UH-60 Blackhawk NVG Study Guide – Flashcards

UH-60 Blackhawk -==-__-==- NVG Study Guide ******************************************************************* >SECTION I: Anatomy & Physiology of the Eye >SECTION II: Day vs. Night Vision >SECTION III: Visual Deficiencies >SECTION IV: Dark Adaptation >SECTION V: Spatial Disorientation >SECTION VI: Distance Estimation & Depth Perception >SECTION VII: Operational Theory of the ANVIS >SECTION VIII: Miscellaneous NVG Related Questions >SECTION IX: Hypoxia and Aeromedical Considerations >SECTION X: Hemispherical Illumination *** Please post additions / corrections to the comments with current reference, if applicable. ***

...

The Cornea

The pupil

The iris

The iris adjust the size of the pupil by using its ciliary muscles, which are attached to the pupil in order to regulate the amount of light entering the eye.

The lens.

It directs (refracts) the light upon the retina.

The retina. The 10 layer membrane is called the "Jacob's Membrane"

(10 layer "Jacob's Membrane) with photoreceptors called "rods" and "cones"

They convert light energy into a chemical change which stimulates nerve impulses. These impulses are transmitted to the brain via the optic nerve.

The Rods are used at night or low-intensity light vision. (Scotopic)

The chemical Rhodopsin is in the Rods. For night vision to take place, Rhodopsin must slowly build up in the Rods. Rhodopsin is also called "Visual Purple".

Rods are about 1000 times more sensitive to light than cones.

The chemical Iodopsin allows for immediate response to light and creates visual stimulation in the Cones. Iodopsin is always present in the Cones.

...

The Central portion of the retina (the Fovea) is composed of all cones. Since cones cannot see in the dark, a night blind spot of 5-10 degrees develops.

The day blind spot results from the position of the optic nerve on the eye retina. There are no rods or cones on the optic nerve, therefore it creates a blind spot. This day blind spot is not noticed since we use both eyes to see (one eye overlaps the viewing area of the other eye). The day blind spot is 5.5 to 7.5 degrees wide.

- Occurs during daylight or bright light. - Rhodopsin is bleached out. - Produces sharp images and color vision. - Involves the cones only.

- Occurs at dawn, dusk, and in full moonlight. - Reduces color vision and decreases visual acuity. - Involves both rods and cones. - Most dangerous time to fly.

- Occurs at night. - Decreases visual acuity. 20/200 or less. - Causes loss of color perception. - Causes night blind spot. - Requires us of peripheral vision and recognition of objects by silhouettes. - Involves the rods only.

20/200 means that a person must stand at 20 feet to see what can normally be seen at 200 feet under daylight conditions.

...

Presbyopia Night Myopia Myopia Hyperopia and Astigmatism

Presbyopia is part of the normal aging process, which causes the lens of the eye to harden.

When myopic people view blue-green light at night, it causes more blurred vision. A combination of myopia's blurred vision and blurred vision caused by the blue-green lights is called Night Myopia.

Myopia is also called "nearsightedness." The focal point of the eye is IN FRONT OF the focal plane. This causes distant objects to be out of focus.

Hyperopia is also called "Farsightedness." The focal point of the eye is BEHIND the retinal plane, near objects are out of focus.

Astigmatism is an unequal curvature of the cornea that may cause an out-of-focus condition. If an astigmatic person focuses on a vertical plane (power poles) the horizontal plane (wires) will be out of focus in most cases.

...

DSST Definition Starting Level Sensitivity Time to Dark adapt Time to Readapt after High Intensity Lighting

Dark adaptation is the process by which the eyes increase their sensitivity to low levels of illumination.

-The lower the starting level of illumination, the less time required to adapt -Each person adapts at a different rate -Exposure to intense sunlight for 2-5 hrs increases visual sensitivity for up to 5 hours -Cumulative effect - the rate of dark adaptation and degree of night visual acuity decrease, may persist for several days.

Fully dark adapted, rods become 10,000 times more sensitive Dilated pupil allowes 100,000 times more total eye sensitivity

30-45 mins to dark adapt.

It takes 5 to 45 mins to regain dark adaptation after you are exposed to a bright light.

