Night Systems Flashcards
NVG Field of View
40 degrees
4 main components of NVGs
Objective LensImage Intensifier TubesEyepiece LensPosition Adjustment Shelf
Objective Lens
Focuses incoming rays of light on the image intensifier tubes
Focal Range of Objective lens
25mm to infinity
3 components of Image intensifier tubes
PhotocathodeMicro channel Plate (MCP)Phosphor Screen
Photocathode
Converts incoming visible light and near IR energy into electrical energy in the form of electrons.
Micro-Channel Plate (MCP)
Multiplies electrons from the photocathode so that for each electron that enters the MCP, thousands exit
Phosphor screen
Converts electron beam energy into light
Eyepiece Lens
Focuses light from the phosphor screen onto the eye
Diopter Adjustment
Located on the eyepiece lenses. Allows the user to move the focus point to the appropriate location on the back of the retina
Position adjustment shelf
Holds the 2 NVG tubes and has the connection point for the helmet shelf
Collimation
The process by which NVGs take 2 separate pictures from each monocular and align them for viewing
Results of improper collimation
Oblong field of view2 separate pictures Shadowing on the edges of the field of view
Effects of Improper Collimation on the User
Eye fatigue and Eye strain
How should interpupillary distance be adjusted
Initially set at 60, then adjust each monocular individually to center in front of each eye
Effects of incorrect interpupillary distance
Outside edges blurred - Monoculars too far apartInside edges blurred - Monoculars too far apart
How should eye relief be adjusted
25mm from the eye
Effects of improper eye relief
Too close - Impaired look under scanToo far - field of view is decreased
How should tilt be adjusted
So that optical axes of binoculars is perfectly aligned with the eyes
How should NVGs be vertically adjusted
To be placed directly in front of the eyes
NVG focusing procedure
- Preset Diopter at 02. Cover the tube3. Adjust objective lens (outer) until lines on coarse grid come into focus4. Turn diopter (inner) CCW until image is blurred, pause 2 seconds to allow the eyes to relax then turn CW until image comes into sharp focus5. Fine tune with the objective lens (outer) to bring as many grids into focus
Shading
Dark area along the edge of the image
Possible adjustments to fix shading
adjust tilt, IPD, or vertical
What damage can cause shading
failing photocathode caused by a defective vacuum seal on the image intensifier tube
Edge Glow
Bright area along the outer edge of the image
Causes of edge glow
incompatible light source in goggles FOV. Can alleviate by cupping hand around objective lens
Bright or dark spots
Caused by turning NVGs on in bright room or subjecting them to laser damage
Honeycomb pattern
Normal during times of very high luminance. During normal luminance indicates damaged NVGs
Causes of Image Flickering
Impending failure of the tubeFaulty wiringImpending battery failure
Veiling glare
Decreased contrast causing haze across entire image
Causes of veiling glare
Excessive scratches, pits chips in objective lensIncompatible lighting
Scintillation
Sparkling of image caused by low light levels where resolution is limited by internal noise
HUD Velocity Vector
Shows known drift from the reference pointFull scale displacement indicates 76 ft/sec (45 knots) on the cruise layer and 25.3 ft/sec (15 knots) on the hover layer
HUD nacelle angle indicator tick mark locations
0, 30, 60, 75, 90, and 97.5 degrees
What does a solid box around the HUD Qm reading mean
Average Qm exceeds limits that would cause MFD Qm box to turn yellow or red
What does a solid box around the RADALT reading on the HUD mean?
You have descended below the RADALT Low set point
HUD VVI scale
Cruise: +/-2000ft in 200 fpm incrementsHover: +/-1000ft in 100 fpm increments
HUD Velocity vector tick mark meanings
5, 10, and 15 knotsDistance to Waypoint: 0.05, 0.1, and 0.15 nm
SLAP Solar/Lunar Daily Illumination Graphs
Shows solar/lunar illuminance vs. time for a 24 hour period with 4 values displayed:1. Clear to scattered (100% illuminance)2. Partly cloudy (50% illuminance)3. Mostly cloudy (33% illuminance)4. Dark overcast (10% illuminance)
BMCT
Begin Morning Civil Twilight - Begins when center of the sun is 6 degrees below the horizon in east
EECT
End Evening Civil Twilight - When center of the sun is 6 degrees below the horizon in the west
BMNT
Begin Morning Nautical Twilight - when the center of the rising sun is 12 degrees below the horizon. Illuminance levels once the sun passes 12 degrees are not compatible with NVG operations
EENT
End Evening Nautical Twilight - When center of the setting sun is 12 degrees below the horizon. Once this occurs illuminance levels are compatible with NVG operations
Solar Twilight
When the sun’s elevation is between -18 and 0 degrees
Lunar Twilight
When the moon’s elevation is between -18 and 0 degrees
Percent Lunar Illumination
Percent of the lunar disk illuminated, computed at midnight on each day.
Solar/Lunar Azimuth
Azimuth position of the sun/moon in degrees clockwise relative north from the targets perspective
Solar/Lunar Elevation
Elevation angle of the sun/moon relative to the horizon
Indications that you may be entering into IIMC when using the NVGs
Increased Halo EffectDegraded NVG imageObscuration of the moon and starsIncreased image scintillationLoss of ground lights
Low light level
less than 0.0022 lux
