When do cones stop working
at 50% illumination
How big is the night blind spot
5-10 degrees
How do you compensate for the night blind spot
scanning, off center viewing by 10 degrees
What causes the night blind spot
lack of rods in the photocentralis
What is the goggles field of view
40 degrees
What vision is in use when flying under NVGs
mesopic
What is vection
You are still, other moving objects give you the illusion you’re moving
Crater illusion
When landing at night, the position of the landing light may be too far under the nose of the aircraft. This will cause the illusion of landing into a hole (crater)
Are you required to wear glasses behind NVGs
yes
How long does dark adaptation take after flipping goggles up
2-3 min
best visual acuity for goggles
20/25, 100% illum, clear air, high contrast
Dark adaptation after flash blindness
5-45 min depending on brightness and duration of flash
Operational defects (4)
Shading
Emission points
Edge glow
Flashing/flickering/intermittent operation
Break away force for NVGs
10-15Gs
monocular cues
Geometric perspective
Retinal image size
Aerial perspective
Motion parallax
Parts of the NVD
Other peoples money pays for everything
Objective lens
photcathode
microchannel plate
phosphor screen
fiberoptic inverter
eye piece lens
What is the visual acuity for worst NVD conditions
20/70 - 0% illum, hazy air, overcast
Can we fly using NVGs with an operational defect? what about a cosmetic blemish?
No operational defect. Yes cosmetic blemish
How fast does the moon move
15 degrees per hour (1 degree / 4 min)
Can you mix lithium batteries and alkaline batteries in the same battery pack?
No*
What is the normal day field of view
120 vertical, 200 lateral
What is the normal night field of view unaided
80 degrees vertical, 120 lateral
photopic light
Light intensities that are bright enough to stimulate the cone receptors and bright enough to “saturate” the rod receptors
fovea centralis
area on retinal wall towards ears, high concentration of only cones, makes 85% of visual info, causes night blind spot
Mesopic vision
occurs at dawn or dusk and involves both rods and cones, occurs when using NVGs
scotopic vision
Low light vision - uses rods
Cones
individually connected to nerves, function down to 50% illumination, high resolution low sensitivity to light, mostly located in the fovea
optic disk
optic nerve connection/day blind spot (covered by overlapping fields of view)
Outboard from the back of the eyes (5 and 7 o clock position for left and right eyes viewed from the top)
parafovea
the area surrounding the fovea, where vision is less acute. used for offset scan when looking at an object
Best possible unaided night visual acuity
20/200
Size of day blind spot and what causes it
5.5-7.5 degrees, the optic nerve
How wide should scans be
30 degrees
Geometric perspective
-Linear perspective (converging lines to vanishing point)
-Apparent foreshortening (changing altitude makes objects appear shorter/flatter or taller)
- vertical position in field (far away appears higher on the horizon){
Retinal image size
Known size of object
Increasing/decreasing size
Terrestrial association
Overlapping contours
aerial perspective
Fading colors/shades
Loss of detail/texture
Position of light source/shadow
motion parallax
apparent, relative motion of stationary objects viewed by a moving observer. Fast moving objects near, slow moving objects far. Awareness must be maintained in two directions to detect helicopter movement
Optical flow
apparent angular rate and direction of movement of objects (due to aircraft movement) created with peripheral vision
Reduced peripheral when aided makes judging airspeed/rate of climb or descent difficult
Contributors to SD
Bank > 30 degrees
Rapid head movement
Lack of ANVIS experience
Size distance illusion
Viewing unfamiliar object, judged to be same as familiar object, distorts distance estimation
Structural illusion
AC windshield
Size constancy
Almost the same as size distance, clarify
Use extreme caution when
flying from high to low ambient light conditions
How do we prevent crater illusion
-Have landing/search light in proper position
-Anything except fully stowed
What does ANVIS stand for?
Aviators Night Vision Imaging System
What are the terrain cues?
-Size
-Shape
-Contrast
-Reflectivity
What are the geometric prospectives?
-Linear perspective
-Apparent Foreshortening
-Vertical Position in the field