Night Vision Protection (ROSCEL) - Red Lens Goggles and Red Lighting: Preserves up to 90% of dark adaptation, and starts dark adaptation if worn prior to flight. - Oxygen supply: Rhodopsin is oxygen dependent - Sunglasses: Neutral Density 15 (ND-15) lenses to minimize effects of sunlight on rhodopsin production. - Cockpit Lighting: Adjust to lowest readable level - Exterior Lighting: Dim or turn off if possible and mission permitting. - Light Flash Compensation (CAAT) * Close One Eye * Auto Weapons Fire - use short bursts * Alter Course - avoid built-up areas *Turn Away - fly around flares, spotlights, etc.

...

Type I: (Unrecognized, most dangerous) Type II: (Recognized) Type III: (Incapacitating, xfer controls)

80%

The Visual Illusions are FFFCRASHCSAR: - FALSE HORIZON - Clouds may be confused with the horizon. - FASCINATION/FIXATION - Fascination (fixed inside, as on an instrument), Fixation (fixed outside, as on a target) - FLICKER VERTIGO - A light flickering at 4 to 20 cycles per second can cause unpleasant feelings to make you sick. - CONFUSION OF GROUND LIGHTS WITH STARS: When this happens, pilots may unknowingly position the aircraft in an unusual attitude trying to keep the stars (but really they are ground lights) above them. - RELATIVE MOTION - You may mistake the motion of another object as your motion. An example is during formation flight when you notice another aircraft moving but you think it is your aircraft that is moving. - AUTOKINESIS - When a static light is stared at for about 6 to 12 seconds in the dark, the light appears to move. - STRUCTURAL ILLUSION: A straight line may be bent or 1 light may look like 2 lights. May be caused by looking through the curved windshield or through desert heat waves. - HEIGHT/DEPTH PERCEPTION - When flying over low contrast areas such as desert, snow or water, you may think you are higher than you actually are. - CRATER ILLUSION: While landing using NVGs, if the IR searchlight is pointed too far down, it appears the aircraft is landing in a crater. The pilot may continue lowering the collective, causing a hard landing. - SIZE-DISTANCE - A false perception of distance. When you see an unfamiliar object (a runway not seen before), you may think of it as being the same size as a familiar object (a runway that you have seen before). Therefore, you may mistakenly judge that the runway is too far or too close. - ALTERED PLANES OF REFERENCE: When approaching a line of mountains or clouds, you may feel the need to climb even though your altitude is adequate. - REVERSIBLE PERSPECTIVE - This occurs when an aircraft appears to be going away from you when in fact it is actually coming toward you.

Otolith Organs (sense linear acceleration) Semicircular Canals (sense angular acceleration)

Somatogravic Illusions

Somatogyral Illusions

Somatogravic Illusions: -Oculogravic: Acceleration/deceleration causes perceptions of a nose-high attitude. -Oculoagravic: Downward motion (such as autorotation) causes eyes to track upward and sense a nose-low attitude. -Elevator: Upward acceleration causes eyes to track downward and percieve nose-high attitude.

Somatogyral Illusions: -Leans: Most common form. After rolling into or out of bank, pilot may falsely perceive position and lean his body to compensate. -Graveyard Spin: Usually occurs in fixed-wing aircraft. When recovering from a spin, pilot perceives spin in opposite direction, reenters spin and continues down. -Coriolis Illusion: Overwhelming sensation caused by rotating head in an additional plane, causing fluid to rotate in different directions, resulting in head-over-heels tumbling sensation.

Never, Never, Trust, and Avoid Never fly VMC / IMC at the same time Never fly without reference to a horizon Trust your instruments, develop a good cross-check Avoid physiological stressors (DEATH - Drugs, Exhaustion, Anxiety, Tobacco, Hypoglycemia)

DR. T Delay intuitive reactions Refer to instruments Transfer the controls

...

The 4 main monocular cues are GRAM: - Geometric Perspective - an object may have a different shape when viewed at varying distances and different angles. - Retinal Image Size - The brain perceives the actual size of an object from the size of an image on the retina. - Aerial Perspective - The clarity of an object and the shadow cast by it are cues. - Motion Parallax - The most important cue. While moving across the landscape, near objects appear to move backward while far objects seem to remain fixed. This motion difference is used to tell what objects are close and what objects are far.

