CHAPTER 10 - NVIS Flashcards
Where can you pull SLAP data from?
Environmental report in MSHARP
Sun Moon (SUMO) tool within JMPS
Solar/Lunar Illumination Report in AFW-WEBS
What lux level constitutes LLL?
<0.0022 lux
What is the primary reason to operate at night?
To reduce the threat level
Which lights are designed specifically for tactical formation flying?
Covert formation and anti-collision lights
Which lights may provide sufficient illumination of the runway environment if not using taxi or landing lights?
Wingtip lights or steady bright or dim navigation lights
What are the 3 options for goggling/degoggling procedures?
Chock to chock
Airborne
At outlying field or landing zone
How will goggling or degoggling be accomplished?
Back to front; one crew position at a time
What are some cues you’re inadvertently entering IMC?
- increased halo effect around light sources
- gradual reduction in light levels, visual acuity, depth perception, terrain contrast
- obscuration of moon and stars or ground light sources
- increased scintillation
Which exterior light does not have both a normal and covert setting?
Leading edge lights
How many formation lights do we have?
9 incandescent
14 electroluminescent
When covert is selected, which lights are disabled?
Bottom anti-collision light and leading edge lights
And
Navigation dim/bright switch
Why can’t you see the HUD with the AN/AVS-9R?
The wavelength of the light in the HUD is filtered out
Which portion of the EM spectrum do NVGs operate?
Optical radiation portion
The human eye is only sensitive to energy in which spectrum?
Visible spectrum (400 to 700 nanometers)
All EM energy sources obey the same laws of physics and travel at the same velocity. How do they differ?
Only in their frequency or wavelength
Visible light and near IR energy posses what characteristics?
Mid IR and Far IR?
Reflected energy
Radiated energy
What portion of the EM spectrum do NVDs operate?
Visible and near IR
What are NVGs entirely dependent on to create an image?
Some form of external illumination source
Difference between illumination and luminance
Illumination - light generated from a source
Luminance - reflected light
What does lux stand for?
Lumens per square meter
What is albedo?
The relationship between illumination and luminance yields a ratio called albedo
Most surfaces have different albedos, so while illumination from moon may remain constant, luminance from different terrain features may significantly vary
NVGs detect energy reflected from objects and terrain (luminance)
What are the 3 major factors that influence NVD performance?
Illumination
Terrain contrast
Atmospheric conditions
What is the primary source of natural illumination for NVG operations?
Moon
How much sunlight does the moon reflect?
7%
What are the 4 factors that influence the amount of light provided by the moon?
Lunar cycle
Moon angle
Lunar albedo (reflectivity)
Variation in Earth-moon distance
How long is a lunar month?
29.5 days
What is the lux on a full moon?
Quarter moon?
- 1
0. 01
What is starlight illumination?
Moonless, clear night sky
When is the moon at its brightest?
Directly overhead
Provides less illumination as it rises and sets
Which is brighter; a rising full moon or an overhead quarter moon?
Overhead quarter moon
During the lunar cycle, when is the moon brighter?
Moon is 20% brighter during the first quarter (waxing) than it is during the third quarter (waning) due to differences in the lunar surface
Does the earth-moon distance play a significant role?
No, deemed insignificant for NVG purposes
On a moonless night, where is 40% of the energy from?
Provided by emissions from atoms and molecules in the upper atmosphere called airglow
What are the 3 defined categories of twilight?
Civil
Nautical
Astronomical
What is civil twilight?
Sunset until center of sun is 6 degrees below horizon
6 degrees below horizon until sunrise
What is nautical twilight?
Center of sun is between 6 and 12 degrees below the horizon
What is astronomical twilight?
Center of sun is between 12 and 18 degrees below the horizon
Does the sun have more effect closer to sunset or sunrise and why?
Sunset
Length of time the atmosphere is exposed to the suns irradiation which causes ionization processes that release near IR energy
Define terrain contrast
Degree of albedo differences in the night scene
The greater the difference in contrast the easier it is to see terrain or objects
What does the Automatic Brightness Control function do?
NVG image brightness remains constant from approx full moon to approx quarter moon illumination
What does texture do?
Provides recognition and depth perception cues, improves comfort level of crew
Flying over forests can be easier even though they do not reflect as much light as the desert or snow
What is the difference between day and night shadows?
Amount of energy present inside the shadow
During day, eye can see into shadows
What is the primary source of atmospheric attenuation?
Absorption
What is the most significant absorbing gas? What is the second?
Water vapor (humidity)
Carbon dioxide
How does humidity effect NVG performance?
Visible and near IR wavelengths pass more readily thru an area of high absolute humidity as long as particles are small (fog, light rain)
What is scattering?
As light travels thru atmosphere, it can strike a particle thereby changing the path of energy
What are some common errors when it comes to focusing NVGs?
Incorrect IPD - some think increasing will increase FOV. Causes low visual acuity, eye fatigue, near-sightedness, inflight headaches
Too much negative diopter - if someone is near-sighted, causes eye fatigue
What are the 3 motion-based visual cues?
Static Cue Motion
Optical Flow
Peripheral Vision Motion
What does terrain texture provide?
recognition and depth perception cues and improves the comfort level of the crew.
Why can flying over forests be easier than flying over desert or snow?
because forests have more texture, even though snow or deserts reflect more light (however in low light conditions, you lose contrast between trees and end up blending)
What are some pros and cons of shadows?
Cons - can’t see into shadows at night due to lack of energy
Pros - can assist in detecting certain terrain features / help discern terrain features while flying over low contrast terrain such as sand dunes
What can atmosphere do to NVDs?
attenuate light, reducing the level of energy reaching the NVDs
What are 3 ways attenuation can occur? Which one is not important to us?
refraction (not important)
absorption
scattering
What are the 2 types of scattering?
molecular and aerosol
