NVGs and Night Operations Flashcards
Describe how light passes through the ANVIS.
OPMPFE
Objective Lens (inverst image, minus blue filter)
Photocathode (changes photons to electrons)
Microchannel Plate (multiplies electrons)
Phospher Screen (electrons to protons, creates the lighted image)
Fiber Optic Inverter (inverts the image)
Eyepiece Lens (allows the eye to see the image)
What is Automatic Brightness Protection (ABC)?
ABC automatically adjusts the microchannel plate (MCP) voltage to maintain image brightness at preset levels by controlling the amount of electrons that exit the MCP. ABC is to protect the wearers vision, not to protect the goggles.
What is Bright Source Protection (BSP)?
Reduces the voltage to the photocathode when exposed to bright light sources. This protects the goggles from damage and enhances its life (however, it lowers resolution). Exposure to bright light sources could result in damage to the photocathode, MCP, or the operator’s eye.
What is an operational defect?
Defects that relate to the reliability of the image intensifier and are an indication of instability. An operational defect is an immediate cause for rejection.
What are the operational defects?
FESE
Flashing, Flickering, or Intermittent Operation
Edge Glow
Shading
Emission Point
Describe Flashing, Flickering, or Intermittent Operation.
Light appears to flicker or flash. Can be in either one of both monoculars.
Describe Edge Glow.
A bright area in the outer portion of the viewing area (could be caused by a series of emission points). Check by covering the light entering from the objective lens. If it remains, it is edge glow.
Describe Shading.
You will not see a fully circular image, regardless of the adjustment. Begins at the edge and works inward. There will be a high contrast area with a distinct line of demarcation.
Describe an Emission Point.
A steady or fluctuating pinpoint of bright light in the image area and does not go away when all light is blocked from the OBJ lens.
What is a cosmetic blemish?
A manufacturing imperfection/maintenance imperfection that does not affect image intensifier reliability.
Not normally a cause for rejection unless they interfere with ability to perform the mission.
What are the cosmetic blemishes?
IF I C BOB
Image Distortion
Fixed Pattern Noise
Image Disparity
Chicken Wire
Bright Spots
Output Brightness Variation
Black Spots
Describe Image Distortion.
Evidenced by vertical objects (poles/trees) appearing to bend when you move your head vertically or horizontally.
Ground surfaces may appear to swell or sink as well.
Explain Fixed Pattern Noise.
AKA Honeycomb
Faint hexagonal pattern throughout the viewing area that most often occurs at highlight levels.
Explain Image Disparity.
Difference in brightness between the two image intensifier assemblies within the same binocular.
Explain Chicken Wire.
An irregular pattern of dark thin lines in the field of view either throughout the image or in parts of the image.
Under worst conditions, these lines will form hexagonal shaped lines (think of it as the beginning of honeycomb).
Explain Bright Spots.
These are SIGNAL induced - a bright spot is a small bright area that may flicker or remain constant.
Explain Output Brightness Variation.
Evidenced by areas of varying brightness in or across the image area. DO NOT CONFUSE WITH SHADING. There are no distinct lines of demarcation.
Explain Black Spots.
These are blemishes in the image intensifier or dirt, hair or debris between the lenses.
What 6 things do we use to talk about the characteristics of the NVGs?
DIAL VP
Definition
Intensification
Acuity
Limited field of view
Voltage low indicator
Power supply
What is the definition of the NVGs?
Helmet mounted binocular vision, passive light intensifier device that allows pilots to fly at terrain flight altitudes during low ambient light levels.
What is the intensification of the NVGs?
2000-3000 times
What is the visual acuity of the NVGs?
Best is 20/25 when looking through the center of the tubes. At the periphery, the acuity can decrease to 20/70.
What is the field of view of the NVGs with a proper OSAP?
40 degree FOV
How do you know if you have a low battery (voltage) on the NVG?
A blinking red light at the bottom of the helmet mount (comes on at approximately 2.2 -2.4 VDC).
How much time is remaining on the battery pack if the low voltage pack indicator comes on?
Approximately 30 minutes.
What are the 3 sources of power available for the NVGs?
1) Battery pack
2) Aircraft via power converter
3) COPS (Clip on Power Source)
What is the breakaway force for the NVGs?
10-15 Gs
What are the considerations for using NVGs?
CALM WWAD SOS
Color Discrimination
Airspeed and Groundspeed Limits
Lights
Magnification
Weather
Weapons
Aircraft Lighting
Depth Perception and Distance Estimation
Scanning Techniques
Obstruction Detection
Spatial Disorientation
Explain the NVG Consideration - Color Discrimination
Color Discrimination is absent under NVGs
Monochromatic (single color): White hue due to type of phosphor used
Explain the NVG Consideration - Airspeed and Groundspeed Limits
Never out fly your visibility/the capability of the NVGs.
Consider:
- Type, age, and condition of NVGs
- Cleanliness of aircraft windscreen or sensor window
- Moisture content in the air (humidity)
- Individual and collective proficiency and capability
- Weather Conditions (fog, rain, low clouds, dust) and ambient light
Explain the NVG Consideration - Lights
PET
Performance Relations - proportional to ambient light available (high ambient light = high visual acuity and potential fixed pattern noise, honeycomb, chicken wire)/ (low ambient light = low visual acuity and potential scintillation)
Effects of Bright Light: ABC (voltage to the micro-channel plate reduced) and BSP (voltage to the photocathode)
Tunnel Vision: landing light, searchlight, or IR - avoid concentrating on the area illuminated by the light.