The visual cues associated with Geometric Perspective are LAV: - Linear Perspective - Parallel lines, such as runway lights and roads tend to converge as distance increases. - Apparent Foreshortening - Distant objects appear elliptical. As you get closer, the true shape appears. - Vertical Position in the Field - Farther away objects appear higher up on the horizon.

The visual cues that are associated with Retinal Image Size are KITO: - Known Size of Objects - Familiar objects that are seen larger than usual are deemed to be close while smaller are deemed to be far away. - Increasing or Decreasing Size of Objects - If the image size is increasing, the brain says the object is getting closer. If the size is decreasing, the object is getting farther away. - Terrestrial Associaton - Comparing a known size object (like a helicopter) with another object associated with the object (like an airfield), then the objects are judged to be about the same distance. - Overlapping Contours - When objects overlap, the overlapped object is farther away.

The visual cues that are associated with Aerial Perspective are FLP: - Fading of Colors or Shades - The shade of an object is clar when closer to the object, but the object get blurry as distance increases. - Loss of Detail/Texture - The farther away from an object, details become less apparent. Like leaves in a corn field can be seen when up close but become a solid mass when far away. - Position of Lights and Shadows - When an object casts a shadow from a light source, the object is closer than the light source if the direction of the shadow is toward you.

...

Objective Lens >>> Photocathode >>> Microchannel Plate >>> Phosphor Screen >>> Fiber-Optic Inverter >>> Eyepiece Lens

-The Objective Lens collect the ambient light, (called photons); inverts the image, and then focuses the image onto the Photocathode. -The Photocathode converts the photons into electrons. -After passing through the Photocathode, the electrons then hit the Microchannel Plate where the electrons are multiplied. The Microchannel Plate multiplies the electrons by means of tiny glass tubes that bounce the electrons off the glass tubes sides, creating more electrons. -These electrons (a lot of them now), then strike the Phosphor Screen. The Phosphor Screen turns the electrons back into photons (called "light"). -The photons then go through the Fiber-Optic Inverter. The Fiber-Optic Inverter is a bunch of fiber optics that are twisted. This inverts the photons (and thus the image). -This image is then sent to the eyepiece Lens. -The human eye looks at the Eyepiece Lens and observes the image.

These defects are an immediate cause for rejection: (FEESI) - Flickering or Flashing of one or both monoculars - Edge Glow - Emission Points - Shading - Intermittent Operation

- Black Spots: Probable dirt between lenses. - Image Disparity: Defference in brightness between 2 tubes. - Image Distortion: Trees or poles tend to wave or bend. - Output Brightness Variation: Varying brightness across an image.

Honeycomb usually occurs at high light levels or when viewing very bright lights.

Bright Spots can be checked by cupping your hand over the lens to block out the light. If the Bright Spots go away, then you know it is only a cosmetic blemish. If the spot remains, it is an emission point and the tube is rejected.

(DAALVP) Definition - A helmet-mounted, light-intensification device that allows aircrews to conduct operations at terrain flight altitudes during low ambient light levels. Amplification - ANVIS amplifies light 2,000 to 3,000 times. Acuity - 20/25 under optimum conditions Limited field of view - 40 degrees Voltage Low Indicator - A red LED light on the helmet mount will come on when the battery is at 2.4 volts or less. Power Supply - 3 sources: 1. Battery (2 x 1.5v lithium OR 2x 1.5v Alkaline) 2. Aircraft 3.8vdc 3. Clip On Power Source (COPS)

The 11 NVG operational considerations are CALMWWADSOS: - Color Discrimination - There is no color when looking through the NVGs, only a green hue. - Air/Ground Speed Limits - While wearing NVGs, you tend to overfly their capability to see. - Lights - NVGs are affected by bright lights. The bright light may create: Whiteout, Halo effect, Tunnel Vision Performance is related to amount of available ambient light. - Magnification - There is no magnification with the NVGs. - Weather - Since the NVGs can see through fog and rain, you may fail to detect entry into IMC. - Weapons - When rockets and machine guns are fired, the intensity of the light source may temporary degrade the NVGs. - Aircraft Lighting - * All cockpit red light must be extinguished. * The use of blue-green aircraft instrument lights will not degrade the NVGs. * Unless modified, the aircraft's position lights degrade the NVGs. - Depth Perception and Distance Estimation - Depth perception and distance estimation is difficult using NVGs. Rely upon the monocular cues to help. - Scanning Techniques - NVG scanning is the same as for night unaided scanning. - Obstruction Detection - Wires and small limbs are hard to see with NVGs. Locate wires by looking for the structural supports - Spatial Disorientation - Avoid making drastic changes in attitude and bank angles since they tend to cause Spatial Disorientaion.

"Chromatic Adaption" is the term used to describe the pinkish or brownish tint you see after you remove the goggles. It is a normal reaction for your eyes.

- Automatic Brightness Control (ABC): ABC automatically reduces the voltage to keep the image intensifier's brightness within a set limit. This can be seen when you look into a bright light source. As you first look at the bright light, the image will get brighter and then the brightness dims. - Bright Source Protection (BSP): BSP does the same as ABC - protects the image intensifier from brightness damage. BSP lowers resolution on a bright night; therefore the images may not be a sharp as you may expect.

...

The binocular breakaway force is 10 g to 15 g

ANVIS 6 can accommodate the use of eyeglasses. Be aware that the eyeglass upper rims can obscure the low-battery indicator.

The lanyard cord must be worn while flying with the ANVIS.

The steady (or flashing) red light on the bottom of the ANVIS visor mount alerts the user when remaining battery life is about 30 minutes.

On the older dual battery power packs, labeled "G1" or "G2" on the side of the battery pack, the low battery indicator will only come on as a steady red light. The blinking power pack has a "G3" on the side.

The Battery Pack can use 2 1.5v AA Alkaline or Lithium batteries.

The battery life (until low-battery light turns on) is: - AA alkaline batteries: 70 deg F and above = 10 to 22 hours 0 deg F = 5 to 10 hours - AA Lithium batteries: 70 deg F and above = 34 hours 0 deg F = 28 hours

No. Do not mix batteries in the same AA cartridge.

- Take off the battery cap to the lower (Alternate) compartment and pull the AA cartridge partly out to break electrical contact. - Turn the power switch of the secondary compartmen to ON. The visor red light should come on or blink. - Return the power switch to OFF and put the battery cap back on. - Repeat the same procedure for the upper (Primary) compartment.

No. The Low-Battery Indicator must be checked without the binoculars attached.

The operating temperature range for the ANVIS is minus 32 deg C to plus 52 deg C.

The indications are a visual loss such as you looking through a haze or through eyeglasses that are starting to fog.

The ANVIS 6 Operator's Checks start on page 2-6 of the ANVIS 6 -10. You are expected to go to this page when asked to dmonstrate a proper check of the goggles.

If necessary, clean and dry the lenses using clean water and lens paper.

Clean the dual contacts with a pencil eraser.

As long as the Eyepiece Focus Ring stops at each extreme of travel, then it is OK. It cannot rotate freely with no stops.

The aircrew member is the ultimate person responsible for determining whether the goggles interferes with his ability to perform the mission.

The maximum counterweight is 22 ounces.

To prevent damage, destruction, or loss of the goggles, the lanyard must be worn while flying the ANVIS.

"OSAP" stands for Optimal Sight Adjustment Point. The OSAP occurs when you adjust the goggles so that the optical axes of the goggles are aligned with your visual line of sight.

A "LIF" is a Light Interference Filter. A LIF is a laser protection filter for the binocular. It is screwed on to the Objective Lens.

Yes, the ANVIS 6 may be used while wearing a protective mask.

- Turn both Objective Focus rings fully counterclockwise. - Turn both Eyepiece Focus rings so that the Reference dot and "0" diopter mark are aligned. - Turn on the ANVIS. - Look at a high contrast target. - Cup your hand over the left Objective Lens. - Slowly rotate the right Objective Focus ring clockwise to the sharpest image. - Turn the right Eyepiece Focus ring countercloskwise until the image blurs slightly. Then turn the Eyepiece slowly clockwise till you get a clear image. - Cup your hand over the right Objective Lens and do the same procedures. - Use both eyes and... - Turn the left Objective Focus ring so it is slightly out of focus. - Fine tune the right Eyepiece Focus ring to obtain a sharp image. - Turn the left Objective Focus ring back to its original position. - Still using both eyes, do the same for the right Objective Ring. - Turn off the ANVIS.