Explain the NVG Consideration - Magnification
NVGs do not magnify an image; they enhance the illumination of an object.
Magnification is 1:1 (meaning there is none).
Explain the NVG Consideration - Weahter
Aviators may fail to detect entry into or presence of IMC because we can see through slight obscurations (fog, rain, haze, dust, smoke).
Watch for:
- HALOs: artificial light may produce brighter appearing halos around the source
- Scintillation: video noise
- Loss of celestial lights/moon
Explain the NVG Consideration - Weapons
While firing, aircrews may briefly lose sight of the target - cause for concern for the impact area. The recovery from bright flash illumination is more rapid with NVGs than unaided.
Explain the NVG Consideration - Aircraft lighting
Red cockpit lighting is not compatible and not authorized
External aircraft lighting should be turned off depending on the operation
Explain the NVG Consideration - Depth Perception and Distance Estimation
Depth perception in a given situation is dependent upon:
- Available light
- Type and quality of NVGs
- Degree of contrast in the FOV
- User experience
Explain the NVG Consideration - Scanning Techniques
Aviators’ head and eyes must rotate slowly and continuously to view an entire area.
Explain the NVG Consideration - Obstruction Detection
Obstructions w/poor reflective surfaces (wires, small tree limbs) are difficult to detect. Best way to find wires is to look for support structures.
Explain the NVG Consideration - Spatial Disorientation
Maneuvers requiring large bank angles or rapid attitude changes tend to induce spatial disorientation. An aviator should avoid making drastic changes in attitude/bank angles and use proper scanning and viewing techniques.
What are some limitations of night vision?
Reduction in visual acuity
Color vision decreases/disappears
The night blind spot
What are the 3 night vision techniques that can be used to overcome reduced visual acuity and color vision?
SOS
Scanning
Off Center Viewing
Shapes or Silhouettes
How can scanning help overcome some of the night vision limitations?
Begin scanning at the greatest distance which an object can be perceived and look left and right, slowly moving inward. Overlap viewing areas by 10 degrees. Use the stop-turn method (stopping no more than 2-3 seconds)
How does off-center viewing help overcome some of the night vision limitations?
Because of the night blind spot, if you stare directly at an object, you will not be able to see it. You should look 10 degrees above, below, or to the side of an object.
How does the night vision technique Shapes or Silhouettes help overcome some of the night vision limitations?
Reduced visual acuity at night requires objects be identified by their shapes or silhouettes. Familiarity with architectural designs/vehicles/important terrain relief is imperative.
What are the visual illusions?
FFSHAVSCC
Fascination/Fixation
False Horizon
Size/Distance Illusion
Height/Depth Perception Illusion
Autokinesis
Vection (induced motion)
Structural Illusion
Confusion with Ground Lights
Crater Illusion
Fascination/Fixation
Fascination: Task Saturation (in cockpit) - so engrossed with a problem or task within the cockpit, they fail to scan outside.
Fixation: Target Fixation (out of cockpit) - Fixating on an object outside the cockpit so much you fail to scan/crosscheck.
Solution: Refrain from staring, scan.
False Horizon
Aviator confuses cloud formations with the horizon or the ground, thus they may fly the aircraft in a banked attitude.
Solution: Scan instruments and other visual cues.
Size/Distance Illusion
Crewmember misinterprets an object of unfamiliar size and shape by comparing it with what they are accustomed to seeing based on experience. There are three types.
What are the three types of Size/Distance Illusion?
1) Size Constancy Illusion - An example is landing at an unfamiliar runway. A narrower runway may lead a pilot to believe he/she is higher and further away.
2) Shape Constancy Illusion - Commonly encountered with sloping runways. An upsloping runway may give the pilot the illusion of being too high.
3) Aerial Perspective Illusion - Visual cues are of a different size or perspicuity (clarity an discrimination) than expected. An example is mistaking short immature trees for full grown ones. Also, objects within a hazy environment are often thought to be further away than they actually are.
Height/Depth Perception Illusion
The height-depth perception illusion is due to a lack of sufficient visual cues and causes an aircrew to lose depth perception (i.e. flying over desert, snow, water, the aviator may fly extremely low due to a lack of cues.)
Solution: Trust instruments and scan horizon.
Autokinesis
Primarily occurs at night when ambient visual cues are minimal and a small dim light is seen against a dark background. Aviator visually fixates on light for 6-12 seconds, the light appears to move up to 20 degrees in any direction and continues to “move.”
Solution: Avoid fixating on objects, develop a good scan.
Vection (Induced Motion Illusion)
Falsely perceived self-motion (at a stop light, car next to you starts moving and you thing you’re moving).
Solution: Proper scanning - experience/knowledge of the occurrence.
Structural Illusion
Caused by effects of heat waves, rain, snow, sleet, or the shape of the windscreen - objects may appear obscure/not their true shape/size.
Solution: Experience/knowledge
Confusion with Ground Lights
Aviator mistakes ground lights for stars - which prompts aviator to place the aircraft in an unusual attitude to keep the misperceived ground lights above them.
Crater Illusion
Landing at night, under NVG conditions, the IR searchlight is too far under the nose of the aircraft - it will cause the illusion of landing with up-sloping terrain in all directions (a crater).
Solution: Proper use of landing and search light and scanning.
What are the five major components of the eye?
Cornea
Iris
Pupil
Lens
Retina
What is the cornea?
A circular, transparent protective tissue that projects forward and protects the eye.