During the OUTDOOR binocular focus adjustment procedure, you should look at a target about 100-200 feet away.

During the INDOOR binocular focus adjustment procedure, you should look at a target about 20 feet away.

When exposed to a bright light source, a "halo effect" (whitish circle) is created around the image of the light source. The brighter the light source, the bigger the halo. In addition, a halo will increase when increased moisture (fog, mist) is in the air.

Visual clues to alert you that you are entering IMC are: - Increased Halo Effect. - Increased "Image Noise" (like "snow" seen with poor TV reception).

The techniques for scanning are the basically the same for UNaided as it is for aided. Aided differences are: - Rotate your head slowly left to right. - At the same time, move your eyes from the left limit of vision seen inside the goggles to the right limit. --This will cover about 80 degrees of viewing field while only turning your head 40 degrees

If you are an NVG RL1 aviator assigned to an NVG-designated position, you must complete 9 hours of NVG flight while at the controls. If you have a compatible simulator, you may apply up to 3 hours of simulator time toward the 9 hours.

To be considered NVG current, aviators must fly (while at the controls): - Every 60 days, a 1 hour NVG flight at night in the aircraft. (TC 3-04.33 2-6)

While conducting NVG terrain flight (below 200 feet) training, the max airspeed and altitude limits will apply: - NOE is up to 25 feet AHO at 40 KIAS - Contour is between 25 - 80 feet AHO at 70 KIAS - Low Level is between 80 - 200 feet AHO at up to VNE

A search light or landing light with an IR band-pass filter or pink light is required for NVG operations.

If the IR filter search light or landing light becomes inoperative during a mission, the PC will evaluate the impact on mission accomplishment. PC actions vary from a minor mission adjustment to termination of flight.

Yes

Compensate for the Night Blind Spot by using off-center viewing. Look 10 deg above, below, or to the right or left of the object. This way, the eye's peripheral vision can maintain contact with the object.

While using off-center viewing, avoid viewing an object for no more than 2 to 3 seconds. The object will disappear if viewed longer than this time because the rods achieve photochemical equilibrium by this time.

7 paces from the pilot doors, 14 paces forward from the nose, and an additional 7 paces forward.

Announce, then switch to alternate battery.

Fog over land means water over land soon, loss of ambient light, accuity reduced, scintillation, and the halo effect.

Before both engines are started and remain on until blades have stopped. Except: refuel, terrain flight, other cases where the light may cause disorientation/distraction.

...

Types of Hypoxia: Hypoxic - (Altitude) Occurs when not enough O2 is in the air or when decreasing partial pressure of O2 prevents diffusion across alveolar membranes. Hypemic - (Anemia, Blood Loss, Chemical Interference) Reduction in O2 carrying capacity in the blood. Histotoxic - (Alcohol, narcotics, poisons) Interference with tissues ability to receive O2 from blood. Stagnant - (extreme G forces, blockage, trauma) Circulation is inadequate to deliver O2 to body tissues.

Stages of Hypoxia (ICDC): - Indifferent (0' to 10,000') - Night vision deteriorates ~4,000' - Compensatory (10,000' to 15,000') - Pulse rate, blood pressure, circulation, and cardiac output increase to compensate for reduced O2. May become drowsy and make frequent errors in judgement. - Disturbance (15,000' to 20,000') - Subjective/Objective symptoms present. *Fatigue, dizziness, headache, breathlessness, euphoria *Poor judgement, personality change, decreased coordination *Cyanosis - Critical (20,000' to 25,000') - Within 3 to 5 minutes, judgement and coordination deteriorate. Subsequently, confusion, dizziness, incapacitation, and unconciousness.

Prevention of Hypoxic Hypoxia: - Limit Time at Altitude - Use Supplemental Oxygen - Pressurize Cabin

...

3 sources of natural light: 1. Lunar 2. Solar 3. Starlight

15 degrees per hour (1 degree every 4 minutes)

End of Evening Nautical Twilight -sun is 12 degrees below horizon, about 48 minutes after sunset.

Before Morning Nautical Twilight - sun is 12 degrees below horizon, about 48 minutes before sunrise.